Figure 3: Absorption of moisture in ester oil in comparison to mineral oil in [ppm] by weight at 25°C and 50% relative
humidity. h = hours.
7 Accumulators
An accumulator is normally not required in dedicated heat pump applications.
Durability is ensured by the Copeland Scroll’s inherent ability to handle liquid
refrigerant in flooded start and defrost cycle operation. However, large volumes of
liquid refrigerant which repeatedly flood back to the compressor during normal off
cycles or excessive liquid refrigerant floodback during steady operation can dilute
the oil in any compressor to the point where bearings become inadequately
lubricated and wear may occur. If an accumulator is fitted, and there is no
crankcase heater, it should be piped to allow free liquid drainage during the off
cycle as shown in Figure 4.
Figure 4: Accumulator
8 Crankcase
Heaters
No crankcase heater (CCH) is required when the system charge does not exceed the following values:
3,6 kg
for
ZH 15 K4E ... ZH 26 K4E
4,5 kg
for
ZH 30 K4E ... ZH 45 K4E
A CCH is to prevent refrigerant migrating into the shell during standstill
periods. It is recommended to fit a CCH if the compressor is located outside
the building, the system charge is above the limits shown, and no
accumulator is piped to provide free liquid drainage during the off cycle as
shown. For correct mounting location of a CCH please see Figure 5.
Fig. 5: Crankcase heater location
9 Discharge
Temperature
Protection
Internal discharge temperatures reached under some extreme operating conditions
(such as loss of charge or extremely high compression ratio) can cause compressor
damage. In order to guarantee positive compressor protection, the compressor
should be equipped with an external discharge temperature sensor.
Copeland can provide such a thermostat as an accessory (see spare parts list ZH).
This thermostat is not insulated and the equivalent set point for an insulated sensor
is 120°C maximum. The thermostat should be positioned as shown in Figure 6
below.
Figure 6: Discharge line thermostat
C6.2.9/0203-1004/E 5
