Combustion Sources of Carbon Monoxide. Carbon Monoxide Repairs. Topics Addressed in Session. Why CO can be Harmful Inhalation Time and Symptoms

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1 Affordable Comfort Conference 2002 Saturday, April 20, 8:00 12:00 Rick Karg R.J. Karg Associates April R.J. Karg Associates Topics Addressed in Session Combustion sources of CO. How CO is produced in combustion appliances. Measurement of CO: As-measured & air-free. Combustion basics. Combustion basics using gas range as model. ANSI Standards for manufacturers. CO problems and solutions. Overview of gas ranges. Overview of heating systems. Overview of water heaters. Carbon monoxide action levels. Getting into CO measurement. 2 Ambient Concentration 0.02 % (200 ppm) Why CO can be Harmful Inhalation Time and Symptoms Slight headache w/in 2 3 hours. CO Concentrations vs. Air Leakage ACH NIOSH recommended ceiling exposure limit = 200 ppm. This level should not be exceeded at any time in the workplace 0.04% (400 ppm) 0.08 % (800 ppm) 0.16% (1600 ppm) 0.32% (3200 ppm) 0.64% (6400 ppm) 1.28% (12,800 ppm) Frontal headache w/in 2 3 hours; life threatening after 3 hours. Dizziness, nausea and convulsions w/in 45 minutes; insensible w/in 2 hours; death w/in 2 3 hours. Headache, dizziness and nausea w/in 20 minutes; death w/in 1 hour. Headache, dizziness and nausea w/in 5 10 minutes; death w/in 30 minutes. Headache, dizziness and nausea w/in 1 2 minutes; death w/in minutes. Death w/in 1 3 minutes. COppm Ambient Indoor Air NIOSH Time Weighted Average for 10 hour workday 0.5 ACH during 40 hour workweek, 35 ppm OSHA standard, 50 ppm 1.0 ACH 1.5 ACH 2.0 ACH U.S. Consumer Products Safety Commission standard,15 ppm Time, hours 3 4 Equipment Needed for Testing Combustion Appliances Digital CO/Oxygen combustion analyzer Combustion gas detector CO Hot Pot (gas ranges) U-Tube manometer for gas pressure Digital or analog manometer for checking draft Various hand tools Calculator Gas Match or other lighting device Flashlight Combustion Sources of Carbon Monoxide 5 6

2 Sources of Carbon Monoxide Internal combustion engines Unvented appliances and fires Vented appliances Sources of Carbon Monoxide Internal combustion engines Unvented appliances and fires Vented appliances 7 8 Sources of Carbon Monoxide Internal combustion engines Automobiles Usually more serious during engine warm up. Negative pressure can pull CO into house (this tends to be most common with ducted HVAC distribution). Be especially careful with tuck-under and attached garages. Generators This is usually only a problem during emergency conditions. Sources of Carbon Monoxide Internal combustion engines Unvented appliances and fires Vented appliances 9 10 Sources of Carbon Monoxide A Significant Source of CO Unvented appliances and fires Space heaters Gas ranges/ovens Electric ovens Outdoor grills Cigarettes Incense burned over charcoal Kerosene lamps, candles, etc

3 Sources of Carbon Monoxide Internal combustion engines Unvented appliances and fires Vented appliances Sources of Carbon Monoxide Vented appliances Furnace heat exchanger failure Draft failure Blocked, restricted or cold vent system Draft reversal Exhaust appliances Other combustion appliances Leaking ductwork Return leaks to the Combustion Appliance Zone (CAZ) Supply leaks to the outdoors How CO is Produced in Combustion Appliances Carbon Monoxide from Combustion In all combustion sources of CO 1. the ratio of carbonaceous fuel to oxygen is either too high to permit the complete formation of CO 2, or 2. the temperature is too low to permit oxidation to occur. Source: An Introduction to Air Chemistry, Samuel Butcher and Robert Charlson, Academic Press, 1972, pp Carbon Monoxide from Combustion In all combustion sources of CO 1. the ratio of carbonaceous fuel to oxygen is either too high to permit the complete formation of CO 2... Caused by a. Too much fuel for amount of oxygen b. Not enough oxygen for amount of fuel 1) Improper air adjustment 2) Wrong fuel for setup (LP for nat. gas setup) 3) Dirty or improperly aligned burners Carbon Monoxide from Combustion In all combustion sources of CO the temperature is too low to permit oxidation to occur. Caused by a. Quenching by impingement 1) Pots and pans, no grate, improper grate spacing b. Quenching by too much airflow 1) Strong draft, air blowing across burner 17 18

