Altitude compensation – Bryant 581C User Manual
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PERFORMANCE DATA — 581C
ALTITUDE COMPENSATION* — 581C024-060
STANDARD UNIT
*As the height above sea level increases, there is less oxygen per cubic
foot of air. Therefore, heat input rate should be reduced at higher altitudes.
†Orifices available through your Bryant distributor.
ALTITUDE COMPENSATION* — 581C024-060
LOW NOx UNITS
*As the height above sea level increases, there is less oxygen per cubic
foot of air. Therefore, heat input rate should be reduced at higher altitudes.
†Orifices available through your Bryant distributor.
ALTITUDE DERATING FACTOR*
*Derating of the gas heating equipment to compensate for the effects of alti-
tude is always required. Orifice change is not required if the fuel heating
value (at sea level) is below the limits listed in the table at left. Derating con-
ditions 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.
PERFECT HUMIDITY™ ADAPTIVE DEHUMIDIFICATION COIL PRESSURE DROP
ELEVATION
(ft)
50,000 BTUH NOMINAL INPUT
Natural Gas
Orifice Size†
Liquid Propane
Orifice Size†
0-2,000
43
49
2,000
44
50
3,000
44
50
4,000
44
50
5,000
45
51
6,000
45
51
7,000
46
51
8,000
47
52
9,000
47
52
10,000
48
52
11,000
49
53
12,000
50
54
13,000
51
55
14,000
52
56
ELEVATION
(ft)
60,000 AND 90,000 BTUH
NOMINAL INPUT
120,000 BTUH
NOMINAL INPUT
Natural Gas
Orifice Size†
Natural Gas
Orifice Size
0-2,000
38
32
2,000
40
33
3,000
41
35
4,000
42
36
5,000
43
37
6,000
43
38
7,000
44
39
8,000
45
41
9,000
46
42
10,000
47
43
11,000
48
44
12,000
49
44
13,000
50
46
14,000
51
47
ELEVATION
MAXIMUM HEATING VALUE
AT SEA LEVEL (Btu/ft
3
)
0-2000
1100
2001-3000
1050
3001-4000
1000
4001-5000
950
5001-6000
900
IMPORTANT: Local utility companies may be reducing heat content of gas at
altitudes above 2000 ft. If this is being done, changing spuds may not be
required.