February 1979 EPA-600/8-79-005
GUIDELINES FOR ADJUSTMENT OF ATMOSPHERIC GAS BURNERS
FOR RESIDENTIAL AND COMMERCIAL SPACE HEATING
AND WATER HEATING
Adjustment Procedures to Minimize Air Pollution
and to Achieve Efficient Use of Gas
Service guide for skilled service
technicians in adjustment of gas
burners.
Training guide for advanced
burner service courses.
Supplement to manufacturers'
service instructions.
Incorporates suggestions of reviewers
from industry, including:
Gas Appliance Manufacturers Association
American Gas Association
Independent Service Organizations
Air Pollution Control Association
SEPA
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, N. C. 27711
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports- >
9. Miscellaneous Reports
This report has been assigned to the SPECIAL REPORTS series. This
series is reserved for reports which are intended to meet the
technical information needs of specifically targeted user
groups. Reports in this series include Problem Oriented
Reports, Research Application Reports, and Executive
Summary Documents. Typical of these reports include state-
of-the-art analyses, technology assessments, reports on the
results of major research and development efforts, design
manuals, and user manuals.
EPA REVIEW NOTICE
This report has been reviewed by the U.S. Environmental
Protection Agency, and approved for publication. Mention of
frade names or commercial products does not constitute
endorsement or recommendation for use.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
-------
TABLE OF CONTENTS
Page
PURPOSE OF THESE GUIDELINES 1
Scope 1
RECOMMENDED ADJUSTMENT PROCEDURES FOR GAS BURNERS 3
Preparation Steps 3
Combustion Adjustment Steps 7
Combustion Diagnosis Steps 11
Final Checks 13
APPENDIX: BACKGROUND INFORMATION
A. Pollutants of Main Concern 18
B. Field-Type Instruments and Significance of Measurements 21
C. Typical Emission Characteristics of Residential Gas Burners 25
D. References & Bibliography 28
ACKNOWLEDGMENTS
These Guidelines were prepared by D. W. DeWerth and R. L. Himmel
of the American Gas Association Laboratories and D. W. Locklin of Battelle-
Columbus under contract from the U.S. Environmental Protection Agency
(Contract 68-02-2653). R. E. Hall was Project Officer for the EPA. Sugges-
tions from many industry reviewers have been included — representing the
gas industry, the appliance manufacturing industry, and the appliance servicing
industry. These significant contributions are acknowledged.
-------
The contents of this manual are offered as guidance. The United States
Government, its employees, and its research contractors, Battelle-Columbus
and A.G.A. Laboratories, do not assume responsibility or liability for con-
sequences arising from the implementation or failure to implement the
guidance contained herein.
-------
GUIDELINES FOR ADJUSTMENT OF ATMOSPHERIC GAS BURNERS
FOR RESIDENTIAL AND COMMERCIAL SPACE HEATING
AND WATER HEATING
PURPOSE OF THESE GUIDELINES
The most important reason for adjusting a gas burner is to provide safe reliable opera-
tion. A second important reason is to provide for efficient fuel utilization, which helps to
minimize operating costs. Effective means of meeting these goals include: (1) keeping the
burner and pilot orifices, and the burner ports, free of dirt and lint; (2) properly adjusting the
burner aeration; and (3) maintaining an acceptable CO level.
Recently, minimizing air pollution has become an additional important reason for
proper adjustments. Of course, burner adjustments for this purpose must also meet the
former objectives. Fortunately, adjusting for low air-pollutant emissions is consistent with
adjusting for reliable performance and efficient operation.
These Guidelines have been prepared for use by service managers in training of tech-
nicians and by skilled technicians in their gas-burner service work.* By following the step-by-
step procedures outlined in these Guidelines, the skilled gas-burner service technician will be able
to adjust residential and commercial heating equipment and water heaters to minimize air pollu-
tion, attain optimum efficiency, and provide safe reliable operation.
Scope
These procedures are intended for adjustment of atmospheric-type gas burners for
residential and commercial space heating and water heating systems. The procedures are sup-
plemental to manufacturers' installation instructions, the National Fuel Gas Code2, and other
installation codes or handbooks3-4-5.** They apply to burners fired with either natural gas or
liquefied petroleum (LP) gases.***
'Similar Guidelines for oil-fired space-heating equipment are cited in Reference 1.
"Attention is called to the series of American Gas Association publications on fundamentals of appliance servicing, listed in
the Bibliography.
"Information in these Guidelines pertaining specifically to LP gases is in italics.
-------
The adjustment procedures apply to atmospheric-type gas burners of the single-port and
multiported types such as ribbon, slotted-port, and drilled-port burners (see Figure 1) as used in
in manufacturer-designed burner/furnace units, burner/boiler units, or complete water heaters.
Although the principles apply to conversion-type gas burners, these burners require special ad-
justment procedures. For conversion burners, the burner manufacturer's instructions should be
followed.6
Retrofit modifications, such as those under study in the gas industry's Space Heating
Efficiency Improvement Program (SHEIP) for improving seasonal efficiency, are not included
in these Guidelines. Inquiries can be directed to the American Gas Association, 1515 Wilson
Boulevard, Arlington, Virginia 22209.
1. Single Port
2. Ribbon
3. Slotted Port
4. Drilled Port
Figure 1. Types of gas burners frequently used in space-heating and water-heating appliances.
