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41
Table 16—Orifice Size* and Manifold Pressure (In. W.C.) for Gas Input Rate
(Tabulated data based on 21,000 btuh per burner, derated 4 percent for each 1000 ft. (305 M) above sea level)
ALTITUDE
RANGE
FT. (M)
SPECIFIC GRAVITY OF NATURAL GAS
AVG. GAS
HEAT VALUE
AT ALTITUDE
(BTU/CU FT.)
0.58 0.60 0.62 0.64
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
Orifice
No.
Manifold
Pressure
U.S.A.
0 to 2000
(0 to 610)
900 42 3.2 42 3.3 42 3.4 42 3.5
925 43 3.7 43 3.8 42 3.2 42 3.3
950 43 3.5 43 3.6 43 3.7 43 3.8
975 43 3.3 43 3.4 43 3.5 43 3.7
1000 44 3.6 43 3.3 43 3.4 43 3.5
1025 44 3.4 44 3.6 43 3.2 43 3.3
1050 44 3.3 44 3.4 44 3.5 43 3.2
1075 45 3.8 44 3.2 44 3.3 44 3.4
1100 46 3.8 45 3.7 44 3.2 44 3.3
U.S.A.
2001 to
3000
(610 to
914)
800 43 3.8 42 3.2 42 3.3 42 3.4
825 43 3.5 43 3.7 43 3.8 42 3.2
850 43 3.3 43 3.5 43 3.6 43 3.7
875 43 3.2 43 3.3 43 3.4 43 3.5
900 43 3.0 43 3.1 43 3.2 43 3.3
925 43 2.8 43 2.9 43 3.0 43 3.1
950 43 2.7 43 2.8 43 2.9 43 2.9
975 43 2.5 43 2.6 43 2.7 43 2.8
1000 43 2.4 43 2.5 43 2.6 43 2.7
U.S.A.
3001 to
4000
(914 to
1219)
775 43 3.5 43 3.7 43 3.8 42 3.2
800 43 3.3 43 3.4 43 3.5 43 3.7
825 43 3.1 43 3.2 43 3.3 43 3.4
850 43 2.9 43 3.0 43 3.1 43 3.2
875 43 2.8 43 2.9 43 3.0 43 3.1
900 43 2.6 43 2.7 43 2.8 43 2.9
925 43 2.5 43 2.6 43 2.7 43 2.7
950 43 2.4 43 2.4 43 2.5 43 2.6
U.S.A.
4001 to
5000
(1219 to
1524)
750 43 3.3 43 3.4 43 3.5 43 3.6
775 43 3.1 43 3.2 43 3.3 43 3.4
800 43 2.9 43 3.0 43 3.1 43 3.2
825 43 2.7 43 2.8 43 2.9 43 3.0
850 43 2.6 43 2.7 43 2.8 43 2.8
875 43 2.4 43 2.5 43 2.6 43 2.7
900 43 2.3 43 2.4 43 2.5 43 2.5
925 43 2.2 43 2.2 43 2.3 43 2.4
* Orifice numbers 43 are factory installed.
310AAV