Operation
Polycold Cryochiller
Compressor Safety Chain
Installation and Operation Manual
Brooks Automation
6-8
214072 Revision B
Compressor Safety Chain
If the compressor does not start, it is usually caused by an item in the Compressor Safety Chain.
The compressor safety chain consists of several hardware and software interlocks that cause the com-
pressor to stop or prevent the compressor from starting.
Table 6-3: Compressor Safety Chain
Safety Chain Item
Description
Compressor ON/OFF switch
(SW1)
Switch on HMI panel controls compressor contactor. Must be manually
turned on for contactor to close and compressor to run.
Circuit breaker CB1 (CB1)
CB1 controls input power for entire compressor unit
Must be manually turned on or manually reset.
Circuit breaker CB2 (CB2)
CB2 controls power to the low voltage transformers
Must be manually turned on or manually reset.
Circuit breaker CB3 (CB3)
CB3 controls low voltage power to the control PC Board.
If off, the main control PC Board looses power and contactor opens
and all electrical valves close
Must be manually turned on or manually reset.
Emergency Off Button (EMO)
(if equipped on unit)
EMO provides emergency control for compressor contactor.
If the EMO button is pressed in, compressor contactor opens.
EMO button must be manually disengaged to enable contactor
Optional Remote Emergency
Off Button (EMO)
(if equipped on unit)
Remote EMO provides remote emergency control for compressor con-
tactor.
If the Remote EMO connection is open, compressor contactor opens.
Remote EMO connection must be closed to enable contactor
Compressor Over Temp
Switch
Over Temp switch is a thermal cut out switch located inside the com-
pressor motor and wired in series with the compressor power.
Opens when compressor motor temperature is above the rated value.
Closes when compressor motor temperature is below rated value.
Pressure switch (PS1)
Pressure switch is mounted in compressor discharge line. Wired in
series with EMO and SW1. Trigger pressure is preset.
Switch opens if discharge pressure is above the rated value.
Switch closes when pressure is below rated value.
Software “Thermal Overload”
Fault
Software monitors system performance comparing suction and dis-
charge pressures. Generates “Thermal Overload” fault when condi-
tions are met. Fault condition opens the compressor contactor.
Fault resets after a 30 minute wait period.