4 Two Methods of Measuring Carbon Monoxide: As-Measured & Air-Free CO as-measured vs. CO air-free ANSI Standards usually state air-free values. CO as-measured is percentage or concentration. CO air-free is emission rate, adjusted (normalized) for zero excess-air conditions. Indoor ambient air CO must always be read asmeasured CO as-measured Measured as percentage or ppm: 0.08% = 800ppm Measured with, e.g., Monoxor II or Testo 325. Diluted to varying degrees by excess air. Not a rate of emission, but a concentration. Protocol requires for measuring range top burners. Indoor ambient air CO must always be read asmeasured. 21 CO air-free Diluted CO as-measured sample is adjusted to simulate oxygen-free (air-free) conditions, that is, conditions with zero excess air (excess oxygen). This normalized CO air-free reading is still expressed as a ppm value, but it is actually an emission rate. ANSI Standards are usually expressed in air-free values. Read with, e.g., Testo 300 or Bacharach PCA. 22 CO as-measured vs. CO air-free From CO as-measured to CO air-free CO air free 20.9 = x CO O ppm Natural gas & propane CO air free 12.2 = x CO CO 2 ppm Natural gas Oven A As-Measured CO = 18 ppm Oxygen = 20% Air-Free CO = 400 ppm Oven B As-Measured CO = 209 ppm Oxygen = 10% Air-Free CO = 400 ppm CO air free 14 = x CO CO 2 ppm Propane 23 24

5 100 COppm to COAFppm Multiplier Ranges Combustion Basics Multiplier 10 Range-Top Burner Gas Oven Vented Appliance Percent Oxygen (Excess Air) in Combustion Gas Symbol L.E.L U.E.L Btu/cf Specific Gravity Ignition Temp. o F Properties of Gases Natural CH 4 5% 15% Propane C 3 H 8 2.4% 9.8% Butane C 4 H % 7.3% Primary Air Combustion Air Air mixed with fuel before combustion. Secondary Air Additional air required for combustion during combustion process. Excess Air Air (oxygen) in excess of ideal amount Bunsen Burner Gas Flame Analysis % BY VOLUME OF DRY FLUE GAS % CARBON DIOXIDE % CARBON MONOXIDE % OXYGEN % THEORETICAL AIR FUEL RICH SIDE EXCESS AIR SIDE IDEAL MIX OF AIR AND FUEL % CARBON DIOXIDE Theoretical Combustion Air Curves Actual percentage values vary for fuel being measured 29 30

6 Quality of Flames Combustion Basics Using Gas Range Operation as a Model Standing-pilot range Accessible top burners Standing pilot Pilot light Pressure regulator & burner Pressure regulator 35 36

7 Pressure regulator Burner removal Burner removed Adjustable orifice Orifice - adjustable - gas pressure check Range Top Burner Schematic Adjustable orifice Orifice 41 42

8 Adjustable Orifices Adjustable orifice Orifice adjustment Tighten down for LP Burner grate gone bad Cracked range top Zeroclearance grate Surface Burner Grate Height Pot cools flame by impingement, but inhibits draft, reducing quenching by airflow. Net effect on CO...? 47 48

