SG Series Boilers – Installation and Service Manual
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Small adjustments to the input rate can be made by varying the manifold pressure. Normally it should be
adjusted no more than 0.2 inch w.c. for natural gas or 0.5 inch w.c. for propane from the manifold
pressure specified on the rating plate.
WARNING
Exceeding the allowable input rate can produce dangerous concentrations of carbon monoxide,
and cause the boiler to overheat resulting in severe personal injury, death or substantial
property damage. Carbon monoxide is a lethal, colorless and odorless gas.
Input Rate Test
Consult gas company to determine the heating value of the gas supplied in Btu per cubic feet. Operate
boiler for 15 minutes starting with all parts at room temperature and check input by clocking gas meter
with all other gas appliances turned off, including their pilot flames. Use the following formula:
INPUT (Btu/h) =
Clocked Seconds
Timed) FeetCubic of (Number x Gas) of Value(Heating(3600) ×
To ensure accuracy for rating, clock enough cubic feet of gas so that there is at least one revolution of the
test dial and the clocked time is at least 60 seconds.
Two Stage or Full Modulating Gas Valve
When a two stage or modulating gas valve is used, it must be checked for correct input at both "High"
and "Low" fire settings. The clocked input rate MUST be within the "Minimum Input" and the "Input" as
specified on the boiler's rating plate. To force a two stage or full modulating gas valve to low fire, see the
valve manufacturer's instructions. Perform the Input Rate Test described above and adjust manifold
pressure of High and Low settings as necessary. For altitudes above 2000 feet, DO NOT derate the
"Minimum Input" rate.
3.7 CHECK FOR DRAFT HOOD SPILLAGE
WARNING
Continuous spillage at the draft hood relief opening may result in severe personal injury, death
or substantial property damage.
After the main burners have operated for 5 minutes, check to see that combustion products are going up
the chimney or gas vent properly by passing a lighted match (or smoke from a cigar, cigarette, or pipe)
around the edge of the relief opening of the draft hood. If the chimney or gas vent is drawing properly,
the match flame or smoke will be drawn into the draft hood. If not, the combustion products will tend to
extinguish this flame. While performing this test, make sure all exhaust fans, air movers, and gas
appliances are operating and doors and windows are closed. If the combustion products are escaping
from the relief opening of the draft hood, IMMEDIATELY shutdown the boiler and make proper
adjustments or repairs.
3.8 CHECK OF CONTROLS
After the unit has been operated for awhile, lower the aquastat setting below the water temperature and
the burner should shut off. Set the aquastat higher than the water temperature and the main burner
should ignite. Return the aquastat to its original setpoint and make sure boiler cycles normally. Repeat
this type of check on the optional aquastat (when used), thermostat and other system controls to ensure
all are working satisfactorily. If any of the safety or controls do not function, necessary corrections should
be made immediately.
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