Service manual

SC Series Boilers – Installation and Service Manual
22
Adjustments to the input rate can be made by varying the manifold pressure. Normally it should be
adjusted no more than 0.1 inch w.c. for natural gas or 0.4 inch w.c. for propane from the manifold
pressure specified on the rating plate for that altitude application.
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 foot. 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.
3.8 CHECK OF CONTROLS
After the unit has been operated for a while, lower the aquastat setting below the setpoint or actual boiler
water temperature and burner should shut off. Rotate the aquastat higher than setpoint 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 safety high-limit aquastat, thermostat and other system controls to
ensure all work satisfactorily. If any of the safety or controls do not function, necessary corrections
should be made immediately.
3.9 CHECK FOR GAS LEAKS
To identify gas leaks, smell for gas around boiler area and gas piping connections (See Section 1.1). To
check a specific area, including the manifold joint connected to the gas valve, for leakage, spray a
mixture of soap and water onto the suspected area – active bubbling indicates a gas leak. The gas leaks
of the manifold joint connected to the gas valve outlet should be checked when the boiler is on. DO NOT
TEST FOR LEAKS WITH AN OPEN FLAME. Gas leaks must be repaired immediately.
3.10 CHECK THE CONDENSATE DRAIN TUBE
Check that the tube loop is approximately 4" diameter. The water should fill the loop to form a liquid-filled
trap and not be plugged with excessive sediment.