Subpanel size

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Alan32575

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Durham, NC
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Electrician
So I'm adding a 100a subpanel that will hold a 50amp furnace, 2x 15amp lighting circuits, 1x 20 amp kitchen GFCI circuit and maybe 1x bathroom circuit.

My question is do I need to go the full 100a breaker to the sub?
 
No.
You need to calculate your actual load but from data given 85 amps would be max load if you placed your breakers correctly.
 
Alan32575 said:
So I'm adding a 100a subpanel that will hold a 50amp furnace, 2x 15amp lighting circuits, 1x 20 amp kitchen GFCI circuit and maybe 1x bathroom circuit.

My question is do I need to go the full 100a breaker to the sub?
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It is a feeder circuit. it needs to be at least what the feeder circuit calculations say it has to be.
 
Note that if you are installing a common 100A panel that is supplied with a 100A main breaker, and you feed this with say a 70A breaker from the supplying panel, you will raise some eyebrows.

This _is_ perfectly code compliant unless there is some sort of selective coordination requirement (not likely in a residence).

But some people might be confused, and if your customer expects a '100A panel' then they might not be happy. Make sure your customer knows they are getting a feeder and panel to suit their loads, not a 100A panel.

-Jon
 
I realized I can run the furnace on the main panel. I'm pulling the old 10-3 and following in behind with the new wire for my furnace. So that won't be burdening my sub.
 
winnie said:
Note that if you are installing a common 100A panel that is supplied with a 100A main breaker, and you feed this with say a 70A breaker from the supplying panel, you will raise some eyebrows.

This _is_ perfectly code compliant unless there is some sort of selective coordination requirement (not likely in a residence).

But some people might be confused, and if your customer expects a '100A panel' then they might not be happy. Make sure your customer knows they are getting a feeder and panel to suit their loads, not a 100A panel.

-Jon
Click to expand...


I 100% agree and I already told the customer.
 
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