Bryant 579F User Manual page 194

ALTITUDE COMPENSATION* —
579F180-300
NATURAL GAS ORIFICE SIZE†
ELEVATION
(ft)
Low Heat
0-3,000
3,000- 7,000
7,000- 9,000
9,000-10,000
above 10,000
*Includes a 4% input reduction per each 1,000 feet.
†Orifices available through your Bryant distributor.
PERFORMANCE DATA — 579F (cont)
Fan Performance Using Accessory Power Exhaust (579F180-300)
High Heat
30 29
31 30
32 31
33 31
35 32
ALTITUDE DERATING FACTOR*
ELEVATION (ft)
0-2,000
2,001-3,000
3,001-4,000
4,001-5,000
5,001-6,000
*Derating of the unit is not required unless the heating value of the gas
exceeds the values listed in the table above, or if the elevation
exceeds 6000 ft. Derating conditions must be 4% per thousand ft
above 2000 ft. For example, at 4000 ft, if the heating value of the gas
exceeds 1000 Btu/ft , the unit will require a 16% derating. For eleva-
3
tions above 6000 ft, the same formula applies. For example, at 7000 ft,
the unit will require a 28% derating of the maximum heating value per
the National Fuel Gas Code.
IMPORTANT: Local utility companies may be reducing heat content of
gas at altitudes above 2000 ft. If this is being done, then changing
spuds may not be required.
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MAXIMUM HEATING VALUE
(Btu/ft 3 )
1,100
1,050
1,000
950
900