C6.2.44/0219/E
17
4.2.3 Motor protection
Conventional inherent internal line break motor protection is provided for all ZRD*KRE compressor
models.
4.2.4 Protection devices
Independently from the internal motor protection, fuses must be installed before the compressor.
The selection of fuses has to be carried out according to VDE 0635, DIN 57635, IEC 269-1 or
EN 60-269-1.
4.2.5 Crankcase heaters
IMPORTANT
Oil dilution! Bearing malfunction!
Turn the crankcase heater on 12 hours
before starting the compressor.
A crankcase heater is used to prevent refrigerant migrating into the shell during standstill periods.
Due to the Copeland scroll’s inherent ability to handle liquid refrigerant in flooded conditions a
crankcase heater is not required when the system charge does not exceed the charge limits shown
in
Table 5
.
Compressor
Refrigerant
charge limit
ZRD36KRE & ZRD48KRE
3.6 kg
ZRD61KRE to ZRD92KRE
4.5 kg
Table 5
If a crankcase heater is fitted it is recommended
that the heater be turned on for a
minimum of
12 hours
prior to starting the compressor. This will
prevent oil dilution and bearing stress on initial
start-up. The crankcase heater must remain
energised during compressor off cycles.
The crankcase heater must be mounted below the
oil Schraeder valve located on the bottom shell
(see
Figure 18
).
The crankcase heater should be wired in such a way that it is turned on whenever the compressor
is switched off.
4.3 Pressure safety controls
4.3.1 IPR valve (Internal Pressure Relief valve)
The internal pressure relief valves for all ZRD*KRE compressors are located between the high
and low sides of the compressor. They are designed to open when the discharge-to-suction
differential pressure exceeds 26-31 bar. When the valve opens, hot discharge gas is routed back
into the area of the motor protector to cause a trip. During developmental blocked fan testing, it is
sometimes noted that the valve opens, but the compressor does not shut off while the discharge
pressure continues to climb. This condition is normally caused by floodback and may be corrected
by using a more restrictive expansion device or reducing the refrigerant charge.
4.3.2 High-pressure control
The cut-out setting for the high-pressure control shall be determined according to regional
standards, usually EN 378, part 2 in Europe.
The maximum pressure value for the individual compressor type, PS high side, is printed on the
nameplate of the compressor.
The high-pressure cut-out should have a manual reset feature for the highest level of system
protection.
Figure 18: Crankcase heater location
