Feeder to sub panel

crtemp

Senior Member
I just did a job moving a sub panel over 1 stud bay for a customer and it is fed by a 60 amp breaker. The feeder wire is 6/3 nm copper. I was under the impression that 6/3 is only good for 55 amps. This panel was inspected a little over a year ago and passed. I'm not sure who originally installed it but this is obviously on too big of a breaker correct?

Smart \$

Esteemed Member
I just did a job moving a sub panel over 1 stud bay for a customer and it is fed by a 60 amp breaker. The feeder wire is 6/3 nm copper. I was under the impression that 6/3 is only good for 55 amps. This panel was inspected a little over a year ago and passed. I'm not sure who originally installed it but this is obviously on too big of a breaker correct?
Quite possibly not. 240.4(B) permits the next greater standard size breaker rating if conductor ampacity does not correspond to a standard breaker rating.

infinity

Moderator
Staff member
55 amps is not a standard size OCPD in 240.6 so you can go up to the next standard size of 60 amps. {240.4(B)} Load would have to be 55 amps or less.

crtemp

Senior Member
55 amps is not a standard size OCPD in 240.6 so you can go up to the next standard size of 60 amps. {240.4(B)} Load would have to be 55 amps or less.
That makes sense. The sub panel in question just has a few lighting circuits in it. Are the lighting circuits in that panel calculated by square footage like normal (3 va per sq ft)?

Smart \$

Esteemed Member
That makes sense. The sub panel in question just has a few lighting circuits in it. Are the lighting circuits in that panel calculated by square footage like normal (3 va per sq ft)?
If one of the 3VA/ft[SUP]2[/SUP] occupancies (and/or area within). However, being a subpanel you have to determine by the area it serves, which may be less than the entire building/structure.

crtemp

Senior Member
If one of the 3VA/ft[SUP]2[/SUP] occupancies (and/or area within). However, being a subpanel you have to determine by the area it serves, which may be less than the entire building/structure.
Ya. It just does a couple bedrooms and a family room

kwired

Electron manager
Load calculations for dwellings are not quite as straight forward, most of what is mentioned in the NEC is for calculating a service or feeder supplying the entire dwelling. 3VA per square foot for general lighting kind of works at the feeder and service level when supplying the entire dwelling, but when it comes to calculating a single branch circuit you kind of are on your own to some extent when it comes to dwellings. The small appliance branch circuits and the laundry circuit are about the only specific circuits the NEC assigns a definite value to, next would come fixed appliances and typically their nameplate values.