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(Units with Expansion Valve (TXV))
Single Stage Cooling Application: Refer to the Design Su-
perheat & Subcooling table.
Two Stage Cooling Application: Run unit on Low Stage
cooling and refer to Design Superheat & Subcooling table.
1. Purge gauge lines. Connect service gauge manifold
to access fittings. Run system at least 10 minutes to
allow pressure to stabilize.
2. Temporarily install thermometer on liquid (small) line
near liquid line access fitting with adequate contact
and insulate for best possible reading.
3. Check subcooling and superheat. System should
have a subcooling and superheat within the range
listed on the Design Superheat and Subcooling table.
a. If subcooling and superheat are low, adjust TXV
superheat, then check subcooling.
NOTE: To adjust superheat, turn the valve stem
clockwise to increase and counterclockwise to
decrease.
b. If subcooling is low and superheat is high, add
charge to raise subcooling then check superheat.
c. If subcooling and superheat are high, adjust TXV
valve superheat, then check subcooling.
d. If subcooling is high and superheat is low, adjust
TXV valve superheat and remove charge to lower
the subcooling.
NOTE: Do NOT adjust the charge based on suction
pressure unless there is a gross undercharge.
4. Disconnect manifold set, installation is complete.
Design Superheat & Subcool
Superheat
Model
±2°F
GPGM524***41
8
GPGM530***41
13
GPGM536***41
8
GPGM542***41
9
GPGM548***41
9
Cooling Operation
NOTE: Mechanical cooling cannot be reliably pro-
vided at ambient temperatures below 50° F.
1. Turn on the electrical power supply to the unit.
2. Place the room thermostat selector switch in the
COOL position (or AUTO if available, and if automatic
changeover from cooling to heating is desired).
3. Set the room thermostat to the desired temperature.
TROUBLESHOOTING
Ignition Control Error Codes
The following presents probable causes of questionable unit
operation. Refer to Diagnostic Indicator Chart for an inter-
pretation of the signal and to this section for an explanation.
Subcooling
Expansion
Cooling
±1°F
Device
Stage
5
TXV
low
9
TXV
low
10
TXV
low
7
TXV
low
7
TXV
low
Remove the control box access panel and note the number
of diagnostic LED flashes. Refer to Diagnostic Indicator
Chart for an interpretation of the signal and to this section
for an explanation.
Fault Recall
The ignition control is equipped with a momentary
push-button switch that can be used to display on the
diagnostic LED the last five faults detected by the con-
trol. The control must be in Standby Mode (no thermostat
inputs) to use the feature. Depress the push-button switch
for approximately 2 seconds. NOTE: Do not hold for longer
than 4 seconds. Holding the button for 4 seconds or higher
will erase the memory! Release the switch when the LED
is turned off. The diagnostic LED will then display the flash
codes associated with the last five detected faults. The
order of display is the most recent fault to the least recent
fault.
Abnormal Operation - Heating
Internal Control Failure
If the integrated ignition control in this unit encounters an
internal fault, it will go into a "hard" lockout and turn off the
diagnostic LED. If diagnostic LED indicates an internal
fault, check power supply to unit for proper voltage, check
all fuses, circuit breakers and wiring. Disconnect electric
power for five seconds. If LED remains off after restoring
power, replace control.
External Lockout
An external lockout occurs if the integrated ignition con-
trol determines that a measurable combustion cannot be
established within three (3) consecutive ignition attempts.
Outdoor
Ambient
If flame is not established within the seven (7) second
(°F )
trial for ignition, the gas valve is de-energized, 30 second
82
inter-purge cycle is completed, and ignition is re-attempted.
82
The control will repeat this routine three times if a measur-
82
able combustion is not established. The control will then
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shut off the induced draft blower and go into a lockout
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state.
If flame is established but lost, the control will energize the
circulator blower at the heat speed and then begin a new
ignition sequence. If flame is established then lost on subse-
quent attempts, the control will recycle the ignition sequence.
The diagnostic fault code is 1 flash for a lockout due to
failed ignition attempts. The integrated control will automat-
ically reset after one hour, or it can be reset by removing
the thermostat signal or disconnecting the electrical power
supply for over five seconds. If the diagnostic red LED indi-
cates an external lockout, perform the following checks:
• Check the supply and manifold pressures
• Check the gas orifices for debris
• Check gas valve for proper operation
• Check flame sensor
A drop in flame signal can be caused by nearly invis-
ible coating on the sensor. Remove the sensor and
carefully clean with steel wool.
19
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