9 Oven with vent outlet Oven vent outlet Oven bottom vents Oven burner w/o oven bottom Oven pilot Oven burner lit American National Standard Institute (ANSI) Standards for Manufacturers ANSI Standards for CO - Manufacturers Household Cooking Gas Appliances (Z21.1) 800 ppm air-free after all burners operate for five minutes (range top burners have 5 pounds of water on each). Storage Water Heaters, 75,000 Btuh or less (Z ). 400 ppm air-free for natural and induced draft and for power burners. Unvented Room Heaters (Z ). 200 ppm air-free. Gas-Fired Low-Pressure Steam and Hot Water Boilers (Z21.13). 400 ppm air-free. Gas-Fired Central Furnaces, except Direct-Vent (Z21.47). 400 ppm air-free with outlet of drafthood blocked Decorative Gas Appliances for Installation in Solid-Fuel Burning Fireplaces (Z21.60). 25 ppm as-measured or 400 ppm air-free. 53 Carbon Monoxide Problems and Solutions 54

10 Gas Atmospheric Furnace Gas Pressure Make sure pressure is set for 3 to 5 W.C. for natural gas or 9 to 11 for propane. If conversion from natural gas to propane was done improperly, CO is a likely by-product Orifice Size Dirty, damaged, or improperly sized orifice can result in CO. Clean dirty orifices. Replace damaged orifices (over tightening an adjustable orifice can damage it by distorting the shape of the needle). Replace orifices that are sized incorrectly. Adjustable orifice Range Top Burner Schematic Primary-Air Shutter Adjustment If it is open or closed too far, CO can result. To adjust, open all the way, then slowly close until you see a well-defined blue flame that stays just above the burner ports

11 Secondary-Air Supply Make sure nothing is restricting secondary airflow to the burners. This is an unusual cause of carbon monoxide. Burner Air Tube Condition Dirty air tubes can block or misdirect airgas flow. Check and clean all burner air tubes. Spider webs, dust, or other obstructions can lead to burner problems and CO production Range Top Burner Schematic Gas Injection into Air Tube Orifice must inject air-gas mixture straight into the burner mixing tube. If the gas is injected at an angle, the amount of primary air will be reduced (less negative pressure) and CO will result. Problems can be caused by damaged orifice, orifice spud, or Venturi section of tube Oven burner schematic Oven burner schematic Problem... Skewed gas flow due to over tightening of adjustable orifice 65 66

12 Burner Ports Clogged or dirty burner ports can result in CO emissions. Clean each dirty port. Over-Gassed Burners If flame appears to be too large or noisy, reduce the gas flow to the burner by Properly down sizing the orifice. Reducing the gas pressure (propane to natural gas conversion). In gas oven, over gassed burner might extend flames beyond the edges of the flame spreader. If this has happened, check for warped flame spreader plates Gas Oven Flame Spreader Plate Warpage A warped spreader plate can increase CO emissions. If warped, replace. Furnace Heat Exchanger Damage CO might result from blocked heat exchanger of from holes or cracks in heat exchanger. Carefully inspect heat exchanger and watch flame carefully when blower of air handler turns on Draft Hood or Draft Diverter If the hood or diverter have been damaged or altered so that airflow is restricted, CO can be a result. If needed, repair or replace hood or diverter. Venting Blockage, Restriction or Reversal If the vent system is blocked, restricted or suffers from reversal, CO often results. Always check for these potential problems with worst-case draft test procedures

13 Over-fire draft read here, just above burner Oil burner Oil-Fired Boiler Barometric damper Breech draft, CO, and efficiency are taken here Service switch Circulator pumps Oil Appliance CO Problems/Solutions Off-Center Fires Nozzle spray that is off center in firing chamber can cause impingement and resulting CO emissions because of incomplete combustion. Correct by replacing nozzle, tube, or bracket Oil Appliance CO Problems/Solutions Narrow or Broad Fires Too narrow or broad nozzle spray angle can cause flame impingement and resulting CO emissions. To correct, change nozzle size and/or pattern. Oil Appliance CO Problems/Solutions Burner Air Supply If the air supply on an oil power burner is open or closed too far, CO can result. Adjust the air supply correctly within the CO 2 curve knee Oil Appliance CO Problems/Solutions Furnace Heat Exchanger Damage CO might result from blocked heat exchanger of from holes or cracks in heat exchanger. Carefully inspect heat exchanger and watch flame carefully when blower of air handler turns on. Oil Appliance CO Problems/Solutions Improper Oil Pressure Oil pressure alters droplet size and spray pattern. Pressures that are too low might cause incomplete combustion and CO (typical oil pressure is 100 psi)

