GPGM3 Installation Manual
22
Pressure Switch Stuck Open
A pressure switch stuck open can be caused by a faulty
pressure switch, faulty wiring, a disconnected or damaged
blower.
If the control senses an open pressure switch during the
pre-purge cycle, the induced draft blower only will be ener-
gized. If the pressure switch opens after ignition has begun
cycle begins, and the induced draft blower remains on. The
Pressure Switch Stuck Closed
A stuck closed pressure switch can be caused by a faulty
pressure switch or faulty wiring. If the control encounters
a pressure switch stuck closed, the induced draft blower
Open Thermal Protection Device
If the primary limit switch opens, the gas valve is immediate-
ly de-energized, the induced draft and air circulating blowers
are energized. The induced draft and air circulator blowers
remain energized until the limit switch recloses. The diag-
A primary limit will open due to excessive supply air tem-
total external duct static, blower motor, blower motor speed
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ly reset once the temperature falls below a preset level.
Primary Limit
A primary limit will open due to excessive supply air tem-
total external duct static, blower motor, blower motor speed
-
ly reset once the temperature falls below a preset level.
Auxiliary/Secondary Limit
faulty limit, or a failed circulator blower can cause this limit
-
a heating cycle may also cause the auxiliary limit to open.
The automatic reset secondary limit is located on top of the
circulator blower assembly.
Rollout Limit
blocked or cracked heat exchanger, a failed induced draft
device is a manual reset limit located on the burner brack-
corrected before resetting the limit.
Flame Detected with Gas Valve Closed
combustion and air circulator blowers are energized. The
The control can be reset by removing the power supply to
the unit or it will automatically reset after one hour. Miswir-
ing is the probable cause for this fault.
Under some conditions, the fuel or air supply can create a
amber diagnostic LED. The unit will continue to operate
The automatic ignition control has a built-in feature that
prevents damage to the compressor in short cycling situa-
tions. In the event of intermittent power losses or intermit-
tent thermostat operation, the ignition control will delay out-
put to the compressor contactor for three minutes from the
-
cate the compressor contactor output is being delayed.
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High Pressure Switch/Low Pressure Switch
Some models include a high pressure cutout switch and/
or a loss of charge cutout switch. The high pressure cutout
switch protects the refrigeration system from excessive
operating pressures. The loss of charge cutout switch pro-
tects the refrigeration system from very low operating pres-
sures due to a loss of refrigerant. Compressor operation
will be disabled if either of these devices opens. If either
indicate that a refrigeration system pressure switch is open.