Detached garage

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ddcrawford

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I have constructed a new detached garage/workshop and want to find out if I am going down the right path to get power to it.

I am planning on a 100A two-pole breaker in my main house panel, running three #3 THHN and one #8 THHN ground to a GE TM1210 panel (100A main breaker, 12 space panel) and will install a ground rod at the garage.

Is this what I need to do (install a load center with a main breaker) to get around the 6 breaker rule? By doing this can I now use the full complement of breakers this box will handle if needed?

Is my approach a sound way of getting the power to the garage?

Thanks for the help!
 
Re: Detached garage

I forgot to include that I will need to disconnect the bond between neutral and ground in the detached garage panel.
 
Re: Detached garage

It sounds good but we are not allowed to give much help to those outside the trade.

What kind of engineer are you and are you allowed to install wiring without a license?
 
Re: Detached garage

Originally posted by iwire:
It sounds good but we are not allowed to give much help to those outside the trade.

What kind of engineer are you and are you allowed to install wiring without a license?
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I'm an electrical engineer, I do aircraft wiring design (power and signaling). I will be hiring someone to do this work, I just want to get the facts correct on how to accomplish this.
 
Re: Detached garage

Originally posted by ddcrawford:
I'm an electrical engineer, I do aircraft wiring design (power and signaling). I will be hiring someone to do this work, I just want to get the facts correct on how to accomplish this.
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Cool, it is just a forum rule that we do not give help to DIY type questions.

* This NEC? Forum is for those in the electrical and related industries.
Questions of a "How-To" nature by persons not involved in the electrical industry will be removed without notice.
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That out of the way it sounds fine, although Jim does bring up a valid point about not limiting yourself to a small panel. Of course only you know what your intentions with this garage are.

The 3 and 8 AWG THHN with a 100 amp breaker is fine.

Yes you will have to install a grounding electrode. If that happens to be a ground rod you have to prove less than 25 ohms resistance or you must install a second rod.

Most of us just install 2 rods and do not bother with the testing as it takes a specialized meter. (A standard ohmmeter will not do it)

Yes you must remove the bond from neutral to ground in the panel if it has already been installed.

The outlets in the garage will need to be GFCI protected.

[ December 31, 2005, 09:27 AM: Message edited by: iwire ]
 
Re: Detached garage

I have constructed a new detached garage/workshop ...
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If your area is using the 2005 code and if you have 20' or more of #4 or larger rebar in the footing, you may have a problem with 250.50 which required the use of the concrete encased electrode if it is present.
Don
 
Re: Detached garage

Originally posted by don_resqcapt19:
If your area is using the 2005 code and if you have 20' or more of #4 or larger rebar in the footing, you may have a problem with 250.50 which required the use of the concrete encased electrode if it is present.
Don
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Ouch. ;)
 
Re: Detached garage

I agree with Don, you would need to go with the concrete encased electrode if the footing has 20' or more of 1/2" or larger rebar. If so, than you won't need the ground rod(s).

[ December 31, 2005, 10:05 AM: Message edited by: infinity ]
 
Re: Detached garage

Originally posted by iwire:
Originally posted by don_resqcapt19:
If your area is using the 2005 code and if you have 20' or more of #4 or larger rebar in the footing, you may have a problem with 250.50 which required the use of the concrete encased electrode if it is present.
Don
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Ouch. ;)
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I do have steel in the footing but there is also a plastic vapor barrier, so the concrete is not in direct contact with the soil. I assume this means I have to use ground rods instead.
 
Re: Detached garage

Originally posted by ddcrawford:
I do have steel in the footing but there is also a plastic vapor barrier, so the concrete is not in direct contact with the soil. I assume this means I have to use ground rods instead.
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That is a great question that I have not seen it suitably answered.

For what it is worth I agree with you.
 
Re: Detached garage

I do have steel in the footing but there is also a plastic vapor barrier, so the concrete is not in direct contact with the soil.
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I'm not a concrete expert but from what I have seen on new foundations prior to pour is the black plastic vapor barrier on top of the cushion sand,with the rebar on top, EC&M Magazine November 2005 has an article in code basics page 46 under the subheading Dispelling Common Myths, athough the article is on pools, the paragragh on page 46, I think would apply in this situation.

[ December 31, 2005, 11:44 AM: Message edited by: Jhr ]
 
Re: Detached garage

Hopefully your concrete is not poured yet.If not buy an acorn and some number 4 solid and stub it out near the panel.This might need inspected before you pour.If its already poured then it is not available.
 
Re: Detached garage

Originally posted by jimwalker:
If its already poured then it is not available.
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If it was already poured before the rule was added then I agree it not available.

If the foundation was poured after the rule was added and there is qualifying steel in it only your AHJ will be able to say if its available or not. :)
 
Re: Detached garage

Originally posted by Jhr:
EC&M Magazine November 2005 has an article in code basics page 46 under the subheading Dispelling Common Myths, athough the article is on pools, the paragragh on page 46, I think would apply in this situation.
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1100723312_2.jpg

How? This article is dealing with equipotential bonding, not grounding electrodes. The concepts are distinctly different.

Grounding electrodes act to "limit the voltage imposed by lightning, line surges, or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during normal operation." (250.4(A)(1))

Equipotential bonding is not for that purpose.

680.26(A) Performance. The bonding required by this section shall be installed to eliminate voltage gradients in the pool area as prescribed.
FPN: This section does not require that the 8 AWG or
larger solid copper bonding conductor be extended or attached to any remote panelboard, service equipment, or any electrode.
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The myth that Mike Holt is attempting to dispel is that the earth is always at an even, zero potential. The purpose of 680.26 is to compensate for that by artificially creating an even-potentialled "earth" to stand on when near a pool.
 
Re: Detached garage

Originally posted by don_resqcapt19:
I have constructed a new detached garage/workshop ...
Click to expand...
If your area is using the 2005 code and if you have 20' or more of #4 or larger rebar in the footing, you may have a problem with 250.50 which required the use of the concrete encased electrode if it is present.
Don
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I just looked and the city uses the 2002 NEC, so I'm guessing that makes the concrete encased electrode issue a moot point...correct??
 
Re: Detached garage

I do have steel in the footing but there is also a plastic vapor barrier, so the concrete is not in direct contact with the soil
NEC 2002 250.52 (A) (3) Then bonding the steel in the foundation would not be required, use a ground rod.

[ December 31, 2005, 05:03 PM: Message edited by: Jhr ]
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