Table 3—Downflow and Downflow/Horizontal, 2-Speed, Hot Surface Ignition, Non-Condensing
Furnace Orifice Size and Manifold Pressure for Correct Input-Continued
(Tabulated Data Based on 21,000 Btuh High Heat/13,500 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.
Only
725
44
3.8/1.6
43
3.4/1.4
43
3.5/1.4
43
3.6/1.5
43
3.7/1.5
750
44
3.5/1.5
44
3.6/1.5
44
3.8/1.6
43
3.4/1.4
43
3.5/1.4
775
44
3.3/1.4
44
3.4/1.4
44
3.5/1.5
44
3.6/1.5
44
3.7/1.5
4001
800
45
3.7/1.5
44
3.2/1.3
44
3.3/1.4
44
3.4/1.4
44
3.5/1.5
825
46
3.7/1.5
46
3.8/1.6
45
3.8/1.6
44
3.2/1.3
44
3.3/1.4
to
850
46
3.5/1.4
46
3.6/1.5
46
3.7/1.5
46
3.8/1.6
45
3.8/1.6
875
47
3.7/1.5
46
3.4/1.4
46
3.5/1.5
46
3.6/1.5
46
3.7/1.5
5000
900
47
3.5/1.5
47
3.6/1.5
47
3.8/1.6
46
3.4/1.4
46
3.5/1.5
925
48
3.8/1.6
47
3.4/1.4
47
3.6/1.5
47
3.7/1.5
47
3.8/1.6
950
48
3.6/1.5
48
3.7/1.5
48
3.8/1.6
47
3.5/1.4
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
700
44
3.5/1.5
44
3.6/1.5
44
3.8/1.6
43
3.4/1.4
43
3.5/1.4
725
44
3.3/1.4
44
3.4/1.4
44
3.5/1.4
44
3.6/1.5
44
3.7/1.5
750
45
3.7/1.5
44
3.2/1.3
44
3.3/1.4
44
3.4/1.4
44
3.5/1.4
775
46
3.6/1.5
46
3.8/1.6
45
3.7/1.5
44
3.2/1.3
44
3.3/1.4
5001
800
46
3.4/1.4
46
3.5/1.5
46
3.7/1.5
46
3.8/1.6
45
3.7/1.5
825
47
3.7/1.5
47
3.8/1.6
46
3.4/1.4
46
3.6/1.5
46
3.7/1.5
to
850
47
3.4/1.4
47
3.6/1.5
47
3.7/1.5
47
3.8/1.6
46
3.5/1.4
875
48
3.7/1.5
48
3.8/1.6
47
3.5/1.4
47
3.6/1.5
47
3.7/1.5
6000
900
48
3.5/1.4
48
3.6/1.5
48
3.7/1.5
47
3.4/1.4
47
3.5/1.4
925
48
3.3/1.4
48
3.4/1.4
48
3.5/1.5
48
3.6/1.5
48
3.8/1.6
950
49
3.7/1.5
49
3.8/1.6
48
3.3/1.4
48
3.5/1.4
48
3.6/1.5
975
49
3.5/1.4
49
3.6/1.5
49
3.7/1.5
48
3.3/1.4
48
3.4/1.4
1000
49
3.3/1.4
49
3.4/1.4
49
3.6/1.5
49
3.7/1.5
49
3.8/1.6
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
650
44
3.5/1.5
44
3.7/1.5
44
3.8/1.6
43
3.4/1.4
43
3.5/1.4
675
44
3.3/1.4
44
3.4/1.4
44
3.5/1.4
44
3.6/1.5
44
3.7/1.5
700
45
3.7/1.5
44
3.2/1.3
44
3.3/1.3
44
3.4/1.4
44
3.5/1.4
6001
725
46
3.6/1.5
46
3.7/1.5
45
3.7/1.5
45
3.8/1.6
44
3.2/1.3
750
47
3.8/1.6
46
3.5/1.4
46
3.6/1.5
46
3.7/1.5
46
3.8/1.6
to
775
47
3.6/1.5
47
3.7/1.5
47
3.8/1.6
46
3.5/1.4
46
3.6/1.5
800
48
3.8/1.6
47
3.5/1.4
47
3.6/1.5
47
3.7/1.5
47
3.8/1.6
7000
825
48
3.6/1.5
48
3.7/1.5
48
3.8/1.6
47
3.5/1.4
47
3.6/1.5
850
48
3.4/1.4
48
3.5/1.4
48
3.6/1.5
48
3.7/1.5
47
3.4/1.4
875
49
3.8/1.6
48
3.3/1.4
48
3.4/1.4
48
3.5/1.5
48
3.6/1.5
* For 060125 and 125-20 sizes only, input is 20,500 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.
—9—
