TM 5-3895-374-24-2
OPERATING AND INDICATING LIGHTS
Ten lights are provided on the stack side of the panel box to simplify operation and problem determination. A
discussion of each light follows.
PUMP MOTOR this light illuminates when the pump motor thermal overloads trip. Possible problems could
be a defective pump, a defective pump motor, defective or incorrectly sized thermal overloads, or a short in
the wiring. The heater will not run when this light is lit.
BURNER MOTOR this light illuminates when the burner motor thermal overloads trip. Possible problems
could be a defective burner motor, defective or incorrectly sized thermal overloads or a short in the wiring.
The heater will not run when this light is lit.
LOW OIL this light illuminates when there is insufficient heat transfer fluid in the expansion tank to safely run
the heater. This light is illuminated by the Magnetro: low oil float switch located in the stack end of the
expansion tank. More heat transfer fluid must be added to the heater before the heater will operate again.
Refer to Section 3.3 for the proper procedure for adding heat transfer fluid to the system.
FLAME FAILURE this light illuminates when the Flame Safeguard System fails to detect a flame during
normal burner operation. When a flame failure occurs, the burner and pump are shut down and will not run
again until the reset button on the programmer is depressed. Section 9: HEATER TROUBLESHOOTING
has a complete discussion of flame failures.
HEAT DEMAND this light illuminates as part of the normal heater operating sequence when the temperature
controller calls for heat (i.e. the difference between the heat transfer fluid temperature and the set point on
the temperature controller is great enough to activate the burner).
LIMIT CIRCUIT this light illuminates as part of the normal heater operating sequence at the same time the
HEAT DEMAND light illuminates. This light illuminates when certain components have passed a preignition
safety check. Section 9.5: PROBLEM DETERMINATION explains what should be checked if the light does
not illuminate.
IGNITION this light illuminates as part of the normal heater operating sequence during the time when the
ignition transformer is energized and ignition is attempted. It normally stays illuminated for approximately 20
seconds.
MAIN FUEL VALVE this light illuminates as part of the normal heater operating sequence when the main fuel
valve to the burner opens. This light should remain illuminated as long as the burner is running.
HIGH LIMIT this light illuminates when the high limit switch shuts down the burner. The circulating pump will
continue to run. The programmer will display the message "OFF". The burner will not start until the
temperature of the heat transfer oil drops below the temperature of the high limit switch setting. When the
burner starts again, the high limit light will go off. More information on the high limit switch can be found in
Section 6.3.
TIME CLOCK ENABLED - this light illuminates whenever the auto-manual switch, on the time clock, is in the
auto position. If the heater will not run, check this light to see if the time clock is prohibiting the heater from
coming on.
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