CORRECTION FOR ONE OR MORE IS USUALLY REQUIRED

Example A. 

Burner catalog capacity = 10 000 cfh air. Gas fl ow set for 1000 cfh--no corrections. 1000 Btu/cf gas, 
100°F combustion air, 80°F gas, 8697 in 16 osi gas line at sea level.

Point #1 correction: 1.03 × 1 000 000 Btu/hr = gas for 1 030 000 Btu/hr

Point #2 correction: 1.044 × 1 030 000 Btu/hr = gas for 1 075 300 Btu/hr

Point #4 correction:              = air for 963 000 Btu/hr

 
 Net 

eff ect =         = 1.117 × 10 cf air/cf gas = 11.17% XSFuel

Example B. 

If the conditions in Example A are predictable, the proper 8697 metering orifi ce can be selected by 
dividing the required gas fl ow (for the burner air capacity) by 1.117. Thus, if 1000 cfh gas is needed, 
select a metering orifi ce for 1000 ÷ 1.117 = 896 cfh at 3½  "w.c. diff erential. The nearest orifi ce available 
is 8697-972. Use this and apply the correction as in Example A.

Example C. 

For setting air/fuel ratio on an existing 8697 installation with the conditions of Example A, divide the 
burners catalog air capacity by 1.117 and set the gas fl ow accordingly. OR, multiply the nominal 8697 
capacity  by 1.117.

(Thus, an 8697-972, rated at 972 cfh gas with 3½  "w.c. diff erential, will have an eff ective gas fl ow, rela-
tive to the air fl ow, of 972 × 1.117 = 1086 cfh gas at 3½  "w.c. This 1086 is not the true gas fl ow--just a 
fi gure relative to air fl ow for setting ratio.)

air for 1 000 000 Btu/hr

1.037

1 075 300

963 000

Precautions | Metering Orifice

Bulletin 8697

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WARNING: 

Situations dangerous to personnel and property may exist with the operation and maintenance of any combustion equipment. The presence of fuels, oxidants, hot and cold combustion products, hot 

surfaces, electrical power in control and ignition circuits, etc., are inherent with any combustion application. Components in combustion systems may exceed 160°F (71°C) surface temperatures and present hot 
surface contact hazard. Fives North American Combustion, Inc. suggests the use of combustion systems that are in compliance with all Safety Codes, Standards, Regulations and Directives; and care in operation.

Fives North American Combustion, Inc. 

4455 East 71st Street - Cleveland, OH 44105 - USA

www.fi vesgroup.com

CONTACT

fna.sales@fi vesgroup.com
T +1 800 626 3477 - F +1 216 373 4237