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4.2.3 Protection devices
Independently from the internal motor protection, fuses must be installed before the compressor.
Selection of fuses has to be carried out according to VDE 0635, DIN 57635, IEC 269-1or EN 60-
269-1.
4.2.4 Crankcase heaters
IMPORTANT
Oil dilution! Bearing malfunction! Turn the crankcase heater on 12 hours
before starting the compressor.
Figure 13: Crankcase heater location
with liquid refrigerant under certain circumstances and system configurations, notably after
longer off cycles when the compressor has cooled. This may cause excessive start up clearing
noise or the compressor may lock up and trip on protector several times before starting. The
addition of a crankcase heater will reduce noise and dimming light complaints since the
compressor will no longer have to clear out liquid during start.
Crankcase heater – Three phase
A crankcase heater is required for three-phase compressors when the system charge exceeds
the compressor charge limit listed in Table 3 hereunder.
Model
ZR18K*
ZR22K* to ZR80K* / ZP23K* to ZP83K*
ZR94K* to ZR190K* / ZP90K* to ZP182K*
ZR250K* / ZP235K*
ZR310K* to ZR380K* / ZP295K* to ZP385K*
Table 3
The crankcase heater must be turned on a minimum of 12 hours prior to starting the
compressor and must remain energised during the compressor off cycle.
4.3
Pressure safety controls
4.3.1 High-pressure control
A high-pressure control with a maximum cut out setting of 28.8 bar(g) (ZR models) or 43 bar(g)
(ZP models) respectively is recommended.
The high-pressure control should have a manual reset feature for the highest level of system
protection.
4.3.2 Low-pressure control
IMPORTANT!
Loss of system charge! Bearing malfunction! A low-pressure control is
highly recommended for loss of charge protection. Do not bridge or by-pass
the low-pressure cut out.
Even though these compressors have an internal discharge temperature sensor, loss of system
charge etc. will result in overheating and recycling of the motor protector. Prolonged operation in
this manner could result in oil pump out and eventual bearing failure.
C6.2.19/0507-0708/E
Crankcase heater – Single phase
A crankcase heater is recommended on single-
phase compressors when the system charge is
over the charge limit shown in Table 3
hereunder. A crankcase heater is required for
systems containing more than 120% of the
compressor refrigerant charge limit listed in the
table. This includes long-line length systems
where the extra charge will increase the
standard factory charge above the 120% limit.
Experience has shown that compressors may fill
Refrigerant Charge Limit
2.7 kg
4.5 kg
7.0 kg
11.3 kg
13.6 kg
11
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