Service manual

SC Series Boilers – User’s Information Manual
6
9 CHECK AIRFLOW PRESSURE SWITCH TUBES
The Minimum Airflow pressure switch is a safety device that will prevent the boiler from firing if there is
an air intake, boiler heat exchanger or vent blockage. In addition, the device will prevent the boiler from
firing if there is not enough air to the combustion chamber. A RED light indicates the switch is closed.
The boiler is also equipped with an Optimum Airflow pressure switch to allow the installer to easily
adjust the boiler operation to the optimum combustion airflow for any installation and venting
configuration. This switch is not a safety device. A RED light
indicates the switch is closed.
These devices sense a positive combustion air differential
pressure between the air chamber and burner venturi inlet
when the blower is energized and monitor combustion
airflow.
There are two silicone tubes connecting the air differential
pressure switches with the air chamber and burner venturi
inlet. The clear tube should be connected to the air chamber
and the positive side (P1) of the switches. The red tube
should be connected to the burner venturi inlet and the
negative side (P2) of the switches. Ensure that the tubes are
connected correctly and tightly, and are not cracked.
The two indicator lights are located on the right top corner of
the boiler to indicate the pressure switch status (open or
closed). When there is a call for heat, the blower will energize
and the controller will try to light the boiler. The Minimum Airflow switch must close (indicated by RED
light) before the controller will allow the boiler to light. The Optimum Airflow pressure switch may be either
open or closed (indicated by RED light). The Optimum Airflow switch is for the installer’s use and should
be ignored once the boiler is has been set-up.
10 CHECK BURNER SYSTEM
To maintain safe and efficient operation, examine the burner system regularly through the inspection
window in the front of the boiler behind the door.
Check condition of burner system
It is possible for parts of the burners system to
become plugged, cracked, eroded and/or
dislodged resulting in unsafe operation.
Check for lifting
Flames should not lift excessively from the
burner ports. The flames may lift slightly during
ignition or when the burners are cold.
Check ignition and extinction
Ignition should flow quickly and smoothly across
all the burners. Popping noises or explosions
from the burners during ignition, extinction or
unmoral burner operation indicates the need for
service.
Check flame color
An extremely yellow flame, as seen on a burning
candle or match, is an indication of incomplete
combustion and is usually accompanied by the
formation of soot and carbon monoxide (carbon
monoxide is a lethal, colorless and odorless
gas). If soot is allowed to accumulate, it will
partially restrict free passage of products of
combustion to the flue. Under typically
operating conditions, the flame should have a
distinct bright blue inner cone and a blue/light
orange outer cone.