Installing a 220 Volt Receptacle, 120 Volt Receptacles and Lighting Circuits in a Garage
January 18, 2007
Q: I’m going to run 220 to my garage, two wires will be hot and a neutral, I’m going to run the outlets using one hot side and a neutral and the lights using the other hot wire and a neutral, at the 220 outlet i will have two hots, will the third wire be a neutral or ground?
A: You can’t do this! This is a National Electrical Code (NEC) violation and extremely unsafe. The circuit breaker will not protect your 120 volt circuits and someone will get seriously injured.
To do this properly, I recommend installing a sub-panel in your garage. I would feed your sub-panel with either 50 amps or 100 amps of power. You need to install 2 – hots, 1 – neutral and 1 – ground. Grounding is extremely important and a major factor to allow your circuit breakers to trip during a fault.
If you do not wish to install a sub-panel in your garage, I recommend installing 3 circuits. One circuit for your 120 volt receptacles and one circuit for your lighting. In this application, I would install a 12/3 NMB with ground. With this cable, you will share the neutral so you need to ensure your 2 – 120 volt circuits are on separate phases in your breaker box. The best way to do this is install your new circuit breakers one above another on the same side of your breaker box. You also need to install a GFCI receptacle at your first receptacle location to protect all receptacles in your garage.
The third circuit is for your 220 volt receptacle. The size of this cable depends on what you are going to power up with it. Most welders, compressors and 220 volt A/C units do not need a neutral. This means you may run 2 – hots and 1 – ground. However, you need to check the specifications for the unit you are going to power up with your 220 volt receptacle.
You wire size depends on the amperage and distance from the breaker box. If your cable length is 125 feet or less you need 10 AWG for 30 amps, 8 AWG for 40 amps and 6 AWG for 50 amps. The rule of thumb is to increase your wire by 1 size for every 100 feet of length after the initial 125 feet.
Before you begin, be sure the power is off to the circuit you are working on and double check with a volt-meter. You also need to check with your local building codes department to ensure you may do your own electrical wiring. Some areas do not allow homeowners to install their own electrical wiring and you may need to hire a licensed or qualified electrician.
We sell a great book for homeowners and “do-it-yourselfers” that wish to do their own electrical wiring but, do not know much about electricity. The book is Wiring Simplified – 41st Edition and it is based on the 2005 National Electrical Code (NEC).
If the above information I have given does not work for your situation or you need further clarification, feel free to post your questions in the comment section.
Do you need assistance with your electrical wiring project? Please visit my DIY Electrical Wiring Help from a Master Electrician page. Where I provide electrical wiring tips, expert electrical advice, answers to your electrical questions and electrical consulting & design services over the phone, via instant messenger or via email.