Main Control & Safety Features; Figure 14: Xcm25D Controller Functionality Overview - Emerson Copeland EazyCool OM 501 Series Application Manuallines

Condenser fan
control
Monitoring of the discharge
line temperature

Figure 14: XCM25D controller functionality overview

2.8.3 Main control & safety features
Suction pressure control: Each unit is equipped with a suction pressure transmitter.
The XCM25D controls the suction pressure by evaluating the input signal of the pressure
transmitter. The suction pressure regulation for OM(T)E or OL(T)E units has to be defined
by the setpoint (C16) and proportional band (C17). The signal of the suction pressure
transmitter is also used for additional functionalities, pump-down and keeping the
compressor running within the approved envelopes.
Condensing pressure control: Each unit is equipped with a high-pressure transmitter.
The XCM25D controls the condensing pressure by regulating the fan speed
corresponding to the ambient temperature. The unit controller regulates the condensing
pressure with a constant temperature difference to the ambient ("floating HP" ; factory
setting E66 = 8K).
Different control options are available. As soon as fan modulation is enabled (E01 = "2-
Modulated fan") the parameter E38 allows to choose "floating HP" (factory setting) or
control of condensing temperature inside compressor envelope. In this mode, the
compressor can run different minimum condensing temperatures based on the suction
pressure of the compressor. This is the most energy efficient way to minimize the
condensing temperature as much as possible. But it means also that the fan is running
full speed more often than in floating HP mode.
Automatic liquid injection on OL(T)E: A mechanical injection valve allows liquid
refrigerant to be injected into the scroll set of the compressor to reduce discharge
temperatures generated when the unit operates at increasing compression ratios. There
is a bulb on each compressor top cap connected to the injection valve which allows
individual regulation for each compressor. On Digital models a solenoid valve is
energized in parallel to the digital modulation solenoid valve to avoid injection during part
load conditions. The discharge line protection is realized by help of discharge line
thermostats (S3 / S4 ; Klixon), installed directly on the discharge pipe.
Compressor phase reversal: Ensures that the compressors keep running in one
direction only (clockwise = right rotation) – necessary for a compliant Scroll compressor
to compress and pump refrigerant. Reset is automatic once the phase rotation is correct
for the compressor.
Motor current overload protection: The motor current overload protection is realized
by adjustable motor circuit breaker Q02 & Q03
C6.1.9/0617/E
Digital Scroll
Liquid injection
control
Electrical
protection
Superheat
control EVI
Alarm
management
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