Combustion Appliance Basics
July 2009
Overview of Heating Systems
Combustion
Appliance
Appliance Basics
Basics
Would You Build a Fire in Your Basement? Why not?
National Weatherization Conference 2009
What would you have to do to make it safe? This is what codes address
Rick Karg
R.J. Karg Associates
[email protected]
©2009 R.J. Karg Associates Click 3
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Overview of Heating Systems
Overview of Heating Systems
Where Does the Vent System End?
Where Does the Vent System Begin?
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Overview of Heating Systems
Overview of Heating Systems
Oil Boiler w/o Service for 2.5 Years
What We Will Talk About
Clogged heat exchanger at top
Introduction to combustion appliances.
Underside of heat exchanger from firebox
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R.J. Karg Associates
Importance of using the same terms. Gas-fired vent categories. Draft types
Gas-fired systems. Oil-fired systems. Measuring combustion efficiency. Tools for combustion safety. Some good guidelines. 6
Combustion Appliance Basics
July 2009
Overview of Heating Systems
Overview of Heating Systems
Terminology is Critical
Introduction to Combustion Appliances
If others used the term baseball for the chair you are sitting in, we would have a communication problem. Well, we have a problem:
What is a power venting? What is atmospheric draft? What is direct vent? What is an induced draft fan?
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Overview of Heating Systems
Overview of Heating Systems
Definitions
Vent Categories (NFPA 54)
Furnace Boiler Vent categories (coming up) Draft types (coming up) Atmospheric burner (coming up) Direct-vent appliance (coming up)
I
•Non-condensing •Negative pressure •Atmospheric equipment •Category I fan-assisted equipment •AFUE usually from 65% - 83% •NFPA 54 written for this category •Non-airtight vent connector
Negative Pressure Click 4
IV
Condensing
Positive Pressure
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Overview of Heating Systems
Overview of Heating Systems
Vent System Draft Types
Vent System Draft Types
Natural draft
Energy supplied by buoyancy of heated air. Negative pressure in vent connector.
Induced draft
II
•Condensing •Positive pressure •AFUE usually 90%+ •Airtight vent connector •Fan assisted draft •Must be corrosion resistant
- Static Pressure in Vent +
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Non-Condensing
Temp. •No or little equipment in this category •Condensing •Negative pressure
Try to use terms from codes Click 1
III •Non-condensing •Positive pressure •AFUE usually from 83% - 87% •Airtight vent connector •Fan assisted draft
Energy supplied by fan at exit at wall. Negative pressure in vent connector.
Forced draft
Energy supplied by fan at appliance. Positive pressure in vent connector. 11
R.J. Karg Associates
Atmospheric
Induced Draft
Forced Draft 12
Combustion Appliance Basics
July 2009
Overview of Heating Systems
Overview of Heating Systems
Induced Draft Fan
Atmospheric Burner
Natural draft and atmospheric burner
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Overview of Heating Systems
Overview of Heating Systems
Direct-Vent Appliance
Atmospheric Gas Furnace
“Appliances that are constructed and installed so that all air for combustion is directly from the outside atmosphere and all flue gases are discharged to the outside atmosphere.” (National Fuel Gas Code, NFPA 54)
Category I Natural draft
Sometimes referred to as “sealed combustion” Direct-Vent Water Heater
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Overview of Heating Systems
Atmospheric Gas Water Heater
Source: Heating with Gas, Natural Resources Council Canada, 1996
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Overview of Heating Systems
Atmospheric Gas Water Heater Concentric, double-wall vent connector
Typical natural draft, atmospheric water heater.
In vent connector, negative pressure and high temperature.
Category I
Direct-vent unit Natural draft Category I
Sealed combustion chamber
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R.J. Karg Associates
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Combustion Appliance Basics Overview of Heating Systems
Fan-Assisted Gas Furnace Mid-Efficiency Category I Natural draft Not atmospheric
Induced-Combustion Fan (No Draft Diverter) edit by R. Karg
July 2009
Overview of Heating Systems
Gas Water Heater Induced draft unit with negative pressure and high temperature in vent connector. Category I Induced draft fan installed at exit point at wall.
