KENYA STANDARD

KS 1895:2008

PUBLIC REVIEW DRAFT, SEPTEMBER 2008

ICS 27.160

Code of practice ⎯ Solar heating systems for swimming pools

Public Review Draft, September 2008

© KEBS 2008

Edition 1.0

PUBLIC REVIEW DRAFT, SEPTEMBER 2008

KS 1895:2008 TECHNICAL COMMITTEE REPRESENTATION

The following organizations were represented on the Technical Committee Kenital Solar (K) Ltd ASP Solar (Kenya) Ltd Sollatek Ltd Department of Electrical & Electronic Engineering, JKUAT Renewable Energy Department, Ministry of Energy Chloride Exide Kenya Limited Energy Alternatives Africa Ltd Solarnet Automotive and Industrial Battery Manufacturers (AIBM) (K) Ltd RENCON Associates Telesales Solar Ltd Kenya Industrial Research and Development Institute, KIRDI Kenya Bureau of Standards — Secretariat

REVISION OF KENYA STANDARDS

In order to keep abreast of progress in industry, Kenya standards shall be regularly reviewed. Suggestions for improvement to published standards, addressed to the Managing Director, Kenya Bureau of Standards, are welcome. © Kenya Bureau of Standards, 2007

Copyright. Users are reminded that by virtue of Section 25 of the Copyright Act, Cap. 12 of 2001 of the Laws of Kenya, copyright subsists in all Kenya Standards and except as provided under Section 26 of this Act, no Kenya Standard produced by Kenya Bureau of Standards may be reproduced, stored in a retrieval system in any form or transmitted by any means without prior permission in writing from the Managing Director.

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© KEBS 2008 — All rights reserved

KS 1895:2008

PUBLIC REVIEW DRAFT, SEPTEMBER 2008

ICS 27.160

Code of practice ⎯ Solar heating systems for swimming pools

KENYA BUREAU OF STANDARDS (KEBS) Head Office: P.O. Box 54974, Nairobi-00200, Tel.: (+254 020) 605490, 602350, Fax: (+254 020) 604031 E-Mail: [email protected], Web:http://www.kebs.org KEBS Coast Region P.O. Box 99376, Mombasa 80100 Tel: (+254 041) 229563, 230939/40 Fax: (+254 041) 229448 E-mail: [email protected]

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KEBS Lake Region P.O. Box 2949, Kisumu 40100 Tel: (+254 057) 23549,22396 Fax: (+254 057) 21814 E-mail: [email protected]

KEBS North Rift Region P.O. Box 2138, Nakuru 20100 Tel: (+254 051) 210553, 210555

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KS 1895:2008

PUBLIC REVIEW DRAFT, SEPTEMBER 2008

Foreword This Kenya standard was developed by the Renewable Energy Resources Technical Committee under the supervision of the Electrical Industry Standards Committee and is in accordance with the procedures of the Bureau. This standard gives recommendations for the use of solar energy for heating swimming pools. Because swimming pools do not need to be heated to a high temperature, but nevertheless need a great deal of energy, they are a particularly suitable application for solar heating. The relatively low temperature requirements allow collectors (often simple unglazed types) to operate at high collection efficiencies. In addition the swimming pool itself provides a heat store reservoir while the pool filtration system offers a means of circulating the pool water through the solar collector circuit for a minimum extra cost. This code is intended to assist the swimming pool industry and building services engineers to provide well constructed and durable equipment for swimming pool heating. Reference is also made to the use of pool covers. Emphasis is on general principles but guidance is given on the method of operation and expected performance of solar heating systems; this should be furnished to customers, by way of preliminary information, in the interests of consumer protection and to help ensure satisfactory system service. The code provides a basis for estimating performance to be expected of a swimming pool solar heating system used in typical situations

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KS 1895:2008

PUBLIC REVIEW DRAFT, SEPTEMBER 2008

Contents 1

Scope .................................................................................................................................................. 1

2

Normative references ......................................................................................................................... 1

3

Definitions ........................................................................................................................................... 6

4

Relevant statutory requirements ......................................................................................................... 7

5

Components........................................................................................................................................ 8

6

System design .................................................................................................................................. 12

6.1 6.2 6.3 6.4

General ............................................................................................................................................. 12 Design considerations ...................................................................................................................... 12 Typical system designs ..................................................................................................................... 15 Collector location .............................................................................................................................. 17

7

Thermal performance ....................................................................................................................... 18

8

Electrical considerations ................................................................................................................... 23

9

Installation ......................................................................................................................................... 23

9.1 9.2 9.3 9.4 9.5 9.6 9.6.1 9.6.2 9.6.3 9.6.4 9.7 9.8 9.9 9.10 9.11 9.12

General ............................................................................................................................................. 23 Pre-installation checks ...................................................................................................................... 23 Plumbing and pipework considerations ............................................................................................ 24 Connections to existing filtration system .......................................................................................... 24 Special considerations ...................................................................................................................... 25 Heat loss mechanisms ...................................................................................................................... 25 Evaporative losses ............................................................................................................................ 25 Convective losses ............................................................................................................................. 25 Radiative losses ................................................................................................................................ 26 Conductive losses ............................................................................................................................. 26 Passive pool heating ......................................................................................................................... 26 Active pool heating ........................................................................................................................... 29 Plumbing schematics ........................................................................................................................ 30 Piping ................................................................................................................................................ 45 Flow control and safety devices........................................................................................................ 48 Instructing the homeowner ............................................................................................................... 50

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Commissioning, handover and documentation ................................................................................ 51

Annex A Details of the model system referred to in clause 6 for thermal performance .................................. 54

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PUBLIC REVIEW DRAFT, SEPTEMBER 2008

PUBLIC REVIEW DRAFT, SEPTEMBER 2008

KENYA STANDARD

KS 1895:2008

Code of practice ⎯ Solar heating systems for swimming pools 1

Scope

This Kenya Standard code gives recommendations and guidance for the design, performance, installation and commissioning of solar heating systems for indoor and outdoor swimming pools. Brief consideration is given to the thermal properties of pool covers. The code does not deal with the filtration systems for swimming pools to which solar heating systems are often connected.

2

Normative references

The following referenced documents are indispensable for the application of this Kenya Standard. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 9059:1990, Solar energy — Calibration of field pyrheliometers by comparison to a reference pyrheliometer ISO 9060:1990, Solar energy — Specification and classification of instruments for measuring hemispherical solar and direct solar radiation ISO 9459-1:1993, Solar heating — Domestic water heating systems — Part 1: Performance rating procedure using indoor test methods ISO 9459-2:1995, Solar heating — Domestic water heating systems — Part 2: Outdoor test methods for system performance characterization and yearly performance prediction of solar-only systems ISO 9459-5:2007, Solar heating — Domestic water heating systems — Part 5: System performance characterization by means of whole-system tests and computer simulation ISO 9488:1999, Solar energy — Vocabulary ISO 9553:1997, Solar energy — Methods of testing preformed rubber seals and sealing compounds used in collectors ISO 9806-1:1994, Test methods for solar collectors — Part 1: Thermal performance of glazed liquid heating collectors including pressure drop ISO 9806-2:1995, Test methods for solar collectors — Part 2: Qualification test procedures

ISO 9806-3:1995, Test methods for solar collectors — Part 3: Thermal performance of unglazed liquid heating collectors (sensible heat transfer only) including pressure drop ISO 9808:1990, Solar water heaters — Elastomeric materials for absorbers, connecting pipes and fittings — Method of assessment ISO 9845-1:1992, Solar energy — Reference solar spectral irradiance at the ground at different receiving conditions — Part 1: Direct normal and hemispherical solar irradiance for air mass 1.5

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KS 1895:2008 ISO 9846:1993, Solar energy — Calibration of a pyranometer using a pyrheliometer

PUBLIC REVIEW DRAFT, SEPTEMBER 2008

ISO 9847:1992, Solar energy — Calibration of field pyranometers by comparison to a reference pyranometer ISO/TR 9901:1990, Solar energy — Field pyranometers — Recommended practice for use

ISO/TR 10217:1989, Solar energy — Water heating systems — Guide to material selection with regard to internal corrosion ISO 4952:2006, Structural steels with improved atmospheric corrosion resistance ISO 11303:2002, Corrosion of metals and alloys — Guidelines for selection of protection methods against atmospheric corrosion ISO 11972:1998, Corrosion-resistant cast steels for general applications KS 1851-1, Thermal solar systems and components — Solar collectors — General requirements KS 1851-2, Kenya Standard — Thermal solar systems and components — Solar collectors — Test methods KS 1852-1:2008, Kenya Standard — Thermal solar systems and components — Factory made systems — General requirements KS 1852-2:2008, Kenya Standard — Thermal solar systems components — Factory made systems — Test methods KS 1855-1:2008, Kenya Standard — Thermal solar systems and components — Custom built systems — Part 3: General requirements KS 1855-2:2008, Kenya Standard — Thermal solar systems and components — Custom built systems — Part 2: Test methods KS 1855-3:2008, Kenya Standard — Thermal solar systems and components — Custom built systems — Part 3: Performance characterization of stores for solar heating systems KS 1869, Standard test method for determination of solar reflectance near ambient temperature using a portable solar reflectometer KS 1869, Standard test method for determination of solar reflectance near ambient temperature using a portable solar reflectometer KS 1870:2008, Standard specification for rubber seals used in flat-plate solar collectors KS 1871:2008, Standard practice for determining resistance of solar collector covers to hail by impact with propelled ice balls KS 1890, Standard practice for installation and service of solar space heating systems for one- and twofamily dwellings KS 1891, Standard practice for evaluating absorptive solar receiver materials when exposed to conditions simulating stagnation in solar collectors with cover plates KS 1892, Standard practice for evaluating solar absorptive materials for thermal applications KS 1898, Standard guide for on-site inspection and verification of operation of solar domestic hot water systems

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© KEBS 2008 — All rights reserved

KS 1895:2008 ISO 559:1991, Steel tubes for water and sewage

PUBLIC REVIEW DRAFT, SEPTEMBER 2008

ASTM B42:2002, Standard specification for seamless copper pipe, standard sizes ISO 7598:1988, Stainless steel tubes suitable for screwing in accordance with ISO 7-1 ISO 49:1994, Malleable cast iron fittings threaded to ISO 7-1 ISO 4144:2003, Pipework — Stainless steel fittings threaded in accordance with ISO 7-1 ASTM A126:2004, Standard specification for gray iron castings for valves, flanges, and pipe fittings BS 417-2, Specification for galvanized low carbon steel cisterns, cistern lids, tanks and cylinders — Part 2: Metric units ISO 12468-1:2003, External exposure of roofs to fire — Part 1: Test method ISO 12468-2:2005, External fire exposure to roofs — Part 2: Classification of roofs ISO 3008:2007, Fire-resistance tests — Door and shutter assemblies

IEC 60364 (All parts), Low-voltage electrical installations ASTM E119:2007, Standard test methods for fire tests of building construction and materials

ASTM E861:1994(2007), Standard practice for evaluating thermal insulation materials for use in solar collectors ISO 9774:2004, Thermal insulation for building applications — Guidelines for selecting properties

ISO 13787:2003, Thermal insulation products for building equipment and industrial installations — Determination of declared thermal conductivity CISPR 14-1, Electromagnetic compatibility — Requirements for household appliances, electric tools and similar apparatus — Part 1: Emission CISPR 14-2, Electromagnetic compatibility — Requirements for household appliances, electric tools and similar apparatus — Part 2: Immunity — Product family standard BS 864-2, Capillary and compression tube fittings of copper and copper alloy — Part 2: Specification for capillary and compression fittings for copper tubes BS 864-3, Capillary and compression tube fittings of copper and copper alloy — Part 3: Compression fittings for polyethylene pipes ISO 9906:1999, Rotodynamic pumps — Hydraulic performance acceptance tests — Grades 1 and 2

ISO 15783:2002, Seal-less rotodynamic pumps — Class II — Specification ISO 9908:1993, Technical specifications for centrifugal pumps — Class III ISO 9905:1994, Technical specifications for centrifugal pumps — Class I BS 1565-2, Galvanized mild steel indirect cylinders, annular or saddle-back type — Part 2: Metric units BS 1566-1, Copper indirect cylinders for domestic purposes — Part 1: Specification for double feed indirect cylinders

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KS 1895:2008

PUBLIC REVIEW DRAFT, SEPTEMBER 2008

BS 1566-2, Copper indirect cylinders for domestic purposes — Part 2: Specification for single feed indirect cylinders BS EN 1057, Copper and copper alloys — Seamless, round copper tubes for water and gas in sanitary and heating applications BS 3198, Specification for copper hot water storage combination units for domestic purposes

ISO 4427-1:2007, Plastics piping systems — Polyethylene (PE) pipes and fittings for water supply — Part 1: General ISO 4427-2:2007, Plastics piping systems — Polyethylene (PE) pipes and fittings for water supply — Part 2: Pipes ISO 4427-5:2007, Plastics piping systems — Polyethylene (PE) pipes and fittings for water supply — Part 5: Fitness for purpose of the system ISO 22391-1:2007, Plastics piping systems for hot and cold water installations — Polyethylene of raised temperature resistance (PE-RT) — Part 1: General ISO 22391-5:2007, Plastics piping systems for hot and cold water installations — Polyethylene of raised temperature resistance (PE-RT) — Part 5: Fitness for purpose of the system ISO 4422-1:1996, Pipes and fittings made of unplasticized poly(vinyl chloride) (PVC-U) for water supply — Specifications — Part 1: General ISO 4422-2:1996, Pipes and fittings made of unplasticized poly(vinyl chloride) (PVC-U) for water supply — Specifications — Part 2: Pipes (with or without integral sockets) ISO 4422-3:1996, Pipes and fittings made of unplasticized poly(vinyl chloride) (PVC-U) for water supply — Specifications — Part 3: Fittings and joints ISO 4422-4:1997, Pipes and fittings made of unplasticized poly(vinyl chloride) (PVC-U) for water supply — Specifications — Part 4: Valves and ancillary equipment ISO 4422-5:1997, Pipes and fittings made of unplasticized poly(vinyl chloride) (PVC-U) for water supply — Specifications — Part 5: Fitness for purpose of the system EAS 205, Controls for household appliances BS 4072, Wood preservation by means of water-borne copper/chromium/arsenic compositions

