Nesting a new load center in the existing load center's enclosure?

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Amplitude Electrical

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Electrical Contractor
I have a question regarding a panel upgrade request that I had from a client. The method I propose is my own, not his.

Client owns a piece of commercial property being used as a store. Building is 50+ years old, and insurance company has requested that he replace the Zinsco panel that is currently in operation. The current panel is rated for 200 amps and 20 circuits. No conduits are exposed; all conduit runs are concealed within wall (plaster & lath). The existing panel physical dimensions are 81cm X 51cm X 14cm (32" X 20" X 6"). The replacement panel measures only 26" x 14" x 4"

My Idea, to avoid removing any sections of plastering or wall sections, is to remove all of the internal components ("guts") of the existing panel, and "nest" the new panel inside of the old enclosure, because it is significantly smaller. I would thereby create a "gutter" around the new panel and not have to remove any wall sections.

I would support the new panel enclosure with steel stud sections or brackets rated for the weight of the panel. I would fabricate a new dead front with a cutout hole the size of the new panel enclosure, and secure the panel dead front to that. To connect the existing conductors I would install plastic bushings into the new panel KOs to feed all of the wires into the new enclosure.

I haven't asked the building department to upgrade in this method yet, but I just wanted to ask here first: can anyone think of any blatant code violations such an installation would have?
 
Same here. We replaced fused panels with load centers, had a cover made to fit between old and new. Splices in the wireway between old panel wall and new. Old panel was in a concrete wall, RMC conduits in wall.
 
You can probably get a new panelboard (buss and breakers) that will fit in your existing box instead of installing a load center inside the box.
 
tom baker said:
Same here. We replaced fused panels with load centers, had a cover made to fit between old and new. Splices in the wireway between old panel wall and new. Old panel was in a concrete wall, RMC conduits in wall.
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I replaced some Frank Adams fused panels one time with QO loadcenters, the original opening on these particular ones happened to fit nearly perfectly around the QO loadcenter cabinet without additional modification, got lucky on that one I guess.
 
curt swartz said:
You can probably get a new panelboard (buss and breakers) that will fit in your existing box instead of installing a load center inside the box.
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You are technically right, but these days I'm all about using supplies that are available NOW, or at least available to ship- not supplies that have a 3-month lead time due to "supply chain issues..."

As an example- I got a call from the utility provider out here the morning I had scheduled a panel upgrade and he asked if the job was still on. I said yes. Then I was I was chatting with him while he was restoring the power, and he told me he had to start calling contractors the morning of the scheduled shutdown because he's had a problem with contractors cancelling work because they couldn't get a new panel. I've had to get creative on a couple jobs due to parts unavailable; seems to be the name of the game for the foreseeable future.
 
curt swartz said:
You can probably get a new panelboard (buss and breakers) that will fit in your existing box instead of installing a load center inside the box.
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How is that different than taking the panelboard out of the load center and just installing it in the existing enclosure? I was going to suggest that, but then I figuring the load center's enclosure is useful for holding the load center's dead front, making the remaining custom cover fabrication easier.

Cheers, Wayne
 
Violates the 110.26 conditions , but I do it anyway. I have also put load centers inside Nema 3R Hoffman pedestal enclosures and passed all the inspections, probably cause 110.26 just didn't occur to the authority on hand.....
 
And if the AHJ balks SQ D and Eaton will build custom panelboards and covers and list them for existing cabinets, of course they charge exorbitant prices. I have had done this in hospitals.
 
macmikeman said:
Violates the 110.26 conditions , but I do it anyway. I have also put load centers inside Nema 3R Hoffman pedestal enclosures and passed all the inspections, probably cause 110.26 just didn't occur to the authority on hand.....
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What is in violation?

Where does it say you can't put a cabinet inside a cabinet or other enclosure?

I've put loadcenters inside corrosion resistant enclosures many times as well. For one thing to get a corrosion resistant loadcenter or even panelboard in cabinet designed to fit took forever and cost a small fortune even before recent supply issues.
 
macmikeman said:
Violates the 110.26 conditions , but I do it anyway.
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Care to expand on that? If you're thinking of the depth of the working space, then 110.26(A)(1) says "Distances shall be measured from the exposed live parts or from the enclosure or opening if the live parts are enclosed." Which can reasonably be read to mean the outer enclosure in the case of multiple enclosures.

Cheers, Wayne
 
I have put new panel guts in existing enclosures many times, but I haven't put an enclosure inside another one.
 
LarryFine said:
I have put new panel guts in existing enclosures many times, but I haven't put an enclosure inside another one.
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I've done it several times too, but I have to say, I had one AHJ that didn't like it because he claimed that interior was listed WITH its respective box and cover. I was using the cover, which I agreed with him might be involved in the withstand rating since it holds the breakers in place (in some designs), but the box? He argued that the sheet metal thickness might affect the withstand rating. I eventually convinced him by pointing out that the sheet metal box for the new panel I used was actually thinner than the old one I left in the wall. But it was a 3 day back-and-forth pain in the butt.
 
Jraef said:
I had one AHJ that didn't like it because he claimed that interior was listed WITH its respective box and cover.
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So which is it, UL wise? The NEC definition of "panelboard" clearly does not include the cabinet. But is some part of the UL listing predicated on a specific cabinet? Or on certain specs of the cabinet, in excess of what Article 312 would require?

I always assumed that the reason the "wire bending space" table was in article 312 was because you might put an arbitrary panelboard in an arbitrary cabinet, in which case it would incumbent on you to confirm that the result complies.

Cheers, Wayne
 
roger said:
And if the AHJ balks SQ D and Eaton will build custom panelboards and covers and list them for existing cabinets, of course they charge exorbitant prices. I have had done this in hospitals.
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The prices aren’t too bad for loadcenter retrofits when you factor costs of having a fab shop cut you a cover. I would at least call and ask. The Eaton retrofit stuff from a US facility, so maybe not that long of a lead time.


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Don’t depend on the supply house to get you the right one either. I replaced Square D panelboard last year, probably 10-20 years old. Gave the supply house all of the numbers including the can size. New interior and cover was 6” too short. Since they screwed up, they sent a steel plate that wasn’t even painted to cover the open space. Had to drill and paint it.
 
hillbilly1 said:
Don’t depend on the supply house to get you the right one either. I replaced Square D panelboard last year, probably 10-20 years old. Gave the supply house all of the numbers including the can size. New interior and cover was 6” too short. Since they screwed up, they sent a steel plate that wasn’t even painted to cover the open space. Had to drill and paint it.
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I assume you talking about a real panelboard and not a "loadcenter". If you missed some particular accessory you might have needed a shorter box, as the accessory happened to come with rail extension and cover blank if used. Something like a feed through lugs can do that it to you if not paying attention to all the details.
 
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