A.O. Smith 120 trough 500 - Manual (Page 10)

BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
9
INSUFFICIENT MAKE-UP AIR
BACKDRAFT
Insufficient make-up air is a major cause of combustion problems. One common example
is in a restaurant installation where exhaust vent equipment was not considered in sizing
make-up air requirements. This may result in air being backdrafted by the restaurant
exhaust equipment through the heater causing flue gas spillage, flame roll out, improper
combustion, inconsistent pilot operation, and/or erratic heater shut down.