Shared neutral in two control panels

D

Thread Starter

DT

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, Panel 2, 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. (neutral to hot)

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.

One side of the contactor would have the three hots from the transformer, the other side would go to the panels 120VAC outlets. 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. Only the hots would go through the contactor. Is there a problem there?. Should I use a 4-pole contactor or transfer switch? Any transients to worry about?. Any safety issues? I can supply a drawing for clarification.

Thank you
 
DEAR,

IS THERE ANY ELCB IN THE CIRCUIT DON'T SHARE THE NEUTRAL. THAT MEANS YOUR DISCONNECTER FOR THE EACH CIRCUIT SHOULD NOT BE AN ELCB. OTHERWISE NO PROBS AT ALL.

REGARDS
ROY.
 
Thank you Roy. There is no Ground Fault Circuit Interrupters. It's just two 3-pole contactors, one for each panel. Each pole has one hot leg. The neutral is bonded at transformer and shared by the other panels, not going through the contactors.
 
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