I have a 200A main panel in the house. In my shop I have a 200A sub panel. I want to install a 100A sub panel in the upstairs of the shop for a one bedroom apartment.

  • I have a 100 amp sub panel.
  • I have 25ft of #2 wire
  • I have 3 20 amp breakers for lights and outlets
    • One will be dedicated to the HVAC
  • I have a double pole 30 amp breaker for the electric stove.

Does all of this sound correct?

1 Answer 1


First, are you sure that 30A is a sufficiently large breaker for your range circuit? Most electric cooking appliances (freestanding electric ranges, cooktop/oven combinations) require a 40A or a 50A circuit.

The 20A breakers do sound correct for the lighting and receptacle circuits, although you will need more of them, as every dwelling unit must have at least two dedicated 20A small appliance branch circuits and a 20A bathroom branch circuit; if laundry facilities are present, yet another dedicated 20A branch circuit must be provided for the laundry room outlets. You will want to use a double-pole breaker for HVAC, though: all but the very smallest HVAC appliances require a 240V circuit, and this includes packaged terminal units, even though they only draw a relatively small amount of current (<20A) compared to a conventional air conditioner.

The overall capacity of the subpanel you have on hand (100A) is more than adequate for an apartment-type dwelling unit; however, you will want to check the number of breaker slots available to you in it -- full-width slots are at a premium these days due to AFCI requirements, which makes depending on tandem breakers to fit all your circuits into your panel quite unwise.

Your 2AWG wire will be adequate for the feeder conductors, since you are feeding a full dwelling unit (apartment) and thus can use the dwelling unit "83% rule" in this case. (If this were part of an apartment, you'd have to upsize to 1AWG in aluminum since a 2AWG Al conductor can only handle 90A at the 75°C termination limits imposed by a typical breaker that accepts that wire size.)

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