Bosch SM024 Installation, Operation And Maintenance Manual page 32

32 | Electrical
If the thermostat is provided with a malfunction
light powered off of the common (C) side of the
transformer, a jumper between "R" and "COM"
terminal of "ALR" contacts must be made.
If the thermostat is provided with a malfunction
light powered off of the hot (R) side of the
transformer, then the thermostat malfunction
light connection should be connected directly to
the (ALR) contact on the unit's UPM board.
Each unit is factory provided with a Unit Protection
Module (UPM) that controls the compressor
operation and monitors the safety controls that
protect the unit.
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.
UPM Board Dry Contacts are Normally Open
(NO)
• Water side freeze protection sensor, mounted
close to condensing water coil, monitors
refrigerant temperature between 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 compressor and enter into 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
Figure #98, item [3] for resistor location),
Refer to Figure #99 for sensor location.
Figure # 99
6 720 220 406 (2015/02)
NOTE: 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 your heat
pump from freezing if a freeze sensor is
included.
• Evaporator freeze protection sensor, mounted
after the thermal expansion device and the
evaporator, monitors refrigerant temperature
between the evaporator coil and thermal
expansion valve. If temperature drops below or
remains 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. (Figure#100)
• The condensate overflow protection sensor is
located in the drain pan of the unit and
connected to the 'COND' terminal on the UPM
board. (Figure #101)
Subject to change without prior notice
SM Series Heat Pump
Figure # 100
SM Series Heat Pump