-------
RECOMMENDED ADJUSTMENT PROCEDURES FOR GAS BURNERS
The following steps are emphasized from the viewpoint of minimizing air-pollutant emis-
sions and maintaining peak efficiency and safe reliable operation. Fourteen steps are described;
they cover preparation steps, combustion adjustment steps, diagnosis, and final checks.
PREPARATION STEPS
1. Clean Burner The most common malfunction attributed to main burners and
and Pilot pilots is caused by excess dirt, lint, or other debris. Blockage
of primary air openings can cause the burner to operate with in-
complete combustion and can lead to soot and excess CO formation. Orifice block-
age also can cause burner ignition problems. See Figure 2 for sketch and description
of primary and secondary air.
WARNING: Shut off all gas to appliance. Valve should be "tagged" to prevent its
being inadvertently opened while system is being worked on. Remove burners and
clean the burner ports, burner and pilot orifices, and primary air openings. Ports
can be cleaned by passing a wooden dowel through the ports or by running water
into the ports. If grease is present, wash with detergent. Make sure the burners are
thoroughly dry before reinstalling. Shake out debris through burner mixing tube.
Replace burners. Be sure that they are properly installed and that the orifice is
centered within the mixing tube.
Before reinstalling burner, visually inspect combustion chambers, furnace heat ex-
changers, and appliance flue ways to determine if there are any leaks. For conversion-
burner installations, leaks between sections of many cast-iron furnaces can be re-
paired with furnace cement. If there are cracks or holes in steel heat exchangers,
the heat exchanger must be replaced.
Make preliminary adjustment of the primary air shutters, if any, by following
Step 6. Turn on the gas and relight the appliance, following lighting instructions
on the appliance.
-------
MIXING TUBE
PRIMARY AIR — aspirotes into burner
air openings and mixes
with gas
FUEL GAS
T ^SECONDARY
J AIR — enters thru combustion
chamber openings provided
and surrounds flame
Figure 2. Definitions for burner air/fuel mixing.
2. Adjust Manifold Adjust pressure regulators to deliver gas to burners at the proper
Pressure pressure.* If the appliance rating plate specifies a manifold
pressure, adjust to that pressure. If not specified, set pressure for
natural gas appliances with regulators at 3.5 inches water column.**
For LP gases, set at 11 inches water column. Regulator may be at tanks. (In some
cases, it may not be possible to adjust the pressure.)
3. Adjust Pilot The pilot flame should be soft blue in color. A propane pilot
flame may have a slightly yellow tip. The flame should sur-
round the tip of the thermocouple or flame sensor. If there is a separate ignition
port, the flame should reach the main burners. There may be an adjusting screw for
pilot gas on the main gas valve or pilot shut-off valve.
•Measured at manifold pressure tap, with main burners operating.
•Although it is EPA policy to use metric units in its publications, nonmetric units are used here to reflect standard field
practice.
-------
4. Adjust Main a. Using a gas meter. After the unit has been operating at
Burner Input least 10 minutes, check the gas input rate by timing one
revolution of the gas meter test dial, making sure that no
other gas burning appliance is operating. Note the number of seconds for one
full revolution, and calculate input as follows:
,nput. etu/hr = cu ft per rev°lution x 3600 sec/hr x HV
sec per revolution
where HV = gross heating value of gas, Btu/cu ft.
Obtain the heating value from the local gas company or the LP gas supplier.
b. Not using a gas meter. Measure the orifice size using a
drill index and determine the input using Table 1 for utility gas or Table 2 for LP
gases.
If necessary, adjust the gas input to within ±5 percent of the value noted on the
manufacturer's rating plate, as follows. To adjust the input rate of an appliance
with an adjustable pressure regulator, first remove the cap covering the pressure
regulator adjustment. Turn the adjustment clockwise to increase manifold pressure
and input rate. Caution: Do not change manifold pressure more than ±0.3 inch
water column. To make larger input changes, resize the orifice.
If the appliance is not equipped with an adjustable pressure regulator, replace orifice
with resized orifice using Table 1 for utility gas or Table 2 for LP gases.
Check Allow the burner to cool and check operation of ignition
Ignition system by cycling several times while the burner is cold to
ensure prompt ignition on cold start. Then operate the
burner at least 10 minutes (or until thoroughly hot) and repeat several ignition
cycle checks to ensure prompt ignition on hot start. (Wait approximately
5 seconds between cycles.)
-------
TABLE 1. ORIFICE SIZING FOR DIFFERENT GAS PRESSURES - NATURAL GAS2
Values in table represent flow of gas. cubic feet per hour at sea level.
Specific Gravity = 0.60
Orifice Coefficient = 0.90
For utility gases of another specific gravity, select multiplier from Table 2-a.
0)
Oifffc*
or Drill
Stm
80
79
78
77
76
75
74
73
72
71
70
69
68
67
66
65
64
63
62
61
60
59
58
57
56
55
54
53
52
51
50
49
48
47
46
45
44
43
42
41
•^AABM^Bt
-------
COMBUSTION ADJUSTMENT STEPS
6. Adjust Burner To adjust primary air, allow at least 10 minutes for the burners
to heat up; close primary air shutter until yellow flame tips
appear, then open air shutter until all yellow completely disappears. The flame should
be clear blue.
