Safety Devices & The Upm Controller - Bosch CE025 Installation And Maintenance Manual

safety devices and the uPM Controller
Always disconnect power before changing
jumper positions on the interface board and
reset the unit afterward.
To the left of the red and green status LED's is a row
of 1/4" male quick connects. These are used to pass
thermostat inputs on to the rest of the control circuit.
Remember to always turn off unit power at the circuit
breaker before attaching or disconnecting any wiring
from these connections to avoid accidental short
circuits that can damage unit control components.
safeTY deVICes and THe
uPM ConTroller
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.
• Optional 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 30°F,
however this can be changed to 15°F by cutting
the R42 resistor located on top of DIP switch SW1.
• The optional condensate overflow protection
sensor (standard on horizontal units) is located in
the drain pan of the unit and connected to the
'COND' terminal on the UPM board.
Revised 05-12
Caution
Subject to change without prior notice
If freeze protection sensor is not installed, a
jumper between freeze contacts must be installed
on the UPM board otherwise unit will not start.
The UPM includes the following features:
• anTI-sHorT CYCle TIMe—5 minute delay on
break timer to prevent compressor short cycling.
• randoM sTarT—Each controller has a unique
random start delay ranging from 270 to 300 seconds to
reduce the chances of multiple units simultaneously
starting after initial power up or after a power
interruption, creating a large electrical spike.
• loW Pressure bYPass TIMer—If the compressor is
running and the low pressure switch opens, then the
control will keep the compressor on for 120 seconds.
6 720 220 048
CE Series 9
Freeze
Protection
Sensor