13
24ANA7 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 degrees 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 5. After 15 minutes, with a call for low or
high stage cooling, 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.
24ANA1 MODELS, COMPRESSOR THERMAL CUTOUT
If the control senses the compressor voltage after start--up, and is
then absent for 10 consecutive seconds while cooling 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 5. After 15 minutes, with a call
for low or high stage cooling, the compressor contactor is
energized. If the thermal protector has not re--set, the outdoor fan
is turned off. If the call for cooling 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 (24ANA7 MODELS)
/ NO 230V AT COMPRESSOR (24ANA1 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.
24ANA7 MODELS ONLY, COMPRESSOR START
DETECTION
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 24ANA7 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 24ANA1 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.
MAJOR COMPONENTS
2--STAGE CONTROL
The two--stage control board controls the following functions:
-- Low-- and high--stage compressor contactor operation
-- Outdoor fan motor operation
-- Low ambient cooling
-- Crankcase heater operation
-- Compressor external protection
-- Pressure switch monitoring
-- Time delays
-- On 24ANA7 models, start relay and capacitor
FIELD CONNECTIONS
On 24ANA7 models with non--communicating (non--Infinity)
system, the two--stage control receives 24vac low--voltage control
system inputs through the R, C, Y1, and Y2 connections located
at the bottom of the control board (see Fig. 10)
All 24ANA1 models are part of a complete Infinity
communicating system and use only the ABCD connections on
the circuit board.
TWO STAGE COMPRESSOR
The two stage compressor contains motor windings that provide
2--pole (3500 RPM) operation. Refer to Table 3 for correct
winding resistance.
COMPRESSOR INTERNAL RELIEF
The compressor is protected by an internal pressure relief (IPR)
which relieves discharge gas into compressor shell when
differential between suction and discharge pressures exceeds 500
-- 550 psi on 24ANA7 models and 550 -- 625 psi on 24ANA1
models.. The compressor is also protected by an internal overload
attached to motor windings.
COMPRESSOR CONTROL CONTACTORS
The contactor(s) have a 24 volt coil. The electronic control board
controls the operation of the appropriate contactors.
24AN
A