14 Oil Appliance CO Problems/Solutions Venting Blockage, Restriction or Reversal If the vent system is blocked, restricted or suffers from reversal, CO often results. Always check for these potential problems with worst-case draft test procedures. Oil Appliance CO Problems/Solutions Cold Oil Outdoor oil tanks can cause burner problems (slow ignition, collapsing sprays, noisy fires, and possible CO) due to high viscosity oil. Install indoor oil tank, use lighter grade oil, or increase oil pressure Solid Fuel Appliance 81 Solid Fuel Appliance CO Problems/Solutions Wood and Coal Combustion Solid fuel burners always produce carbon monoxide. Make sure products of combustion do not vent into the occupied area of a building. Even when doing blower door test, try to test for CO emissions around a solid-fuel burning appliance. 82 Overview of Gas Ranges Standing-pilot range 83 84

15 Older range with vented oven and side heater Enclosed Controls make adjustment more difficult Enclosed Controls Enclosed controls area 87 Sealed burners, convection oven 88 High-end range with sealed range top burners, radiant broil burner, and convection oven. Radiant broiler burner, convection oven 89 90

16 JENN-AIR range, gas burners JENN-AIR electric convection oven Overview of Heating Systems Keeping Warm in Maine! Click 4 NFPA 54 Vent Categories Non-condensing I Negative pressure Atmospheric equipment Category I fan-assisted equipment AFUE usually from 65% - 83% NFPA 54 written for this category Non-airtight vent connector No or little equipment in this category Condensing Negative pressure Negative Pressure II IV III - Static Pressure in Vent + Higher Temperature Non-condensing Positive pressure AFUE usually from 83% - 87% Airtight vent connector Fan assisted draft 275 o F Condensing Positive pressure AFUE usually 90%+ Airtight vent connector Lower Temperature Fan assisted draft Must be corrosion resistant Positive Pressure 95 Gas Atmospheric Furnace 96

17 Category I Gas Atmospheric Furnace Gas Atmospheric Boiler Testing Boiler efficiency, CO, and draft testing Efficiency and CO must be tested in gases before dilution air enters vent system Fuel type? Distribution type? Where do you test efficiency and CO? Fuel type? Distribution type? Click 1 99 Click Gas Atmospheric Boiler CO Emissions Test Electromechanical vent damper Wrong! 101 Click 1 102

18 Atmospheric Boiler Box Diverter Spill switch Gas Space Heater, Unvented Bottom of draft diverter Radiating ceramic area Category I Fan Assisted Furnace Test for efficiency and CO here Not Not tested tested in in the the Wisconsin Wisconsin program program because because of of the the draftprovinproving switch. draft- switch. 105 CO and efficiency measurement Exhaust vent Condensate drain Category IV Gas Furnace Supply-air vent Gas supply Positive pressure in vent connector, draftproving switch and a condensate drain make efficiency and CO testing questionable. Direct-vent unit 106 Oil-Fired Boiler Oil Boiler with Four Zones Barometric damper Over-fire draft read here, just above burner Oil burner Breech draft, CO, and efficiency are taken here Service switch Circulator pumps

19 Oil-Fired Boiler Any signs of problems here? Oil Boiler w/o Service for 2.5 Years Clogged heat exchanger at top Underside of heat exchanger from firebox Solid-Fuel Appliance No efficiency test No draft test CO test? Overview of Water Heaters Anatomy of Storage Gas Water Heater Gas Water Heaters These water heater types should be tested for CO Induced Draft Natural Draft

20 Direct Vent Gas Water Heaters Most programs would not test these water heater types for carbon monoxide. Forced Draft Gas Water Heater Control Temperature control Set control to On for draft and CO tests; set to Pilot for blower door test Water Heater CO Emissions Tests 2 Probe 3 Gas Atmospheric Water Heater How should this unit be tested for: 1. Draft? 2. CO? Carbon Monoxide Action Levels Carbon Monoxide Action Levels Gas furnace or boiler? Gas storage water heater? Gas range Range top burner? Oven bake burner? Gas space heater (vented and vent-free)? Oil furnace or boiler?

