Jumping the gun

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keith gigabyte

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New Kensington, Pa
Ok I'm jumping the gun here asking before I actually look it up but hey here goes.
call from one of my regular real estate companies. House failed home inspection because main breaker is 125 amp and only 100 amp entrance cable. I know it's a 125 amp main because I did some fixture change outs before they put it on market. I'm going to look it up for code violations but who has ever seen a resi panel with 125 amp main breaker? This is about 1975-79 vintage GE and looks to be painted white from factory (panel cover and tub).
Just interested if anyone else has run across these panels.
Also it's underground feed from power company
 
keith gigabyte said:
Ok I'm jumping the gun here asking before I actually look it up but hey here goes.
call from one of my regular real estate companies. House failed home inspection because main breaker is 125 amp and only 100 amp entrance cable. I know it's a 125 amp main because I did some fixture change outs before they put it on market. I'm going to look it up for code violations but who has ever seen a resi panel with 125 amp main breaker? This is about 1975-79 vintage GE and looks to be painted white from factory (panel cover and tub).
Just interested if anyone else has run across these panels.
Also it's underground feed from power company
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Most Main Lug Only panels are rated 125A as far as the bus size is concerned, then you get a kit to add a Main CB if you want it. 100A or 125A, that's up to the service size you get.

Maybe it was originally a 100A main and someone swapped it out with a 125A to get "more power". But if the utility feed was 100A, that was a problem. But what entrance cables are you talking about? If the utility feed lands on the main, as in a meter-main setup, the size of that cable is the utility's business. They have their own rules on cable sizes. What really matters is if the utility knows it's a 125A feed or not, as it relates to their transformer size. If it's the cables from a separate meter to feed the main CB and those are for 100A, then yes that's a problem.
 
Even if the wires do not belong to the utility, and that the NEC does therefore apply, you might be able to apply 310.15(B)(7).
 
mjf said:
copper or aluminum conductors?
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+1

and what size are they?

#2 copper or 1/0 aluminum would be OK here. whether you apply 310.15(B)(7) or not. If not a dwelling you are still rounded up to next standard device but won't have all 125 amps available for load calculations purposes.
 
Not too uncommon in this area. "Standard" size with most manufacturers as either a MB or convertible main lug panel.
I agree with others. I'd check my wire size in relation to 310.15(B)(7). The original "inspector" might not have been aware of that Table.
 
You also need to check the insulation type. Back in the 70's type TW was popular but it is not on the list of permitted conductors in the old 310.15(B)(7).
 
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