Table 2—Upflow and Upflow/Horizontal, 2-Speed and Variable-Speed, Hot Surface Ignition, Non-Condensing
Furnace Orifice Size and Manifold Pressure for Correct Input
(Tabulated Data Based on 20,000 Btuh High Heat/13,000 Btuh Low Heat per Burner,
Derated 4% 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
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
U.S.A.
and
Canada
850
43
3.7/1.5
43
3.8/1.6
42
3.2/1.4
42
3.3/1.4
42
3.4/1.4
875
43
3.5/1.5
43
3.6/1.5
43
3.7/1.6
43
3.8/1.6
42
3.2/1.4
900
44
3.7/1.6
43
3.4/1.4
43
3.5/1.5
43
3.6/1.5
43
3.7/1.6
0
925
44
3.5/1.5
44
3.7/1.6
44
3.8/1.6
43
3.4/1.4
43
3.5/1.5
950
44
3.4/1.4
44
3.5/1.5
44
3.6/1.5
44
3.7/1.6
44
3.8/1.6
to
975
44
3.2/1.3
44
3.3/1.4
44
3.4/1.4
44
3.5/1.5
44
3.6/1.5
1000
45
3.7/1.6
45
3.8/1.6
44
3.2/1.4
44
3.4/1.4
44
3.5/1.5
2000
1025
45
3.5/1.5
45
3.6/1.5
45
3.7/1.6
44
3.2/1.3
44
3.3/1.4
1050
45
3.3/1.4
45
3.4/1.5
45
3.6/1.5
45
3.7/1.6
45
3.8/1.6
1075
45
3.2/1.3
45
3.3/1.4
45
3.4/1.4
45
3.5/1.5
45
3.6/1.5
1100
47
3.6/1.5
47
3.7/1.6
45
3.2/1.4
45
3.4/1.4
45
3.5/1.5
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
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
U.S.A.
and
Canada
U.S.A.
775
43
3.4/1.4
43
3.5/1.5
43
3.6/1.5
43
3.7/1.6
43
3.8/1.6
Altitudes
800
44
3.6/1.5
44
3.8/1.6
43
3.4/1.4
43
3.5/1.5
43
3.6/1.5
2001
825
44
3.4/1.4
44
3.5/1.5
44
3.7/1.5
44
3.8/1.6
43
3.4/1.4
to
850
44
3.2/1.4
44
3.3/1.4
44
3.4/1.5
44
3.6/1.5
44
3.7/1.5
3000
875
45
3.7/1.6
45
3.8/1.6
44
3.2/1.4
44
3.4/1.4
44
3.5/1.5
or
900
45
3.5/1.5
45
3.6/1.5
45
3.7/1.6
45
3.8/1.6
44
3.3/1.4
Canada
925
45
3.3/1.4
45
3.4/1.4
45
3.5/1.5
45
3.6/1.5
45
3.7/1.6
Altitudes
950
47
3.7/1.6
45
3.2/1.4
45
3.3/1.4
45
3.4/1.5
45
3.6/1.5
2000
975
47
3.5/1.5
47
3.6/1.5
45
3.2/1.3
45
3.3/1.4
45
3.4/1.4
to
1000
48
3.8/1.6
47
3.5/1.5
47
3.6/1.5
47
3.7/1.6
45
3.2/1.4
4500
1025
48
3.6/1.5
48
3.8/1.6
47
3.4/1.4
47
3.5/1.5
47
3.6/1.5
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
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
Orifice
No.
Manifold
Pressure
High/Low
U.S.A.
Only
750
44
3.6/1.5
44
3.8/1.6
43
3.4/1.4
43
3.5/1.5
43
3.6/1.5
775
44
3.4/1.4
44
3.5/1.5
44
3.6/1.5
44
3.8/1.6
43
3.4/1.4
800
44
3.2/1.4
44
3.3/1.4
44
3.4/1.4
44
3.5/1.5
44
3.6/1.5
3001
825
45
3.6/1.5
45
3.8/1.6
44
3.2/1.4
44
3.3/1.4
44
3.4/1.4
850
45
3.4/1.4
45
3.5/1.5
45
3.7/1.5
45
3.8/1.6
44
3.2/1.4
to
875
45
3.2/1.4
45
3.3/1.4
45
3.5/1.5
45
3.6/1.5
45
3.7/1.6
900
47
3.6/1.5
45
3.2/1.3
45
3.3/1.4
45
3.4/1.4
45
3.5/1.5
4000
925
47
3.4/1.5
47
3.6/1.5
47
3.7/1.6
45
3.2/1.4
45
3.3/1.4
950
48
3.7/1.6
48
3.8/1.6
47
3.5/1.5
47
3.6/1.5
47
3.7/1.6
975
48
3.5/1.5
48
3.7/1.5
48
3.8/1.6
47
3.4/1.4
47
3.5/1.5
1000
48
3.4/1.4
48
3.5/1.5
48
3.6/1.5
48
3.7/1.6
48
3.8/1.6
* For 060135 and 135-20 sizes only, input is 19,000 Btuh for high fire. Deduct 0.1 in. from manifold pressure shown in table. Change orifice size if manifold pressure falls
below 3.2-in. wc.
—5—
