220 PS dedicated receptacle in detached garage

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Forum topic by chuckjq posted 12-23-2013 03:52 PM 1097 views 0 times favorited 4 replies Add to Favorites Watch
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1 post in 1582 days

12-23-2013 03:52 PM

Topic tags/keywords: 220v receptacle garage workshop electrical panels diy

I want to replace one of two existing 120V receptacles in my detached garage with a 220V/30 amp receptacle. The existing receptacles and lights are fed from 2 120V circuit breakers in the main panel in the house. Can I simply replace the existing 4 + ground 12 gauge wires with 4 + ground 8 gauge wires and feeding the 220V receptacle from the 220V hot wires and the existing 120V circuits from one of the hot wires and the neutral, thereby negating the need for a separate sub panel. I will replace the 2 120V circuit breakers in the main panel with a 40 amp 220 volt circuit breaker. BTW, the conduit going to the garage is 1” rigid conduit about 50’ away. Suggestions will be much appreciated. I am not a licensed electrician but am a computer engineer and grew up working in my dad’s Electric, Plumbing and Heating Company.

4 replies so far

View helluvawreck's profile


30765 posts in 2833 days

#1 posted 12-23-2013 04:16 PM

Chuck, this is something that you should talk to an electrician about and you should let him do the work under the code. If something were to happen you could be in trouble with your insurance and maybe the authorities as well.

He could put you maybe a 60 amp sub service panel in your shop and feed it from a breaker in your house panel with all the other necessary safety precautions. Then you could have a few breakers in your shop. The main thing is that it would all need to be done by the code for your protection. Insurance companies are starting to get very strict about electrical wiring and if there were a fire that was caused by faulty wiring they may simply refuse to pay you. There’s a lot of fine print in insurance policies. This is just my two cents anyways.

helluvawreck aka Charles

-- helluvawreck aka Charles,

View REO's profile


928 posts in 2041 days

#2 posted 12-24-2013 04:37 PM

Pull the 220 through in addition to the existing circuits and dedicate for 220. It is not against code to run a composite circuit of 220 and split off 110’s. you have to use a double breaker not two singles and it can be frustrating to have the whole shop go down because you tripped a 110 circuit. I wouldn’t suggest running 8 gauge and the corresponding breaker to a typical 15-20 amp outlet though. Your circuit protection might become the cord on the faulty item turning into a heater. stick with the 12 gage 20 amp 110 set up and pull in the 220 circuit in addition on its own. there is room in the conduit for the 3/12’s and 4/8’s useing one of the 8’s as a common ground. If it is over 100 feet get local advise on the voltage drop and size the wire accordingly.
most places allow the homeowner to do their own wiring. permits are not that expensive and they are cheap CYA. As Charles has said a sub panel would be the best choice.

View Sunstealer73's profile


166 posts in 2059 days

#3 posted 12-24-2013 10:28 PM

I thought code only allowed a single branch circuit to a detached garage? You can’t run multiple 120 and 240 circuits to a detached garage.

I would empty the existing conduit, pull in larger conductors, and install a sub-panel in the garage.. much more flexibile and would be to code. Pull a permit and do it right.

View jonah's profile


1659 posts in 3265 days

#4 posted 12-25-2013 03:37 AM

You can technically run a hybrid circuit where you are powering 120V receptacles off a 240V breaker, but it is very much against electrical code (and potentially dangerous). It is a bad idea for a lot of reasons.

If you have conduit running from house to garage, do what Sunstealer proposed and run larger wire to a sub panel there. If you don’t have conduit, you can still run direct burial rated wire to a garage sub panel without installing conduit. At least you can where I live.

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