BS 4213:2004, Cisterns for domestic use — Cold water storage and combined feed and expansion (thermoplastic) cisterns up to 500 L — Specification ISO 16422:2006, Pipes and joints made of oriented unplasticized poly(vinyl chloride) (PVC-U) for the conveyance of water under pressure — Specifications BS 4814, Specification for expansion vessels using an internal diaphragm, for sealed hot water heating systems ISO 15874-1:2003, Plastics piping systems for hot and cold water installations — Polypropylene (PP) — Part 1: General ISO 15874-2:2003, Plastics piping systems for hot and cold water installations — Polypropylene (PP) — Part 2: Pipes

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KS 1895:2008

PUBLIC REVIEW DRAFT, SEPTEMBER 2008

ISO 15874-5:2003, Plastics piping systems for hot and cold water installations — Polypropylene (PP) — Part 5: Fitness for purpose of the system BS EN 12288, Industrial valves — Copper alloy gate valves

ISO 6242-1:1992, Building construction — Expression of users' requirements — Part 1: Thermal requirements ISO 6242-2:1992, Building construction — Expression of users' requirements — Part 2: Air purity requirements ISO 15493, Plastics piping systems for industrial applications — Acrylonitrile-butadiene-styrene (ABS), unplasticized poly(vinyl chloride) (PVC-U) and chlorinated poly(vinyl chloride) (PVC-C) — Specifications for components and the system — Metric series ISO 727-1:2002, Fittings made from unplasticized poly(vinyl chloride) (PVC-U), chlorinated poly(vinyl chloride) (PVC-C) or acrylonitrile/butadiene/styrene (ABS) with plain sockets for pipes under pressure — Part 1: Metric series IEC 61000-3-2, Electromagnetic compatibility (EMC) — Part 3-2: Limits — Limits for harmonic current emissions (equipment input current ≤ 16 A per phase)

ISO 22897:2003, Glass in building — Glazing and airborne sound insulation — Product descriptions and determination of properties ISO 16932:2007, Glass in building — Destructive-windstorm-resistant security glazing — Test and classification ISO 3934:2002, Rubber, vulcanized and thermoplastic — Preformed gaskets used in buildings — Classification, specifications and test methods ISO 9050:2003, Glass in building — Determination of light transmittance, solar direct transmittance, total solar energy transmittance, ultraviolet transmittance and related glazing factors

ISO 8873-1:2006, Rigid cellular plastics — Spray-applied polyurethane foam for thermal insulation — Part 1: Material specifications ISO 8873-2:2007, Rigid cellular plastics — Spray-applied polyurethane foam for thermal insulation — Part 2: Application ISO 24510, Activities relating to drinking water and wastewater services — Guidelines for the assessment and for the improvement of the service to users ISO 24512, Activities relating to drinking water and wastewater services — Guidelines for the management of drinking water utilities and for the assessment of drinking water services ISO 2103:1986, Loads due to use and occupancy in residential and public buildings ISO 4354, Wind actions on structures ISO 12494, Atmospheric icing of structures ISO 9453, Soft solder alloys — Chemical compositions and forms ISO 9454-1, Soft soldering fluxes — Classification and requirements — Part 1: Classification, labelling and packaging

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KS 1895:2008

PUBLIC REVIEW DRAFT, SEPTEMBER 2008

ISO 9454-2:1998, Soft soldering fluxes — Classification and requirements — Part 2: Performance requirements ISO 12224-1, Solder wire, solid and flux cored — Specification and test methods — Part 1: Classification and performance requirements

3

Definitions

For the purposes of this code the following definitions apply. 3.1 collector (solar collector, solar panel) the general term for a device in which solar radiation is absorbed and converted to heat which is removed by the heat transfer fluid 3.2 flat plate collector a collector that employs no concentration of the incident solar radiation and in which the absorber plate is essentially planar 3.3 embedded collector a collector in which the fluid passages are embedded either in the ground or within a covering such as paving slabs, asphalt or concrete 3.4 trickle collector a flat plate collector in which the heat transfer fluid is not contained within passageways in the absorber plate but flows down the plate surface 3.5 absorber plate (absorber) the element of a collector that receives and absorbs the solar radiation and converts it into heat 3.6 absorber plate surface coating a coating whose principal function is to absorb solar radiation 3.7 selective surface an absorber plate surface coating that will decrease the radiative emission from the absorber plate whilst maintaining a high absorptance for solar radiation 3.8 unglazed collector a collector with the front surface of the absorber plate exposed to the surrounding air. The rear surface may or may not be insulated 3.9 glazed collector a collector with an absorber plate covered by a translucent glazing material. The rear of the absorber plate will normally be insulated within a weatherproof envelope 3.10 direct system a system in which the pool water passes through the solar collectors

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3.11 indirect system a system in which a fluid other than the swimming pool water passes through the solar collectors 3.12 integrated circuit a system in which the solar collectors form part of the same pipework circuit as the pool filtration plant 3.13 separate circuit a system in which the solar heating circuit is completely separated from the pool filtration circuit 3.14 drainback system a system in which as part of the normal working cycle the collector is automatically drained and refilled 3.15 draindown system a system within which heat transfer fluid is retained until manual draining takes place 3.16 differential temperature controller a device that is able to detect a small temperature difference and control pumps and other electrical devices in accordance with this temperature difference 3.17 pool inlet the point at which water from the filtration circuit is returned to the pool, generally by means of an inlet nozzle 3.18 pool outlets the points at which water is drawn from the pool to be filtered, generally from a sump outlet at the lowest point in the pool and from a skimmer outlet at the pool surface

4

Relevant statutory requirements

4.1

General

There are statutory requirements that have to be observed before the installation of any swimming pool. As these requirements may vary slightly between different parts of the country, the relevant local authority should always be consulted regarding planning and building regulations and, likewise, the local supply authority regarding water supply requirements. 4.2

Planning

As a general rule, permission has to be obtained from the local planning authority before carrying put any development. Consequently, it should be ascertained from the local planning authority as to whether or not the proposed installation constitutes development. 4.3

Building regulations

General regulations have been enacted concerning the design and construction of buildings. Solar heating systems incorporated into buildings have to comply with these regulations in so far as they affect matters of construction, roof loading, weathertightness, fire resistance, insulation, etc.

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KS 1895:2008

PUBLIC REVIEW DRAFT, SEPTEMBER 2008

Advice on some of these matters is given elsewhere in this code. However, responsibility for the application of the regulations in a particular area rests with the local authority, which may require plans to be deposited, showing how it is proposed to comply with the regulations. 4.4

Water supply

Water supply byelaws for preventing waste, undue consumption, misuse or contamination of water supplies have been made by the Water Authorities and Companies. These byelaws require that written notice is given to the local water authority before installing or altering (except for repair or replacement) any water fitting used or to be used in connection with an existing supply of water from the undertaking. It should be noted that whilst the various sets of byelaws are identical except for a few minor respects, the interpretation and enforcement of byelaws rests with the particular water supply authority concerned. Bearing this in mind, it is considered that to attempt to give meaningful detailed guidance on the application of water byelaws in this code could be misleading. However, it can be assumed that where a solar heating system is to be used to heat water for domestic use, as well as to heat swimming pool water, then the recommendations contained in KS 1860 should be taken into account. The application of the water byelaws will depend on for example, whether the solar heating system (for pool water only) is direct or indirect, whether the heat transfer fluid is pool water, potable water or a non-aqueous fluid and how the make up water to the pool and/or solar heating system is supplied. It is therefore recommended that early contact is made with the local water undertaking to discuss the proposed installation and to seek advice. 4.5

Other actions

In addition to complying with the legal requirements detailed in 4.1 to 4.4, it is recommended that the occupier/ owner inform the lessors, mortgagors, insurers, etc. of the property as applicable.

5

Components

5.1

General

This clause describes the principal components used in solar heating systems for swimming pools. 5.2

Collectors

5.2.1

Types of collector

Solar collectors intended for swimming pool applications are commonly of the flat plate variety but they may or may not be glazed and insulated. Embedded and trickle collectors may be used. Collectors are designed so that a heat transfer fluid, often the swimming pool water itself, can pass through the collector in close thermal contact with a matt black or similar heat absorbing surface. When the material used between the fluid passages is a good conductor of heat, e.g. copper, the fluid passages can be spaced apart. When a poorer heat conductor is used, it is important to bring the fluid passages closer together.

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PUBLIC REVIEW DRAFT, SEPTEMBER 2008

Table 7.1 — Some relevant standards for components and fittings Feed and expansion cisterns and expansion vessels BS 417, BS 4213, BS 4814 Tanks and cylinders BS 1566-1, BS 1565, BS 3198 Pumps

ISO 9906

Valves

BS EN 12288

Pipework and fittings British Standards applicable to pipes and pipe fittings include the following

Form and material

BS designation

Type and application

Tubes Copper

BS EN 1057

Hot and cold water services

Plastics ABS PP Unplasticized PVC HDPE

ISO 15493 ISO 15874 ISO 4422 ISO 4427

Cold water services Hot and cold water services Cold water services Cold water services

Stainless steel

ISO 7598

Hot and cold water services

Fittings Copper and copper alloy

BS 864-2

(capillary and compression) Hot and cold water services (compression) Malleable cast iron and cast copper ISO 49 and ISO 4144 Cold water services (screwed pipe fittings) alloy Hot and cold water services Unplasticized PVC ISO 16422 Cold water services ABS ISO 727-1 Cold water services

5.2.2

Selection of collector type

Solar collectors used for pool heating can be installed without glazing or a similar translucent cover in front of the absorber if they operate close to the ambient temperature. Glazing reduces the radiation incident on the absorber and this effect may outweigh the reduction in heat loss from the front of the collector. Similarly rear insulation may marginally improve the performance but the benefit may be too small to warrant the additional cost. Unglazed and uninsulated collectors preferably should be mounted in a position that is sheltered from strong prevailing winds. If such a site is not available consideration should be given to the use of glazed and insulated collectors. In the case of pools maintained at temperatures appreciably above the ambient temperature the incorporation of front glazing gives better thermal performance for the same collector area, but the improvement may not justify the extra cost involved. The use of double glazing on the absorber is not likely to be worthwhile. In indirect systems the use of glazed and insulated collectors may be appropriate because of the temperature differential across the heat exchanger. For the same reason the use of a selective surface may be advantageous.

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Trickle collectors may have the advantage of being cheap but if glazed may have a reduced performance due to the build up of algae. Evaporative heat loss from unglazed trickle collectors may substantially reduce their performance.

NOTE Other forms of collector, e.g. concentrating, evacuated and tracking collectors, are not dealt with in this standard because these types are primarily used for higher temperature applications and insufficient experience is currently available about their use for pool heating.

5.2.3

Selection of materials

In direct systems it is important to select materials for the fluid passages that are suitable for contact with swimming pool water. The materials used should neither contaminate the pool water nor should they become corroded under normal service conditions. Plastics materials, such as polypropylene, polyethylene or EPDM, are generally suitable for contact with pool water and solar collectors manufactured from these materials are available. Black pigmented material is normally utilized and it should be ensured that the material is stabilized against degradation by ultraviolet light. Copper can also be used for the fluid passages in direct circulation solar collectors but it is important to maintain the pH of the pool water at between 7.2 and 7.6 or above in order to prevent corrosion. This, together with the correct total alkalinity and free residual chlorine level, will prevent undue corrosion/erosion of copper pipework at flow velocities up to 1.5 m/s. Iron and carbon steel are unsuitable for the fluid passages because there may be rapid corrosion resulting in the failure of the collectors and rust staining of the pool walls and fittings. It is important to recognize that not all grades of stainless steel will resist corrosion in these applications and grade 316 type is recommended. Some aluminium alloys are not suitable for direct contact with pool water because of the probability of corrosion. Adequate steps should always be taken to guard against bimetallic corrosion and pitting corrosion. For example, in indirect drainback systems (see Figure 3) it is important not to use galvanized steel cisterns combined with copper pipework since pitting corrosion of the steel may occur. The risk is particularly high in systems where the heat transfer fluid is highly aerated. Reference should be made to KS 1860 regarding corrosion protection and the use of heat transfer fluids other than pool water in indirect swimming pool solar heating systems. 5.3

Controls

5.3.1 A control system is an important part of the swimming pool solar heating installation. The purpose of the control is to ensure that fluid is pumped through the collectors only when heat can be gained. 5.3.2 In direct systems it is usual to incorporate the solar collector circuit into the existing filtration circuit. This minimizes the total pumping power used for pool filtration and for solar collection. It is often cheaper and more convenient than using a separate circuit for the solar collectors (see 6.2.1). The filtration pump is normally required to run during times when there may be no solar heat gain. It is therefore preferable to be able to run the filtration plant either continuously or on a time switch and to install the means of diverting the pool water through the solar collector circuit whenever a heat gain is available. This can be achieved by using a valve to divert the flow through the solar collector after filtration. Thus the water has to pass through the solar collectors and then back to the pool. Alternatively, an additional pump may be used in the solar collector circuit which, when activated, draws filtered water and returns it to a point further downstream from where it can return in the normal way to the pool.

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5.3.3 Whether a diverting valve or a pump is used, a control system is required to ensure that the pool water is only circulated through the collectors when there is a net heat gain available. An electronic differential temperature controller incorporating a pair of temperature sensors is usually used to activate the solar pump or diverting valve. One of these sensors detects the pool temperature while the other detects the temperature of a section of the absorber plate which is exposed to solar radiation but is thermally insulated and remote from a fluid passage. A collector sensor mounted in the fluid outlet pipe from a swimming pool solar collector may not be satisfactory because it may not adequately detect the relatively small temperature rises which can be considered as useful in a high flow rate system. The pool temperature sensor is normally mounted in close thermal contact with the water in the filtration circuit prior to the branch to the solar collectors (see 7.7). NOTE In this context the net heat gain is achieved when the value of energy collected exceeds the cost of energy expended by a separate circulating pump. The temperature differential at which the controller turns the system off should therefore take account of any pump energy consumption. Since the relevant temperature differential is likely to be small it is important to select a controller with limited temperature drift characteristics.

