SG Series Boilers – Installation and Service Manual
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3.4 AQUASTAT ADJUSTMENT
An optional aquastat may be installed to control the main burner firing by sensing outlet water
temperature. The optional aquastat should be set a minimum of 20°F (10°C) above the setting of the
high limit of the integrated boiler controller.
3.5 GAS MANIFOLD PRESSURE
The designated manifold pressures are as shown in the table below. A 1/8” NPT tapping is provided on
the manifold or gas valve for connecting a manometer to check this pressure. Both natural gas and
propane models are furnished with gas valves which have a built in gas pressure regulator. If necessary,
adjust to the proper value by removing cap and turning adjusting screw clockwise to increase manifold
pressure or counterclockwise to decrease manifold pressure.
Model Natural Gas Propane
SG
3.5” W.C. 10.0” W.C.
3.6 CHECK INPUT & ORIFICES
For safety, the input shown on rating plate must not be exceeded. Check with the table below that
the orifice size and input rate shown on the rating plate match your
application, i.e. boiler model, fuel
type, and altitude. See SG Dimensions and Specifications section to find your boiler model's input rate.
FOR CANADA
Natural Gas Propane
Model
0 to 2,000 feet 2,000 to 4,500 feet 0 to 2,000 feet 2,000 to 4,500 feet
SG
#43 orifice
standard input
#44 orifice
10% derate input
#54 orifice
standard input
#55 orifice
10% derate input
NOTE: For elevations above 4,500 feet reduce high altitude input 4% for each additional 1000 feet.
Reference Natural Gas and Propane Installation Code B149.1, 3.22 High Altitude Installations
Example of High Altitude Derate
Boiler: SG-270
Altitude: 5,500 feet
Standard Input (0 to 2,000 ft) = 270,000 Btu/h (from page 3)
High Altitude Input (2,000 to 4,500 ft) = Derate Standard Input by 10% (see above table)
= 270,000 Btu/h x (1 - 0.10)
= 270,000 Btu/h x 0.90
= 243,000 Btu/h
% Reduction for additional 1000 ft = 4% x 1 = 4%
Input at 5,500 ft = Derate High Altitude Input by 4%
= 243,000 Btu/h x (1 – 0.04)
= 243,000 Btu/h x 0.96
= 233,280 Btu/h
FOR UNITED STATES OF AMERICA
Natural Gas Propane
Model
0 to 2,000 feet Over 2,000 feet 0 to 2,000 feet Over 2,000 feet
SG
#43 orifice
standard input
Input must be reduced
4% for each 1000 feet
above sea level. *
#54 orifice
standard input
Input must be reduced
4% for each 1000 feet
above sea level. *
*Reference National Fuel Gas Code ANSI Z223.1, 8.1.2 High Altitude.
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