TROUBLESHOOTING
When troubleshooting problems with a WSHP, see Table 18.
Thermistor — A thermistor may be required for single- phase units where starting the unit is a problem due to low voltage. See Fig. 26 for thermistor nominal resistance.
Control Sensors — The control system employs 2 nom- inal 10,000 ohm thermistors (FP1 and FP2) that are used for freeze protection. Be sure FP1 is located in the discharge fluid and FP2 is located in the air discharge. See Fig. 27.
Resistance (kOhm)
90.0
80.0
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0.0
Temperature (C)
Fig. 26 — Thermistor Nominal Resistance
AIRFLOW
(°C)
THERMISTOR
AIR |
COIL |
AIRFLOW
(°C)
EXPANSION
VALVE
FP2FP1
COAX
SUCTION
COMPRESSOR
DISCHARGE
CONDENSATE |
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OVERFLOW | LIQUID |
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(CO) |
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LINE | WATER IN | WATER OUT | ||||
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AIR COIL |
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WATER |
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FREEZE |
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PROTECTION | COIL |
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| PROTECTION |
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LEGEND
COAX — Coaxial Heat Exchanger
Airflow
Refrigerant Liquid Line Flow
Fig. 27 — FP1 and FP2 Thermistor Location
30