5.4

Pool covers

5.4.1 Heat losses from swimming pools occur mainly from the water surface and various types of cover are available to reduce these losses in both indoor and outdoor pools. Covers can be regarded as a useful energy conservation measure with any type of pool and will enable many pools to function more efficiently as natural collectors of solar radiation. 5.4.2

Various types of floating pool cover can be used including the following types:

a)

single skin plastics film;

b)

double skin plastics film with encapsulated air bubbles;

c)

closed cell plastics foam.

All of these types are available in either translucent or opaque grades but the plastics foams are frequently supplied laminated onto an opaque woven material. Other covers are available which are stretched across the surface of the pool above the water level. Covers are moved on and off the pool many times each season. Any pool cover should be sufficiently tough to allow necessary handling. Materials used for covers for open air pools should be adequately resistant to both ultraviolet radiation and to chemicals normally present in swimming pools.

The main function of a cover is to reduce or eliminate evaporation from the surface of the pool. All of the cover types mentioned are effective in this respect since they form a vapour barrier across the top surface of the pool. Any water lying on the top of the cover will reduce its effectiveness. With covers that are suspended above the water it is important to ensure that the edges are reasonably airtight since otherwise water vapour will escape. The second function of the cover is to prevent heat loss by convection. The single film covers are the least effective in this respect. The third function is to reduce the radiation heat loss from the swimming pool. This is the least significant heat loss from the surface of the pool. For a pool that receives sunshine and where the cover may be in place for even only a few daylight hours it is advantageous to select a translucent cover. With such covers there can still be a very significant radiation heat gain to the pool. Sunlight that passes through the cover is largely absorbed by the pool water itself. The water can thus be heated naturally in the same way as with an uncovered pool but with the great advantage that the heat losses from the top surface are substantially reduced.

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5.4.3 Safety is an important consideration as most covers cannot support the weight of a child or pet animal. Due to the risk of drowning, no one should swim beneath a cover. This is particularly important with floating covers.

6

System design

6.1

General

Principal design features of swimming pool solar heating systems are often determined by: a)

the type of pool (indoor or outdoor);

b)

the intended period of use (typically summer only or all year);

c)

possible locations for the collectors, in particular their height relative to the pool surface.

In addition, the choice between a direct or indirect system is fundamental. Whereas satisfactory system design details may in principle be determined by calculation, it is considered helpful to summarize the features that have been found to be crucial to successful operation and to give a brief description of the most popular system types.

6.2

Design considerations

6.2.1

Interaction with existing equipment

Any connection between swimming pool solar heating systems and existing filtration equipment has to be such as to ensure continuing satisfactory performance under all operating conditions. A reduced flow rate through the filtration system may result in inadequate filtration as well as poor mixing of the water in the pool. This could contribute towards increased thermal stratification in the pool with a resultant increase in heat loss from the pool. Moreover care should be taken to ensure that there is no short circuiting of water between the inlets and outlets in the pool which could be caused by a reduced flow rate at the pool inlet nozzles. 6.2.2

Collector drawback and draindown

Many swimming pool solar heating systems need to be designed to ensure that the collectors (and often other exposed components also) may be fully drained under some conditions. Failure of components to be drained satisfactorily may, depending upon their design, result in extensive damage. It is therefore important both that the initial system design is correct and in accordance with manufacturer's recommendations and that users are aware of what constitutes satisfactory behaviour. Two common situations are as follows. a)

Systems in which collectors are located above pool level and drain whenever heat transfer fluid (usually pool water) is not delivered to them under pressure. This is the "drainback" mode of operation and is used typically to provide automatic frost protection or, in the case of some glazed collectors, protection against boiling.

b)

Systems in which heat transfer fluid may be retained within collectors for long periods but in which manual draining to preclude frost damage is necessary usually at the end of each swimming season (see 10.7).

In order to achieve satisfactory drainback careful system design is required and the following points should be considered.

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KS 1895:2008 1)

A suitable air admittance device has to be fitted (see 6.2.3).

2)

There has to be an unobstructed route for water to return to the pool by gravity. The closed port of a 3-way valve can prevent water draining back from the collectors.

3)

Water should be prevented from returning to the pool by means of reverse flow through the filter since this may backwash part of the debris collected by the filter into the pool. Unless the filtration pump is already fitted with a device to prevent reverse flow, a non-return valve should be fitted in the filtration circuit.

4)

The pressure head in the filtration circuit may prevent complete drainback of the solar collector circuit. Any parts of the solar circuit that will not be drained as a result of this should be otherwise protected against frost damage (e.g. by being located indoors).

5)

Means should be provided for checking whether the system drains back as intended, e.g. by fitting a drain valve which would show the presence of water if opened [see 10.2 f)].

Whether automatic drainback or manual draindown is intended all pipes including collector header pipes and fluid passages within the collectors should be laid to adequate falls to allow complete draining e.g. a minimum of 1 in 200. Drain-off valves should be provided at any low points in the circuit that will not drain by gravity and stop valves should be provided to isolate any parts of the circuit that are designed to be left drained during the winter from parts that may be left operational. 6.2.3

Pressures in direct circuits

There are particular considerations regarding pressures in direct circulation systems when solar collectors are installed above the pool water level. The water at the pool surface will be at atmospheric pressure so direct solar heating circuits above pool water level will be at sub-atmospheric (negative) pressures unless maintained at a positive pressure by a pump. The potential reduction in pressure below atmospheric pressure is dependent on the height of the circuit above the pool. When collectors are installed up to about 1 m above pool water level the entire circuit is likely to be maintained at positive pressure when the system circulating pump is running and will only be at negative pressure when the pump is switched off. In such cases the circuit may be designed to drain back into the pool whenever the pump is switched off if an air admittance device, such as a suction relief valve, is incorporated into a high point of the circuit. Automatic air vents used for this purpose may not be relied upon to open, especially under low negative pressure, if of a type held closed by flotation or by spring action. Where collectors are mounted at higher levels there may be negative pressures in the upper parts of the circuit even when the circulating pump is operating and there is a satisfactory flow rate through the solar collectors. In order to prevent air entrainment which may lead to air locking these parts of the circuit have to be airtight.

In such cases drainback cannot be facilitated by means of a suction relief valve unless it can be ensured that the point in the circuit at which this device is fitted is always maintained at a positive pressure while the circulating pump is operating. This may be achieved by fitting the air admittance device upstream of a restrictor valve positioned close to the highest point in the circuit but a significantly higher pump loading may result. Alternatively, an air admittance device in the form of an electrically operated "normally open" valve wired in parallel with the pump may be used in a circuit that is otherwise airtight. In this case particular care has to be taken to ensure that air in the circuit will be expelled on refill by virtue of water velocity and the return pipework should be sized accordingly. If frost protection is to be achieved by manual draining an automatic air admittance device need not be fitted but the system components have to be specified to withstand sub-atmospheric (negative) pressures.

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KS 1895:2008 6.2.4

Circulation of heat transfer fluid

PUBLIC REVIEW DRAFT, SEPTEMBER 2008

In direct solar heating circuits the heat transfer fluid (pool water) may be circulated through the collectors by either the filtration pump or a separate pump. In the latter case the solar heating circuit may either be connected to the filtration circuit or be remote from it with separate inlet and outlet connections to the pool. In indirect systems optimum flow rates will depend much on the detailed efficiency and pressure loss characteristics of the heat exchanger. Whilst the figures given can serve as a guide, manufacturers' recommendations should be studied, also with a view to ensuring that neither the collector nor heat exchanger efficiency is unduly compromised under typical working conditions. Similarly, pumping power should be considered at an early stage in design. The efficiency of all thermal solar collectors decreases with increasing operating temperature and this is particularly severe for unglazed units. It is therefore important that the flow rate of heat transfer fluid is sufficiently high to help ensure efficient operation. In practice a flow rate for water of 0.04 kg/(m2.s) of collector is usually satisfactory; flow rates above 0.06 kg/(m2.s) produce little additional benefit and will incur higher pumping energy requirements. Glazed collectors can work with little loss of efficiency at lower flow rates, typically 0.02 kg/(m2.s) to 0.04 kg/(m2.s) for water.

6.2.5

Pipe sizing and distribution

It is particularly important to ensure balanced flow distribution to all collectors within a pool heating system, especially if unglazed collectors are used. In addition to the usual calculations for pressure loss along flow and return pipes the following special factors should be considered at the design stage: a)

alternative collector interconnection schemes such as reverse return pipework layouts, having regard to manufacturers' recommendations;

b)

the possible need to install balancing (restrictor) valves especially if banks of collectors are to be sited at different heights in a drainback system;

c)

the need to ensure positive subsequent filling of all collectors following draining, e.g. by ensuring that air cannot be trapped in one or more banks of collectors;

d)

the need to size pumps for drainback systems to overcome the total static lift in addition to overcoming the frictional losses in the circuit.

6.2.6

Direct circuits

Pool water can be contaminated with suspended solids and other debris which could block solar collectors and associated pipework. It is therefore important to ensure that only filtered water is passed through the solar collector circuit. This is easily achieved in the case of solar circuits connected to the filtration system, provided that water is diverted to the collectors after the filter. However, in circuits not integrated with the filtration system it is necessary to provide an adequate level of filtration prior to circulation through the solar collectors. This may be achieved by fitting a suitable mesh strainer over the outlet connection from the pool or by fitting an in-line strainer elsewhere in the circuit but the design has to allow for access for cleaning or provision be made for back-washing. Such pool outlet connections are best kept clear of the sump of the pool or the water surface since suspended matter and debris tends to accumulate at these locations. 6.2.7

Indirect circuits

In indirect circuits the pool water is passed through the secondary side of a heat exchanger located in the filtration circuit. The solar collectors are connected to the primary side of the heat exchanger and heat transfer fluid is circulated by means of a separate pump.

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The heat transfer fluid used in the primary circuit may contain a suitable corrosion inhibitor and/or anti-freeze solution to provide frost protection. In sealed circuits heat exchange oils may also be used. Manufacturers' advice regarding the use of dissimilar metals and the suitability of components such as pumps should be sought particularly when using non-aqueous fluids. It is recommended that the corrosion inhibitor and/or anti-freeze solution should be non-toxic and also contain non-toxic biocide compounds to prevent bacteria and algae growth in the primary heat transfer fluid.

6.3

Typical system designs

6.3.1

Direct circulation with separate pump not connected to filtration circuit

Flow and return connections to the pool should be positioned to ensure good mixing with the pool water. The pump may be either located below the pool water level so that it is kept full of water at all times (and protected from frost by being located indoors or by manual draining in wintertime) or be self-priming. Since these systems are not connected to the filtration circuit automatic drainback may be achieved conveniently in most situations. 6.3.2

Direct circulation with separate pump integrated with filtration circuit

A typical circuit is shown schematically in Figure 1. The solar pump is positioned so as to draw filtered water from the filtration circuit and therefore the pump does not normally need to be self-priming. The connection from the solar collector circuit should be positioned so as to introduce solar heated water ahead of any chemical dosing equipment or auxiliary heating plant. Drainback for frost protection may be achieved provided that the pressure head in the filtration circuit is insufficient to hold water in exposed parts of the solar heating system. 6.3.3

Direct circulation with flow diversion by 3-port valve

A typical circuit is shown schematically in Figure 2. A 3-port valve may be installed in the pool filtration circuit with one of the two outlet ports connected to allow circulation through the solar collectors. The pipe from the solar collectors should be connected into the filtration circuit such that flow is maintained through any dosing equipment or auxiliary heater. In order to provide automatic control 3-port valves are normally fitted with an actuator motor connected to the solar heating control system. Since the outlet port to the solar collectors will normally be closed when the filtration pump is switched off (often by a time switch) a drainback system will only function satisfactorily if a means to bypass the closed port of the motorized valve is introduced.

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6.3.4

Figure 1 — Direct circulation with separate pump integrated with filtration circuit Indirect circuits

Three typical types of indirect circuit are as follows. In each case the solar collectors should be connected to the primary side of a suitably sized heat exchanger with the pool water passing through the secondary side (see 7.6). a)

Drainback circuits. These incorporate a drainback cistern situated in a location secure from frost and below collector level but above the level of the circulating pump (see Figure 3). An air admittance device which may take the form of an air break at the drainback cistern should be installed in the circuit. A float operated valve usually controls the level of the water in the cistern and it should be recognized that the float may become submerged during the drainback condition. It is important that the cistern has sufficient reserve capacity that the level does not reach either the cistern overflow or the inlet valve. Such systems can provide frost and boiling protection to the solar collectors.

b)

Sealed and pressurized circuits. These incorporate conventional pressurized sealed circuit equipment such as expansion vessels and pressure relief valves. Such circuits allow great flexibility to the designer regarding acceptable collector positions in terms of height relative to the pool. The use of a suitable heat transfer fluid may remove the risk of freezing or boiling.

c)

Feed and vent cistern circuits. These may be designed in a similar way to conventional forced circulation central heating systems. The cistern should be located above the solar collectors so this type of system is particularly suitable where solar collectors are mounted at low level. The use of a suitable heat transfer fluid can offer frost protection. The venting arrangement should be designed to allow for the discharge of any generated steam.

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KS 1895:2008 Collector location

6.4.1

General

PUBLIC REVIEW DRAFT, SEPTEMBER 2008

6.4

The most suitable location for the solar collectors should be determined by considering the implications on thermal performance, pipework connections and the visual appearance of alternative available positions but having regard to the need for access for inspection and maintenance.

