Getting landed in a 400 amp panel

[User Name]

Hey guys, customer added a big addition to their building, need to get a 200 amp 3ph service to it. This is what I've got to work with, there's a fused 400 amp disconnect to the left. The panel looks like it's doing a lot but it's really not, I'd be surprised if it got over 50 amps at any given time. Really don't want to rip this out for a different box if I can help it. Could a guy tap the mains some how and set a 200 breaker disconnect right beside it? QO only makes a plug in breaker to to 100 in 3ph, they have bigger, but they're bolt on, and this isn't a bolt on panel. Or could a guy take 1 set of each phase out to feed my new panel and leave one set in the old panel?

 

[LarryFine]

Or could a guy take 1 set of each phase out to feed my new panel and leave one set in the old panel?

I was thinking this even before I got to you saying it.

Don't forget to change the 400 breaker to two 200a breakers.

High-leg delta?

 

[User Name]

I was thinking this even before I got to you saying it.

Don't forget to change the 400 breaker to two 200a breakers.

High-leg delta?

Yeah that just popped into my head as I was typing and almost didn't post but thought maybe better see what guys think.

It's a 400 amp fused knife switch that feeds that, and the switch is feed right from the POCO through CTs. Changing that might be even harder than changing that panel. I'm thinking from another job I had kind of this set up but brand new, I should be able to feed two 200s from a 400, it's just a matter of getting 200A main breakers ahead of the panels right?


Yeah 240 w/ wild leg.

 

[RdmanElect]

If you cant find a feedthru breaker at 200A , maybe ask the client what they are running and downsize the the 200a panel.. or tell them that you may need to redo their entire setup here.

 

[LarryFine]

You may be able to feed two 200a panels from one 400a switch using tap rules, if the wires are large enough, and they land on 200a breakers, not main lugs.

If the existing loads are that small, see if you can keep this panel as is, and use one of the 200a breakers, and move those wires to one of the smaller spares.

Also, there should not be two wires in the single lugs unless they're rated for it. What terminals are on the load side of the switch? Maybe replace the wires?

 

[LarryFine]

Yeah 240 w/ wild leg.

I figured because the buses were reconfigured for the two 4-section 2p breakers.

 

[User Name]

You may be able to feed two 200a panels from one 400a switch using tap rules, if the wires are large enough, and they land on 200a breakers, not main lugs.

If the existing loads are that small, see if you can keep this panel as is, and use one of the 200a breakers, and move those wires to one of the smaller spares.

Also, there should not be two wires in the single lugs unless they're rated for it. What terminals are on the load side of the switch? Maybe replace the wires?

I like what you're thinking here, but I don't think I'll be able to back feed one of the existing 200amp breakers. I'll need to maintain 3ph power in this panel for a few loads. And if I backfeed a breaker I believed it would need to have a hold down bracket, I'm guessing they don't make for this setup. But it's ok, maybe I can squeeze in a 200amp breaker disconnect and refeed that panel.

I think the main lugs in this panel are rated for two wires. Usually when the lug hole has got that "snowman" shape they are, which this has. I believe it's 3/0 thhn copper.

I believe the disconnect has two wires rated lugs also, I'd have to double check, if they aren't I know they are replaceable.

 

[hillbilly1]

You could do the tap rule, and use three hole Polaris taps on the existing feed.

 

[Perri Redder]

I would either replace or get new guts for the disconnect if it isn't 2 wire per leg. The old panel works fine, so don't fix it, just downsize the main to 200A.

 

[LarryFine]

I like what you're thinking here, but I don't think I'll be able to back feed one of the existing 200amp breakers.

That's not what I meant. I was thinking of a way to feed your new panel from this one.