Flooded type water cooled screw chiller (PCB Control)
MCAC-CTSM-2012-11
73
The units are equipped with compressor protection modules built in the wiring cabinet of compressor.
INT69 HBY and JTX-A module is designed to detect the motor winding temperature, phase sequence
and phase loss. The detecting signal of JTX-A is voltage type. When motor winding temperature reaches
set point, the module will cut off control circuit immediately. The module with phase sequence control
can prevent motor reversal due to the adverse consequences. When any one phase loses, the module
will cut off main power after a short delay to protect the motor from burning. When phase unbalance
happens, it cuts the power immediately. In order to avoid interference and discriminate between false
voltage drop and malfunction as phase loss or phase unbalance during motor operating, JTX-A will cut
off main power after 3-5s delay.
Thermal overload relay
Each compressor is equipped with one thermal overload relay to protect the compressor against
overcurrent. Bypass the current transducers or make any changes to the factory default set points is
forbidden. The configuration of the module defines the Must Trip Amps (MTA) at which the thermal
overload relay will turn the compressor off.
High/low pressure switch
All compressors have factory-installed high/low-pressure switches. See Table.6.10
Table – High/low-pressure switch settings
UNIT
High-pressure switch setting
Low pressure switch setting
Protection Value
Reset Value
Protection Value
Reset Value
LSBLG***/MCFN 14bar
9bar 1bar
2bar
Table.6.10
If the high pressure switch continuously opens for 3s during operation, the compressor will be shut down.
A manual reset of the control is required to restart the compressor. If the low pressure switch
continuously opens for 1s during operation, the compressor will be shut down. It will reset automatically
when malfunction gets solved and cleared on the malfunction record page of touch screen. Sometimes if
the malfunction cannot be solved by reset, consider replace the pressure switches.
Evaporator protection-Low Water Temperature
PCB is programmed to shut the chiller down if the leaving water temperature drops below 4 °C. When