Service manual

SC Series Boilers – Installation and Service Manual
19
Airflow Adjustment
After the boiler and its venting system have been installed, use the following procedure to adjust the
boiler to the proper airflow:
a) The airflow adjustment can only be done correctly when the boiler is hot.
b) Turn gas valve off.
c) Turn the air adjustor screw located on the blower inlet clockwise to slide the air adjustor closed.
(Airflow adjustments are made by slowly turning the screw which slides the air adjustor located
on the blower inlet to more open or more closed positions as shown in Figure 10.)
d) Set room thermostat above room temperature to call for heat and turn on power to the boiler.
e) The blower will start.
f) Slowly open the air adjustor to make the RED Minimum Airflow indicator light switch on.
Continue to very slowly open the air adjustor until the RED Optimum Airflow light JUST switches
on. Then immediately STOP moving the air adjustor. If the blower turns off before finishing the
setting, the main electric power to the boiler has to be switched off and on to reset the controller.
g) Turn the gas valve on. Reset the main electric power, if necessary. The boiler should ignite
smoothly. The burner flames should be stable with no lift off or surges, and have a distinct bright
blue "V"-shaped flame with a blue/light orange outer mantle.
h) Let boiler run about 20 minutes, then slowly close the air adjustor to make the RED Optimum
Airflow light switch off if it is still on. Shut boiler off and restart it immediately. Make sure that the
boiler relights and the RED Minimum Airflow light switches on. The RED Optimum Airflow light
may switch on or off and should be ignored. If the burner flames are not stable with lift off or
surges, turn the screw clockwise a few turns to close the air adjustor and relight the boiler.
i) Check the flame again. If the air adjustor is opened too much so the airflow is too high,
ignition/flame failure may occur when the boiler is cold. The optimum operating condition of
boiler should be the Minimum Airflow light switch ON and Optimum Airflow light switch OFF when
the boiler is hot.
Too much airflow can result in inefficient combustion, flame lift off and ignition/flame failure. The Optimum
Airflow switch is normally open and will close to turn the Optimum Airflow indictor light on when the actual
airflow is above its set-point. The Minimum Airflow indictor light will always stay on when the boiler is
firing. The indicator lights may be on or off during normal boiler operation. The status of the indicator
lights for airflow is shown below.