Wiring new outlets in a garage. Best option?

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  #1  
Old 11-12-14, 08:27 AM
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Wiring new outlets in a garage. Best option?

Hi all,

I've been reading the forum for quite a while now, and I have to say this is a great source information for a DIY-ers . Thank you guys for sharing your knowledge.

I've installed a sub-panel in my garage and I'm looking for what would be the best way to wire some outlets. I will need one 220v/20amp and two 110v/15amp circuits. This is an attached garage with cinder block walls and drywall on the ceiling. My first idea was to go thru the ceiling and branch in a length of EMT in each location I need a outlet. The more I thing about it though the more I thing running EMT straight down from the sub-panel and then along the walls (about 2 feet high) of the whole garage will be easier, less mess and more efficient on the wire use. So here are my questions:
  1. Is it OK to run EMT straight down from the sub-panel to about 2 feet of the floor and then circling almost the whole garage about (60 feet)? Junction boxes will be placed along the conduit where I need an outlet.
  2. I understand it is OK to run up to 9 12awg THHN conductors in a 1/2 conduit. I'm looking to run 3 12awg (220v plus ground) and 4 14awg (2 110v). Would it be OK to protect the 12awg with 20amp and the 14awg with 15amp breaker, taking derating in consideration.
  3. Is it worth using 3/4 EMT or would I be fine with 1/2?
  4. Is it OK to run a single ground wire as long as it up to the largest circuit, 12awg in my case?
  5. I would like to put some sort of a shut off switch next to the sub-panel that can disconnect the two hot wires for the 220v and the one hot for one of the 110v. this way I can disconnect power to all power tools when I leave the garage. Ideally this shut off will allow for locking so you can't turn it on without a key (child safety). Are there any options like that?

Regards,
Chris
 
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Old 11-12-14, 02:41 PM
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1. I'll let someone familiar with the NEC answer that.

2. 15A = 14AWG, 20A = 12AWG. Conduit fill I will leave.

3. Never hurts to upsize in case you wish to add more in the future.

4. Yes, although your bond wire may not be necessary if it is a complete conduit system back to the panel. I personally don't believe in this method though as it takes just one loose coupling to lose your bond.

5. I would run another small panel off of your current panel strictly for power tools and add a hand off auto switch and a contactor controlling the small panel. Hand would be power always on, off self explanatory, and auto could be wired to an emergency stop button at the garage door. The e stop can also be keyed.
So your main sub panel would do general use receptacles, lighting, overheads etc., small panel would do whatever you wish to have shut off when not around.
 
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Old 11-12-14, 07:26 PM
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If you install a small panel in the garage you can turn off the breakers.

You can run a multiwire branch circuit and save some wire as you would only need one neutral for the 120 circuit.

All 120 volt receptacles need gfi protection.
 
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Old 11-13-14, 08:46 AM
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The conduit plan is fine as long as you have proper wire pull access between bends -- no more than 360 degrees of bend between accessible pull points.

Most panels have a lock and key accessory kit you can get from the manufacturer to prevent your kids from flipping the breakers on.

I would probably use 3/4" pipe, it's not really any more expensive and will be less hassle to pull through bends.
 
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Old 11-13-14, 11:59 AM
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then along the walls (about 2 feet high)
Others have provided good feedback about the code aspects. I'll throw in my opinion about height. I find that outlets at about 55" high work much better than lower receptacles. You don't have to bend down to plug things in, and 4x8 sheets stacked on the wall won't block the receptacles/switches.

Of course, if you have specific tool requirements, that can be different... but just something to consider.

-Mike
 
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Old 11-13-14, 03:41 PM
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Haha zorfdt,
I just spoke those very words to my friend's dad when he asked me to wire his garage.

Me: "I suggest counter height receptacles"
Him: "12" is fine."
Me: "Do you plan on dying in this house?"
Him: "... yes?"
Me: "Then in a few years when your back starts to crap out, you will have an easier time plugging things in from a standing height instead of bending over."
Him: "... put them at counter height."
 
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Old 11-13-14, 04:54 PM
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Guys, thanks for all the replies.

Mr.Awesome: good idea about the contactor. I think I have a magnetic switch lying around somewhere with a 3 pole 30amp contactor in it.

I thought about just using the breakers to turn power off to the tools, but I'm worried that eventually the breakers will go bad from flipping them on and off.
 
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Old 11-13-14, 05:23 PM
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Most breakers are rated to use as switches.
 
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