Source: Heating with Gas, Natural Resources Council Canada, 1996
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Overview of Heating Systems
Overview of Heating Systems
Gas Water Heater
Condensing Gas Furnace
Forced draft fan.
Forced draft water heater with high temperature plastic vent connector.
Category IV Forced draft
Category III Non-condensing Forced draft 21
Source: Heating with Gas, Natural Resources Council Canada, 1996
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Overview of Heating Systems
Overview of Heating Systems
Condensing Gas Furnace
Oil-Fired Water Heater and Boiler
Combustion supply air Exhaust air Cooling coil housing
Sealed combustion chamber
Category IV Forced draft fan
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R.J. Karg Associates
Usually natural draft Not atmospheric 24
Combustion Appliance Basics
July 2009
Overview of Heating Systems
Overview of Heating Systems
Space Heater, Direct-Vent
Wall Furnace, Direct-Vent
Monitor Heater 25
Overview of Heating Systems
Gas oven bakeburner testing
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Overview of Heating Systems
Gas range top burner testing Not vented
Not vented
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Overview of Heating Systems
See www.karg.com/cohotpot.htm
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Overview of Heating Systems
Unvented Appliance
Gas-Fired Heating Systems
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R.J. Karg Associates
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Combustion Appliance Basics
July 2009
Overview of Heating Systems
Overview of Heating Systems
Atmospheric Gas Furnace
Atmospheric Gas Furnace
Category I Natural draft
Source: Heating with Gas, Natural Resources Council Canada, 1996
Category I
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Overview of Heating Systems
Overview of Heating Systems
Fan-Assisted Gas Furnace Mid-Efficiency
Category I Gas Atmospheric Furnace
Induced-Combustion Fan (No Draft Diverter)
Efficiency and CO must be tested in gases before dilution air enters vent system.
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edit by R. Karg
Source: Heating with Gas, Natural Resources Council Canada, 1996
Category I Natural draft Not atmospheric
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Overview of Heating Systems
Overview of Heating Systems
Category I Fan-Assisted
Condensing Gas Furnace Category IV Forced draft Why is this so efficient?
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R.J. Karg Associates
Source: Heating with Gas, Natural Resources Council Canada, 1996
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Combustion Appliance Basics
July 2009
Overview of Heating Systems
Overview of Heating Systems
Lennox Pulse Condensing Furnace
Condensing Furnace, Category IV
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Overview of Heating Systems
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Overview of Heating Systems
Gas-Fired Boilers
Oil-Fired Heating Systems
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Overview of Heating Systems
Overview of Heating Systems
Retention Head Oil Burner
Oil Boiler and Water Heater
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Combustion Appliance Basics
July 2009
Overview of Heating Systems
Overview of Heating Systems
Oil-Fired Boiler, Cold Start, etc.
Oil-Fired Boilers
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Overview of Heating Systems
Overview of Heating Systems
Oil-Fired Furnace
Barometric Damper
ThermoPride
On most oil-fired units
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Overview of Heating Systems
Overview of Heating Systems
Efficiencies Defined
Measuring Combustion Efficiency and
Safety
Steady-State Efficiency:
100% minus the percent up flue. Measured with combustion analyzer while burner is operating.
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R.J. Karg Associates
Smoke test (usually 2 or less). Only on oil-fired, not gas. Oxygen (O2) or carbon dioxide (CO2). Net stack temperature (stack temp. less room air temp.)
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Combustion Appliance Basics
Overview of Heating Systems
Overview of Heating Systems
Efficiencies Defined
Oil Systems Smoke Test
Seasonal Efficiency:
July 2009
Includes stand-by losses. Based on steady-state efficiency, sizing, and burner efficiency curve. Annual Fuel Utilization Efficiency (AFUE) is a calculated estimate of seasonal efficiency. Seasonal efficiency is always less than steady-state efficiency.
