The regulator features:
The side of the regulator has a balanced bell fittings; it a number of interconnected crankcase, so including the compressor is running, including all the same maintain the crankcase pressure. This prevents the compressor is running empty the oil from the compressor suction.
In order to balance the oil level more than two regulators, the compressor must have a common suction pipe (the same suction pressure), and was adjusted to the same oil.