A.O. Smith 120 trough 500 - Manual (Page 6)

BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
5
AIR FOR COMBUSTION
10 CUBIC FEET OF AIR PER 1,000 BTU
Stoichiometric or theoretical complete combustion requires 10 cubic feet of air per 1000
BTUH input of the gas input.
The National Fuel Gas Code also recommends an
additional 2.5 cu.ft. of "excess" air. This 12.5 cu.ft minimum supply air per 1000 BTUH
input applies to natural and propane gas models.
The National Fuel Gas Code also specifies minimum make-up air opening sizes for
various building installations. (Ref: NFPA 54, ANSI Z223.1, sec 5.3)
2.5 CU.
FT.
EXCESS
AIR
10 CU.
FT.
COMB.
AIR
+
1 1 1, , ,0 0 00 0 00 0 0
B B BT T TU U U