NOTE

Figure 2 — Direct circulation with flow diversion by 3-port valve The pipe circuit requirements are described in 6.2 and 6.3

The effect on thermal performance of different collector locations will depend on their relative exposures to both solar radiation and to wind. Generally collectors should be installed in unshaded positions orientated and inclined to intercept a maximum amount of solar radiation. Guidance on the optimum orientation and angle of tilt is given in Clause 7. The effect of exposure to wind will be more pronounced for unglazed collectors and a sheltered position is therefore to be preferred. Pipework lengths should be kept to the minimum possible so as to reduce both pumping power requirements and heat losses. The latter will be unimportant with pipework operating at low temperatures but will become more significant as the temperature rises. Standard calculation methods are available to estimate pipework heat losses and these should be used to help determine the optimum thickness of any insulation. The thermal insulation and method of installation should comply with ISO 9774. 6.4.2

Collector fixing

The method of fixing solar collectors has to be considered carefully taking into account the considerable forces caused by wind lift to which collector fixings may be subjected. Manufacturers' recommendations regarding fixing systems should be followed and where such fixings are to be fastened to other building © KEBS 2008 — All rights reserved

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KS 1895:2008

PUBLIC REVIEW DRAFT, SEPTEMBER 2008

structures, special attention should be paid to the design of the fixings and the load that they may place on the building structure. Fixings should not be liable to corrode, cause rainwater leaks or work loose because of wind vibration. The advice of a suitably qualified person should be sought where appropriate. Where fixing battens or similar items are to be used on flat or sloping roofs, these should always be spaced off the roof or otherwise arranged so that they do not interfere with the normal drainage of rainwater on the roof. Reference should be made to KS 1860 for collector installation practices.

Figure 3 — Typical indirect drainback circuit

7

Thermal performance

7.1

General

The predictions of performance are based on computer simulations which are described in detail in Annex A. In these simulations, the central assumptions are that: a)

the collectors are part of a direct system; that is, the pool water passes through the collectors;

b)

the collectors face south at 45° to the horizontal;

c)

there is auxiliary heating to maintain the pool water at a fixed temperature so that the temperature of the pool water entering the collector is constant.

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The amount of collector area to be chosen for a given application will depend upon the heating requirements for the pool concerned. These requirements will be determined by the size of the pool, the desired water temperature and the degree to which the pool cover is used. For outdoor pools the heating requirements are also strongly affected by the location of the pool, particularly its exposure to wind. For indoor pools the temperature and humidity levels of the air in the pool hall will strongly influence the pool heating requirements.

7.2

Pool temperature (°C) Data set: Kew 1959 to 1979 Energy integrated over January to December NOTE The performance of collectors, particularly those of type 3, will depend on many factors and these curves should be interpreted with reference to Clause 6.

Figure 4 — Average energy output from collectors for a typical year Collector type

It is the characteristics of the collector employed that are of primary importance in determining the thermal performance of the system. Typical values of these are given in Annex A, for three types of flat-plate collectors commonly used for solar heating swimming pools: a single-glazed insulated selective collector (collector 1), a single-glazed insulated matt black collector (collector 2); and an unglazed, uninsulated collector (collector 3). When these collectors are used, the energy output, or heat transferred to the pool water, over a typical year is as shown in Figure 4. Figure 5 shows the output over a typical swimming season, taken here to be the period May to September inclusive. NOTE

In this context a typical year is one in which the weather corresponds closely to the long-term average weather.

7.3

Pool water temperature

The performance of a solar collector, especially if it is unglazed and uninsulated, is strongly dependent on the temperature of the pool water. The effect of pool water temperature on typical energy outputs of the different types of collector is shown in Figure 4 and Figure 5.

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KS 1895:2008 7.4

Positioning of the collector

PUBLIC REVIEW DRAFT, SEPTEMBER 2008

The heat output varies with the orientation and tilt of the collector, which will often be determined by the site. However, the predicted variation is slight. It can be assumed, all other factors being equal, that the output will be at least 90 % of that shown in the figures if the collector faces anywhere between 30° east and 40° west of true south and is tilted from the horizontal between 20° and 50°.

Pool temperature (°C ) Data set: Kew 1959 to 1979 Energy integrated over May to September NOTE The performance of collectors, particularly those of type 3, will depend on many factors and these curves should be interpreted with reference to Clause 6.

Figure 5 — Average energy output from collectors for the period May to September inclusive

Shading from trees, buildings, etc., can produce a significant decrease in system performance, and collectors should be positioned to minimize this. Undue exposure to wind will also reduce the performance, particularly of unglazed collectors. Conversely, if unglazed collectors are mounted in a very sheltered position, energy output may be increased above that indicated. 7.5

Climate

The heat output figures quoted are annual averages calculated with the meteorological data for Kew over the 21 year period from 1959 to 1979. The change in weather from year to year may cause variations of up to 15 % from the long-term averages for glazed collectors. For unglazed collectors there will be an equal or greater variation in performance from year to year. Even in a given year, differences in performance may occur between similar systems in the same locality because of variations in local conditions, for example, exposure to wind.

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Solar radiation availability varies significantly over the United Kingdom. The variation in heat delivered to the pool water is likely to be approximately in accordance with that of the solar energy availability during the months of collector operation. Mean air temperatures and windspeeds also vary widely over the United Kingdom and will have an effect on collector output. For example, unglazed collectors in particular will produce higher collector outputs in parts of the country that are on average warmer than Kew. 7.6

Indirect systems

For an indirect system the heat transferred to the pool water will be reduced because the temperatures in the collector circuit will be higher than for a direct system, to provide a temperature differential to operate a heat exchanger. The actual reduction for a given system would depend on the effectiveness of the heat exchanger used and will be larger if unglazed collectors are used than if glazed collectors are used. It should be noted that heat exchangers not specifically designed for low temperature differentials will prove unsuitable. 7.7

Other factors

The flow rate through the collector should be fairly high so that the temperature rise across the collector is kept low and thus the heat losses are minimized. This is especially important if collectors are unglazed. Recommendations for flow rates are given in 6.2.4. The temperature differential between the pool temperature sensor and the collector sensor at which circulation through the collector is allowed to occur can affect the amount of energy supplied. If the flow rates recommended in 6.2.4 are used, the temperature differential settings should not be critical. However, it is suggested that the temperature difference at which circulation starts should not exceed 2 K and the temperature difference at which it is stopped should not exceed 1 K (see 5.3.3). 7.8

Collector sizing

7.8.1

General

Methods for calculating the heat requirement for indoor pools have been developed. Caution should be exercised when applying these methods for the calculation of heat losses from outdoor pools. The effect of windspeed is most significant but it is not easy to quantify due to its dependence on the amount of shelter provided around the pool. Wind breaks such as hedges or fencing improve the comfort of bathers and reduce heat losses from the pool. 7.8.2

Indoor or outdoor pools with auxiliary heating

Whilst the installed area of the collector may often be influenced by available space, a convenient starting point is to calculate the area necessary to provide all the heat required in the month for which the requirement is lowest, usually July. It can then be assured that the system will rarely produce heat that is surplus to requirements. When the average rate of heat loss from the pool is known, perhaps from previous fuel bills, Figure 6 may be used to determine an appropriate collector area. This figure refers to the calculated longterm average performance of collectors operated at Kew for the month of July. For months other than July, the heat supplied by the collector will be less than that needed to maintain the required temperature. The auxiliary heating system is used to keep the pool temperature at the design value. In that case, the contribution provided by the collector towards the heat requirement may be determined from Figure 4 or Figure 5, according to the period over which the pool is in use. It may happen that the collector heat output is required to be known for individual months other than July, for example where systems are operated at schools or holiday camps. This may be estimated from additional figures given in Annex A.

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For pools in use only from May to September there may be a significant further collector output obtained during the warm-up period (typically during the month of April). The collector should be allowed to pre-heat the pool before the pool is brought into use, with the pool cover left in position to reduce heat loss. The cost of running any pump should be considered when determining the most appropriate length of pre-heat period. The auxiliary heating system should then be turned on as late as possible, working at its full capacity to bring the pool water quickly up to the desired temperature. 7.8.3

Outdoor pools without auxiliary heating

When auxiliary heating is not provided, the pool temperature will vary both from day to day and from month to month. The variation for a given pool will depend on the local weather conditions and the amount of shelter provided. If outdoor swimming is desired over the May to September season, the following ratios of collector area to pool area appear to be satisfactory, provided that a pool cover is used. Location Sheltered Exposed

Ratio of collector area to pool area 0.5 0.8

The area required for this application does not depend much on the type of collector employed, since the pool temperature is normally in the region for which the collector energy output is approximately the same for all collector types.

Pool temperature (°C) [Data set: Kew 1959 to 1979] NOTE The performance of collectors, particularly those of type 3, will depend on many factors and these curves should be interpreted with reference to Clause 6.

Figure 6 — Average energy output from collectors for July 22

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KS 1895:2008

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8 8.1

Electrical considerations General

The electrical component of the system shall be designed and installed in accordance with relevant regulations and standards. Due care and consideration should be given to the environmental conditions when selecting equipment for use. 8.2

Electrical installation

All wiring and apparatus shall be installed in accordance with the requirements of KS 662 or IEC 60364. All plant and equipment shall comply with relevant Kenya Standards. 8.3

Electrical safety

The Kenya Wiring Regulations (KS 662) require that any wiring and apparatus are properly installed and protected to ensure safety, particularly from the effects of fire and shock. This protection is achieved by adequate insulation of all conductors and apparatus and the provision of effective earthing arrangements. It should be ensured that, in the event of a fault, the installation is automatically disconnected from the supply within 0.4 s. Additionally, protection may be provided by the installation of an appropriate type of residual current circuit breaker. 8.4

Controls

Controls shall be in accordance with the requirements set out in EAS 205. 8.5

Avoidance of electrical interference

Where applicable, the requirements given in IEC CISPR 14 and IEC 61000-3-2 shall be complied with, to avoid interference with other systems. 8.6

Testing

All electrical wiring and apparatus associated with a swimming pool solar heating system has to be inspected and tested to confirm the correct polarity, the effectiveness of the earthing and the adequacy of the insulation. Residual current circuit breakers should be tested regularly and an advisory notice to this effect prominently displayed.

9

Installation

9.1

General

Designers of solar heating systems for swimming pools should supply sufficient information to the installer to enable satisfactory installation and commissioning. It should not be assumed that the installer has specialist knowledge beyond that of general plumbing and heating practice. A record should be kept by the installer of any necessary design or layout changes agreed with the purchaser.

9.2

Pre-installation checks

The client or his agent should confirm to the installer that clearance of the statutory requirements has been met prior to commencement of installation. The installation contractor should ensure that he has all necessary system design information including: a)

the required location of the solar collectors together with mounting or fixing details as appropriate;

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b)

design details relating to the height of the collectors above pool level and any necessary arrangements for air purging and/or draining of the collectors;

c)

details of the pipework layout, with particular regard to interconnection to any existing system and to the factors considered in 6.2.5;

d)

instructions for setting up any balancing valves so as to ensure an evenly distributed flow of fluid through the collectors;

e)

in an indirect system, the specified type, source of supply and required concentration of heat transfer fluid, together with any special system cleaning, testing or filling procedures;

f)

details of electrical works including control and earthing arrangements for both existing and new equipment.

It should be checked that the proposed collector arrangement and pipework routes are practicable and that all components for the installation are available. It should also be checked that the existing pool filtration and circulation equipment are in good working order.

9.3

Plumbing and pipework considerations

The manufacturer's recommendations regarding the interconnection of collectors should be followed. All pipework and collector interconnections should be designed to accommodate thermal movement having regard especially to the high stagnation temperatures that may be attained in bright sunlight. These temperatures are not expected to exceed the following: selective glazed surfaces black glazed surfaces black surfaces sheltered from wind

200 °C 150 °C 90 °C

The installation of the pipework and fittings should be carried out in accordance with good plumbing practice, particular attention being given to the following. a)

Adequate support and fixing should be provided for the pipework to ensure that all levels and falls are maintained, and the spacing of the fixings are such as to limit sagging of the pipe between the supports. Means should be provided to accommodate thermal expansion and contraction of the pipework.

b)

Individual support should be provided to heavy components such as pumps, and motorized valves. Pipework used to support other components should be adequately secured.

c)

Unions or flanged joints should be provided on each connection to pumps and motorized valves to allow the removal and replacement of the device without the need to cut the pipework.

d)

The fall of the pipes should be arranged to allow the installation to be reliably drained and vented. Low points, when unavoidable, should be fitted with drainvalves and high points should be fitted with air vents.

e)

Where collectors are mounted directly on the ground, e.g. paving with embedded circulating pipes, or are formed beneath the ground surface, e.g. pipes embedded in asphalt, the foundation should provide sufficient support to prevent movement which might damage pipework connections and be capable of supporting the dead weight of the covering and any expected traffic load without damage.

9.4

Connections to existing filtration system

If the solar heating system is to be integrated with the existing pool filtration system, the following recommendations apply.

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a)

To minimize alteration to the existing pipework, the flow and return connections to the

b)

The connection to the solar collector is fitted to the existing pipework after the filter and before the auxiliary heater (if one is fitted).

c)

The isolating valves on the flow and return pipes for the solar system should be fitted close to the connection points into the filtration circuit.

d)

It should be ensured that pumps, motorized valves and non-return valves are mounted in an acceptable plane with the flow in the correct direction.

e)

Where pumps or motorized valves have to be installed in an exposed position, suitable weather protection should be provided unless they are specifically designed for outdoor use.

f)

No thermal insulation should be applied to an installation before an adequate test is carried out to ensure that the system functions correctly without leakage.

9.5

Special considerations

The provisions for fixings and the foundations for any support frame should be inspected and supervised by a competent person. Wherever possible an opaque heat resistant covering material, e.g. a tarpaulin, should be applied temporarily to collectors to avoid the high temperature rise which can occur should the unfilled collector be exposed to direct sunshine during installation. Care should be taken to avoid burns which can occur when the bare arms or other exposed skin come into contact with any metal or other parts of the collector which may become heated by solar radiation during installation. Apart from the burns, the shock may be sufficient to cause distraction and possible loss of foothold on the roof or supporting frame.

9.6

Heat loss mechanisms

9.6.1

Evaporative losses

The rate of evaporation from a pool surface is dependent upon wind velocity, air temperature, relative humidity and pool water temperature. Warm water evaporates more rapidly than cool water. Up to 70 % of a swimming pool's heat energy loss results from evaporation of water from its surface. Evaporative losses are directly proportional to wind velocities at the pool surface and are higher from warm pools than from cooler pools. Because most of the heat loss from a swimming pool is caused by evaporation of water from the surface, every effort should be made to reduce the evaporation process. Air temperature and relative humidity (both of which influence the rate of evaporation) are beyond our control. 9.6.2

Convective losses

Convective losses occur when air cooler than the pool water blows across the pool surface. The layer of air that has been warmed by contact with the water is carried away by the wind and replaced with cooler air — a process that continues as long as the air is in motion. Detailed observations show the heat energy lost from a pool in this fashion is directly proportional to the wind speed at the surface — doubling when the air velocity doubles. Windbreaks such as hedges, trees, solid fences, buildings and mounds should be placed so as to shield the pool from cool winds.

