Garage wiring

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Old 01-21-20, 09:47 PM
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Garage wiring

Iím looking to run electric out to my attached garage for my wood shop tools. I want to install 20amp 2 pole breaker but only install 20 amp 120v outlets at the moment. I would like to have option of having 240v for future use. If I am correct, I would be using 12/2 wire, which is 2 hot and 1 ground, no neutral. When hooking up the 120v outlet, do I only connect 1 hot wire and the ground and then just wire nut the other hot and save for future use for 240 outlet? Or would I be better off installing 2 120v outlets into each housing and using both hot wires, one for each outlet? Thanks.
 
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Old 01-22-20, 04:26 AM
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The two hots only does not provide the neutral needed for a 120 volt circuit. You should read the subpanel sticky at the top of the forum as well as determine the expected loads in the shop.
 
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Old 01-22-20, 05:01 AM
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You can not run 120 volt circuits from a double pole (240v) breaker. Since you only want a 120 v circuit I suggest using a single pole breaker. Since you want 240v in the future you won't be able to have both (120 & 240) with a single breaker so you will have to install a separate double pole breaker and run a separate wire for your 240 circuit.
 
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Old 01-22-20, 07:04 AM
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Consider adding a small 4 or 6 breaker sub panel.
That way you would have 240 volts on one double pole breaker and a 20 amp. single for the outlets.
By using a 6 breaker panel there would be room left if you wanted to run a 240 volt window air conditioner.
FYI all 120 volt outlets will need to be GFI protected, only need one per circuit installed at the start of the run.
 
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Old 01-22-20, 08:33 AM
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Yes you can run 120V circuits from a double pole breaker. It's called a multiwire branch circuit. You have to use 3 wires plus a ground. A MWBC can provide both 120V and 240V.
 

Last edited by pattenp; 01-22-20 at 08:57 AM.
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Old 01-22-20, 10:15 AM
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So would I only connect 1 of the hots, neutral and ground for a 120v? And then when I want to put in a 240, use the second hot?
 
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Old 01-22-20, 11:27 AM
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You can but i highly recommend putting in a subpanel with a minimum of 30A.
 
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Old 01-22-20, 11:29 AM
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I would highly recommend you have separate 240 volt and 120 volt circuits.
If you only want to run one cable to the garage then run a 10/3 cable and install a 30 amp sub panel.
 
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Old 01-22-20, 11:40 AM
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It looks as though I have a 100 amp breaker box installed and all of my breakers add up to 200 amps. Would that be able to support a subpanel out in my garage? Thanks.
 
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Old 01-22-20, 01:02 PM
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Adding up breakers means nothing. You need to calculate the estimated high load in use at one time. That being said if you have the expansion space in the 100A panel the odds are you are fine adding a 30A feeder to a subpanel.
 
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Old 01-22-20, 04:01 PM
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Honestly, you'd be better served installing a 60 amp (minimum) sub-panel in your garage for your woodworking tools. I would have a 15amp breaker for your lights, 2 separate 20 amp breakers for general use 120v plugs, or a garage door opener, and 2-pole 20amp or 30amp breakers for your equipment. It never hurts to put a bigger panel in, just remember to size your wire properly. 120v plugs in the garage need to be GFCI protected.

Whatever size panel you decide to install, you need a 3 wire cable feeding it, not a 2 wire as stated in the op. 12/2 has a hot, a neutral, and a ground and is good for 120v 20amp circuits. 12/3 has 2 hots, a neutral, and a ground and can be used for 240v 20 amp circuits.

Since the garage is detached, were you planning on running a cable underground?
 

Last edited by Bhamsparky; 01-22-20 at 04:03 PM. Reason: Misspelling
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Old 01-22-20, 04:55 PM
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What is the service to your house, 100 or 200 amp or more? Do you have electric appliances; kitchen stove, clothes dryer, water heater, heat pump, air conditioning? If you only have 100 amp service you may need to look at upgrading the service if you have a lot of high draw electric devices in the house.
 
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Old 01-22-20, 06:26 PM
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I would like to have option of having 240v for future use.
How many amps would you anticipate needing at 240 volts in the future?

I believe a small subpanel is the best way to go so you can provide a couple 20 amp 120 volts circuits out there as well as a 240 volt circuit. The only question is how many amps should the feeder be and that really depends on how many amps you think you may need at 240 volts. What would you be using the 240 volts for? A welder? Air compressor? Most likely a 30 amp or 40 amp feeder would be plenty. You will need a 4-wire feeder such as 10-3 or 8-3 NM-B cable (aka Romex) and a 2-pole breaker, 30 or 40 amp. If you are thinking of a welder, you will probably need either a 50 or 60 amp feed.
 
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