Old 3 wire 200a panels.

[markebenson]

This room I am working on has 2 existing 3 wire wye 3 phase 200a panels feeding it. It was an old restaurant now bar has much more power than required. In this room.

The main electical room however has a newer 4 wire SD 400a main feeding these 2 panels as well as a 3rd 4 wire on the roof.

My question will be should I add an isolated grounding block to these 2 existing panels? Or just treat this room as a 3 wire system .

Thx

 

[LarryFine]

With the SD system having a main in the room, where the neutral bond should be made, everything downstream is a sub-panel, and should have an isolated neutral bus and a separate grounding bus.

 

[markebenson]

Sounds good. Thank you!

 

[drcampbell]

If a panel supplies only L-L and L-L-L loads, a neutral isn't needed.

 

[LarryFine]

If a panel supplies only L-L and L-L-L loads, a neutral isn't needed.

True dat.