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Old 09-16-2008, 06:06 PM   #1
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Default 100 amp sub panel for garage

I just got my restricted license and my first official job involves wiring a garage. I want to send 100 amps to it and the existing panel is 200 amps. The garage will only have a deep freezer, a water heater, one bathroom, and a couple of other branch circuits. I want to do this right and I'm just looking for tips, ideas, etc. If you've done a similar operation before, what size breaker did you use in the main panel? What size wire did you (and how did you) send to the garage? Thanks in advance for you ideas. I'm just making sure that I'm thinking of everything.

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Old 09-16-2008, 08:25 PM   #2
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Well, why don't you tell us how you plan on doing it, and what materials you plan on using, and perhaps we can point out anything you missed.

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Old 09-16-2008, 09:13 PM   #3
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Attached, or detached garage? Heat or A/C in the bathroom? etc?
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Old 09-16-2008, 09:36 PM   #4
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assuming it is detached, you could pull in 6-3 with ground to a four place subpanel, then wire the HW heater with 10-2 and the rest of the branch circuits with 12-2. Use a 60 amp breaker at the main.

You could go bigger, using #4 or #2, and a sub-panel with more spaces, but I don't see why you'd need them.

Another way is to go to a replaceable lug meter socket (if the house doesn't already have one) and run a 100 amp service to the garage from the meter socket. You'd need to check with the utility provider and make certain their existing service drop or lateral is large enough to handle both the house and the garage. A separate service wil require its own grounding.
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Old 09-16-2008, 10:24 PM   #5
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Sorry, should've been a little more specific. The garage is detached and the tenant is still deciding on ac/heat options. I can't run the power feed from the meter, it's going to have to come from the main panel inside the existing house. I was thinking of using a 60 amp breaker and installing a 100 amp panel in the garage in case.
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Old 09-16-2008, 10:35 PM   #6
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Quote:
Originally Posted by halfblank View Post
Sorry, should've been a little more specific. The garage is detached and the tenant is still deciding on ac/heat options. I can't run the power feed from the meter, it's going to have to come from the main panel inside the existing house. I was thinking of using a 60 amp breaker and installing a 100 amp panel in the garage in case.
Until you find out what you're going to power out there, we can't help you much. 60amps should be plenty, however.

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Old 09-17-2008, 12:34 PM   #7
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Okay, Here goes.

Install a 100 amp 2 pole breaker in the main service panel.
If using conduit, Run 3 # 3's/cu and 1 #8/cu green THWN conductors to the sub panel. 4 wire circuit.
Use a 100 amp main breaker panel for the sub. (since you are not sure how many circuits you will need).
Seperate neutrals and grounds at the sub.
Drive at least one 96" electrode (see AHJ) at the sub and connect a bare #6 conductor from the rod to the ground bus.
Bury conduit 18' below grade. (exceptions exist)

Make sure you pull a permit, and ask the AHJ if he has any special requirements for sub panels in unattached structures.

If you are not going to use conduit let us know.
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Old 09-17-2008, 05:09 PM   #8
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Welcome halfblank to the forum and to the contracting world.
What part of GA?
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Old 09-19-2008, 10:06 PM   #9
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I'm a little suprised that you got some kind of electrical license and are asking what are to me some pretty fundamental questions about electrical construction. It seems to me in order to get whatever licensse you have you should be at least minimaly conversant with whatever code applies in your state, which would answer all your questions. Given what seems to me to be a vast ignorance of electrical construction, I recommend you look into casrpentry as a career.
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Old 09-20-2008, 12:22 AM   #10
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Well put Raverill (aside from changing careers to be a carpenter, at least he is trying)....I don't mean to offend anyone here but I have first and second year apprentices who work under me that can figure something like this out on their own...I was a little surprised when I first read this post but I wanted to see where it went before I made any comments

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Old 09-20-2008, 12:57 AM   #11
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Bury conduit 18' below grade. (exceptions exist)
Dude! Eighteen feet below grade! That's gonna cost extra to get the hole that deep...lol
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Old 09-20-2008, 01:00 AM   #12
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I'm a little suprised that you got some kind of electrical license and are asking what are to me some pretty fundamental questions about electrical construction.
I agree...I'm calling shenanigans on this so-called 'restricted' license.
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Old 09-20-2008, 01:11 AM   #13
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Hmmm electrician or homeowner?
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Old 11-09-2009, 02:39 PM   #14
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Quote:
Originally Posted by John Valdes View Post
Okay, Here goes.

Install a 100 amp 2 pole breaker in the main service panel.
If using conduit, Run 3 # 3's/cu and 1 #8/cu green THWN conductors to the sub panel. 4 wire circuit.
Use a 100 amp main breaker panel for the sub. (since you are not sure how many circuits you will need).
Seperate neutrals and grounds at the sub.
Drive at least one 96" electrode (see AHJ) at the sub and connect a bare #6 conductor from the rod to the ground bus.
Bury conduit 18' below grade. (exceptions exist)

Make sure you pull a permit, and ask the AHJ if he has any special requirements for sub panels in unattached structures.

If you are not going to use conduit let us know.
could have used #8 for ground rod!
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Old 11-09-2009, 03:01 PM   #15
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The minimum for a ground rod is #6 no matter what size the service/ feeder is.
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Old 11-09-2009, 03:47 PM   #16
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The minimum for a ground rod is #6 no matter what size the service/ feeder is.
I disagree. Art. 250.66(A) says the connection to the rod need not be larger than a #6 however art. 250.66 first paragraph states the GEC to be based on 250.66. I take this to be if you use #2 copper than a #8 can be used to the rod.
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Old 11-09-2009, 04:53 PM   #17
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I disagree. Art. 250.66(A) says the connection to the rod need not be larger than a #6 however art. 250.66 first paragraph states the GEC to be based on 250.66. I take this to be if you use #2 copper than a #8 can be used to the rod.
thats how I read it too!
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Old 11-09-2009, 04:57 PM   #18
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Ok, let me know how that goes for the inspection.

250.53(E)
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Last edited by Magnettica; 11-09-2009 at 05:01 PM.
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Old 11-09-2009, 04:58 PM   #19
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ive done a dozen times, and has passed!!!
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Old 11-09-2009, 05:00 PM   #20
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im not saying the inspector isnt gonna fight you on it....

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