Residential Air Conditioners and Heat Pumps Using R-22 and Puron® Refrigerant: Application Guideline and Service Manual
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
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Contactor Shorted Detection
If there is compressor voltage sensed when there is no demand for
compressor operation, the contactor may be stuck closed. The control
will flash the appropriate fault code. Check the contactor and control
box wiring.
No 230V at Compressor
If the compressor voltage is not sensed when the compressor should be
starting, The contactor may be stuck open or the unit disconnect or
circuit breaker may be open. The control will flash the appropriate fault
code. Check the contactor, unit disconnect or circuit breaker and control
box wiring.
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
for resistance values versus temperature.
If the outdoor air or coil thermistor should fail, the control will flash the
IMPORTANT:
IMPORTANT:
The outdoor air thermistor and coil
thermistor are factory mounted in the correct locations. Do not re–locate
thermistor sensors.
A08054
Fig. 41 – Resistance vs. Temperature Chart
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
• In cooling if the outdoor air sensor indicates
10
_
F/–12.22
_
C
warmer than the coil sensor (or) the outdoor air sensor indicates
20
_
F/–6.67
_
C cooler than the coil sensor, the sensors are out of
range.
• In heating if the outdoor air sensor indicates
35
_
F/1.67
_
C warmer
than the coil sensor (or) the outdoor air sensor indicates
10
_
F/–
12.22
_
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. (See
)
The thermistor comparison is not performed during low ambient cooling
or defrost operation.
Failed Thermistor Default Operation
Factory defaults have been provided in the event of failure of outdoor air
thermistor and/or coil thermistor.
If the OAT sensor should fail, low ambient cooling will not be allowed
and the one–minute outdoor fan off delay will not occur. Defrost will be
initiated based on coil temperature and time.
If the OCT sensor should fail, low ambient cooling will not be allowed.
Defrost will occur at each time interval during heating operation, but
will terminate after 5 minutes.
If there is a thermistor out of range error, defrost will occur at each time
interval during heating operation, but will terminate after 5 minutes.
Thermistor Curve:
The resistance vs. temperature chart shown in
enables the technician to check the outdoor air and outdoor coil
thermistors for proper resistance. Unplug the thermistor assembly from
the circuit board and measure resistance across each thermistor. For
example, if the outdoor temperature is 60
_
F/15.56
_
C, the resistance
reading across the outdoor air thermistor should be around 16,000
Ohms.
Status Codes
shows the status codes flashed by the amber status light. Most
system problems can be diagnosed by reading the status code as flashed
by the amber status light on the control board.
The codes are flashed by a series of short and long flashes of the status
light. The short flashes indicate the first digit in the status code, followed
by long flashes indicating the second digit of the error code. The short
flash is 0.25 second ON and the long flash is 1.0 second ON. Time
between flashes is 0.25 second. Time between short flash and first long
flash is 1.0 second. Time between code repeating is 2.5 seconds with
LED OFF.
Count the number of short and long flashes to determine the appropriate
flash code.
gives possible causes and actions related to each
error.
Example:
3 short flashes followed by 2 long flashes indicates a 32 code.
shows this to be low pressure switch open.
