e.r.i.c. TECHNICAL SECTION 2006

Insufficient air flow Individuals consume approx. 350,000 kg of air during their lifetime. This can be compared with the intake of solid nourishment, which is a fraction of the amount of air. In an investigation by the National Swedish Institute of Public Health it was discovered that we have experienced a doubling in allergy problems every 10th year since 1960 and currently some 40% of our children in infant schools suffer from some form of allergy. The fact that this is purely due to ventilation and air flow is probably not true, but that there is a link between too small air flow rates and allergies is probably obvious. To transport any contamination in the room air out requires at least that correctly designed air flow rates are maintained.

Figure 1. Compilation of 5000 different OVK systems. S F FT FTX

= Natural draught system = Exhaust air system = Supply and exhaust air system = Supply and exhaust air system with recovery

1 2 3

Tenement building Office Schools

It is evident from the diagram that the most basic systems (S) showed the worst results while the more complex (FTX) showed the best results. One explanation for this can be the FTX systems are newer than the other systems and above all offices are equipped with some form of cooling function. Maintenance personnel probably hear immediately if the cooling does not work. Despite this the diagram still illustrates that only about 50% of the FTX installations were approved. Reasons for the problem The reasons for the deficiencies vary, but the most important reasons for impaired function are: • Imbalance has occurred in the system due to it being sensitive to different types of disturbances. You could say that the system is not “forgiving” but is affected by disturbances instead of being corrective. Consequently, insufficient air flow rates can occur in parts of the system while in other parts the air flow becomes too large resulting in troublesome noise and draughts. • System maintenance has been neglected, which affects operating reliability. • Activities have changed and the original air flow rates are not good enough for the new activities. • Trimming has not been carried out correctly or according to the changes in activities. Frequently systems are also designed with a constant air volume, which does not always permit a change in the air flow.

Figure 2. Distribution of a total intake of 350,000 kg air. 6 and 7 inserted in the diagram for comparison. 1. Air in the home 2. Air in public buildings 3. Air in industry 4. Outdoor air

5. Air when travelling 6. Fluids 7. Solid nourishment

Noise and imbalance Noise is one of the most common problems associated with ventilation installations. One reason is because a too large pressure drop in the final nozzle and adjustment damper are permitted. Today, both the products and know-how exist to prevent these problems. Despite this it is not unusual for users to solve the problems themselves. Manipulating the ventilation installation by blocking a nozzle causing noise or a draught is not an unknown solution. The problem is then solved in the room in question, yet it is only really moved to other parts of the system. In the worst scenario if this happens in several parts of the system the entire installation will become imbalanced. Energy Investigations show that approx. 40% of all energy produced in Sweden is used to supply our buildings with requisite ventilation, cooling and heating. Many ventilation installations currently run with a constant flow, despite the load varying. The call for demand controlled solutions will in all probability grow with the increase in energy costs. Demand controlled air flow By tradition many ventilation installations are designed with a constant air volume, which is controlled at given operating

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Introduction to e.r.i.c. The compulsory ventilation inspection (OVK) which, according to Swedish law, must be carried out on ventilation systems at regular intervals has during the last decade provided us with a good picture of the status of our ventilation installations. In many cases the results have been astonishing and give us a reason for reflection. It can be established that most ventilation installations do not conform to the demands that were once made on them, see figure 1.

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times. Irrespective of the load in the premises a constant air volume is delivered During the last few years the interest in controlling the air flow to match the need in the premises has increased, which opens the door for new solutions within this field. Traditional solutions employing VAV systems have been criticised as they require extensive service and maintenance, as they are frequently fitted with dynamic pressure sensors that can be blocked by contamination and thereby lose their function. Future solutions within this field will require products and systems offering high reliability and a minimum of service and maintenance. Future demans and solutions The vision of tomorrows’ ventilation system that satisfies man’s demands, both expressed and implied, is of a system that can be adapted to the needs of the individual at different times. In addition the following demands should be made: • Noise problems caused by the ventilation system are to be eliminated. • Imbalance should not be created by changes or by the effects of external factors. • Simple trimming is facilitated in both new constructions and conversions. • Flexibility to change for different activities and demands. • Operating costs minimised through demand controlled air flow.