LP gas burner flames and large single-port natural-gas burner flames may have slightly
yellow tips; these are satisfactory if no soot forms and there is no flame impinging
on the heat exchanger. Single-port burner flames may have an orange quality; these
are satisfactory. Any burner flame may have an orange quality, caused by dust;
these, too, are satisfactory.
The primary air setting for matched units has a relatively narrow range of adjustment.
(Some burners, particularly on water heaters, do not have air shutters.)
Too much primary air causes noisy hard flames which could result in flame lifting,
flashback, and emission of unburned hydrocarbons. Too little primary air
causes yellow flames which could produce high CO and soot emissions. Fig-
ure 3 illustrates the desired adjustment region for a typical gas burner, consider-
ing variables of input rate and primary air.
Secondary air is controlled by the burner and appliance design; they should not
need modification. Conversion burners, however, may need secondary air adjust-
ment; the manufacturer's instructions should be followed.6
7. Sampling Flue gas samples for analysis* should be taken from inside
the appliance approximately 1 inch ahead of the draft hood
inlet. (See Figure 4.) If several flue outlets are provided, individual samples
should be taken from each, or a partial sample should be taken from each outlet
to make up the full sample. For example, if there are four outlets, 25 percent
of the sample should be taken by inserting and traversing the probe in each
outlet.
"CO2 is usually measured with a wet-chemical analyzer. CO is usually identified by using a color-sensitive chemical-indicator tube.
(See Appendix. Section B, for instruments and their use.)
-------
TABLE 2. ORIFICE SIZING FOR DIFFERENT GAS PRESSURES - LP GASES2
Values in table represent flow of gas. cubic feet per hour at sea level.
TABLE 2. (Continued)
00
Ssw per Cubic Foot'
Soecific Gravity
tenure at Orifice, Inchei Water
O-fice Coefficient
Column
Propane Butane
2,500 3,175
1.53 2.00
11 11
0.9 0.9
For altitudes above 2,000 feet, firit telect the
equivalent orifice lize at tea
Orifice or
Drill the
.008
.009
.010
.011
.012
80
79
78
77
76
75
74
73
72
71
70
69
68
67
66
65
64
63
62
il
60
55
SB
£7
56
55
54
53
52
51
50
£9
*B
A7
*4
A;
level from Table 1-C4.
Propane
500
641
791
951
1.130
1,430
1,655
2.015
2.545
3.140
3.465
3.985
4,525
4.920
5,320
6.180
6,710
7.560
8,040
8.550
9^30
10.200
10.800
11,360
11.930
12.570
13.220
13.840
14.550
16,990
21,200
23.850
27.790
31.730
35430
38.500
41.850
45,450
48.400
51.500
52,900
Butane or
Butane Propane
Mixture*
554
709
875
1.053
1.250
1,590
1,830
2,230
2,815
3/480
3340
4/410
5.010
5/450
5,900
6,830
7,430
8,370
8,910
9,470
10,670
11,300
11,900
12,530
13,280
13,840
14.630
15.300
16,090
18.790
23.510
26.300
30430
35,100
39,400
42,800
45,350
50.300
53.550
57,000
58,500
Orifice or
Drill Siie
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
Prepane
58,050
62,200
68,700
72,450
75,400
77,850
81.000
85.000
89.200
95.000
97.000
101,000
105.800
113,200
129.700
145,700
154.700
163.100
169.900
175,500
181,700
186.800
193,500
198,600
203,700
217,100
225.600
Butane or
Butane-Propane
Mixture!
64,350
69,000
76,200
80,200
83.500
66.200
89.550
94.000
98.800
105.300
107,200
111,900
117,000
125/400
143,600
163/400
171,600
180,000
187,900
194,600
201,600
206,400
214,500
220,200
225,000
241.900
249,800
TABLE 2-a. MULTIPLIERS FOR UTILITY GASES OF
ANOTHER SPECIFIC GRAVITY
Specific Gravity
0.45
0.50
0.55
0.60
0.65
0.70
0.75
0.80
0.85
0.90
Multiplier Specific Gravity
1.155 0.95
1.095 1.00
1.045 1.05
1.000
0.961
0.926
0.894
0.866
0.840
.10
.15
.20
.25
.30
.35
0.817 1.40
Multiplier
0.795
0.775
0.756
0.739
0.722
0.707
0.693
0.679
0.667
0.655
-------
4J
-------
LOCATION FOR
FLUE SAMPLING
1/4" Die.
Hole
Vent
^or
Chimney
==> . _ Draft
Hood
n-1
Typical Boiler
Gas
Burner
Relief Opening for
"Dilution Air
-j mtrm
-^=c 1
a. Vertical flue outlet
Typical
Furnace"
urner
LOCATION FOR
FLUE SAMPLING
Draft
I Dilutii
Dilution
Air
Vent
• or
Chimney
b. Horizontal flue outlet
Figure 4. Location for sampling flue outlet of gas-fired appliances.
10
-------
Typical CO values for properly adjusted appliances, operating at rated input, range
from 25 to 100 ppm (0.0025 to 0.010 percent); however, values as high as
300 ppm may be encountered in the flue-gas sample, since this is equivalent to
the maximum value of 400 ppm (air-free) at a C02 level of 8.5 percent, allowed
by the ANSI standards2. See Step 10 for proper adjustment methods.
