Bryant 581A/B - Manual (Page 163)

163
PERFORMANCE DATA — 579F (cont)
ALTITUDE COMPENSATION* —
579F180-300
*Includes a 4% input reduction per each 1,000 feet.
†Orifices available through your Bryant distributor.
ALTITUDE DERATING FACTOR*
*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
3 , the unit will require a 16% derating. For elevations 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.
Fan Performance Using Accessory Power Exhaust (579F180-300)
a50-4028
ELEVATION
(ft)
NATURAL GAS ORIFICE SIZE†
Low Heat High Heat
0-3,000 30 29
3,000- 7,000 31 30
7,000- 9,000 32 31
9,000-10,000 33 31
above 10,000 35 32
ELEVATION (ft)
MAXIMUM HEATING VALUE
(Btu/ft 3 )
0-2,000 1,100
2,001-3,000 1,050
3,001-4,000 1,000
4,001-5,000 950
5,001-6,000 900
0TF
Q004
-0
12
579
F18
0
-300