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Basic philosophy The basic idea of the e.r.i.c. system is that the flow requirement should be controlled in the room and that the system should adapt itself according to this with as low energy consumption as possible. This means that each room can live its own life and, for example, direct control (i.e. half the flow at the weekend and other time-based control) of the flow in the unit becomes redundant. There are three reasons to vary the flows to the different rooms:

• Comfort. If under tempered air is used to create the required room temperature, the flow is varied depending on the thermal loads. If the personal loads in the room vary, the flow can vary, to ensure the air quality. • Energy. If only half the class are in the classroom or if only half of the office is manned, it is sufficient to ventilate for half the personal load. By only ventilating when it is needed saves the energy for fans, heating and cooling. • Noise. The higher the air velocities the more noise generated from the fans and duct system. By not running at maximum flow to all the rooms, the air velocities and pressure rises in the system are reduced, which gives lower noise generation. Figure 3 illustrates an e.r.i.c. system where the unit transports the air to the branch ducts, which have a constant static pressure. The constant pressure means that the flow can vary out to the different rooms without flow measurement and without flow variation in one room affecting another. The flow in the room can be controlled based on the cooling requirement, carbon dioxide content (CO2) or presence. Combinations with control of lighting, cooling and heating valves are also possible.

Figure 3. Typical e.r.i.c. system. 1. System Manager KSM 2. Pressure sensor for the unit’s pressure control 3. Zone Manager KZP/KZM 4. Slave controller KSA 5. Room Manager KCD/KCW

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Technical section

e.r.i.c. system e.r.i.c. system is an acronym for Easy and Reliable Indoor Climate. The starting-points when developing the system have been reliability, operating safety and economy, as well as that the system should be characterised as a comprehensive solution. The system does not differ dramatically from a conventional system without the possibility of individual control. However, one basis where the e.r.i.c. system does differ from a conventional system is that the system has been designed to maintain a constant pressure in branch ducts via branch duct dampers.

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TRADITIONAL GROUPING OF VENTILATION SYSTEMS The choice of an appropriate technical solution is an important step in planning. System selection ought to be made bearing in mind the following four main factors: Suitability. The ability of the technical solution to satisfy the quality demands imposed. Operating reliability. The ability of the technical solution to provide long-term satisfactory operation. Resource economy. The technical solution’s energy efficiency, cost efficiency, etc. When selecting the technical solution you should always seek simplicity, intelligibility and tolerance against deviations in operating conditions. Avoid technical solutions that do not permit room usage to be changed, windows to be opened or in any other way is sensitive to external disturbances. Basic principles and characteristic properties There are different ventilation engineering solutions that can meet the demands of correct air flow to all parts in a system. The main categories discussed are: • CAV system (Constant Air Volume), system with constant air volume. The most basic and in general most “inexpensive” option. • VAV system (Variable Air Volume), system with variable air flow, which is generally controlled via a room thermostat. The fan is equipped with some kind of pressure regulation. • DCV system (Demand Controlled Ventilation), requirement control of the air flow, which is generally controlled via an air quality or presence detector. • Naturally all system solutions can be designed with either mixing or thermally controlled ventilation (displacement ventilation). CAV as well as DCV systems can be combined with optional heating and cooling equipment for controlling the room temperature. Figure 4. Principle of a CAV system. 1. Exhaust air 2. Supply air 3. Ventilation unit (FTX)

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CAV system The CAV system is used where both heat generation and contamination production are low and fairly constant. The supply air flow is primarily determined by the air quality demands. If the hygienic air flow to transport away the heat is not sufficient, you can supplement with products for waterborne cooling. Disadvantages: CAV systems are usually based on the branching principle with adjustment dampers in each branch. The pressure drops across the terminals are selected so that when combined with the pressure drops across the adjustable dampers they give the right flow distribution. The disadvantage of this principle is that the system can easily become imbalanced due to disturbances from thermal rising forces, changes of damper positions, etc. Further disadvantages are the relatively high pressure drop across the damper and terminal necessary to ensure that the flow variations do not become too high. This in turn can result in the noise problem becoming an inconvenience at the same time as energy consumption becomes unnecessarily high. A lowering of the fan speed, in order to reduce energy consumption during specific periods, means that the flow distribution cannot be upheld, because the pressure drop across the terminal and damper decreases. VAV/DCV system Used when the personal load varies. Radiators are an appropriate heating method. The room’s cooling requirement is adjusted using a variable air flow. Disadvantages: The VAV/DCV systems differ from the CAV systems among others through pressure regulation on the main ducts for the supply and exhaust air. This is necessary from both energy and noise points of view. Another difference is that in the immediate connection to the supply air terminal devices there are controllers that control the air flow rate through the terminals. A basic problem with this is, as the flows are reduced, the pressure drop increases. This can have serious consequences. An increased pressure drop generally creates higher noise levels. The pressure in the main ducts must guarantee the whole time that the worst positioned branch duct receives sufficient air. If the flow distribution in the system allows a temporary lower pressure, the set point value must still be maintained. Naturally this has a negative effect on the operating costs.

