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#84135 - 03/11/03 02:01 PM sub panel main
gserve Offline
Member

Registered: 03/11/03
Posts: 92
When is a main breaker required in a sub panel in a residential detached garage? Aso what is the min. feeder ampacity for 3 circuits?

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#84136 - 03/11/03 05:11 PM Re: sub panel main
The Watt Doctor Offline
Member

Registered: 12/23/01
Posts: 443
Loc: Mont Belvieu, TX
gserve,
Consider the following:
408.16 Overcurrent Protection.
(A) Lighting and Appliance Branch-Circuit Panelboard Individually Protected.
Each lighting and appliance branch-circuit panelboard shall be individually protected on the supply side by not more than two main circuit breakers or two sets of fuses having a combined rating not greater than that of the panelboard.
Exception No. 1: Individual protection for a lighting and appliance panelboard shall not be required if the panelboard feeder has overcurrent protection not greater than the rating of the panelboard.
I'm sure the exception will work for you. As far as the ampacity of the feeder is concerned, I can't tell you anything without knowing the rating of the branch circuits.
Hope it helps,
Doc
_________________________
The Watt Doctor
Altura Cogen
Channelview, TX

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#84137 - 03/11/03 05:27 PM Re: sub panel main
resqcapt19 Offline
Member

Registered: 11/10/00
Posts: 2209
Loc: IL
Don't forget that 225.31 requires a disconnect at the detached garage. 225.33 permits up to 6 breakers to serve as the required disconnect. 225.39(D) requires that the feeder disconnecting means have a rating of not less than 60 amps for this application. Note that the section does not actually require a 60 amps feeder, but only a 60 amp disconnecting means. I think that the intent was to require a 60 amp feeder circuit, but the code words don't actually say that.
Don
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Don(resqcapt19)

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#84138 - 03/11/03 05:37 PM Re: sub panel main
WebSparky Offline
Member

Registered: 02/21/03
Posts: 144
Loc: Cleveland, Ohio
Don't forget the grounding electrode!

And GFCI's!
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Dave

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#84139 - 03/11/03 05:49 PM Re: sub panel main
gserve Offline
Member

Registered: 03/11/03
Posts: 92
The branch circuits are 1 15A lighting 1 20A receptacle and 1 20A 240V air compresser

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#84140 - 03/11/03 05:56 PM Re: sub panel main
gserve Offline
Member

Registered: 03/11/03
Posts: 92
Speaking of the elctrodes can I use the main service electrodes which are about 15' away from the garage without driving additional electrodes for the garage GES?

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#84141 - 03/12/03 07:25 PM Re: sub panel main
The Watt Doctor Offline
Member

Registered: 12/23/01
Posts: 443
Loc: Mont Belvieu, TX
I can dig it Don. So, gserve, you could set a small load center with 6 breaker spaces or less (if they make one less than 6 spaces), and not need to have a disconnect. If you want to add a panel of any greater size (in terms of breaker space), as Don pointed out, you're going to have to add a main, which can serve as a disconnect, or add a disconnect.
Regards,
Doc
_________________________
The Watt Doctor
Altura Cogen
Channelview, TX

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#84142 - 03/12/03 07:52 PM Re: sub panel main
resqcapt19 Offline
Member

Registered: 11/10/00
Posts: 2209
Loc: IL
Doc,
The six disconnect rule is not based on the number of spaces in the panel, but the number of breakers installed. Just because it is possible to install more breakers in the future, doesn't make it a violation today.
Don
_________________________
Don(resqcapt19)

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#84143 - 03/13/03 04:59 PM Re: sub panel main
The Watt Doctor Offline
Member

Registered: 12/23/01
Posts: 443
Loc: Mont Belvieu, TX
I'm with you Don. The reason I mentioned it, is because a friend of mine ran into this problem. He had some AHJ hammer him for it. The AHJ's was trying to prevent additional disconnects from being added in the future. My response was....How does he know that you won't add 2 pole breakers for other equipment, and therefore need a 12 space panel? (it was a single phase application) My buddy replied, "Who know's?"
So, let me retract my earlier statement, and say, "Based on some prior experience that a friend of mine had, be prepared, gserve, for the possibility that an AHJ, may walk onto your project, and want assurance that you, or someone in the future will not add breakers in that MLO panel, which would be a violation." So, gserve, it might be a good idea to give them a call, and see what kind of response you get from them.

Trying to be helpful,
Doc
_________________________
The Watt Doctor
Altura Cogen
Channelview, TX

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