36
TROUBLESHOOTING
(Fig. 16 and 17, and Table 14)
When troubleshooting problems with a WSHP, consider the
following:
Thermistor —
A thermistor may be required for single-
phase units where starting the unit is a problem due to low
voltage. See Fig. 16 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. 17.
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
0.0 20.0 40.0 60.0 80.0 100.0 120.0 140.0
Temperature (F)
Resistance (kOhm)
Fig. 16 — Thermistor Nominal Resistance
SUCTION
COMPRESSOR
DISCHARGE
COAX
EXPANSION
VALVE
FP2
FP1
LIQUID
LINE
WATER IN
WATER OUT
CONDENSATE
OVERFLOW
(CO)
AIR COIL
FREEZE
PROTECTION
WATER
COIL
PROTECTION
THERMISTOR
(°F)
(°F)
AIR
COIL
AIRFLOW
AIRFLOW
LEGEND
Fig. 17 — FP1 and FP2 Thermistor Location
COAX —
Coaxial Heat Exchanger
Airflow
Refrigerant Liquid Line Flow
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