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KS 1895:2008 9.6.3

Radiative losses

PUBLIC REVIEW DRAFT, SEPTEMBER 2008

Swimming pools radiate energy directly to the sky, another important energy loss mechanism. Even with a small difference in temperature between the pool surface and the sky, radiative losses may exceed 10 % of the total swimming pool energy losses. 9.6.4

Conductive losses

Since a swimming pool is in direct contact with the ground or air around it, it can lose heat energy by conduction. The amount of energy transferred even from above ground pool walls to the air is quite small compared to the amount lost from the pool surface to the air. Dry ground and concrete are relatively good insulators, so the energy lost through the sides and bottom of an in-ground pool is also small. In fact, much of the energy conducted into the ground during the day is recovered when the pool temperature drops slightly during the night. In general, conductive losses through the walls of in-ground pools may be ignored. However, pools immersed in groundwater that is influenced by tidal motion will lose an increased amount of energy through their walls. Heat flows from the pool to the ground-water surrounding it. As the groundwater is moved by the tides, it will be replaced periodically by cooler water. The quantity of heat loss in this situation is higher than for pools in dry ground and is not negligible. This loss is still low compared to losses through evaporation, convection and radiation.

9.7

Figure 7 — Swimming pool heat loss mechanisms

Passive pool heating

The use of passive techniques is the simplest and most cost-effective method of keeping swimming pools warm. A passive solar system is one in which the heat flows naturally — without the assistance of pumps and

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fans. Every effort should be made to incorporate the following three features in new pool construction to minimize the expense of supplementary energy for pool heating: 1.

Place the pool in a sunny spot.

2.

Reduce the wind velocity at the pool surface with suitable windbreaks.

3.

Use a pool cover when the pool is not in use to minimize evaporation losses.

Swimming pools themselves are very effective solar energy collectors. The water absorbs more than 75 percent of the solar energy striking the pool surface (Figure 8). If possible, locate the swimming pool so it receives sunshine from about three hours before until three hours after solar noon. During this time period, the sun's rays travel through a relatively short atmospheric path and thus are at their maximum intensity. Additionally, there is less tendency for the sun's rays to be reflected from the pool surface during midday than during early morning and late afternoon, because they strike the pool surface at a small angle of incidence.

9.7.1

Figure 8 — The swimming pool as a solar collector Screen enclosures

Screen enclosures reduce the amount of solar energy that strikes the pool surface. When the sun shines perpendicularly to the screen material, only about 15 % of the energy is obstructed since the screen area is 85 % open air space. However, when the sun strikes the material at an angle, much less of the radiation gets through, and the amount available to warm the pool is reduced by as much 30-40 % on a clear day. More auxiliary energy will be required to maintain comfortable swimming temperatures if the pool has a screen enclosure. 9.7.2

Windspeed reduction

Reducing wind velocity at the water surface reduces convective and evaporative losses. Solid fences or tall hedges located close to the pool perimeter are effective windbreaks. Buildings, trees and mounds also protect the pool from the cooling effect of prevailing winter winds. Locate the pool to take maximum advantage of these obstructions, being careful they do not shade the water surface from the sun. Windbreaks are particularly desirable near the ocean or adjacent to lakes, where the average wind speed is higher than in more sheltered locations. Figure 9 shows an example of a well-shielded pool.

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9.7.3

Figure 9 — A well-protected pool Pool covers

Pool covers are effective in reducing heat losses. There are two basic types of pool covers on the market today: opaque and transparent. By reducing evaporation they reduce the quantity of chemicals needed, and they help to keep dirt and leaves out of the pool. Pool covers also reduce pool maintenance costs. 9.7.3.1 Transparent pool covers Transparent covers will not only reduce evaporative losses but they will also turn the pool into a passive solar collector. Sunlight passes through the cover material and is absorbed by the pool water. Because evaporation accounts for about 70 % of pool heat loss, the beneficial effect of pool covers can be dramatic. Transparent pool covers are made from a variety of materials, such as polyethylene-vinyl copolymers, polyethylene and polyvinylchloride (PVC). Attention to a few details will extend the life of transparent pool covers. They should not be left folded or rolled up on a hot deck or patio. The sunlight will overheat the inner layers and may even burst the air pockets in bubbled covers. When removing or installing a pool cover, avoid dragging it over the pool deck or any rough surface or sharp obstruction. Although it is recommended that a single, continuous pool cover be used whenever possible, the use of sectioned covers can ease handling in the case of larger pools. 9.7.3.2 Liquid films Materials like cetyl alcohol spread to form a layer only a few molecules thick on a water surface. They can reduce evaporation by nearly 60 percent. Of course the materials offered for this purpose are not toxic but they are fairly expensive and must be re-dosed frequently (usually at the close of the daily swimming period). The chemical films do not reduce convective or radiation losses, but they do allow solar gains. 9.7.3.3 Opaque covers Opaque covers are useful for pools that must remain uncovered during daylight hours. Most commercial pools fall into this category. The following types of opaque covers are the most common: woven, plastic safety covers; skinned, flexible foam covers; and rigid or semi-rigid closed cell foam blocks or blankets. The woven safety covers will reduce evaporation losses (if they float and are waterproof) though not as well as a continuous film type cover. Skinned foam covers vary in thickness from less than 1/8 inch to more than ½ inch. In common insulating terms, their effectiveness in reducing heat losses ranges from R-1 to R-4. If they fit snugly to the edges of the pool, they will virtually eliminate evaporation losses during the periods when they are in place. Foam block covers such as expanded polystyrene have insulating values between R-4 and R-12, depending on their thickness. If properly fitted and placed on the pool surface, they, too, will nearly

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eliminate evaporation losses during the hours they are used. Their effectiveness in reducing convective and radiative losses increases directly with their R-value.

9.8

Active pool heating

Many types of solar collectors are suitable for pool heating. The temperature difference between the water to be heated and the surrounding air is small, so expensive insulating boxes and transparent covers that reduce collector heat loss are not often required. Cool winds above 10 km/h substantially reduce the efficiency of unglazed collectors. 9.8.1

Low-temperature collectors

Types of low-temperature collectors include black flat-plates, black flexible mats (both with passages for pool water) and black pipes. 9.8.2

Flat-plate collectors

Several types of flat-plate collectors, specifically designed for pool heating, are available in both plastic and metal. Flat-plate collectors for pools feature large-diameter headers at each end and numerous small fluid passageways through the plate portion. The header's primary function is to distribute the flow of pool water evenly to the small passageways in the plate. The header is large enough to serve as the distribution piping, which reduces material and installation labor costs. The fluid passageways, which collect energy from the entire expanse of the surface, are small and are spaced close together across the plate (if it is made of plastic) so most of the collector surface is wetted on its back side. Representative cross sections of plastic collectors are shown in Figure 10. EPDM flexible mat collectors have the same general cross section, as do plastic collectors.

Figure 10 — Typical collector designs

High water flow rates also tend to keep collector-to-air-temperature differences low. The total amount of energy delivered to the pool (the most important variable) is the product of the amount of water flowing through the collector multiplied by the water's temperature rise. Five hundred gallons of water raised 1°F contains as much energy as 10 gallons of water raised 50°F, but the collector operating at 10°F above pool temperature will operate less efficiently. Thus, high flow rates increase collector efficiency. Many manufacturers frequently recommend a flow rate as high as one gallon per minute for each 10 square feet of collector area. But such high flow rates are not needed to keep the temperature rise in the collectors below 10°F for best efficiency. Higher flow rates result in high-pressure drops across the collector array. This requires an increase in the horsepower of the circulating pump. Thus, flow rates are usually limited to about one gallon per minute for each 10 square feet of collector area for the configurations shown in Figure 10. Because even plastic pool heating collectors are expensive, the plastic used must withstand years of exposure to sunlight. The ultraviolet portion of sunlight can break chemical bonds in most plastics and will

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eventually destroy the material if the process is not retarded. Collector manufacturers use several proprietary combinations of additives or stabilizers and UV inhibitors in the chemical mix of the collector material. These stabilizers and UV inhibitors provide protection from the damaging radiation and retard degradation of the plastic in addition to improving the collector's ability to absorb and conduct the sun's energy. Accurate estimation of plastic durability is difficult; therefore, explicit warranties are desirable. Most manufacturers currently offer a five-year or longer limited warranty. Some plastic collectors are expected to last 25 years. Plastics are available in numerous formulations and types, many of which are relatively immune to attack from common chemicals. Polypropylene, acrylonitrile-butadiene-styrene (ABS), polyethylene, polybutylene, polyvinylchloride (PVC) and ethylene-propylene with diene monomer (EPDM) are frequently used collector materials. Some have been used to make pool collectors for more than 20 years and have demonstrated their ability to withstand attack by swimming pool chemicals and sunlight for at least that period of time.

Flat-plate collector designs utilizing metals are slightly different from plastic configurations. Metal is a better heat conductor, so relatively long fins can separate the tubes without causing excessive operating temperatures on portions of the collector surface.

9.9

Plumbing schematics

9.9.1

Flow control devices

Solar pool heaters are generally connected to existing pool plumbing systems. This section explains how to make the connections. A schematic of a frequently used pool filtration loop is shown in Figure 11a. The pump draws the water from the skimmer and main drain, forces it through the filter and returns it to the pool through the conventional heater. Lint, hair and leaf catching strainers are usually installed ahead of the pump. Solar systems designed to operate with small pressure losses can be added as shown in Figure 11c. A spring-loaded check valve is installed downstream from the filter to prevent collector water from backwashing through the filter and flushing trash into the pool from the strainer when the pump is shut down. A manually operated or automatic valve is placed in the main line between Ts that feed the collector bank and return the solar heated water (Figures 11b and 11c). Ball valves may be placed in the feed and return lines for isolating the solar system from the pool filtration system when the filter is being backwashed or when adjustments are being made to the solar system. When solar heating is desired, the pump timer is adjusted to operate during daylight hours, and the valve in the main line is closed somewhat to restrict or fully interrupt the flow and force water up through the collectors. Valves on the lines to and from the solar system should be fully open.

Closing the valve in the main line may increase flow through the collectors. It may seem logical to reduce the flow rate through the solar array to make the return water warmer, and this can be done; however, it is not logical — the collectors will be forced to operate at higher temperatures, their efficiencies will drop, and less solar energy will be delivered to the pool. The temperature rise through the collectors should be kept low, less than 10°F on warm, sunny days, unless the manufacturer's specifications call for a higher temperature differential. Forcing water through the solar system uses some of the pump's power, thus reducing the flow rate through the pool filtration system. As the main line valve is closed, pressure on a gauge mounted on the filter or discharge side of the pump will rise slightly. If the valve is closed entirely, all of the flow is diverted through the solar array and the collection efficiency increases. If the pressure at the filter does not rise unduly, the solar system should be operated in this way. However, the more the pressure rises, the slower the flow through the filtration system. This will increase the length of time required for the entire pool's contents to be filtered. Thus, it may be necessary to allow some of the flow to bypass the collectors. An inexpensive plastic flow meter can be used on the main line connection to monitor flow rates through the filtration system. Check with local building officials to determine minimum filtration flow rates or pool turnover times required in your area.

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When the existing pool pump lacks enough power to circulate sufficient flow through the solar system and the filtration system, a booster pump may be required. It should be installed as shown in Figure 11d. Common pool-circulating pumps with or without the strainer basket are suitable for this application. The booster pump should be placed in the line feeding the solar collectors, not in the main circulation line. In this position it will operate (consuming electricity) only when circulation through the solar collectors is wanted. Of course, the booster pump may be operated by the same time clock as that for the filter pump, but more often it will have a separate control. If both pumps operate from the same timer, it should be set so the pumps come on during daylight hours. In this case, the timer must be rated for the sum of the circulation pump and the solar booster pump. If the booster pump is separately controlled, the filter pump may run for a longer portion of the day, and the booster pump should turn on during appropriate periods but only when the filter pump is operating. Manual flow control or control with time clocks is simple and inexpensive but has drawbacks. Since clocks do not sense weather conditions, the circulating pump may be running when there is insufficient solar energy available to warm the pool water. Collectors may lose energy rather than gain it if weather conditions are unfavorable. Automatic flow controls overcome this difficulty. The most common plumbing schematic for systems using these devices is shown in Figure 12.

Figure 11 — Plumbing schematics © KEBS 2008 — All rights reserved

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Figure 12 — Automatic control plumbing schematic

Accurate differential temperature control is difficult to achieve because of the small temperature rise that takes place in solar pool heaters. A sensor, tapped into the piping at a convenient place ahead of the collector return line, measures the pool water temperature. Another sensor is housed in a plastic block and placed near the solar collectors, so its temperature parallels that of the collector (or it may be attached to the collector outlet). When the pool water temperature exceeds the collector temperature, the control valve remains in the open position and the flow bypasses the collector loop. When the collector temperature exceeds the pool water temperature, the valve is closed, forcing the flow through the collectors. In practice it has proven equally effective to control the flow through the collectors with a single solar sensor, which turns on the solar pump and/or activates the diverting valve above a fixed solar intensity level. When operating properly, a differential controller automatically adjusts to changing conditions, monitoring variations in collector temperature caused by clouds, other weather factors and the approach of evening. When collector temperature drops, the control de-energizes the valve and flow bypasses the collector. Maximum pool temperature limits can be programmed into some controls. Control valves may be actuated hydraulically or electrically. One of the earliest valves used was a hydraulically operated pinch valve consisting of a cylinder with an expandable bladder inside. A high-pressure line connected to the discharge side of the pump is used to expand the bladder, pinching off the flow and diverting it through the solar system. A low-pressure line connected to the suction side of the pump deflates the bladder and allows the flow to pass unimpeded. An automatic controller accomplishes switching between the high- and low-pressure lines. Electrically operated valves are also used. A differential controller may be used to operate a solenoid that, in turn, activates the main valve in much the same way the pinch valve is activated. Be sure the valve you select is specifically designed and constructed for use on pool systems. Automatic control schematics, taken from the installation diagrams of two low-temperature collector manufacturers are shown in Figures 15 and 16. The most common method to divert the flow of water to the solar collectors from the pool is to use a 3-way valve on the solar supply line. Similar to the in-line ball valve or isolation valve, the three-way diverter valve is commonly used in the swimming pool and spa industries.