Figure 5. Principle of VAV system. 1. Exhaust air 2. Supply air 3. Ventilation unit 4. VAV unit

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NEW SYSTEM SOLUTIONS Interest in new ways of constructing ventilation systems is increasing. The reasons for this are several: 1. System solutions have not permitted simple trimming. This has resulted in system imbalance with subsequent high pressure drop in specific parts and with that too high noise levels. In other parts of the system the air flow rate has been too low resulting in impaired air quality. 2. A low installation cost has been prioritised when planning of the unit. The consequence of this has been units that are too small with high noise levels resulting in noise problems. 3. Imbalance usually occurs between the supply and exhaust air. Imbalance in the building causes pressure differences with the surroundings, which results in increased energy costs and damage to the facade. 4. Consideration to the user’s wishes. As a user you what to influence your climate. 5. An important aspect today is also to keep down energy consumption. In Swedish buildings about 40% of all energy produced is consumed solely to provide them with ventilation, heating and cooling. It is therefore necessary to put together system solutions that can minimise energy consumption without forgoing comfort. In the light of experience available, not least from the compulsory ventilation inspections, we can easily describe the demands we should make on modern climate systems. Demands on new system solutions: 1. System designs so that these accept the normal disturbances that always exist in our surroundings, a.k.a forgiving system solutions. 2. System designs so that traditional trimming work is eliminated and assurances are given that the design flow can also be maintained. 3. System designs so that energy consumption can be minimised. 4. System designs so that the risk of noise disturbances are minimised. 5. System designs that are flexible so they can be easily adapted to variable activities. 6. System designs so that there is always a balance between the supply and exhaust air flow rates. 7. System designs so that individual regulation of the temperature and air quality is given priority. 8. System designs that eliminate draught problems when the air flow is requirement controlled. In order to satisfy these demands an important part of our new system solution, e.r.i.c., is that we maintain the static pressures constant at an appropriate position in the branch ducts. Pressures are not set higher than necessary to produce the planned air flow rates. Can all of these demands be satisfied? Yes, by using a system that maintains the pressure constant all the way out to the branch ducts!

Why pressure control? By maintaining the pressures constant on the branch ducts conditions are created for: 1. Flexible installation. Individually, variable air flow rates can be achieved without jeopardising the balance in the system. Terminals for constant and variable flows can be mixed without problem on the same branch duct. 2. Silent installations due to optimal low pressure drops in both the main as well as branch ducts. 3. Energy efficient installations as no extra pressure drop occurs to assure the air flow rates.

Figure 6. Relative energy consumption depending on the type of system. 1. Relative energy consumption fan % 2. Relative air flow requirement %

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LCC ANALYSIS Life cycle cost (LCC) A ventilation system involves different costs, which occur at different times during the system’s life span. These costs are collectively known as the lifecycle cost. Since the installation cost is only part of the lifecycle cost it is often better to choose and dimension a system based on the lifecycle cost rather than just the installation cost. The costs associated with a ventilation system are the installation cost, which consists of material and labour, annual energy costs, annual operating and maintenance costs, possible renovation or conversion and scrapping. All costs in a LCC analysis are converted to today’s value according to the following method. Theory The following formula is used to calculate the current value of future costs, where Cinst is the installation cost, Cyearly is the cost incurred each year for n years (e.g. power and maintenance costs), Ci is one or more one-off costs that crop up after i years, and r is the discount interest rate.

Figure 7. Spread of costs in a typical office block with a CAV system supplemented with chilled beams. 1. Waterborne climate installation 2. Air conditioning plant 3. Maintenance 4. Energy

The chart on the right shows one example of how the lifecycle cost may be broken down for a modern office building in central Sweden with chilled beams and a CAV system. The total air handling cost is roughly SEK 2,200/m2 over the lifetime, which is assumed to be 20 years. e.r.i.c. One of the purposes of the e.r.i.c. system is to reduce the annual energy requirement and in doing so reduce a large part of the LCC. As the system has more complicated control than conventional systems the maintenance costs increase, yet this is counteracted by less trimming and improve flexibility.

Research project Swegon AB is involved and supports a research project investigating LCC analyses for different climate and ventilation systems. As this project progresses the result will be presented on our website.

