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Table 14—Model 58MXB Orifice Size and Manifold Pressure for Correct Input
For Use with 140 Size Furnaces Only
(Tabulated Data Based on 23,000 Btuh per Burner, Derated 2% for Each 1000 Ft Above Sea Level) *
ALTITUDE
RANGE
(FT)
AVG GAS
HEAT VALUE
AT ALTITUDE
(BTU/CU FT)
SPECIFIC GRAVITY OF NATURAL GAS
0.58
0.60
0.62
0.64
0.66
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
U.S.A.
and
Canada
850
41
3.6
41
3.7
41
3.8
40
3.6
40
3.8
875
42
3.8
41
3.5
41
3.6
41
3.7
41
3.8
900
42
3.5
42
3.7
42
3.8
41
3.5
41
3.6
0
925
42
3.4
42
3.5
42
3.6
42
3.7
42
3.8
950
42
3.2
42
3.3
42
3.4
42
3.5
42
3.6
to
975
43
3.7
43
3.8
42
3.2
42
3.3
42
3.4
1000
43
3.5
43
3.6
43
3.7
42
3.2
42
3.3
2000
1025
43
3.3
43
3.4
43
3.6
43
3.7
43
3.8
1050
43
3.2
43
3.3
43
3.4
43
3.5
43
3.6
0%
1075
44
3.5
44
3.6
43
3.2
43
3.3
43
3.4
derate
1100
44
3.3
44
3.4
44
3.5
43
3.2
43
3.3
ALTITUDE
RANGE
(ft)
AVG GAS
HEAT VALUE
AT ALTITUDE
(Btu/cu ft)
SPECIFIC GRAVITY OF NATURAL GAS
0.58
0.60
0.62
0.64
0.66
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
U.S.A.
and
Canada
U.S.A.
775
41
3.7
41
3.8
40
3.6
40
3.7
39
3.6
Altitudes
800
42
3.8
41
3.6
41
3.7
41
3.8
40
3.6
2001 to
825
42
3.6
42
3.7
41
3.5
41
3.6
41
3.7
3000 or
850
42
3.4
42
3.5
42
3.6
42
3.7
41
3.5
Canada
875
42
3.2
42
3.3
42
3.4
42
3.5
42
3.6
Altitudes
900
43
3.7
43
3.8
42
3.2
42
3.3
42
3.4
2001 to
925
43
3.5
43
3.6
43
3.7
42
3.2
42
3.3
4500
950
43
3.3
43
3.4
43
3.5
43
3.7
43
3.8
975
43
3.1
43
3.3
43
3.4
43
3.5
43
3.6
5%
1000
43
3.0
43
3.1
43
3.2
43
3.3
43
3.4
derate
1025
43
2.8
43
2.9
43
3.0
43
3.1
43
3.2
ALTITUDE
RANGE
(ft)
AVG GAS
HEAT VALUE
AT ALTITUDE
(Btu/cu ft)
SPECIFIC GRAVITY OF NATURAL GAS
0.58
0.60
0.62
0.64
0.66
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
U.S.A.
Only
750
41
3.6
41
3.8
40
3.6
40
3.7
40
3.8
775
42
3.8
41
3.5
41
3.6
41
3.7
40
3.6
800
42
3.5
42
3.7
42
3.8
41
3.5
41
3.6
3001
825
42
3.3
42
3.4
42
3.6
42
3.7
42
3.8
850
43
3.8
42
3.2
42
3.4
42
3.5
42
3.6
to
875
43
3.6
43
3.7
42
3.2
42
3.3
42
3.4
900
43
3.4
43
3.5
43
3.6
43
3.8
42
3.2
4000
925
43
3.2
43
3.3
43
3.5
43
3.6
43
3.7
950
43
3.1
43
3.2
43
3.3
43
3.4
43
3.5
7%
975
43
2.9
43
3.0
43
3.1
43
3.2
43
3.3
derate
1000
43
2.8
43
2.9
43
3.0
43
3.0
43
3.1
* Orifice numbers 43 shown in BOLD are factory installed.
Percents of derate are based on midpoints of U.S. altitude ranges.
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