Two separate 120VAC services from output of one 3-phase, 480 to 208 Transformer

Not open for further replies.


I have a 3-phase, 480 to 208 transformer in the first compartment of a control panel that has three compartments. For simplicity I'll call these Panel 1, Panel2, and Panel 3, with Panel 1 being the one housing the transformer and a Main disconnect switch. The output of this transformer gives me 3 hots and one neutral, which I can use to supply 120VAC to three circuits in Panel 2. No problem there.

The problem is the third compartment, or panel 3. Panels 2 and 3 have to be independent because they will power two different machines. If one panel is turned off, the other should keep working. I want to supply 120VAC to both panels, yet keep one live if the other is off. Each panel has its own disconnect switch.

I thought of a way of doing this by using 3-pole contactors; one for Panel 2 and one for Panel 3. If Panel 2 is turned on, a 24VAC signal from that panel would energize the coil of the contactor and supply 120 VAC to that panel only. Same goes for Panel 3.

However, the neutral wire would be shared. Is there a problem there?. Should I use a 4-pole contactor or transfer switch? Any transients to worry about?. Please see attached image.

Thank you


Not open for further replies.