Figure 7: Xcm25D Controller Functionality Overview - Emerson Copeland EazyCool ZX Series Application Manuallines

Condenser fan
control
Monitoring of the discharge
line temperature

Figure 7: 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.
Setpoint and proportional band need to be defined during commissioning. The signal of the
suction pressure transmitter is also used for additional functionalities, eg, pump-down and
keeping the compressor running inside 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
high pressure transmitter signal.
Automatic liquid injection on ZXME: The electronic controller automatically instructs liquid
refrigerant to be injected into the suction line of the Scroll compressor to reduce discharge
temperatures generated when the unit operates at increasing compression ratios. The electronic
controller reacts automatically to a thermistor which is attached to the discharge line on all ZXME
models. The controller converts this signal for the linear stepper motor driving the liquid injection
valve to a position that enables the compressor to continue operating within its safe envelope.
Automatic enhanced vapour injection (EVI) on ZXLE: Control of an electronic expansion
device based on the superheat in the additional heat exchanger for the EVI Scroll compressor to
create subcooling in liquid refrigerant coming from the receiver. In case of excessive discharge
line temperatures (DLT) the superheat control is ignored and the controller will work in liquid
injection mode in order to reduce the discharge gas temperature.
Compressor phase reversal (ZXME/ZXLE): Ensures that the compressor remains 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 (ZXME/ZXLE/ZXDE): This feature eliminates the need for
external current protection for the compressor motor.
Fixed high-pressure switches: This is a non-adjustable protection device designed to prevent
the compressor from operating outside of its safe high pressure range. Reset is automatic for a
set number of trips (7), then the unit will lock out and require manual restart. This feature is
important to prevent the ZX unit from cycling under these controls for a long period of time.

ZXLE & ZXME models: 28 bar cut-out / 21 bar cut-in.

ZXDE models: 28.8 bar cut-out / 24 bar cut-in.
Discharge temperature protection: Each unit is equipped with a discharge line sensor (NTC).
The information from the NTC sensor is used to activate liquid injection when required. The
XCM25D controller will stop the compressor if discharge temperatures reach unacceptable
levels.
Option: Adjustable low-pressure switches PS1: This device protects the system against low
pressure operation. It must be adjusted depending on running conditions and potential special
requirements like pumpdown. The compressor envelopes published in Select must be respected
10
Digital Scroll
control (ZXDE)
Electrical
protection
Liquid injection
(ZXME)
Superheat
control EVI
(ZXLE)
Alarm
management
C6.1.6/0613-0915/E