FISCHER [CF] EASY User Manual page 72

2.15 Compressor motor protection
The electronic controller protects the compressor motor against the following:

over current;

phase loss;

incorrect phase rotation.
If the compressor motor current exceeds a predefined (non-adjustable) current limit, the
electronic controller shuts down the unit and generates an error signal. For this function two of
the main phase supply lines to the compressor (compressor via the contactor) are routed
through the current sensors.
2.16 System pressure protection
2.16.1 High-pressure safety switch
A high pressure switch is registered by the electronic board. The sensing device is a non-
adjustable, high-pressure switch that will open in the event of an abnormally high discharge
pressure (above 28 bar on CFME & CFLE models, 28.8 bar on CFDE models).

The unit will stop then and restart automatically after a 5-minute delay and after unit
pressure has decreased to 21 bar (24 bar for CFDE models).

After 7 successive HP cut-outs over 1 hour, the unit will lock out.
2.16.2 High pressure: pressure relief valve / burst disc
There is a connection port sideways on the top of the unit liquid receiver for a pressure relief
valve or a burst disc. It is a thread with a 3/8"-NPT connection. The pressure relief valve and/or
burst disc are not factory assembled.
2.16.3 Low-pressure safety switch – Optional
In a way similar to the high-pressure sensor, the electronic controller registers the switching
action of the adjustable low-pressure switch, which will open in the event of an abnormally low
suction pressure:

The unit will stop then restart automatically after a 3-minute delay and when the unit
reaches cut-in pressure level.
The unit is always equipped with a suction pressure transmitter which is also taking care for
protection against vacuum operation. The use of the optional low-pressure cut-out will provide
the highest protection level for the unit. In rare instances of controller breakdown the optional
low-pressure switch would allow to run the unit in emergency mode.
2.17 Other inputs at the plant controller XCM25D
2.17.1 Customer-supplied control (room thermostat)
The electronic controller accepts a normal 230V AC input (DI3) On/Off signal (such as the
switching action of a normal commercial thermostat) and relays a similar action as an output to
the compressor contactor in the case of a thermostat-controlled (parameter "C05") system (see
wiring diagrams in Appendix 2). If the system is controlled by low-pressure cut-out for a multiple
evaporator system and/or pumpdown system, the controller XCM25D accepts signals directly
from an adjustable low-pressure switch (optional).
2.17.2 Case temperature controller
An alternative method of system temperature control can be used. The electronic controller
accepts an input from a common commercial thermostat (DI3).
2.17.3 Ambient temperature sensor
An ambient temperature sensor is supplied by Emerson Climate Technologies and connected to
the electronic controller. This temperature sensor has several functionalities like emergency
mode control, lower fan speed limitation and crankcase heater control. The sensor is located at
the housing on the backside of compressor compartment.
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