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Some of the 3-way manual valves are made to be used for solar pool heating. The 3-way valve has a motorized diverter that attaches to the top of the valve to convert the manual valve into an automatic or motorized valve. Other 3-way diverter valves are manufactured with the motor assembly on the valve. In this case, a differential controller sends low voltage power to the diverter actuator (or motor) and rotates the valve sending the water from the filter to the solar collectors. A check valve after the 3-way valve allows the solar collectors to drain into the pool when the pump is not operating. This may provide freeze protection if the system tilt and piping was installed to allow continuous drainage.

© KEBS 2008 — All rights reserved

Figure 13 — Plumbing schematic

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9.9.2

Figure 14 — Plumbing schematic Corrosion problems

Improper pool chemistry can cause accelerated corrosion. The pool water pH should normally be maintained between 7.4 and 7.8. Under acid conditions (low pH), chloride and sulfate ions in the pool combine with water to form acids capable of breaking down protective films. Low pH also accelerates the corrosion of most metals. Excessive concentrations of copper ions in pool water may lead to the formation of colored precipitates on the pool wall if the pH is allowed to drop. Since many common algaecides are based on copper compounds, the concentration of free copper ions in pool water may relate to the use of these chemicals as well as the corrosion of copper piping materials. Care should be exercised in maintaining proper pH levels whether copper or plastic piping is used in a solar pool heater. 9.9.3

Sizing filter pumps and pipe runs

For simple installations, sizing the filters, pumps and pipe runs to circulate and keep the necessary pool water clean and heated may be successfully accomplished by following the instructions contained in the following sections. 9.9.4

Sizing filtration and circulation systems

Proper sizing of swimming pool filters, circulation pumps and pipe runs may be accomplished by using the information provided in this section in conjunction with data routinely provided by manufacturers of those components.

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9.9.4.1 Filter sizing graphs Filter sizing is accomplished by using graphs, such as Figure 15, provided by filter manufacturers. The following types of filters are those most often used to keep swimming pools clean.

Sand, gravel or anthracite filters are sometimes operated at a flow rate as high as 20 gallons per minute (gpm)/ft2. It should be noted that some code jurisdictions limit the flow rate through these filters to three gpm/ft2. Diatomaceous earth (DE) filters usually operate well at about two gpm/ft2. Both sand and DE filters may be cleaned by backwashing and discharging the dirty water into a sewer or other appropriate outlet. An air gap in the discharge line is often required to ensure against backflow contamination from the sewer. Cartridge filters are usually operated at a flow rate of about one gpm/ft2 and may be reverse flushed and reused. When the cartridges become excessively dirty they are simply replaced.

Figure 15 — Diatomaceous earth filter sizing graph for flow rate of 2 gpm/ft2

In pool filtration systems, the need for cleaning is indicated by high readings on a pressure gauge, which is located between the filter and the pump. Filter manufacturers specify the readings at which they recommend maintenance. The pressure drop due to properly sized clean filters is usually about five psi. The backwashing valve assembly on DE and sand filters may add another five psi. 9.9.4.2 Pump sizing graphs To size the pumps it is necessary to establish a flow rate in gpm and then add up all the pressure drops that occur when water flows through the system at that rate. Figure 16 is a graph on which pressure drop and flow rate are plotted for typical swimming pool circulation pumps.

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Figure 16 — Pump performance

Figure 17 — Relative pressure

9.9.4.3 Sizing connecting piping Connecting piping may be sized using pipe flow charts (Figures 18 and 19). Piping should be large enough to prevent excessively high flow rates that cause erosion of interior pipe and fitting surfaces. Some code jurisdictions limit the rate of water flow through copper pipes to five feet per second. Adequately sized piping and pumps help reduce maintenance and operating costs.

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Figure 18 — Pressure drop plastic pipe Water Flow Rate, Gallons Per Minute NOTE Fluid velocities in excess of 5 to 8 ft/sec. are not usually recommended

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Figure 19 — Pressure loss and velocity relationships for water flowing in copper pipe

Examples The following examples are intended to help clarify sizing procedures. The owner of a 20-by-40-foot swimming pool with an average depth of 4.5 feet wants to circulate the total pool volume through the filtration system in eight hours. (The turnover rate is currently one complete recirculation per eight hours.) The owner plans to use a DE filter and wants to know what size filter and pumps will be required (1) with no heater, (2) with a gas heater, (3) with a solar heater and a gas heater for back-up and (4) with a solar heater without a back-up. The pump will be located so the center of its impeller is three feet above the surface of the pool. One hundred feet of pipe will be required unless solar collectors are used. In that case, 200 feet of connecting pipe will be required. The high point of the solar collector array will be 12 feet above the center of the pump impeller. The solar collectors will be connected to the circulation

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piping as shown in Figure 12b. The owner also wants to know what size connecting pipe should be installed under any of the four alternative conditions. STEP 1: Determine the pool volume. Pool volume (gal) = 20' × 40' × 4.5' × 7.48 gal/ft2 = 26,900 gal.

STEP 2: Determine the DE filter cross sectional area if 2 gpm/ft2 of filter area is an acceptable flow rate through it, and the pool volume of 26,900 gallons must turn over every eight hours. Figure 15 shows a cross sectional area between 27/ft2 and 33/ft2 will be required. The filter that provides 33/ft2 of cross sectional area will be the better choice because it will allow a turnover time of slightly less than eight hours.

STEP 3: Determine the flow rate through the filtration system. Because the entire volume must turn over once each eight hours, 26900 Flow rate = = 3360 gallons per hour (gph) 8 3360 Flow rate = = 56 gpm 60

STEP 4: If no heater is included in the system, determine the total pressure, which the pump will be required to overcome at a flow rate of 56 gpm. Cause of pressure drop

Source of information 2

100 ft 1-½" plastic pipe Fitting Valves Filter Lift head Total

schedule

40 Figure 12

Lbs/In (Psi) 8

About ½ of pipe drop Manufacturer's specs. Manufacturer's specs.

4 5 5

Pressure drop Ft of water (Psi × 231) 18.5 9.2 11.6 11.6 3 54

Figure 16 shows a one-hp pump (of the specific design covered by that graph) will circulate 56 gpm against a 57-foot head. A ¾-hp pump will circulate only 45 gpm against a 51-foot head, so the one-hp pump will be the safest choice. Discussion — It is interesting to note if 2-inch schedule 40 pipe is used, the pressure drop in the pipe is only three psi or seven feet of water, so the total pressure drop is about 37 feet of water. Figure 16 shows a ¾-hp pump is powerful enough to circulate 52 gpm against a total head of 37 feet of water. (Turnover time increases to 8.6 hours.) Figure 11 illustrates the relative magnitude of the pressure drops.

STEP 5: Determine the size pump that will be required if a gas-fired pool heater is added which causes an additional pressure drop of five psi. Cause of pressure drop 100 ft -1 ½" schedule 40 plastic pipe Fittings Valves Filter Pool heater Lift head Total

© KEBS 2008 — All rights reserved

Psi 8 4 5 5 5

Pressure drop Ft of water 18.5 9.2 11.6 11.6 11.6 3 65

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KS 1895:2008 Figure 16 shows a one-hp pump will pump about 50 gpm against 65 feet of water. This is probably close enough to the required volume for practical purposes. (The turnover time is a littler longer — nine hours.) Discussion: Under these conditions, using two-inch pipe reduces the total pressure drop to about 50 feet of water but this does not allow us to use a 3/4-hp pump because the smaller pump will only circulate 46 gpm against a 50-foot head. (In this case, the turnover time would be increased to 10 hours should the 3/4-hp pump be used.)

STEP 6: Determine the size pump that will be required if we add a solar collector system and a gas-fired back-up heater. A pressure drop of two psi is expected across the solar collectors. The system contains an extra 100 feet of pipe and a vacuum breaker located 12 feet above the center of the pump's impeller.

40

Using 11/2" and 2" pipe Cause of pressure drop 100 ft of 1 1/2" pipe Fittings for 1 1/2" pipe 100 ft of 2" pipe Fittings for 2" pipe Valves Filter Solar panels Gas heater Static head (3' + 12") Total

Pressure drop Psi 8 4 3 1+ 5 5 2 5

Ft of water 18.5 9.2 6.9 2.3+ 11.6 11.6 4.6 11.6 15 92

Using Only 2" Pipe Cause of pressure drop 200 ft of 2" pipe Fittings for 2" pipe Valves Filter Solar panels Gas heater Static head (3' + 12") Total

Pressure drop Psi 6 3 5 5 2 5

Ft of water 13.9 6.9 11.6 11.6 4.6 11.6 15 75

Figure 17 shows if 100 feet of 1-1/2-inch pipe and 100 feet of two-inch pipe are used to make the connections, a two-hp pump will move only 35 gpm against the 92-foot water head. This increases the turnover time to about 13 hours, so a 2 1/2-hp pump will be required. If 200 feet of two-inch pipe is used, a 11/2-hp pump will move 52 gpm against the 75-foot head. Again, in this example, 52 gpm will probably turn the pool volume over in an acceptable period of time (8.6 hr). Discussion: Another option applicable to retrofitting a gas-heated pool piped initially with 1-1/2-inch pipe and a one-hp pump is the addition of a second small pump installed as pictured in Figure 5d. The additional pump will be required to overcome a static head of 12 feet of water and a friction head of 28 feet of water if 11/2-inch pipe is used to connect the solar panels to the system. The pressure loss across the panels will still be 4.6 feet of water. The total pressure drop, which the added pump will be required to overcome, will be 12 + 28 + 4.6 or about 45 feet of water head. Figure 10 shows a 3/4-hp pump will circulate 49 gpm against a 45-foot head. It should be noted the two pumps working in series will assist each other and in most cases the turnover times will be no more than eight hours.

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Two pumps require more maintenance than does one, but the solar booster pump may be turned off when circulation through the panels is not desired. This reduces electrical consumption. A final option for pool heating is the addition of solar collectors without a fossil-fired back-up system. Referring to the immediately preceding piping options, the elimination of the gas-fired heater reduces the pressure drop from 92 to 80 feet of water if an additional 100 feet of 1-inch pipe and 100 feet of 2-inch pipe are used to make the connections. Figure 16 shows a 2-hp pump will pump 54 gpm against an 80-foot head. (The turnover time is 8.3 hours.) If 2-inch connecting pipe is used throughout, the total pressure drop is reduced to about 63 feet and a 1 hp pump will deliver 50 gpm against a 63-foot head (the turnover time is nine hours). A 1.5 hp pump will circulate about 65 gpm against a 63-foot head (the turnover time is 7 1/2 hours). Table 7.1 presents each of the pool heating options and the corresponding pipe and pump sizes which yield the various pool turnover time periods. Table 7.1 — Pool heating options Components

Pipe size

System with no heater

100 ft of 1 1/2" schedule 40 plastic 100 ft of 2" schedule 40 plastic System with gas or oil heater 100 ft of 1 1/2" (5 psi pressure drop) 100 ft of 2" System with gas and solar (15 100 ft of 1 1/2" plus 100 ft of 2" ft static head) 200 ft 1 1/2" 200 ft 2" System with solar only (15 ft 100 ft 1 1/2" plus 100 ft 2" static head) 200 ft 2"

Pump size required 1 hp 3/4 hp 1 hp 1 hp 2 1/2 hp 2 pumps (1 hp+3/4 hp) 1 hp 2hp

Turnover time (in hours) 8 8.6 9 7.2 8 8

1 hp 1 hp

9 7.5

8.6 8.3

None of the stated options alter the turnover rate of the pool sufficiently to require resizing the DE filter. It should contain between 27/ftp2p and 33/ftp2p of filtration area.

9.9.5

Pressure drop across the valves and fittings

Many swimming pool installers use the simple rules of thumb cited in the previous examples to determine pressure drops caused by the resistance to liquid flow of valves and filters. However, it is important for the solar installer to realize the actual pressure drops vary with both flow rate and mechanical characteristics of specific valves and fittings. Table 7.2 presents frictional losses expressed in equivalent lengths of pipe for commonly used fittings. (Most fitting manufacturers supply similar tables.) The sum of the equivalent length of all the fittings on the circulation system may be added to the actual length of pipe in the system before the pressure drop is read from Figure 18 (plastic pipe) or Figure 19 (copper pipe). The pressure drop across the backwash valve assembly is accepted as being five psi in the example. Actually, this pressure also varies with flow rate and the mechanical design of specific valves. The variation from valve to valve is too great to make a generalized tabular presentation of pressure drop much more useful than the five psi rule of thumb value. Most filter and backwash valve suppliers can make available accurate tables or graphs for their valves. The information is usually given in psi, which may be converted to feet of water head by multiplying by 2.31.

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Table 7.2 — Fittings — Friction losses expressed as equivalent lengths of pipe (feet) Type of fitting

Material (in ") tee Steel

1

11/4

11/2

2

21/2

3

31/2

4

5

6

8

10

12

Standard with flow through Plastic branch Copper

6

8

9

11

14

16

.

20

26

31

40

51

61

9

12

13

17

20

23

29

.

45

.

.

.

6

8

9

11

14

16

18

20

26

31

40

_

_

90 degree long Steel radius elbow, or Plastic run of standard tee Copper

1.7 3

2.3 4

2.8 5

3.6 7

4.2 8

5.2 10

. .

6.8 12

8.5 .

10 17

14 .

17 .

20 .

1.7

2.3

2.8

3.6

4.2

5.2

6.1

6.8

8.5

10

14

.

.

Adapter slip/ Plastic solder fitting to Copper thread insert coupling Plastic

3 1

3 1

3 1

3 1

3 1

3 1

. 1

3 1

. 1

3 1

. 1

_ .

_ .

3

3

3

3

3

3

.

3

.

3

.

_

.

