Specifications

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stcudorP retaW htimS .O .A Service Workbook
Ashland City, Tennessee 2005© Training Department
AIR FOR COMBUSTION
DOWNDRAFT
Insufficient make-up air is a major cause of combustion problems. One common example is a mechanical
room where exhaust vent equipment was not considered in sizing make-up air requirements. This may
result in air being pulled down the exhaust vent of the Genesis causing flue gas spillage, flame roll out,
improper combustion, and/or erratic heater shut down. It can also cause the production of carbon monoxide
that could result in serious personal injury or death. In order to assure proper operation, perform a worst
case depressurization test as outlined on Appendix H of the 1999 Edition of the National Flue Gas Code
(ANSI Z223.1/NFPA-54).
AIR FOR COMBUSTION
CONTAMINATED AIR
Along with adequate make-up air, the quality of the air is important. Contaminants in combustion air can
lead to premature heater failure. Vapors from bleaches, soaps, salts, etc
. are drawn into the combustion
chamber with the make up air and, once fired, mix with water vapor in the gases to form extremely corro-
sive hydrochloric or hydrofluoric acid and other corrosive by-products. Dust drawn in may build up on the
blower or clog the main burner ports. Also, be certain to examine the exterior area around the air intake of
a direct vent installation for these contaminants.