Bosch GreenSource SM024 Installation And Maintenance Manual page 31

SM Series Heat Pump
• 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 30°F. (Figure#98)
Figure # 98
• 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 #95)
If unit is employing a fresh water system (no
anti-freeze protection), it is extremely
important to have the Freeze1 R30 resistor
set to 30°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.
Figure # 99
SM Series Heat Pump
UPM Board Factory Default Settings
TEMP
LOCKOUT
RESET
ALARM
TEST
UPM DIP SWITCH DEFAULT POSITION
lockout
reset
alarm
test
The UPM Board includes the following features:
• ANTI-SHORT CYCLE TIMER:
break timer to prevent compressor short cycling.
• RANDOM START:
Each controller has an unique
random start delay ranging from 270 to 300 seconds
on initial power up to reduce the chance of multiple
unit simultaneously starting at the same time after
power up or after a power interruption, thus
avoiding creating large electrical spike.
• LOW PRESSURE BYPASS TIMER:
compressor is running and the low pressure switch
opens, the controller will keep the compressor ON
for 120 seconds. After 2 minutes if the low pressure
switch remains open, the controllers will shut down
the compressor and enter a soft lockout. The
compressor will not be energized until the low
pressure switch closes and the anti-short cycle time
delay expires. If the low pressure switch opens 2-4
times in 1 hour, the unit will enter a hard lockout. In
order to exit hard lockout power to the unit would
need to be reset.
• BROWNOUT/SURGE/POWER INTERRUPTION
PROTECTION:
The brownout protection in the
UPM board will shut does the compressor if the
incoming power falls below 18 VAC. The compressor
will remain OFF until the voltage is above 18 VAC
and ANTI-SHORT CYCLE TIMER (300 seconds) times
out. The unit will not go into a hard lockout.
Electrical | 31
30°F
2
Y
PULSE
NO
4 2
R Y
Cont pulse
yes no
5 minute delay on
If the
6 720 220 406 (2013/1)