COMBUSTION DIAGNOSIS STEPS
10. Check A well-adjusted gas burner should be capable of operating
Performance with a CO level not greater than 100 ppm in the flue gases
with a CO2 level between 6.0 and 8.5 percent for natural
gas and 7.0 to 10.0 percent for LP gases. If these values cannot be reached,
check the following:
a. Too low a CO2 level could mean circulating air leakage into the com-
bustion air due to a faulty seal around the secondary air opening of
the unit. Seal such leaks by tightening the screws or bolts or replac-
ing the sealing gasket.
Too low a C02 level could be caused by a defect in the furnace heat
exchanger. If the CO2 levels obtained with and without the blower
operating differ by more than 0.4 percent, make a repeat check of the
combustion chamber and heat exchanger; if a leaking heat exchanger
is found, repair or replace it.
b. If the CO2 and/or CO levels are too high, this could mean an improper
combustion air supply. Spillage from the appliance draft hood can be
detected by placing a lighted match at the edge of the hood relief open-
ing. If the match flame is not drawn into the hood, spillage is occurring.
A negative pressure in the appliance room also can indicate inadequate
air supply. Spillage can result from a blocked chimney or vent.
If inadequate air supply is suspected, refer to Section 1.3.4 of the
National Fuel Gas Code ANSI Z223.1 or comparable provisions in
local codes for specific detailed recommendations for providing air for
combustion and ventilation.2 If this does not solve the problem, there
may be internal blockage.
11
-------
42
o
•o
o
o
o
o
I
0>
o
o
CM
O
o
60 40 20
0 20 40X60X80.
y//////
/ Proper
Adjustment^
/f Region /
o
o
20
16
12
8
4
NATURAL GAS
100
60 40 20 0 20 40 60 80 100
Deficiency of
Air, percent
Excess Comb. Air, percent
Desirable air adjustment
for best efficiency
approx. 10.0 percent C02
Limit of good practice
approx. 7.0 percent C02
Desirable air adjustment
for best efficiency
approx. 8.5 percent CO2
Limit of good practice
approx. 6.0 percent C02
Figure 5. Effect of fuel/air ratio on CO and CO2 concentration for
typical natural gas and LP gas burners, showing proper
adjustment region.
12
-------
11. Efficiency To determine the steady-state thermal efficiency of the
Checks furnace/burner or boiler/burner unit, follow this step. Mea-
sure the flue gas temperature, after at least 10 minutes of
operation, at the same point that the CO2 sample was taken. Determine the net
flue gas temperature by subtracting the room temperature from the flue gas tem-
perature reading. Using this net temperature value and the percent C02 (see
Step 8), determine the appliance flue loss from Figure 6 for natural gas or
Figure 7 for LP gases.1 The appliance thermal efficiency is equal to 100 — flue
loss. Use the values shown in Table 3 to determine if the unit is operating at a
satisfactory efficiency level. (See Appendix B.)
FINAL CHECKS
12. Ignition Check operation over several repeated cycles, at about
5 second intervals, to ensure prompt ignition.
13. Controls Check settings of all operating and limit controls before
leaving installation. For practical performance and good
efficiency for modern forced-warm-air systems, usual practice is to set the fan
control at 115-125°F ON and 90-100°F OFF. The water heater thermostat
should be set to WARM or 120°F; where the water heater serves a dishwasher,
settings up to 140°F may be needed. Higher settings reduce efficiency and
shorten life of the storage tank.
14. Regular An annual burner checkup is recommended, with at least a
Checkup visual inspection by a trained service technician, plus cleaning
as necessary. Furnace blowers and motors and boiler circu-
lating pumps should be lubricated before each heating season according to manu-
facturers' instructions. Furnace filters should be cleaned or replaced at least every
60 days during the heating season.
13
-------
FOR NATURAL GAS
\5^r
Example: 8.2 percent
22 percent flue loss '
(78 percent efficiency)
440 F net
Figure 6. Nomograph for determining flue loss and steady-state efficiency
from CO2 and flue-gas temperature — firing natural gas7.
Limited to use with natural gas as follows:
Heating value, gross: 970 — 1100 Btu/standard cubic foot
Specific gravity: 0.57 - 0.70
Ultimate CO2: 11.7 - 12.2 percent
14
-------
TABLE 3. TYPICAL INSTALLED STEADY-STATE THERMAL
EFFICIENCIES OF CONVENTIONAL GAS-FIRED
DOMESTIC AND COMMERCIAL FURNACES,
BOILERS. OR WATER HEATERS
Thermal Efficiency*8*, percent
System
Forced Air Heating
Gravity Heating
Hot Water or Steam Boiler
Hot Water Heater
Excellent
75 or more
70 or more
75 or more
72 or more
Acceptable
72-75
67-70
72-75
68-72
(a) Overall thermal efficiency = 100 — flue loss, percent, where flue loss is expressed as a
percent of the gas input (gross heating value) that is lost up the flue. This assumes that
any jacket loss is useful heat.
Experienced service technicians will observe that these principles and/or procedures are
essentially the same as recognized good practice. Adjustment of gas burners by these procedures
will help to ensure safe and reliable operation, to minimize emissions, and to provide efficient
use of fuel.
