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After the brownout defeat is set, power down and reinstall the
OAT/OCT sensor and remove the short from the forced defrost
pins. As long as the short on the forced defrost remains, the OAT
and OCT faults will not be cleared. The code will continue to be
flashed.
The control is shipped with the brownout active. The change in
status is remembered until toggled to a new status. A power
down/power up sequence will not reset the status. it may be
necessary to do the toggle twice to cycle to the desired state of the
defeat.
230V Line (Power Disconnect) Detection
If there is no 230v at the compressor contactor(s) when the indoor
unit is powered and cooling or heating demand exists, the
appropriate fault code is displayed. Verify the disconnect is closed
and 230v wiring is connected to the unit.
Compressor Voltage Sensing
The control board input terminals labeled VS and L2 (see Fig. 7)
are used to detect compressor voltage status and alert the user of
potential problems. The control continuously monitors the high
voltage on the run capacitor of the compressor motor. Voltage
should be present any time the compressor contactor is energized
and voltage should not be present when the contactor is
de- -energized.
Contactor Shorted Detection
If there is compressor voltage sensed when there is no demand for
compressor operation, the contactor may be stuck closed or there
may be a wiring error. The control will flash the appropriate fault
code.
If the control senses the compressor voltage after start- -up and is
then absent for 10 consecutive seconds while cooling or heating
demand exists, the thermal protector is open.
de- -energizes the compressor contactor for 15 minutes, but
continues to operate the outdoor fan. The control Status LED will
flash the appropriate code shown in Table 6. After 15 minutes,
with a call for low or high stage cooling or heating, the compressor
contactor is energized. If the thermal protector has not re- -set, the
outdoor fan is turned off.
If the call for cooling or heating
continues, the control will energize the compressor contactor every
15 minutes. If the thermal protector closes, (at the next 15 minute
interval check) the unit will resume operation.
If the thermal cutout trips for three consecutive cycles, then unit
operation is locked out for 4 hours and the appropriate fault code is
displayed.
No 230V at Compressor Contactor
If the compressor voltage is not sensed when the compressor
should be starting, the appropriate contactor may be stuck open or
there is a wiring error. The control will flash the appropriate fault
code. Check the contactor and control box wiring.
Troubleshooting units for proper switching between
low & high stages
Check the suction pressures at the service valves. Suction pressure
should be reduced by 3- -10% when switching from low to high
capacity.
Compressor current should increase 20 to 45% when switching
from low to high stage. The compressor solenoid when energized
in high stage, should measure 24vac across pin numbers PL5- -2 HI
and PL5- -5 C . When the compressor is operating in low stage, the
24v DC compressor solenoid coil is de- -energized. When the
compressor is operating in high stage, the 24v DC solenoid coil is
energized.
The solenoid plug harness that is connected to the compressor has
an internal rectifier that converts the 24v AC signal to 24v DC.
DO NOT INSTALL A PLUG WITHOUT AN INTERNAL
RECTIFIER.
Unloader Test Procedure
The unloader is the compressor internal mechanism, controlled by
the DC solenoid, that modulates between high and low stage. If it
is suspected that the unloader is not working, the following
methods may be used to verify operation.
1. Operate the system and measure compressor amperage.
Cycle the unloader on and off at 30 second plus intervals at
the User Interface (from low to high stage and back to low
stage). Wait 5 seconds after staging to high before taking a
reading. The compressor amperage should go up or down
at least 20 percent.
2. If the expected result is not achieved, remove the solenoid
plug from the compressor and with the unit running and the
User Interface or thermostat calling for high stage, test the
voltage output at the plug with a DC voltmeter. The read-
ing should be 24 volts DC.
3. If the correct DC voltage is at the control circuit molded
plug, measure the compressor unloader coil resistance. The
resistance should be approximately 330 or 1640 ohms de-
pending on unloader coil supplier. If the coil resistance is
infinite or is grounded, the compressor must be replaced.
Temperature Thermistors
Thermistors are electronic devices which sense temperature. As the
temperature increases, the resistance decreases. Thermistors are
used to sense outdoor air (OAT) and coil temperature (OCT).
Refer to Fig. 8 for resistance values versus temperature.
90
The control
80
70
60
50
40
30
20
10
0
(-17.77)
Fig. 8 - - Resistance Values Versus Temperature
If the outdoor air or coil thermistor should fail, the control will
flash the appropriate fault code. (See Table 6.)
IMPORTANT: The outdoor air thermistor and coil thermistor
should be factory mounted in the final locations. Check to ensure
thermistors are mounted properly per Fig. 9 and Fig. 10.
Thermistor Sensor Comparison
The control continuously monitors and compares the outdoor air
temperature sensor and outdoor coil temperature sensor to ensure
proper operating conditions. The comparison is:
S In cooling if the outdoor air sensor indicates ≥ 10_F
(≥ 5.6_C) warmer than the coil sensor (or) the outdoor air sensor
indicates ≥ 20_F (≥ 11_C) cooler than the coil sensor, the
sensors are out of range.
S In heating if the outdoor air sensor indicates ≥ 35_F (≥ 19.4_C)
warmer than the coil sensor (or) the outdoor air sensor indicates
≥ 10_F (≥ 5.6_C) cooler than the coil sensor, the sensors are out
of range.
If the sensors are out of range, the control will flash the appropriate
fault code as shown in Table 6.
The thermistor comparison is not performed during low ambient
cooling or defrost operation.
11
THERMISTOR CURVE
0
20
40
60
80
(-6.67)
(4.44)
(15.56)
(26.67)
TEMPERATURE °F (°C)
100
120
(37.78)
(48.89)
A08054
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