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Help with service sizing


Tom Raymond
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I looked at the service equipment at my brothers house yesterday and need some help to make sure I'm on the right track.

The house was built mid 60's and the equipment is original, except for newer triplex overhead with crappy splices at the weather head wrapped in electrical tape (utility does really nice work huh?).

I'm pretty sure the SEC is 2AWG aluminum (I'm sure about the aluminum). Outside the cable is painted, and there is only about 16" visible on the interior and I could not find any sizing on it. I'm estimating 2ga based on conductor diameter and my charts.

The panel is a GE split, rated 125 amps, and the main disconnect consists of three 50 amp double pole breakers.

I think I have a 100 amp service here, right?

I was looking at this because he recently had a breaker melt do to an arc at a power strip that got squished by his desk, and he wants to finish a portion of his basement including a mini laundromat (two washers and driers) and needs to add several circuits as well as repair the one that faulted.

I can clean up the mess in the existing panel and add a sub for the extra circuits, but I'm thinking a new 150 amp panel (with 100 amp disco) might be a better approach, and a 200 amp upgrade the best.

Any suggestions?

Tom

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Mid-60's original and no sign that there's ever been an issue with an overheated SEC due to reloading?

It sounds like it might be a #2 tin-coated copper SEC, in which case it's rated for 125-amps and correct.

Did the SEC have a woven loom over the top of the rubber insulation or was it clean thermoplastic insulation?

If you upgrade, I'd recommend going for 200 amps; the cost isn't that much different and it gives him more wiggle room as more and more ampacity requirements are placed on the home as technology, and load, continue to march onward.

ONE TEAM - ONE FIGHT!!!

Mike

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I would suggest doing a heavy up to 200 amp. Like stated earlier the cost diffence is low.

It would also be wise to do a load calculation one the house including what the owner wishes to install in the future. By the time you buy a disconnect, a new panel, and a sub panel, you most likely could get a 200 amp main breaker panel.

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Mid-60's original and no sign that there's ever been an issue with an overheated SEC due to reloading?

It sounds like it might be a #2 tin-coated copper SEC, in which case it's rated for 125-amps and correct.

Did the SEC have a woven loom over the top of the rubber insulation or was it clean thermoplastic insulation?

If you upgrade, I'd recommend going for 200 amps; the cost isn't that much different and it gives him more wiggle room as more and more ampacity requirements are placed on the home as technology, and load, continue to march onward.

ONE TEAM - ONE FIGHT!!!

Mike

Yes the loom was woven. I was not aware that tin coated copper was still in use that late. I could only see what looked like a manufacturers name on the loom but it was virtually illegible, it didn't help any that the bottom of the panel is nearly six feet above the floor.

I will recommend a 200 amp upgrade all the way to the weatherhead.

Tom

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