Gate valve (fully open) Swing check valve Ordinary _ entrance

.60

.80

.95

1.15

1.4

1.6

1.9

2.1

2.7

3.2

4.3

5.3

6.4

7

9

11

13

16

20

23

26

33

39

52

67

77

1.5

2.0

2.4

3.0

3.7

4.5

5.2

6.0

7.3

9.0

12

15

17

9.9.6

Energy conservation

The solar heater for a swimming pool should be sized to provide enough heat to satisfy the purchaser. Virtually all installers and purchasers can agree to that. However, the solar installer's responsibilities do not stop there. The system he or she installs should not increase the electrical consumption of the pool's circulation system any more than absolutely necessary. This requires large enough pipe diameters to keep their friction losses low, proper flow through the solar collectors to maximize heat collection yet minimize pressure drop, and adequate collector sizing to minimize the number of hours the pump must operate each day. Obviously, it is pointless to oversize the solar-related components to an extent that reduces the time required for heat collection below that required for acceptable filtration. 9.9.7

Collector installation

Acceptable solar collector mounting practices are discussed in this section. Because unglazed, lowtemperature collectors are most often used for swimming pool heating in Florida, procedures for mounting unglazed plastic flat-plate collectors, flexible solar mats and pipe arrays will be discussed first. The optimum collector slope for spring and fall operation is equal to the latitude of the site. The best slope for winter is the latitude plus 15° and the collectors should face south if possible. If roof space, which faces within 45° of south, is available, the collectors can be mounted directly on the roof. Remember that only a small penalty is paid for modest deviations from optimum slope or orientation. Supports can be constructed to mount collectors at the ideal orientation, but except in new construction, the additional cost is generally prohibitive. Occasionally it may be necessary to increase the collector area to compensate for less than optimum slopes or orientations. Collectors should be securely fastened to withstand maximum expected wind loads typically from 160 to 240 km/h. Check the local building regulations for wind load provisions in your area. Procedures — To begin the installation, lay out the collectors on the available roof area avoiding as much as possible any area shaded by trees, parts of the building or other obstructions. If large numbers of collectors

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are involved, they may have to be divided into several banks with collectors in each bank plumbed in parallel. Plumbing arrangements from bank to bank are discussed in the next section. Once the placement is established, the collectors should be connected. Short, flexible couplings made of EPDM or butyl rubbers often are used. They usually are slipped over the ends of the headers and are clamped firmly with stainless steel clamps. Once fastened together, the collectors are cumbersome to move about. Be sure they're in their final positions before the connections are made. Collectors often are mounted directly on the roofs. An insulating support structure is sometimes used to protect the panels from abrasive roofing materials and prolong their life by protecting the bottom of the collector from the abrasion caused by expansion and contraction of low temperature collectors. Refer to the manufacturer recommended installation procedure. Collectors should be laid on the roof and fastened down at the header on both ends. At least two, and preferably three, cross straps should span the panel to further secure it. Figure 21 shows one possible arrangement. Once again, refer to the manufacturer's recommended installation procedures. One end of the panel can be fastened to the roof with a short strap or clamp around the header. The other end should be fastened with an elastic material or spring to allow for expansion as the collector temperatures change — a 10-foot plastic collector may expand and contract as much as an inch in length. Straps should be installed across the panel body — one at either end — within a foot of the headers, and one across the middle are recommended. The straps should be made of material, such as nylon or plastic-coated metal, that will not scratch or abrade the collector since they will rub across its surface. The bands should be snugged to clips fastened approximately an inch from the edge of the collector.

Figure 21 — Collector hold-down straps

Figure 22 shows a typical mounting clip, which may be made of rigid plastic or metal. On asphalt shingle roofs, the clips may be fastened directly on top of the shingles — 1/4-inch lag bolts long enough to penetrate the roof sheathing are generally recommended. In keeping with good construction practice, the lag screws should be screwed into as many roof rafters as possible (rather than just roof sheathing) to keep the collectors secure. A pilot hole should be drilled for the lag screw and after the drill chips are cleared away a sealant should be injected with a cartridge gun into the hole. An excess of sealant should be used to form a seal between the mounting clip and the roofing material when the lag bolt is tightened. Polysulfide and the newer polyurethane sealants adhere well to common building materials and appear to be very durable.

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Figure 22 — Typical collector mounting clip

Sealing mounting brackets on tar and gravel (built-up roofing) requires careful cleaning around the bracket. Scrape off the old gravel down to the tar, and clear off all dirt and residue. If the tar surface is very dirty or irregular, soften it with a solvent such as mineral spirits. After sealing the clip with polysulfide, pour roofing tar over the bracket base and cover with gravel. This last step is necessary to prevent ultraviolet damage to the tar and premature roof failure. Mounting collectors on other roof types is more difficult. On cedar shake roofs, mounting screws should pass through the shakes and fasten securely to the plywood or purlins beneath. Don't be stingy — use good quality sealant and enough of it to form a good, sealed penetration. Don't tighten the fasteners tight enough to split the shake. Concrete tile roofs, especially common in south Florida, present special mounting difficulties. The safest solution is to construct a rack to support the collectors above the tile surface. The rack should be constructed of a durable material, such as aluminum. It should be strong enough to withstand maximum anticipated wind loads. Substrate and collectors may be fastened to the rack. The rack itself must be securely fastened to the roof trusses, not to the sheathing. This practice should also be used when installing a reverse pitch rack on the backside of a roof. Figure 23 illustrates a typical mounting bracket arrangement. To install the bracket, a tile must be removed or broken, exposing the waterproof membrane on the sheathing below. This waterproof surface (commonly called slate), not the tiles, forms the moisture barrier and must be resealed where mounting bolts penetrate it.

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Figure 23 — Mounting bracket for tile roofs

The mounting location should be free of dust and debris. Roofing mastic should be applied to the bracket and slate to form a seal when the bracket is drawn down. (Pitch pans around the roof penetrations may be required in some areas.) A substitute for the broken tile may be made from cement mix (using adjacent tiles as a model) and tinted to match the roof. Aluminum and copper materials should be protected from contact with the cement by a layer of tar to reduce corrosion. Fastening schemes have been proposed which rely upon sealing the roof penetration at the tile surface. Since the waterproof membrane is not the tile itself but rather the slate membrane beneath, these methods are not effective and should be avoided. Spanish or barrel tile roofs present another tough collector mounting problem. It is extremely difficult to walk on them without breaking some tiles, and it is also difficult to make substitute tiles.

9.10

Piping

Solar swimming pool collectors are designed to operate with high flow rates; therefore, the primary objective in piping solar systems is to provide uniform, high-volume flow at the lowest cost and the lowest pump power possible. 9.10.1 Piping to collectors For low-temperature collectors, plastic pipe can be used in the plumbing from the pool pump to the solar collectors. PVC and ABS pipe are the most commonly used materials for this particular application and have performed satisfactorily. Neither material can withstand high temperatures. Due to the moderate operating temperatures, pipe insulation is not required. Local plumbing requirements should be adhered to when installing piping leading to and from the collectors. Since large-diameter pipe is quite heavy when filled with water, sturdy supports will be required. Pipe cuts should be deburred before assembly to reduce resistance to flow. Leaks can be avoided by using the correct cement for the pipe involved and properly preparing joints. Because plastic expands and contracts considerably with temperature changes, allowances should be made for change in length. Your pipe supplier can provide you with specific data on the kind of pipe used for a particular job. 9.10.2 Piping between collectors About the same amount of water should pass through each collector. On large installations it is necessary to divide the solar collecting panels into groups and connect the groups with pipe. This requires the piping layout be carefully designed and constructed. Most situations encountered can be satisfied using principles

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discussed in this section, but for extremely complicated cases it may be wise to consult a hydraulic flow specialist. Pool heating collectors are almost always connected in parallel. Parallel connections are shown in Figure 24a, series connections in Figure 24b. In the series arrangement, water passes through one collector and then through the next, increasing the pumping horsepower required to maintain adequate flow, as well as causing the downstream collectors to operate at higher, less efficient temperatures. Parallel connections, in which the water is returned directly back to the pool after passing through one collector, are the better choice because those difficulties are avoided.

Figure 24 — Collector connections

The feed and return lines leading to each collector should be approximately the same length. Figure 25a illustrates the preferred arrangement, and Figure 25b shows a common, but less efficient, connection where the flow tends to be short-circuited through the first few collectors and those at the end are starved for flow (causing a reduction of their performance). In Figure 25a, the length of the water path is the same for all collectors, so the flow is evenly distributed. This style of piping will require extra pipe, but improved collector performance compensates for the additional cost.

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Figure 25 — Flow balancing in collector groups

Groups of collectors at different heights should be plumbed in such a way they all receive water from the lowest point in the system and return it from the highest point. Figure 26 illustrates a properly plumbed system. The dashed line indicates a tempting, but unsatisfactory, arrangement. If the return lines do not come from a common height, flow through the panels will be uneven, causing a reduction in performance. Even with this piping layout, a balancing valve may be required to reduce the flow rate in the lower collector(s).

Figure 26 — Plumbing collectors at different heights

Balancing valves can be used to obtain uniform flow distribution in other difficult situations, which occur when site requirements make it impractical to balance the flow with simple plumbing arrangements. Balancing valves and, if economics permit, flow meters should be installed in the feed line to each group of collectors. Starting with all valves completely open, gradually close the appropriate valve until the desired flow for each group is obtained. An alternative to the use of flow meters is to measure the outlet temperature of the various collector groups and adjust the balancing valves until these temperatures are within a few degrees of each other.

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Connections between collectors and plumbing pipe are commonly made with synthetic rubber couplings, which slide over the header and connecting pipe and are clamped tightly around each by stainless steel bands. To accommodate thermal expansion and misalignment, these couplings are longer than those used between panels. A vacuum relief valve may be required on the highest collector group to admit air into the system when the pump shuts down and allow the collectors to drain. If necessary, because of height differences, vacuum relief valves can be installed in more than one group of collectors to facilitate drainage. The vacuum relief valve must not admit air into the system during pump operation. If it does, the system may be noisy and will consume excessive amounts of chemicals due to constant bubbling. This means such a valve must be installed at a point where the system pressure is above atmospheric pressure. This requires some experimentation on systems installed on roofs of multistory buildings. In such cases, the water flowing down the return pipe may cause a vacuum in that pipe. Installing the vacuum relief valve on the return end of the highest supply header will keep the valve pressurized until there is a vacuum caused by draining the supply header. The tilt of the array must allow complete drainage. Unfortunately, some pipe layouts will not allow gravity drainage of the collectors. For example, in piping over the ridge of a roof, the supply and return are higher then the level of the collectors. This prevents proper drainage of the collectors. Installing a freeze protection valve on the bottom header of the collector array may allow gravity to drain the panels during freezing conditions.

9.11

Flow control and safety devices

One of the most important components in the flow control system is the control (diverter) valve normally installed in the main filter flow path after the collector feed-line and before the collector return (Figure 11b and 11c). Although this valve can be as simple as a manually operated ball valve, for convenience, it is generally operated automatically. Several types of control valves are available. These include automatic and manual valves. The automatic valves include: ⎯

3-way diverter or ball valves

⎯

bladder-type pinch valves

⎯

or specially constructed variations of irrigation valves

8.11.1 Automatic valves Typically, the valves are operated by an electronic differential controller, which measures collector temperature and compares it to pool temperature. The high temperature (collector) sensor is mounted in a dull plastic housing that has an absorptivity for solar energy approximating that of the solar panel or in-line on the return outlet or pipe near the collector. Since the sensor temperature should simulate the collector temperature, it should be mounted alongside a collector panel and fastened to the same surface to which the panels are fastened. All wire connections should be made secure and watertight, preferably with silicone wire connector nuts, heat-shrinkable insulating tubing or as a last resort, durable sealant. The lower sensor, which measures pool temperature, should be protected from direct contact with the pool water to prevent galvanic corrosion. Most sensors are a encapsulated with epoxy into a pipe thread brass fitting of 1A" or Vz" MIP, installed in a "well" in the pipe between the pool and the circulation pump, or immersed into the water flow. Many times the sensor can be inserted into the drain port of the pump suction basket. It is important to ensure the "cold" sensor registers the temperature of the pool water not the ambient air or warmth from sunshine on the sensor capsule. The electronic controller itself requires electrical power. Sometimes it can be connected in parallel with the pool pump or timer, but since 120V or 240V electricity is involved installers should consult their local building 48

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officials to find out if an electrician is required to make the connection. Approved conduit should be used for this wire. In the installation of the automatic 3-way actuator and controller, the low voltage output from the controller powers the motor and turns the valve. It is important to ensure proper alignment of the motor, directional flow and direction of diverted flow. Be careful not to actuate the valve and stop flow from the filter. Pressures in excess of the filter's maximum operating pressure could damage the filter. Normal operation is flow to the pool from the filter. When the signal from the high temperature sensor indicates heat collection is available at the collectors, the controller activates the valve and diverts the flow from the pool to the collectors. In the installation of a pinch valve control system, it is necessary to connect two pressure lines between the pool pump and the control box. Small-diameter (1/8-inch) plastic lines are generally used. Since most pool pumps have a 1/4-inch, threaded pipe plug in the side of the strainer housing (near the bottom), the lowpressure line is usually attached to an adapter at that point. The high-pressure line should be tapped into the pipe on the discharge side of the pump. When the high temperature sensor registers the collectors are warmer than the pool water, the electronic control opens the line from the discharge side of the pump and inflates the bladder in the pinch valve. This diverts flow through the solar system. When the high temperature sensor signals the collectors are cooler than the pool water, the line from the suction side of the pump is opened, forcefully deflating the bladder and allowing flow to bypass the collectors. Another possible control valve, the irrigation style, achieves the same results but operates in a slightly different fashion. It is plumbed into the system by standard piping procedures. A small suction line is tapped into the pump inlet strainer housing, but in this case, the suction line is connected to the valve body itself. A pressure line is not used. A low voltage wire also connects a small solenoid valve mounted on the valve body to the control box. Most irrigation type valves will increase the pressure and reduce the flow rate of the system. The system control compares collector temperature with pool temperature as before. If solar heat is available, an electrical signal causes the solenoid valve to open the suction line. This suction closes the main valve diaphragm, diverting flow through the collectors. When solar energy is not available, the solenoid valve remains closed, the main valve diaphragm (which is spring loaded) opens, and the flow bypasses the collector array. (In another version the spring loading keeps the main valve diaphragm closed and the solenoid induces its opening.) 9.11.2 Manual valves Manual valves can be two- or three-way ball valves or standard flow diverter valves. Operation of these valves is completely manual and includes isolating the flow to the pool by diverting flow to the collectors. It is important that the isolation valve to the pool is between the collector supply and return lines in the system piping design. 9.11.3 Activating the system After installation is completed, it is necessary to activate and test the system for proper operation. A few of the most important checks are discussed here. 9.11.3.1 Purging the system Bits of plastic from rough pipe cuts, sand and other debris should be flushed from the system to avoid clogging small fluid passages in the collectors. Purging can be accomplished by leaving one or two strategically placed joints open. The circulation pump can be briefly turned on to flush water through the system, then final connections can be made. Small amounts of pool water can be discharged onto grass or sand, but large volumes should be piped to safe drains.

