I've got an 5 HP 3 phase air compressor wired through a rotary phase converter into a single phase 240 service panel, 3 legs of power ( one manufactured two from the service panel) and a ground/neutral. The compressor shuts off and turns on with a 110 volt pressure sensing switch. When I wired the pressure switch I jumped the 110 volt supply from one leg of the 3 phase supply and my 110 neutral is the 3 phase ground. This works fine but is it dangerous? cheebster direcway com add the at and the dot
Equipment Ground
Aug 18, 2004
2 Replies
grounds are meant to carry current in case of a fault. Neutrals are a grounded conductor that are intended to carry current for single phase loads. It is a violation of the NEC to do what you have done. Will it work, sure. Will it kill anyone, probably not. Up to you if you change it. My suggestion is to use the voltage from the supply side and that neutral for the coil. Not at all uncommon to have several sources of voltage in a starter
Yes that wiring configuration is dangerous. The basic principal of machine safety is that it should take two or more failures to create a hazard.
As you have it wired if the Equipment Grounding Conductor goes open the entire metal frame of the air compressor will go hot to 120 volts. If you had a separate neutral conductor the compressor would stop working but there would be no immediate danger to a user.
-- Tom H
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