Johnson Controls SABROE HeatPAC, Operating Manual

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Operating manual - HeatPAC with reciprocating compressor
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009332 en 2021.07
Design and function
3.2.8 High-pressure regulation system (electrical)
The HeatPAC unit has an electrical expansion system. The system is connected to the condenser outlet
and regulates the liquid level in the receiver and controls the expansion between the high and low pres-
sure sides of the refrigeration plant.
The liquid level in the condenser is controlled by the level sensor, pos. 1, Fig. 16, fitted in the receiver.
The sensor registers whether there is refrigerant vapour or liquid in the receiver. At increasing liquid lev-
el, the level sensor signals to an electrical regulator in the electrical panel, which signals the expansion
valve, pos. 2, Fig. 16, to open and vice versa.
During normal operation, the receiver should be a little more than half full.
In UniSAB III, the set point for the liquid level must be set at 20% in order for the receiver to be a little
more than half full. See subsection 8.5 for set-up of the AKS 4100 280 mm level sensor.
Fig. 16: High-pressure regulation
3.2.9 Automatic oil recovery system from evaporator
The relatively small amount of oil leaving the compressor and oil separator with the discharge gas is
gradually collected at the bottom of the evaporator.
An oil recovery pot, Fig. 18, is connected to the evaporator by a pipe. From the recovery pot, the oil is
automatically returned to the compressor.
A float is fitted in the oil recovery pot, pos. 9, Fig. 17. It has the exact density which allows it to float on
the collected oil and sink in R717.
The float has a built-in reed switch which activates the solenoid valve, pos. 8 in Fig. 17, in the oil return
line to the compressor and the solenoid valve, pos. 7 in Fig. 17, on the hot gas line. The oil is led directly
to the compressor suction side, driven by the pressure difference between the LP and HP sides.
The oil pot has an integrated piston which is driven by the discharge gas. The piston closes the connec-
tion to the evaporator during the oil recovery cycle.
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