15
-------
FOR PROPANE HD-5 GASES
CO
u
vi
<
o
m
o
o
o
Uj UJ O
z o «v»
Q. UJ
° °- «
K . N
°- OT
o
x
° 8
UJ
3
O
<0
•I
K
U
a.
O
O
tr
E
UJ
a.
UJ
K
0)
(9
O
O
CM
O
O
10
O
O
o
o
m
c
o
<0
o
o
8-il
CO
o
o
ffl
Figure 7. Nomograph for determining flue loss and steady-state efficiency
from CO2 and flue-gas temperature — firing LP gases7.
Limited to use with LP propane gases as follows:
Heating value, gross: 2466 — 2542 Btu/standard cubic foot
Specific gravity: 1.522 — 1.574
Ultimate CC^: 13.7 - 13.8 percent
16
-------
APPENDIX: BACKGROUND INFORMATION
Information on the air-pollutant effects of residential burner adjustments has been
developed in recent investigations8'14. The findings of these investigations, combined with
good practice, are the basis for the Guidelines.
This Appendix contains additional background information:
A. Pollutants of Main Concern
B. Field-Type Instruments and Significance of Measurements
C. Typical Emission Characteristics of Residential Gas Burners
D. References/Bibliography
17
-------
A. POLLUTANTS OF MAIN CONCERN
Pollutants and Their Measurement
Air pollutants of main concern for the purposes of these Guidelines can be divided into
two broad classes, depending upon how much the service technician can control them by
adjustment:
Class 1. Pollutants that may result from incomplete combustion and are
generally strongly affected by burner adjustment:
- Carbon monoxide, CO
- Hydrocarbons, HC
- Aldehydes
- Particulates (smoke or soot).
Class 2. Pollutants only partially affected or unaffected by burner adjustment
(and not recommended as adjustment criteria):
— Nitrogen oxides: NO and N02 (usually considered together
and identified as NOX)
- Sulfur oxides: S02 and 803 (usually considered together
and identified as SOX).
The following comments describe each of the Class 1 pollutants from the viewpoints
of its definition, hazards associated with it, how it is detected or measured, and how its
emissions are affected by service adjustments. (The Class 2 pollutants are not discussed
further, because service adjustments have little or no control over them.)
Carbon Monoxide, CO
CO is a toxic gas formed by incomplete combustion. When gas burning equipment is
properly adjusted, the CO emission level is extremely low. When the low levels of CO emitted
18
-------
by properly operating residential gas-heating equipment are diluted in the atmosphere, CO is
not considered dangerous and is depleted with time in the atmosphere by being oxidized to
C02- With improper combustion, and if flue gases leak into living spaces, CO levels in living
spaces can be dangerous.
For field adjustment of gas-fired equipment by methods suggested in these Guidelines,
CO should be measured, using a color-sensitive tube or portable electrochemical device.
Yellow flames, smoke, and "smelly" combustion (as indicated by the presence of aldehydes),
indicate incomplete combustion. However, these are not always reliable indicators: if the
primary air adjustment is too far open, flame lifting could occur, and CO levels could increase
rapidly without smoke or odor.
Hydrocarbons, HC
Emissions of hydrocarbons, which consist of unburned or partially burned fuel, occur
when combustion is incomplete. Incomplete combustion can occur at very fuel-gas-rich
settings (because of a lack of air) or at very fuel-gas-lean conditions (because of lifting
flames).
Large amounts of unburned fuel gas emitted from an improperly operating installation
can be detected by odor. (An odorant is added to fuel gases for safety purposes.) At lower
levels of HC emissions, too low to be detected by smell, the emissions generally follow trends
of CO emissions; hence, CO measurements are usually good indicators of hydrocarbon emis-
sions. An exception may occur at extremely high primary air settings, where HC emissions
may be higher than normal, while CO readings may be low.
Although HC emissions are generally not toxic to the same extent as CO, they can
be accompanied by unpleasant odors and can contribute to photochemical smog in the atmo-
sphere. Extremely low levels of HC are emitted when gas-fired equipment is properly
adjusted.
For routine adjustment of residential gas burners, it is not necessary to measure HC
because stable burner flames adjusted to acceptable CO levels will emit essentially no HC.
Aldehydes
Aldehydes, especially formaldehyde, are formed when fuel gas combustion is in-
complete. The aldehyde smell is responsible for the strong penetrating odor generally asso-
ciated with incomplete combustion. During incomplete combustion, however, the level of
concentration of aldehydes is not as significant as the CO and HC which also are present.
19
-------
Participate and Smoke
Smoke consists mainly of tiny unburned particles of carbon and is an important in-
dicator of severe maladjustment of gas-burning equipment. It can block flue passages and
foul heat-transfer surfaces with soot. Fuel utilization efficiency is very poor and an unsafe
condition may exist if smoke is present.
If smoke is suspected, check for visible signs from the vent or chimney (or from the
draft hood of the appliance, using a flashlight). Low levels of smoke below the visible range
can be detected using a smoke tester commonly used in adjusting oil burners.15 Do not mis-
take condensed water vapor for smoke during cold weather.
A smoky condition should be remedied immediately. Shut down the unit and clean
the carbon formation completely from all surfaces including the heat exchanger, burners,
orifices, ignition system, and flue outlet. Check the complete venting system, and clean it
as necessary. Then readjust the burner to correct the problem.