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e.r.i.c. SYSTEM The system can be divided on the following three levels. System level System level concerns the System Manager that communicates with the branch dampers and the units to optimize the pressure after the fan so that the fan always runs at the lowest possible speed to give as low energy consumption and noise generation as possible. Zone level Zone level concerns constant pressure control in the branch ducts. Also included on the zone level is the slave control of the exhaust air.

Around the clock operation No control of the unit for night or day operation is needed, as flow control is managed out in the rooms. If no one is present then automatic mini-flow is used in all rooms and whole system runs at low speed. With no presence the flows can be reduced to a minim flow and the SFP value is reduced by 88%. Accordingly, fan energy is in principle negligible in this operating mode. During the night the fans should not be switched off for reasons of hygiene. The motive for this is quite self-evident: 1. You should, due to the building emissions, have a purifying air flow even during the night. 2. The fans must be running to avoid contamination from entering the duct system due to back draught.

Room level Room level concerns control of the indoor climate. This control is done with an active terminal, room controller and en room unit. Waterborne products, radiators and preheating batteries can also be controlled by using the room controller. Control can take place based on temperature, presence and CO2 concentration. ENERGY OPTIMISATION WITH e.r.i.c. System level The concept of the Swegon e.r.i.c. system is based on pressure control in the branch ducts where a constant pressure is maintained at pressure sensor points, for example, at approx. 35 Pa. The control damper at the beginning of the branch ducts handles pressure regulation. The System Manager is a controller that communicates (LONTALK®) with the branch damper and the unit. Optimisation is achieved through the System Manager keeping track of the damper positions and minimising the unit’s rise so that at least one of the dampers on the supply respective exhaust air sides is always nearly fully open irrespective of the operating mode. The system also allows energy optimisation on very small installations at a reasonable cost. The System Manager and unit can also communicate with other central units in the building, for example, so that pumps and supply temperatures in the heating/ cooling system can be adjusted for minimal energy consumption. In this way energy is saved and noise disturbances are eliminated by the unit always running at as low a speed as possible.

Night cooling To save cooling energy you can utilize the lower outdoor temperature at night to cooling the carcassing. The night cooling function is easily achieved through a controller or a master system sending a command to the rooms for night cooling. The terminals are then opened to their max-positions and a max-flow is obtained until the signal for normal operations is sent from the master system.

Figure 8. The e.r.i.c. system. 1. Exhauxt air 2. Supply air 3. System Manager 4. Zone Manager, branch damper

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Unit Units with a large flow range should be chosen for the e.r.i.c. system. The unit should be equipped with pressure control of the fans. When the System Manager KSM is used the unit’s pressure control should have LON communication with KSM. It is recommended to use an outdoor temperature compensated supply air temperature with the e.r.i.c. system.

Technical section

Heating battery In winter the air flow is not controlled to the same degree by the cooling requirement and can therefore be regulated down to a minimum flow, which with the e.r.i.c. system can be as low as 20% of the maximum flow. When active terminals are used it is no problem to supply a minimum flow with subnormal temperatures of up to 12K. At such low flows a rotating heat exchanger has a temperature efficiency of over 80% (up towards 85%). This means that the supply air temperature could be 14°C at -22°C outdoors (23°C on the exhaust air). You should consider the cost of installing and maintaining a heating battery.

Figure 9. Zone/branch level. Separate constant pressure on the supply and exhaust air. 1 and 2. Pressure sensor KSP 3. Branch damper

Supply air temperature As all room controllers can communicate the system contains available information about the size of the cooling or heating requirement in all rooms. This gives the possibility of selecting the most optimal supply air temperature so that: • the heat exchanger is utilised to full in heating instances • free cooling is always utilised instead of increased flows in cooling instances • the supply air temperature is not lower than necessary in summer instances. Zone level The system composition with constant static pressure in branch ducts contributes to low noise levels and energy consumption. As the system is always in balance infiltration is reduced. See figure 9. Room level Through only ventilating when and where there is a need energy can be saved and the noise level; from the duct system and fan are reduced. The need is controlled directly from the room. If no one is there only the set minimum flow is supplied. The presence detector can also be connected via the room controller to the lighting. See figure 10. Radiators Through both controlling the air and radiators with the room controller the risk of simultaneous heating and cooling is eliminated. Window contact If a window contact is connected to the room controller the room ventilation is switched off when a window is opened. Energy can be saved by not supplying air via the ventilation system if the user has chosen to air the room by opening the window.

