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TROUBLESHOOTING
When troubleshooting problems with a WSHP, consider the fol-
lowing and see Table 15:
UNIT PROTECTION MODULE (UPM)
Each unit is factory provided with a UPM board that controls the
compressor operation and monitors the safeties. The UPM board
should be one of the first areas to start with troubleshooting an
equipment issue. (See Fig. 45.)
Safety controls include the following:
•
High-pressure switch located in the refrigerant discharge
line and wired across the HPC terminals on the UPM.
•
Low-pressure switch located in the unit refrigerant suction
line and wired across terminals LPC1 and LPC2 on the
UPM board.
•
UPM board dry contacts are normally open (NO).
•
Water-side freeze protection sensor, mounted close to con-
densing water coil, monitors refrigerant temperature be-
tween condensing water coil and thermal expansion valve.
If temperature drops below or remains at freeze limit trip
for 30 seconds, the controller will shut down the compres-
sor and enter a soft lockout condition. The default freeze
limit trip is 26°F, however this can be changed to 15°F by
cutting the R30 or Freeze1 resistor located on top of DIP
switch SW1. Refer to Fig. 48, Item 3 for resistor location.
If unit is employing a fresh water system (no anti-freeze
protection), it is extremely important to have the Freeze1
R30 resistor set to 26°F in order to shut down the unit at
the appropriate leaving water temperature and protect heat
pump from freezing if a freeze sensor is included.
•
Evaporator freeze protection sensor, mounted between the
thermal expansion device and the evaporator, monitors re-
frigerant temperature between the evaporator coil and ther-
mal expansion valve. If temperature drops below or re-
mains at freeze limit trip for 30 seconds, the controller will
shut down the compressor and enter into a soft lockout
condition. The default freeze limit trip is 26°F.
(See Fig. 49 and 50.)
•
The condensate overflow protection sensor is located in
the drain pan of the unit and connected to the 'COND' ter-
minal on the UPM board.
1
2
3
4
5
17
1
Board Power Indicator
2
UPM Status LED Indicator
3
Water Coil Freeze Protection Temperature Selection [R30]
4
Air Coil Freeze Protection Temperature Selection
5
UPM Settings
6
Water Coil Freeze Connection
7
Air Coil Freeze Connection
8
LED Status-Diagnostic Connection
9
24VAC Power Input
10
Compressor Contact Output
11
High Pressure Switch Connection
12
Call for Compressor Y1
13
Low Pressure Switch Connection
14
24VAC Power Common
15
Condensate Overflow Sensor
16
Dry Contact
17
UPM Ground Standoff
Fig. 48 — Unit Protection Module (UPM)
Fig. 49 — Water-Side Freeze Protection Sensor
60
13
12
15
7
9
11
10
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