Lennox LCH092H Unit Information page 42

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
Compressors
1
2
FIGURE 13
Condenser Fans
2
B5
1
B4
3
B21
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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