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40 Circuit 100 Amp Panel ?

Brian G

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I ran onto an odd situation yesterday. The house I was looking at had a 12 circuit 200 amp panel built-in with the meterbase, with 6 double pole breakers in it (exterior). One was a 90 amp feeding a 40 circuit 200 amp main lug panel inside. The wires running between were no larger than #3, and they didn't wire it as a sub panel. The inside panel was almost exclusively 20 amp single pole breakers, except for 2 30 amp double poles, and almost full.

When I wrote it up I said:

A. It should have been wired as a sub panel

B. The sub panel is not being used in accordance with the manufacturers' specs or the UL listing

C. Recommended rewiring to the proper configuration and the full rating of the sub panel.

Nobody makes (or ever has made) a 40 circuit 100 amp panel. The largest I know of is 24 circuits, a far cry from 40. So my thinking is that even if the actual load is well within 90 amps (which is not my department), this is a bad arrangement and I'd be nuts to say anything otherwise. I'd be interested in hearing any comments from other angles I might have overlooked.

If they fix it they're gonna have a problem getting a 200 amp feed from the main panel, because no 200 amp breaker I'm aware of will fit in a normal double pole space, nor am I aware of any "add-on" 200 amp main kit. Not my problem of course.

Brian G.

In the Land of Sub Panel Ignorance [:-dunce]

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I've seen similar configurations before, and like you, suggested further evaluation by an electrical contractor. But . . . the electricians took the stance that as long as all the wires were properly fused--#3 copper is on the threshold of suitability for 90 amps, but acceptable--no further modifications were required. The thinking behind the arrangement you described is, in the event of an emergency, rescue workers can shut off the power and enter the house to save the occupants without fear of electrocution. The interior panel--again, as explained to me--is there for the homeowner's convenience.

The last time I wrote this condition up as a defect and was later shot down, I phoned the electrician, who was well-spoken and reasonable. "Yes, the rules you mentioned are being broken," he said. "But there aren't any exigent safety concerns, so I can't responsibly tell the homeowner she has to pay me a couple of thousand dollars to rework her electrical system."


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Yeah, I halfway expect to hear some stuff like that back from the sellers end. My clients are from out of town, so when we talk I'm probably gonna lean harder on the lack of proper sub panel wiring than the oversized (but maybe not overloaded) 100 amp panel. In any event, my job is to find this stuff and report it.

Brian G.

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