Connections
27
Gas Pressure - Orifice Sizes
PILOT PRESSURE FOR Q3451A PILOT
Natural Gas 5-7”w.c.
Propane Gas 8-10”w.c.
Natural Gas
Minimum gas valve
inlet pressure 4½ ”w.c.
.............................
Maximum gas valve
inlet pressure 14 ”w.c.
.............................
Propane Gas
Minimum gas valve
inlet pressure 11 ”w.c.
.............................
Maximum gas valve
inlet pressure 14 ”w.c..............................
Manifold orifices - natural gas (1,000 Btu/cu. ft.)
Boiler size
ECV
Orifices required Low altitude
0-610 m
0-2000 ft.
Orifice size ø
High altitude
610-1370 m
2000-4500 ft.
Orifice size ø
Gas valve.
manifold pressure
“w.c.
65 2 2.65 2.55 3.5
80 2 2.95 2.80 3.5
100 3 2.70 2.60 3.5
115 3 2.85 2.75 3.5
140 4 2.75 2.65 3.5
155 4 2.85 2.80 3.5
180 5 2.80 2.65 3.5
200 5 2.95 2.80 3.5
Manifold orifices - propane (2,500 Btu/cu. ft.)
Boiler size
ECV
Orifices required Orifice size Low altitude
0-610 m
0-2000 ft
Gas valve/manifold
pressure “w.c.
High altitude
610-1370 m
2000-4500 ft.
Gas valve/manifold
pressure “w.c.
65 2 1.60 10 8
80 2 1.80 10 8
100 3 1.65 10 8
115 3 1.75 10 8
140 4 1.70 10 8
155 4 1.75 10 8
180 5 1.70 10 8
200 5 1.80 10 8
All orifice sizes given in mm! Orifice size is stamped onto each orifice for identification. When ordering orifices, state boiler
size, type of gas, number of orifices required and orifice size.
5167 450 v1.4
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