12
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, VR and L2 on 286A
models and VS and L2 on 288A models (see Fig. 6) 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.
286A Models -- Compressor Thermal Cutout
The control senses the compressor voltage at VR and VS. When
starting or running, a phase difference of the voltages on the inputs
will indicate the thermal protector is closed. If the phase difference
is 5
_
or less for 10 seconds, the internal protector is open. The
control de--energizes the appropriate 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
appropriate 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.
288A Compressor Thermal Cutout
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.
The control
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.
Low or High Contactor Open (286A models) / No 230V
at Compressor Contactor (288A models)
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.
286A Models Only -- Compressor Start Detection on
Models with Bristol Compressors Only
In low stage, if the specified start voltage at VR terminal is not
achieved, the start relay is de--energized after 1 second and the
control will flash the appropriate fault code.
In high stage, if the specified start voltage at VS terminal is not
achieved, the start relay is de--energized after 1 second and the
control will flash the appropriate fault code.
If the specified start voltage is not achieved for 3 consecutive low
stage starts, low stage operation is locked out for 30 minutes. If the
specified start voltage is not achieved for 3 consecutive high stage
starts, high stage operation is locked out for 30 minutes. The
control will flash the appropriate fault code.
Troubleshooting 286A units for proper switching
between low & high stages
Check the suction and liquid pressures at the service valves.
Suction pressure should be reduced by 5--10% when switching
from low to high capacity. There should be a 10--20% increase in
liquid pressure when switching from low to high capacity.
Compressor current should increase 100--250% when switching
from low to high stage.
Troubleshooting 288A 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.
NOTE
: The liquid pressures are very similar between low and
high stage operation, so liquid pressure should not be used for
troubleshooting.
Compressor current should increase 20--45% when switching from
low to high stage. The compressor solenoid when energized in
high stage, should measure 24vac.
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 UI (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 per-
cent.
2. If the expected result is not achieved, remove the solenoid
plug from the compressor and with the unit running and the
UI calling for high stage, test the voltage output at the plug
with a DC voltmeter. The reading 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 32 to 60 ohms depending on com-
pressor temperature. If the coil resistance is infinite, much
lower than 32 ohms, 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. 7 for resistance values versus temperature.
286A
/288A
