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2 Read the voltage at the appropriate high voltage fan
motor plug (J86, J87, or J88) using the VAC meter set
ting.
3 If high voltage is present, check the low voltage plug
(J336, J337, or J338) for a signal from the Unit Con
troller. Use either the duty cycle (%) or a VDC meter
setting.
Note - The VDC reading may fluctuate and is normal for a
PWM signal.
ULTRA FAN MOTOR IDENTIFICATION
FIGURE 13
Compressors
1
2
Condenser Fans
2
B5
3
B21
1
B4
11-Temperature Sensors RT37 and RT38
Ultra high efficiency units are equipped with a temperature
sensor (thermistor) located on the back of each compres
sor underneath the crankcase heater. The A55 Unit Con
troller uses input from RT37 (compressor 1), RT38 (com
pressor 2) and A185 pressure transducer to calculate sump
superheat for each compressor. The Unit Controller uses
this information to optimize system reliability.
Verify the sensor value using the menu path:
MAIN MENU > DATA > IN/OUTPUTS > SENSORS > LOCAL
Sensors should read within +/- 5 degrees of actual com
pressor sump temperature. Make sure the sensor is mak
ing sufficient contact with the compressor shell.
12-Pressure Transducer A185
Ultra high efficiency units are equipped with a pressure
transducer located on the common suction line. The Unit
Controller uses the input from the transducer, RT37 and
RT38 to calculate sump superheat for each compressor.
The Unit Controller uses this information to optimize sys
tem reliability.
Verify the sensor value using the menu path:
MAIN MENU > DATA > IN/OUTPUTS > SENSORS > LOCAL
A185 should read within +/- 10 psi of actual suction pressure.
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