Subpanel

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Archieb1941

Member
Location
Maryland
Hello everyone- I just recently got back into electrical work and eager to start learning. I was in a house a few days ago and noticed that they had a 6-3 wire going to the subpanel on a 60 amp breaker. My question is with the subpanel. It was a 100 amp main breaker with about 10 circuits in it. 4 were going to the kitchen, sump pump , outlets, and lights. Is it legal to do that. It just seemed to be a lot on 60 amps. Thank you and look forward to learning more.
 
The only way to ensure that the 60 amp feeder is adequate is to perform a load calculation. Just eyeballing circuit breaker sizes won't tell you much.

When you have a moment plus update your profile to include your occupation. Thanks.
 
Yes I definitely know what you mean as far as comparing to a main panel. I will try to do a load calculation. As far as the the 100 amp box I assume it’s ok to have only 60 amps going to it?
 
Disclaimer: I am not a professional electrician, nor do I portray on on TV, and I did NOT sleep at a Holiday Inn Express last night.

That being said..........

Shouldn't a sub-panel have a 4 wire feeder H-H-N-G ? (Pls excuse my terminology if it's wrong..)
 
OldBroadcastTech said:
Disclaimer: I am not a professional electrician, nor do I portray on on TV, and I did NOT sleep at a Holiday Inn Express last night.

That being said..........

Shouldn't a sub-panel have a 4 wire feeder H-H-N-G ? (Pls excuse my terminology if it's wrong..)
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Yes the feeder should have 4 conductors. For multi-conductor cables the EGC is not included in the cable designation. For example 6/3 NM cable is really 4 conductors sometimes called 6/3 + ground.
 
There was a time when a subpanel could be fed by 3 conductors (L-N-L) under certain conditions. If you have such a scenario, it may have been compliant when installed.
 
retirede said:
There was a time when a subpanel could be fed by 3 conductors (L-N-L) under certain conditions. If you have such a scenario, it may have been compliant when installed.
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What conditions? Separate structure prior to the 2008 NEC?
 
Technically, if the loads on the subpanel is over 55A, then the feeder breaker should be a 50A. 6-3 NM has to use the 60 deg column and that would be 55A.
 
Little Bill said:
Technically, if the loads on the subpanel is over 55A, then the feeder breaker should be a 50A. 6-3 NM has to use the 60 deg column and that would be 55A.
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I think you mean if the calculated load on the subpanel is over 55A, then 6/3 NM is too small.

Although the OP doesn't specify the cable type, maybe it's 6/3 MC. : - )

Cheers, Wayne
 
wwhitney said:
I think you mean if the calculated load on the subpanel is over 55A, then 6/3 NM is too small.

Although the OP doesn't specify the cable type, maybe it's 6/3 MC. : - )

Cheers, Wayne
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I'll admit the OP didn't specify the cable type. But normally when someone says 6-3. they mean NM. Kind of hard to look at 6-3 MC and know the size by just seeing the sheathing. On NM, the sheathing has the size printed on it, MC does not, or at least I've never seen it.

My point was that don't assume 6-3 NM is good for 60A unless the loads are known/calculated.
 
wwhitney said:
My point was that If the load is over 55A, the cure is to lower the load or increase the cable size. Reducing the OCPD to 50A just adds another problem, now both the cable and the OCPD are too small.

Cheers, Wayne
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I’d bet that a panel with a 60A NEC load calc will operate without issues when fed by a 50A feeder in 90% of the installations.

But, you are correct, it isn’t correct code-wise.
 
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