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9.11.3.2 Pressure testing The entire system should be pressurized to the maximum operating pressure. This can be accomplished in a number of ways. If piping passes through critical areas, such as an attic or public area, which is not recommended, a continuous run of piping is recommended. Avoid couplings and fittings in areas where a leak could cause significant damage. The system should be pressurized with an air compressor and tested for leaks. Testing the pipe to twice the operating pressure is recommended, but be sure not to exceed the pressure rating of the pipe. Leaks can be located readily by listening for the hiss of escaping air. Installations where all piping is routed through areas where a temporary leak will do no harm may be pressure tested by turning on the circulating pumps. The appropriate valves in the circulation system should be closed to produce the highest possible pressures in the new piping. Be sure to have someone standing by; ready to turn the pump off in the event a leak is discovered. During the pressure check, every connection should be visually inspected and shaken to ensure that it is well made. 9.11.3.3 Testing control devices Automatic control devices should be checked for proper operation. Consult the manufacturer's specifications for the controls being used and determine the possible operating modes. Test in all of these modes and make a permanent record of the results. Checking control operation immediately after installation can prevent costly callbacks later. 9.11.3.4 Testing flow rates Proper flow through the collector array and filtration system is required. Inexpensive flow meters are available and should be used to confirm desired rates have been achieved. As previously mentioned, turnover time must not be increased above an acceptable level. 9.11.3.5 Testing temperature rises The temperature difference between the feed line to the solar system and the warmer return line should be checked. Remember, the temperature rise on even a sunny day should be quite modest, approximately 510°F, for low-temperature collectors. Thermometers installed in these lines can be used to make accurate readings. If the temperature rise is too large, it indicates not enough water is passing through the collectors. Check the system thoroughly and correct the problem because collector efficiency drops dramatically as the operating temperature rises. It sounds strange to the homeowner but lots of water being warmed slightly provides more heat than a little water being warmed a lot.

9.12

Instructing the homeowner

There are several important reasons to spend a few minutes instructing the homeowner on the operation of the new solar pool heater. First, it will enable the owner to ascertain whether the system is operating and thus reduce "false alarm" callbacks. Second, it will enable the owner to explain the new unit to friends and neighbors. Third, it will equip the owner to make minor adjustments and reduce service calls for the installer. Explain the operation of all valves and controls and how the water circulates in the various modes. Spend a little time on the automatic control so that the owner can make seasonal or other adjustments that may be required. Provide the owner with the system manual.

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It is very important to explain the amount of energy being delivered to the pool is the product of the temperature rise and the flow rate. High temperature rises feel impressive, but they cause the collectors to operate inefficiently and deliver less heat to the pool. Sometimes this point is difficult to make, so you may have to explain it in several different ways.

10

Commissioning, handover and documentation

10.1

General

The person responsible for commissioning of the completed system should check that all aspects of the installation have been executed in accordance with the designer's and the component manufacturer's instructions. 10.2

Commissioning of direct circulation systems

The following procedures should be carried out. a)

The free movement of all valves and pump impellers should be checked manually where this is possible without dismantling.

b)

For systems integrated with the filtration circuit, the solar equipment should be shut off with valves and the filtration circuit checked for correct operation, and all pressure gauges, where fitted, should read within manufacturer's/designer's limits. Any defects should be remedied before proceeding.

c)

Using manual or motorized valves, as appropriate, water should be diverted through the solar collectors. It may be necessary to override the solar system controller to effect this diversion under unfavourable weather conditions. Alternatively, the collector sensor may be gently heated, thus qualitatively checking the operation of the control system also.

d)

All pipework should be checked for leaks. Correct operation of air vents should be confirmed. If it is desired to prevent air entrainment owing to negative pressure within the system a regulating valve on the delivery side of the solar collectors, may be partly closed. It should be ensured however that this action does not reduce the system flow rate below that recommended by either filtration equipment or solar collector suppliers.

e)

The flow rate through the solar collectors should be assessed, where possible with a flow meter. It should be confirmed that there is no significant imbalance of flow between individual collectors. The designer's recommendations should be followed with regard to adjustment of regulating valves if fitted. The flow is balanced if each collector's outlet temperature is similar. If unglazed collectors are fitted their entire surface should feel cool while exposed to bright sunshine.

f)

If the system has been designed to be automatically self draining this function should be checked [see 6.2.2 5)].

10.3

Commissioning of indirect circulation systems

The following procedures should be carried out. a)

The free movement of all valves and pump impellers should be checked manually where this is possible without dismantling.

b)

For systems integrated with the filtration circuit it should be checked that the filtration circuit operates correctly, and that all pressure gauges, where fitted, should read within manufacturer's/designer's limits. Any defects should be remedied/reported before proceeding.

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c)

Indirect systems in which water or water based fluid is the heat transfer fluid should be thoroughly flushed out with water and tested to ensure that there are no leaks prior to being drained and refilled (see 10.4). When using proprietary heat transfer fluids the manufacturer's instructions should be followed with regard to flushing out the pipework, testing for leaks and filling with the fluid.

d)

It is most important to purge sealed or permanently filled systems of all air and this operation should be carried out at the time of installation by means of appropriately positioned air vents. The best method of achieving air release is to switch the circulating pump on and off a number of times while venting the system. This operation should preferably be carried out in sunny conditions in order to ensure the release of dissolved air. Failure to purge the air fully may necessitate a call back visit. On sealed systems it may sometimes be necessary to re-establish the cold filled pressure and fluid volume.

e)

If the system is designed to fill and drain automatically to achieve frost or boiling protection, the correct functioning of the system or equipment should be checked in accordance with the designer's instructions.

f)

The flow rate through the solar collectors should be assessed and it should be confirmed that there is no significant imbalance of flow between individual collectors [see 10.2 e)].

g)

If the system has been designed to be automatically self-draining this function should be checked.

10.4

Precautions when pressure testing sealed circuits

Care should be exercised when carrying out pressure tests on completed solar heating systems and a pressure relief valve should always be fitted to protect components. If the completed circuit is to be filled with water under pressure to check for leaks, it is recommended that such a test is carried out either with the collectors covered or during hours of darkness in order to avoid: a)

the possibility of substantial temperature fluctuation within the collectors producing sufficient pressure changes to give false test readings;

b)

the possibility of the heat transfer fluid boiling under test.

10.5

Making good

Before an installation can be regarded as being satisfactorily completed the installer has to ensure that any damage caused by the fitting of any part of the system, e.g. the solar collectors, pipes or fixing brackets, is restored and made good. Pipework insulation, where specified in the system design (see 6.4.1) should be completed at this time. In this connection particular attention should be paid to repairing and sealing any damage to the roof lining. Damage to guttering, walls, garden and lawn, by ladders, scaffolding, hoists or other equipment should also be made good. 10.6

Handover and documentation

At the time of handover the client should be provided with an appropriate document certifying that the system has been installed and commissioned satisfactorily. If for any reason it is not possible to complete commissioning, arrangements should be made for this to be completed at a later date. If the operation of the solar heating system is dependent upon the operation of the filtration pump it should be ensured, in conjunction with the pool owner/operator, that it is set correctly so that the pump will run at least during daylight hours. The system should be handed over either in a fully operational state or decommissioned to an extent appropriate to the time of year and system's design. An owner's documentation wallet should be handed over containing the following items.

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KS 1895:2008 The handover document.

b)

A user's data sheet (see 10.7).

c)

Warranties or guarantees issued by the manufacturers of the components or by the installer.

d)

Operating and maintenance instructions describing start-up, normal running and shut-down procedures in a form readily intelligible to the non-technical user. These should also include details of protection provided against frost and overheating if applicable. Details of action to be taken in the event of apparent faults should be provided.

e)

A circuit diagram of any electrical controls.

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a)

If special additives are used in the heat transfer fluid of indirect circuits, durable identifying labels providing the necessary information as to the formulation, solution strength and specific hazard, source of supply and expected life of the liquid should be attached to the appropriate system component in a conspicuous manner for future reference. A separate label should also record the date of the installation and the name and address of the installer. 10.7

User's data sheet

A list of major components should be provided indicating the number, model and make of items of equipment that have been installed. As a minimum the solar collectors, control system components and pumps should be included in the list. The circuit design should be identified as direct or indirect and in the case of the latter, full details of the heat transfer fluid and the means of accommodating fluid expansion should be given. The method of frost protection should be stated and a clear, bold indication of any need to drain the system manually to provide frost protection should be included together with instructions for draining. The method of system control should be stated together with any facility for overriding the automatic control system. Data regarding the need for and frequency of maintenance should be given. Any servicing requirements should also be stated. It is also recommended that the client's attention should be drawn to the fact that it is prudent to check that the solar heating system is included on an existing insurance policy or that alternative insurance arrangements are made. Any special hazards to be avoided should be listed, for example, the high temperature which may be attained by collectors when the fluid flow is interrupted.

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Annex A Details of the model system referred to in clause 6 for thermal performance

A.1

Model system

The figures for heat transferred to the pool quoted in clause 6 are based on computer simulations. Details of the computer model used are as follows. Item Collector orientation

Description South facing and tilted at 45° from horizontal.

Pool temperature

The pool is assumed to be fully mixed and maintained at a fixed temperature by an auxiliary heating source. Pool water is circulated directly through the collectors and the inlet water temperature to the collectors is equal to the pool water temperature. Pumped circulation at fixed flow rate, using the pool water as the heat exchange fluid, having a specific heat capacity of 4.184 kJ/(kg K). Circulation switched on and off at fixed values of temperature differential between inlet and outlet of the collector. Heat losses from pipework are assumed to be zero. Hourly data as provided by the Meteorological Office for Kew from 1959 to 1979 inclusive.

NOTE

Collector pool loop

to

Insulation Weather data

A.2

Details of the collectors modelled are given in A.2.

Solar collector characteristics

Methods of test for evaluating the thermal performance of solar collectors are given in BS 6757. Calculations have been carried out using quantities which are considered likely to characterize properly constructed solar collectors of certain commonly-used types.

Two parameters, η0 and U, are used to characterize the collectors. In the nomenclature used in the book Solar energy thermal processes (J A Duffie and W A Beckman, Wiley, New York, 1975) these may be identified with the quantities F’(ατ)0 and F’UL respectively, where (ατ)0 is the product of the absorptance of the absorber plate surface and the solar radiation transmittance of the cover, if present, at normal incidence; UL is the overall heat loss coefficient and F’ is the collector plate efficiency factor. Typical values of η0 and U are selected to represent the characteristics of single-glazed selective insulated collectors, single-glazed matt black insulated collectors, and unglazed uninsulated collectors, given in Table 2. These figures are derived from results of tests on numerous collectors by the Energy Equipment Testing Service at University College Cardiff, in accordance with BS 6757. The unglazed collectors were tested resting on a backing plate.

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Table 2 — Typical values of rf0 and U for different types of collector Collector type

η0

1. Single-glazed selective 2. Single-glazed matt black 3. Unglazed

0.7 0.7 0.8

U W/(m2.K) 5.3 7.7 20

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A.3

Other assumptions

For all three types of collector it is assumed that the albedo of the surroundings is 0.2 and the incidenceangle modifiers for beam radiation (lb) and diffuse radiation (ld) are as follows: ⎯

for beam radiation lb = 1.1 — (0.1/cos Z) (where Z is the incidence angle)

⎯

for diffuse radiation ld = 0.9

Factors that are assumed to be different for the various collectors are as follows: Collector type (see Table 2) Fluid flow rate [kg/(m2 s)] Temperature differential on K Temperature differential off K Heat removal factor FR

1 0.02 2 0.5 0.969

2 0.02 2 0.5 0.955

3 0.04 0.5 0 0.929

NOTE The temperature differentials used in the model are the assumed fluid temperature differences rather than those which operate the control system (see 5.3.3).

A.4

Collector output

The collector energy output, or heat delivered to the pool per unit area of collector, in a given hour is determined by: Q = F[η0 (lbHb + ldHd) - 3600 U(Tp - Ta)]

where Q F

η0

lb ld Hb Hd U TL Ta

is the hourly output (in J/m2); is the heat-removal factor/plate efficiency factor = FR/F'; is the zero heat-loss efficiency; is the incidence-angle modifier for beam radiation; is the incidence-angle modifier for diffuse radiation; is the hourly beam irradiation (in J/m2); is the hourly diffuse irradiation (in J/m2); is the collector heat loss coefficient [in W/(m2-K)]; is the pool temperature (in °C); is the air temperature (in °C).

The output given by the above equation has been determined for every hour of the 21-year period 1959 to 1979 at Kew. From this, the average total energy output for the whole year, for the period May to September inclusive, and for the month of July is given respectively in Figure 4 to Figure 6. Data for each of the separate months of the year are given in Figure 27 and Figure 28.

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NOTE The performance of collectors, particularly those of type 3, will depend on many factors and these curves should be interpreted with reference to Clause 7.

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Figure 27 — Average energy output from collectors for May, June, July, August and September

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NOTE The performance of collectors, particularly those of type 3, will depend on many factors and these curves should be interpreted with reference to Clause 6.

Figure 28 — Average energy output from collectors for October, November, December, January, February, March and April

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