Rewiring Garage

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  #1  
Old 07-13-04, 08:22 AM
wld_drvr
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Rewiring Garage

Hello to all,

I have purchased a house recently which was built in 1949 with a detached garage. I would like to rewire my garage and bring it more up todate. Currently this is how my garage is set up.

At the back of the house is the main panel with a 20 amp breaker. From there 14/2 no ground is run to the garage. Inside the garage is a single 30 amp breaker box (cartridge type) and from there a wire running to a fuse box with glass fuses. The wiring in the garage is most knob and tubing with some 14/2 no ground thorwn in.

I went to my local Home Depot and this is the plan we came up with. I am sure their advise is sound but I just wanted a second opion.

At the main breaker box I should replace the 20 amp breaker with a 30 amp breaker. From there I should run 12/2 ground to the garage ( the distance from the main breaker to the garage is roughly 10 feet).

Inside the garage i should install a 100 amp sub panel and continue with 12/2 ground. Even thought the main breaker box at the house doesnt have a ground rod attached I should run a grounding rod at the garage and ground my sub panel.

I palnned on running my lights on one circuit and the outlets on another one. Just in case I plugged something in and threw a breaker I would still have lights to find my way back to the panel box. My outlets with be mostly used for small tools and such. I planned on using a 20 amp breaker with 20 amp outlets just in case further down the road I wanted to add a table miter saw or a small bench saw.

Home depot told me to run 15 amp outlets with a 20 amp breaker. They said that this would be ok and help to save me some money.

Thanks in advance for any imput on this subject.
 
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Old 07-13-04, 08:48 AM
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I went to my local Home Depot and this is the plan we came up with. I am sure their advise is sound but I just wanted a second opion.

At the main breaker box I should replace the 20 amp breaker with a 30 amp breaker. From there I should run 12/2 ground to the garage ( the distance from the main breaker to the garage is roughly 10 feet).
NO. 12 ga. wire is not enough for a 30 amp circuit. 10 ga. will be required, minimum for 30A.

Inside the garage i should install a 100 amp sub panel and continue with 12/2 ground. Even thought the main breaker box at the house doesnt have a ground rod attached I should run a grounding rod at the garage and ground my sub panel.
Using a 100A panel as the sub in the garage is fine. However, you'll have a much better setup if you run 240V from the house to the garage panel. If you run 10-3 you'll be able to run 30A at 240V, which is 60A for 120V circuits. You'd need a 30A double-pole breaker instread of a single however, which could be an issue if your panel is full.

Home depot told me to run 15 amp outlets with a 20 amp breaker. They said that this would be ok and help to save me some money.
Perfectly true. I would still use "spec" grade outlets though. The ones that cost $1.69 each, not $0.39.

One thing. You haven't said how the wire is run to the garage. Underground? Aerial?
 
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Old 07-13-04, 09:14 AM
wld_drvr
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Thanks for the speedy reply.

The wire from the house to the garage is aerial. Also could you comment on wheter or not running a ground rod at the garage is a good thing to do or not. Since the main breaker at the house doesnt have a ground rod attached to it.
 
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Old 07-13-04, 10:39 AM
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Well, I'm not really up to speed on aerial feeders, so I'm going to let someone else chime in on that.

Yes, drive a grounding rod at the garage.

It used to be that code allowed you to use the incoming water service as the primary grounding electrode. This is no londer true, and while you are not required to update, it's a simple thing to do and is a good idea.

Drive *two* grounding rods, at least 6 feet apart at the house and connect them to the main panel with #4 bare copper.

If you do not run a ground wire between the house and garage, you treat the new panel as a service entrance, in that you bond the ground and neutral together in the panel. I don't suggest you do this.

Instead, I would include a ground wire in your new aerial feeder, install a grounding bar kit in the subpanel, and remove the neutral bonding screw or jumper. Then all neutrals are wired to the neutral bus, and all grounds are wired to the separate grounding bus.

Since it sounds like you're using this garage as a workshop, and that you might be moving to larger tools eventually, I would actually suggest upping the feeder to this subpanel to a 60A. The cost of the breaker will be the same. The wire will cost a bit more, but for a 10' distance, it's trivial. You would still use the same 100A panel as your sub. For a few $ more you gain a world of future flexability.

You'll need to GFCI protect any general-use outlets in the garage (anything that isn't "dedicated" to a specific item like a freezer).

I'm sure I'm missing a thing or two here, but I bet John will come through and point them out like he usually does
 
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Old 07-13-04, 12:32 PM
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It used to be that code allowed you to use the incoming water service as the primary grounding electrode.
Code still allows it, in fact requires it. What isn't code any longer is that you cannot use it as your only grounding electrode.
 
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Old 07-13-04, 01:30 PM
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Right, I should have said it used to be the only required where now it is the primary required, with at least one secondary electrode. Mismatch between brain and keyboard

What kind of wire will the original poster need to use to run the new aerial feeder? That's one I don't know at all (because I have no such feeder in my project, so it's not something I've researched).

I do know that certain height minimums (which may be higher than the current feeder) apply.
 
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Old 07-13-04, 09:33 PM
wld_drvr
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Thanks to all who answered my question. Sorry I didnt reply sooner but I had to leave for work shorty after posting my last reply. I am sure with all of the answers I have here now I can do a great job of rewiring my garage. Everyone here has been a great help and again I thank you.
 
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