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Overview of Heating Systems
Fyrite Pro from Bacharach Combustion analyzer and CO tester
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Overview of Heating Systems
If smoke test is greater than 2, unit needs clean and tune.
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Overview of Heating Systems
Testo 325-1 Combustion analyzer and CO tester
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Overview of Heating Systems
Digital Manometer DG-700 from the Energy Conservatory or another model is a good tool for measuring draft and combustion appliance zone (CAZ) pressure.
Combustible gas detector for natural gas and propane. Use properly.
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Combustion Appliance Basics
July 2009
Overview of Heating Systems
Overview of Heating Systems
Monoxor II from Bacharach
Some Good Guidelines
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Overview of Heating Systems
Overview of Heating Systems
Guideline - 1
Guideline - 2
Combustion safety testing is VERY important.
Test pre-weatherization. Test at the end of a work day? Test post-weatherization. Test
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Clean and tune gas-fired heating systems once every three years.
Clean and tune oil-fired appliances every year.
CAZ depressurization against appliance limits. Spillage. Draft. CO. Combustible gas leaks.
Topic is covered in other sessions at this conference 57
Overview of Heating Systems
Overview of Heating Systems
Guideline - 3
Guideline - 4
For natural gas furnace, replace existing natural draft unit if:
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Steady-state efficiency is equal to or less than 75% and it has an expected life of less than 5 years. Replace with ENERGY STAR unit.
Source: Wisconsin Wx Program Specifics should vary for different climate zones and programs 59
R.J. Karg Associates
For propane gas furnace, replace existing natural draft unit if:
Steady-state efficiency is equal to or less than 80% and it has an expected life of less than 5 years. Replace with ENERGY STAR unit.
Source: Wisconsin Wx Program Specifics should vary for different climate zones and programs 60
Combustion Appliance Basics
Overview of Heating Systems
Overview of Heating Systems
Guideline - 5
Guideline - 6
For oil furnace, replace existing natural draft unit if:
July 2009
Steady-state efficiency is equal to or less than 75% and it has an expected life of less than 5 years.
For boilers, replace existing natural draft unit if:
Source: Wisconsin Wx Program Specifics should vary for different climate zones and programs
If the steady-state efficiency is less than 75% and the boiler is more than 10 years old model a boiler for replacement with NEAT. If SIR is one or greater, replace. Install replacement boiler with highest SIR.
Source: Wisconsin Wx Program Specifics should vary for different climate zones and programs
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Overview of Heating Systems
Overview of Heating Systems
Guideline - 7
Guideline - 8
Minimum efficiencies for replacement units:
Natural Gas/LPG furnaces – 90% AFUE.
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Don’t forget to inspect/analyze the distribution system, especially ductwork.
For site-built homes and mobile homes.
Bad ductwork can significantly reduce overall efficiency.
Gas boilers – 83% AFUE. Oil furnaces and boilers – 83% AFUE.
Oil furnaces for mobile homes – 79% AFUE. Topic is covered in other sessions at this conference
Source: Wisconsin Wx Program Specifics should vary for different climate zones and programs 63
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Overview of Heating Systems
Overview of Heating Systems
Guideline - 9
Guideline - 10
For water heater replacement, use NEAT or another approved modeling software to determine if replacement is cost effective. Might need to replace for health and safety reasons if significant negative pressure in combustion appliance zone (CAZ).
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R.J. Karg Associates
Whenever possible, install direct-vent combustion appliances for safety.
They are aerodynamically uncoupled from the house air, so they are much safer. They don’t use a chimney.
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Combustion Appliance Basics Overview of Heating Systems
What We Talked About
Introduction to combustion appliances.
Importance of using the same terms. Gas-fired vent categories. Draft types
Gas-fired systems. Oil-fired systems. Measuring combustion efficiency. Tools for combustion safety. Some good guidelines. 67
R.J. Karg Associates
July 2009
