Quote Originally Posted by Peter_1
He regulated the LP switch always with a ***** bottle and his manifold before connecting it to the circuit.
This is a very good idea to use. Any pressure switch should be checked for the intended operation. You can use the refrigerant pressure from a bottle (I would not recommend this in today's legal world). However, you can obtain the same result by operating the compressor down to a lower suction pressure to make sure the switch operates at the desired pressure.

Otherwise, you can plan on setting there to watch the switch operation.