Feeding a Sub Panel

Specific Inspection Topics Electrical Inspections
#1

Hi Folks,

Need some input. Today I came across a sub panel that is fed from the main panel. All good so far. However, in the main panel the ungrounded conductors feeding the sub were attached to the buss bars using lugs, no breaker present. These means there is no way to shut off power to the sub if necessary without shutting off power to the home. Also, I don’t really know the size of the service to the sub panel (the sub panel is located in the laundry room of the home).

Should the circuit to the sub panel should be protected by a breaker?

Thanks,

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#2

David,
Do you have any additional photos of this panel? I only ask because I’ve never seen one that looked like that before and I’m curious what the full panel looks like.

#3

If the sub is in the same building as the service a disconnect is not needed.

Did the sub have a breaker to provide OCP?

#4

If the main is 100 amps (cannot tell for sure from the photo) and the feeder conductors to the subpanel are 100 amps then there is no problem. If the sub is in the same structure then it can be a MLO (main lug only) panel.

#5

Thanks for the info folks. Yes, the main is 100 amps and on the same structure. I continued to do some research, checked with and electrician friend, and he also said that as long as the wires feeding the sub can handle 100 amps a breaker is not needed (because the main is only 100 amps).

I have included more pictures of the panel for those who are interested. These panels are pretty common in northern California.

Thanks again for the help. Having you all as a resource is a big help!

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#6

As long as the conductors are rated for 100amp that is ok. An important note to remember is that because you have another load (branch circuit) in the main disconnect the 83% size reduction of the feeders no longer applies so the regular #4cu or 2AL would not be allowed. #3 cu or 1AL would be correct in this case.

#7

Also, you say this goes underground? If so you have the wrong wiring method if that is NM-B or Romex. None metallic sheathed cable is not allowed to go underground, even if in approved conduit. Underground conduit is considered a wet location in the NEC.

#8

As long as the conductors are properly sized, this is not an issue. This is a very common setup for manufactured homes with attached garages.