Adding a subpanel to the garage.

[Chad M]

Hello all, I hope this question isn't too obvious, but I've read enough now to wonder if I'm under thinking the process.

I just moved into a new place and the detached 22x22 garage (with a loft) has a single 10/3 wire entering the building, through a conduit.

I traced the wire to the house's 100 amp panel. This is a 220v circuit on a 30 amp breaker.

Back in the garage, the wire exits the conduit, directly into a 4" junction box in the wall. This looks like the original wiring (1998 date code on the wire).

Each leg of the 220v is servicing a 110v circuit. There are three electrical outlets on one circuit and 7 lights (4 interior, 3 exterior) and one over head door operator on the other.

I'd like to take that 10/3 220v and power up a small subpanel in the garage.

I need a 220v (15 amp) outlet for my compressor and I'd like to add a half dozen more lights to the shop ceiling.

I'm planning on using a 15 amp breaker for the 220v circuit and then run the other two circuits on 15 amp circuits. I don't think I'd be drawing over 10amps on either of those 110v circuits, even with my Hobart 140.

My big question is, and it comes from reading another recent thread; is there something I'm missing? It seems pretty straight forward but I'm not an electrician, though I've successfully (not burned down the last garage in 10 years) done this before.

Thanks for any insight, it's very much appreciated.

Chad.

 

[TRWham]

What you have now sounds like a multi-wire branch circuit (MWBC) and allows more amperage to a detached building while avoiding a sub-panel but still staying within the one feeder restriction. Code does not allow 30A circuits to serve lighting in a dwelling, or 15 or 20A receptacles anywhere, so what you have may not be strictly correct. What size is the wiring inside the garage? Are there any additional circuit breakers in the garage?

You should be able to add a small sub-panel on the existing feeder, but you will need to add ground electrodes and isolate the neutral and ground in the building.

 

[Chad M]

Thanks for the reply.

The garage is 14/2 everywhere else and there are no additional circuit breakers.

I am in Canada and this work looks to have been done in 1998. There is an inspection sticker from the local authority so perhaps this was a standard 20 years ago?

Chad.

 

[TRWham]

I am not very familiar with Canadian code, but the basics are similar. Regardless, what I say is based on experience with NFPA 70 in the US.

You have 14 AWG cables protected by a 30A circuit breaker, which (with some exceptions called out in the NEC) is not correct, and was not in 1998 either. It seems your wiring is already set up for a sub-panel for the most part. Perhaps that is what was originally intended but never completed for some reason.

I would install a sub-panel as you intend and you will find many resources here to keep you straight. The main thing is to install ground rods for the detached structure as required and isolate the ground and neutral as with any other sub-panel.