20
-------
B. FIELD-TYPE INSTRUMENTS AND SIGNIFICANCE OF MEASUREMENTS
For the adjustment procedures outlined in these Guidelines, it is assumed that the gas
burner service technician is familiar with field-type instruments. Typical instruments include:
• Flue-gas analysis
- usually a simple wet-chemical absorbent-type CC>2 analyzer
- Orsat or similar device
• Flue-gas analysis (CO)
- usually color-sensitive chemical in tubes or
— portable electrochemical device
• Flue-gas temperature
- usually a continuous reading meter using thermocouples or
resistance thermometer sensor
- can be a dial-type thermometer or a liquid thermometer,
although accuracy may deteriorate
o Manifold pressure
- usually a water-type U-tube manometer.
Instruments, combining several of these functions in one device, are being introduced.*
The Significance of CC>2 Measurements
CO 2 readings are used to identify the amount of combustion air being supplied to the
burner, compared to the theoretical amount required for combustion. It is seldom possible
*One valid approach is to base adjustments on 02 readings, in which the 02 reading is a more reliable indicator of the ad-
justment relative to stoichiometric air than is a CO2 reading. 16
21
-------
to burn a fuel completely and cleanly unless air in excess of the theoretical amount is pro-
vided. The tabulation below illustrates the relationship between excess air supplied for com-
bustion and the CO2 concentration in the flue gas for residential gas burners operating on
natural or LP gases.
Air/Fuel Mixture
Settings
Theoretical or
"Chemically Correct"
resulting in ultimate C02
Excess Air Supply
(Percent Above
Theoretical)
Typical CC*2 in
Flue Gas. percent
Nat. Gas
12.0
LPCas
13.8
Comments on Combustion
Performance (Assuming
Satisfactory CO Levels)
Stoichiometric mixture
(Cannot be achieved for
reliable operation in
practice)
Typical for Residential
Gas Burners (including
conversion burners)
37
55
90
8.5
7.5
6.0
70.0
8.6
7.0
Excellent
Average
Lower lin
performance within proper
adjustment region
The efficiency of fuel utilization is lowest at the low levels of C02 (high excess air), because
the greater the amount of excess combustion air, the larger the amount of heat carried up the
stack.
The Significance of Fuel-Gas Temperature:
Its Effect on Efficiency
Temperature of gases at the flue outlet ahead of any dilution air (see Figure 4) is
significant in determining the effectiveness of fuel utilization because it (together with the
flue outlet CC>2 reading) is an indicator of the amount of heat lost up the stack.7 Temper-
ature must be measured at the same point as .the C02 sample is taken. The best way to
take this measurement is with a small bead (24 gauge) iron-constantan thermocouple and
suitable potentiometer, although currently available equipment of this type may be more
expensive than thermometers. An effort should be made to obtain a representative flue gas
temperature.
Net flue'outlet gas temperature* can be.considered abnormally high for air heating or
water heating units if it exceeds 480°F. A high temperature may indicate one or more of the
following conditions:
•Net flue gas temperature is the observed temperature minus room temperature.
22
-------
1. Excessive firing rate for available heat-exchanger surface of the
appliance.
2. Dirty or soot-covered heating surfaces.
3. Excessive sediment in bottom of water heater.
4. Deterioration of baffles in flue passageways.
5. Insufficient air or water flow over heat exchanger.
These points should be checked and remedied if temperatures are abnormally high.
Thermal efficiency of heating equipment is the percent of heat released from burning
the gas which is actually transferred to the circulating air or water that is used to heat the
dwelling (or, in the case of water heaters, to heat the stored water). Normally this efficiency
is determined under steady-state conditions; e.g., with continuous burner operation after allow-
ing the equipment to heat up for at least 10 minutes.
Thermal efficiency is equal to 100 percent minus the heat losses up the stack. These
stack losses are generally referred to as flue losses. Other losses can include appliance jacket
heat losses if these losses do not contribute to heating the dwelling. (The jacket losses
usually will only amount to 1 or 2 percent.)
Two measurements are needed to determine flue losses and, therefore, thermal
efficiency:
- Net flue gas temperature (average flue-gas temperature minus room
temperature).
- Percent C02 in the flue gas.
Figures 6 and 7 show the combined effects of these two factors on flue losses:
Figure 6 for natural gas, and Figure 7 for LPgas. These flue-loss charts, based on steady-state
operation, .apply only for the specific fuel gases indicated. To use the nomographs, place a
straight edge on the chart with one edge crossing the CC>2 in flue gases scale at the observed
level and the flue-gas temperature — room temperature scale at the observed net flue-gas
temperature. Read the flue loss at the point where the straight edge crosses the middle
(flue loss) scale.
In the example shown in Figure 6 (for natural gas), the flue loss is 22 percent for an
observed 8.2 percent CO2 in the flue gas and a net flue-gas temperature of 440° F.
Thermal efficiency is 100 percent minus the 22 percent flue loss; or 78 percent.
23
-------
Seasonal Efficiency and Its
Potential for Improvement
Seasonal thermal efficiency is less than the continuous or steady-state thermal
efficiency calculated from Figures 6 and 7 because the efficiency is lowered during cyclic
operation by additional losses up the stack from the unit during OFF periods.17 Seasonal
efficiency will be highest for units that:
1. Have high overall thermal efficiency during continuous operation.
2. Have firing rates matched to the design load. (Overfiring results in
excessively long shutdown periods.)
