Emerson Copeland OMTE-76D Application Manuallines page 20

compressor top cap connected to the injection valve which allows individual regulation f or each
compressor. On digital models a solenoid valve (normally closed NC) is energized in parallel to the
digital modulation solenoid valve to avoid injection during part -load conditions. The discharge line
protection is achieved with discharge line thermostats (B11 & B12; Klixon), installed directly on the
discharge pipe.
Compressor phase reversal: Ensures that the compressors keep running in one direction only
(clockwise = right rotation) – necessary f or a compliant scroll compressor to compress and pump
ref rigerant. Reset is automatic once the phase rotation is correct for the compressor.
Motor current overload protection: The motor current overload protection is achieved by
adjustable motor circuit breakers Q02 & Q03.
Fixed high-pressure switch: This is a non-adjustable protection device designed to prevent the
compressor from operating outside of its safe high-pressure range. Reset is automatic.
▪ OMTE units:
28.8 bar cut-out / 24 bar cut-in.
▪ OLE units:
28.8 bar cut-out / 24 bar cut-in.
▪ OLTE units:
28.8 bar cut-out / 24 bar cut-in.
The high-pressure cut-out device is in the same safety chain as the discharge line thermostat. The
alarm provided by the XCM25D does not indicate if it is high pressure or high discharge temperature
alarm.
Adjustable high-pressure limitation: The unit controller provides the possibility to stop the unit at
a critical discharge pressure which is lower than the cut-out value of the fixed high-pressure switch.
The high-pressure alarm value can be adjusted with parameter E58.
Discharge temperature protection: Each unit is equipped with discharge line thermostats (DLT).
The DLT's are in the same saf ety chain as the high-pressure cut-out switches and have a common
alarm. Each compressor has its own saf ety chain. In addition, there is a discharge line sensor
installed on the discharge pipe of the digital compressor. The controller is using the signal f rom this
sensor for control purposes as well as safety functions.
Adjustable low-pressure alarm: The unit controller f eatures an adjustable low-pressure alarm
managed by the suction pressure sensor. The f actory setting of this alarm is the lowest permitted
pressure of the refrigerant with the lowest pressure-vapour properties. If needed the user can modify
this value as per the required application.
▪ OMTE units:
0.8 bar rel
▪ OLE units:
0.3 bar rel
▪ OLTE units:
0.3 bar rel
Adjustable low-pressure switch PS1: In case of controller breakdown, the low-pressure switch is
used f or emergency operation (pre-wired rescue mode components). It must be adjusted based on
running conditions and possible special requirements. The compressor envelopes published in
Select must always be respected. Further information can be found in section 2.15 "Rescue mode
(emergency mode)".
In standard operation mode the low-pressure switch will work for both compressors as a protection
device.
Each crankcase heater is connected directly to the controller. The crankcase heater will be
energized when the ambient sensor is below a given value (10 °C) and the compressor has been off
f or a period of 5 minutes. The minimum off time does not apply at initial power up.
Liquid line assembly: Composed of a filter dryer and a sight glass/moisture indicator.
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