Sinclair SCV-750EB Service Manual page 16

Prevents excessive refrigerant pressure by opening at 42bar and discharging refrigerant from the refrigerant system.
21. Crankcase heater:
Prevents refrigerant from mixing with compressor oil when the compressors are stopped.
22. Water side heat exchanger electric heater:
Protects the water side heat exchanger from ice formation.
23. Water flow switch electric heater:
Protects the water from ice formation.
24. Pressure gauge joint (high and low pressure side):
Charges or discharges refrigerant.
25. Capillary:
Normally return oil to the compressor.
26. Wired Controller:
Control and query the operation status of the unit.
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