3. Have vents properly sized for burner input.
4. Have Intermittent Ignition Devices (IID's) instead of continuously
burning pilots.
5. Have means to minimize the OFF cycle losses, other than I ID.
In 1976, the gas industry initiated a Space Heating Efficiency Improvement Program
(SHEIP) to accelerate the industry's continuing effort to help its customers increase the
seasonal efficiency of heating equipment. The purpose of SHEIP is to determine the energy
savings possible and to encourage implementation of useful and safe options for improving
the energy efficiency of residential central heating systems. Procedures are being developed
for implementing options that are most cost effective. The status of this program can be
obtained by writing to the American Gas Association, 1515 Wilson Boulevard, Arlington,
Virginia 22209.
24
-------
C. TYPICAL EMISSION CHARACTERISTICS
OF RESIDENTIAL GAS BURNERS
When main burners are properly adjusted, the flue products from the combustion of
gaseous fuels contain relatively harmless nitrogen, carbon dioxide (C02), and water
vapor. When the main burner is operating with incomplete combustion, because of dirty
conditions, or with an improper air-shutter adjustment, the flue products may also contain
carbon monoxide (CO), soot, and hydrocarbons (HC). A by-product of the combustion re-
action is the formation of nitrogen oxides (NOX) due to the high-temperature flames in the
presence of nitrogen and oxygen.
Figure 5 illustrates the effects of combustion air on CO and CO2 concentrations. It
demonstrates that the CO is very low within the proper C02 adjustment region. The figure
also shows that the C02 reading does not always predict the CO level. With a deficiency of
air, it is still possible to obtain a reasonable CO2 level, but with an undesirable CO level.
Therefore, the C02 level cannot be used as an indication of CO concentration. For this
reason, it is important to measure the CO concentration to ensure that it is at an acceptable
level.
Figure 8 demonstrates the expected effect of excess air on CO, HC, and NOX emissions
of a gas burner by showing the relationship of these emissions to excess-air supply (or C02
value). This figure shows the normal operating region of excess air for natural and LP gas
appliances. As noted in the discussion of the CO/CO2 relationship, CO emission levels are at
unacceptable levels under a deficiency of combustion air. HC emissions also are high with a
deficiency of combustion air and may increase under very high excess-air conditions because
of lifting flames. The NOX emissions reach a peak very near a stoichiometric air/gas mixture
(zero percent excess air) because this is the condition of maximum flame temperature.
Figure 8 shows that it is desirable to operate under an excess-air condition of 37—90
percent in order to minimize the pollutant emission levels.
Most gas burners will perform as shown in Figure 8.8-9-10 For some burners the
normal region will be wider or narrower; a few burners will operate outside the region
shown. The overall trend of the pollutant emissions, however, will be similar to that shown
by the figure. In general, conversion burners will have a wider range of adjustment available
to the service technician and will require greater care than designed units.6
25
-------
M
C
_g
'5
0>
1
UJ
o
o
a
o
a:
Increasing Combustion Air
60 40 20 0
Air Deficiency, percent
20 40///60^/80/^ 100 120
Excess Combustion Air, percent
CO-, percent (natural gas)
10.7 9.8 8.5 7.8 6.7
-*— CCg, percent (LP Gas)
Figure 8. Effect of excess air on CO, HC, and NOX burner emission for a
typical natural and LP gas fired heating appliance.
26
-------
The service technician should visualize the interaction of the various pollutants to
develop an appreciation that the CO/C02 relationship is basic to setting a burner for minimum
emissions by use of field measurements. Judging the combustion adjustment by using only
CO2 measurements could result in high CO and HC. This can be avoided by measuring both
the C02 and CO levels.
Additional information on emission levels from various types of gas-fired equipment
is contained in APCA papers by the staff of the American Gas Association Laboratories.8'9'10
27
-------
D. REFERENCES & BIBLIOGRAPHY
References Cited
1. Locklin, D. W., and R. E. Barrett, Guidelines for Residential Oil-Burner Adjustments,
Environmental Protection Agency, Report No. EPA-600/2-75-069-a (NTIS No. PB 248292),
October 1975.
2. National Fuel Gas Code, American National Standard Z223.1-1974, American Gas Associa-
tion, Arlington, Virginia, 1974.
3. Shnidman, L, Gaseous Fuels, American Gas Association, New York, New York, 1954.
4. Fundamentals of Gas Combustion, American Gas Association, Catalog No. XH0373,
Arlington, Virginia, 1973.
5. Gas Engineers Handbook, Industrial Press Inc., New York, New York, 1969.
6. Installation of Domestic Gas Conversion Burners, American National Standard Z21.8-1971,
American Gas Association, Arlington, Virginia, 1971.
7. Griffiths, J. C., Method of Calculating the Flue Loss of Gas-Fired Equipment, American Gas
Association Laboratories Research Report No. 1509, Catalog No. U07176, Cleveland, Ohio,
1976.
8. DeWerth, D. W., and R. L. Himmel, An Investigation of Emissions from Domestic Natural
Gas-Fired Appliances, SP-8 Proceedings, 67th Annual APCA Meeting, Denver, Colorado,
June 1974.