Figure 10. Room level. With active supply and exhaust air terminals the balance between the supply and exhaust air is controlled on a room level. Branches on the supply and exhaust air only need to maintain a constant static pressure. No flow metering is necessary. 1. Exhaust air terminal 2. Supply air terminal 3. Regulator 4. Room unit KST

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ACTIVE SUPPLY AIR TERMINAL Flow control on the supply air By maintaining a constant pressure in the branch ducts flexibility is created with regard to the changes in flow in the terminal. The terminals can be changed individually without this having a negative effect on the balance in the system or the unit’s trimming. Unlike VAV units, no flow metering in the terminal is necessary, which results in reduced maintenance and a stable system. The flow is determined based on the terminal’s opening (between 0 to 100%) and the underlying constant static pressure. Maintaining a constant pressure is therefore motivated even if the installation is designed to operate as a CAV system. The installation automatically compensates for the “disturbances” that always occur in systems. Consequently, maintaining constant pressure allows the terminals with constant and varying flows to be combined on one and the same branch. See figure 11.

Figure 11. Characteristics for a supply air terminal device in a branch with constant static pressure. Unlike systems with varying pressure the noise level decreases here with the reduced flow.

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Technical section

Constant outlet velocity - no draught problem A prerequisite to obtain a good distribution pattern in a room, when heated or chilled air is supplied, and when the air flow varies within a large flow range, is that the supply air velocity when it leaves the terminal is constant. This can be easily achieved through flow regulation taking place in the terminal outlet instead of its inlet. A prerequisite for this is that the pressure is constant in the branch duct. The “disturbances” that occur in the form of varying air flow is automatically compensated for through maintaining constant pressure in the branch duct. Products that are especially suitable to use for constant outlet velocity are circular or square single cone diffusers. Nozzle terminals normally have good properties with varying air flow. The lowest permitted air flow with a subnormal temperature of approx. 5°C is however normally limited to about 30% of the maximum air flow. If you want to further reduce the air flow a terminal with a constant outlet velocity is required. Remembering that you want to establish a uniform distribution pattern in the room, the outlet velocity must be fairly constant when the air flow varies. A reduced outlet velocity means that it is easier for the air to release from the ceiling and drop down to the occupied zone resulting in increased speed. A distinction is made between two types of supply air terminal device: 1. Passive terminals that have the same setting independent of the air flow. 2. Active terminals that have flow regulation in the terminal outlet, which gives a constant outlet velocity independent of the air flow. If, using passive terminals, you reduce the air flow from 100% to 30%, the throw length is also shortened by 30%. If you reduce the flow in the same way with an active supply air terminal device, i.e. a terminal where the outlet velocity is maintained constant through the outlet area changing, the throw length will be 55% of its original length. The reduction is in no way a problem for any of the terminal variants as the air does not release its contact with the ceiling due to the high outlet velocity. Air flow rates also become lower. The flow pattern out into the room is similar to the flow pattern with the larger air flow, but with a smaller penetration depth. The major differences between the passive and active terminals are: 1. the draught risk increases with a passive terminal as the air flow decreases. 2. the draught risk decreases with an active terminal when the air flow decreases. The deficiencies of passive terminals, in connection with flow regulated installations, is one of the reasons why the VAV/ DCV systems have not had a positive development. See figures 12, 13 and 14.

Figure 12. The spread with active air terminals at a nominal air flow.

Figure 13. An active air terminal whose free air supply area decreases to lower the air flow. The speed and strength of the spread remains unchanged. No risk of draught problems.

Figure 14. A passive air terminal whose free air supply area is constant. If the flow is restricted, for example, with a damper, the air speed will diminish and the spread with turn down into the occupied zone. Large risk for draughts.

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ACTIVE EXHAUST AIR TERMINAL DEVICE Flow control of the exhaust air As the exhaust air terminal device does not have the same problem with varying air flow rates as the supply air terminal device, you can select simpler solutions. Criteria for an exhaust air terminal device are: 1. It ought to have the same regulation characteristics and restriction range as the corresponding active supply air terminal device. 2. The appearance should match the supply air terminal device to give an attractive installation. Flow control of the exhaust air terminal device is handled by the same controller as the supply air terminal device. In the new series of controllers separate min/max settings can be programmed for supply and exhaust air terminal devices. This means that you can have different pressure control values for the supply/exhaust ducts. TRANSFER AIR DEVICE Open/Close door In the selection of systems with transferred air and common exhaust air in the corridor it applies that the transfer air device should have a pressure drop