21 Getting Into CO Measurement Suggested Checklist for Analysts Check gas appliances. Visual inspection. Pressure test (manifold pressure). Gas flow check (clock the meter). Heat exchanger test (furnaces only). CO emissions in combustion gases and indoor air. Continued Suggested Checklist for Analysts Check oil appliances. Visual inspection. Heat exchanger test (furnaces only). CO emissions in combustion gases and indoor air. Inspect venting systems. Perform worst-case draft test. Continued... Suggested Checklist for Analysts Check for adequate combustion air. Check for other sources of CO. Automobile exhaust, etc. Check for related code violations. Diagnose the house as a system. Recommend necessary corrections. Recommend UL-listed CO alarm Minimizing Analysts Liability Calibrate equipment according to manufacturer s specs., usually every six months. Receive proper training. Discuss with your liability insurance representative. Record findings on each job. Install or recommend UL-approved CO alarm. Administer regimented client education. CO alarm use and maintenance. Don t use range as space heater. Etc. 125 Worst-Case Draft Test Objective of test: To determine if appliance(s) will draft properly under worst-case conditions. To protect the occupants from the hazards of draft reversal. 126

22 Worst-Case Draft Test Objective of test setup and procedure: To create the highest negative pressure in the building that might occur under normal use. To determine if combustion appliance(s) are drafting properly during the worst-case condition. To determine if combustion appliances are emitting unacceptable levels of CO during the worst-case condition. Worst-Case Draft Test Step-by-step worst-case draft test setup and procedure. Please refer to detailed handout sheet Worst-Case Draft Test Possible reasons for worst-case test failure: Negative pressure from exhaust appliances Very tight house Negative pressure in CAZ from duct system Chimney & vent system problems Insufficient combustion supply air volume Other combustion appliances Reasons for Worst-Case Test Failure Negative pressure from exhaust appliances Whole-house exhaust fan, summertime use Fireplace operation Jenn Air type range exhaust fan Many smaller fans that add up to large CFM total Exhaust appliance or fan in CAZ Clothes dryer Work room exhaust fan Reasons for Worst-Case Test Failure Very tight house For Category I appliances, such as water heaters End of vent system is at top of chimney Beginning of vent system is envelope of house Reasons for Worst-Case Test Failure Negative pressure in CAZ from duct system Return grilles in CAZ Return side leaks in CAZ Supply leaks to outdoors

23 Impact of an Air Handler What happens to air leakage as a result of the closed bedroom door? What if a return is installed in the basement return trunk? What if the supply trunk leaks to the outdoors? Reasons for Worst-Case Test Failure Chimney & vent system problems Chimney height Total height Improper termination above roof Heat loss from venting system (slow priming) Restrictions or blockage Leaky vent system (ambient air leaking into vent) Vent or chimney improperly sized Improper common venting Reasons for Worst-Case Test Failure Insufficient combustion supply air volume Confined space rule from NFPA 54 & 211 Must provide at least 50 ft 3 of connected indoor volume for each 1000 Btu/hr of total appliance input rate. If less than 50 ft 3 per 1000 Btu/hr, must correct by communicating with other indoor space or providing combustion air from outdoors Use 1/20 rule to quickly calculate. Example: 100,000 Btu/hr divided by 20 = 5,000 ft 3 of indoor volume. 135 Reasons for Worst-Case Test Failure Other Combustion Appliances Atmospherically vented combustion appliances Mechanically vented combustion appliances 136