9. Belles, F. E., R. L. Himmel, and D. W. DeWerth, Measurement and Reduction of NOX Emis-
sions from Natural Gas-Fired Appliances, 68th Annual APCA Meeting, Boston,
Massachusetts, June 1975.
28
-------
10. Himmel, R. L, E. H. Tausch, and D. W. DeWerth, Further Measurements of Emissions from
Gas-Fired Appliances, 70th Annual APCA Meeting, Toronto, Ontario, June 1977.
11. Brookman, G. T., and P. W. Kalika, Measuring the Environmental Impact of Domestic Gas-
Fired Heating Systems, SP-8 Proceedings, 67th Annual APCA Meeting, Denver, Colorado,
June 1974.
12. Barrett, R. E., S. E. Miller, and D. W. Locklin, Field Investigation of Emissions from Com-
bustion Equipment for Space Heating, Report No. EPA-R2-73-084a (NTIS No. PB 223148),
June 1973.
13. Hall, R. E., Status of EPA's Combustion Research Program for Residential Heating Equip-
ment - June 1974, SP-8 Proceedings, 67th Annual APCA Meeting, Denver, Colorado,
June 1974.
14. Hall, R. E., Status of EPA's Residential Space Heating Research Program - 1976, ASME
Paper No. 76-NA/FU-4, ASME Winter Annual Meeting, New York, December 1976.
15. Standard Method of Test for Smoke Density in Fuel Gases from Distillate Fuels, ASTM
02156-65(70), ASTM Standards for Petroleum Products (Part 17).
16. Torborg, R. H., and U. Bonne, "Instrumentation for Adjusting Burners for Improved
Efficiency", APCA Paper No. 78-49.6, APCA Annual Meeting, Houston, Texas, June 1978.
17. Janssen, J. E., U. Bonne, R. H. Torborg, and A.N.J. Pearman, Reduced Pollution Through
Increased Seasonal Efficiency of Residential Furnaces, 68th Annual APCA Meeting, Boston,
Massachusetts, June 1975.
Bibliography
The following publications covering fundamentals of gas equipment servicing are excellent
general reference manuals and can be obtained from the American Gas Association, 1515 Wilson
Boulevard, Arlington, Virginia 22209.
a. Fundamentals of Gas Combustion, by A.G.A. Laboratories and Gas Appliance Manufacturers
Association. American Gas Association Catalogue No. XH 0373 (January 1973).
b. Fundamentals of Gas Appliances, by A.G.A. Laboratories and Gas Appliance Manufacturers
Association. American Gas Association Catalogue No. XH 1076 (December 1976).
29
-------
c. Fundamentals of Gas Appliance Venting and Ventilation, by A.G.A. Laboratories and Gas
Appliance Manufacturers Association. American Gas Association Catalogue No. XH 0474
(May 1974).
d. Fundamentals of Gas Controls, by A.G.A. Laboratories and Gas Appliance Manufacturers
Association. American Gas Association Catalogue No. XH 1275 (December 1975).
e. Fundamentals of Electricity, by A.G.A. Laboratories and Gas Appliance Manufacturers
Association. American Gas Association Catalogue No. XH 0175 (March 1975).
f. Fundamentals of Service to the Customer, by A.G.A. Laboratories and Gas Appliance
Manufacturers Association. American Gas Association Catalogue No. XH 0177 (March
1977).
30
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/8-79-005
3.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
Guidelines for Adjustment of Atmospheric Gas Burners
for Residential and Commercial Space Heating and
Water Heating
6. REPORT DATE
February 1979
6. PERFORMING ORGANIZATION CODE
7. AUTHORIS)
D.W.DeWerth, R.L.Himmel, and D.W.Locklin
B. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Battelle-Columbus Laboratories
505 King Avenue
Columbus, Ohio 43201
10. PROGRAM ELEMENT NO.
EHE624
11. CONTRACT/GRANT NO.
68-02-2653
12. SPONSORING AGENCY NAME AND ADDRESS
EPA, Office of Research and Development
Industrial Environmental Research Laboratory
Research Triangle Park, NC 27711
13. TYPE OF REPORT AND PERIOD COVERED
Final; 9/77 - 12/78
14. SPONSORING AGENCY CODE
EPA/600/13
15. SUPPLEMENTARY NOTES TJERL.
2477.
officer is Robert E. Hall, MD-65, 919/541-
16. ABSTRACT
The guidelines contain recommended procedures for adjusting residential
and commercial atmospheric gas burners used for space heating and water heating
to minimize air pollution and for efficienct use of fuel. They are intended for use by
skilled service technicians in adjusting burners, and as a aid to service managers
engaged in training service technicians. In addition to recommended steps for burner
adjustment, the guidelines also include appendixes of background material on pollu-
tants of main concern, field-type instruments and significance of measurements,
and emission characteristics of residential gas burners.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Air Pollution
Space Heating
Water Heaters
Combustion
Nitrogen Oxides
Smoke
Boilers
Aldehydes
Carbon Monoxide
Hydrocarbons
Natural Gas
Residential Buildings
Conservation
Air Pollution Control
Stationary Sources
Energy Conservation
Burner Tune-up
LP Gas
13 B
ISA
21B
07B
13H
07C
2 ID
13M
IS. DISTRIBUTION STATEMENT
Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
33
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
31
------- |