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#174176 - 01/28/08 10:06 AM Upgrade
JValdes Offline
Member

Registered: 06/03/07
Posts: 308
Loc: South Carolina
I have a garage and a house. They are connected by a breezeway. The garage is now considered attached. I want to put a 400 amp panel in the garage. I want to make the 200 amp house panel a sub panel. The garage has no water pipes. The house main panel is bonded to the water pipes. I plan to drive two electrodes at the new 400 amp service in the garage, and pipe a four wire new run to the house panel. Do I have to run a bonding (water pipe) conductor to the house? If so, can I connect the bonding conductor to the isolated ground (bonded and grounded) in the 200 amp sub panel? There is an electrode at the house that is now my sub panel. The neutral and ground will be seperated.
If I must run a (water pipe) bonding wire to the house, can I run it in the conduit with the other four conductors?
Also, Should I size the bonding conductor for 200 amp or 400 amp. I appreciate any comments or suggestions.....John

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#174181 - 01/28/08 12:23 PM Re: Upgrade [Re: JValdes]
ITO Offline
Member

Registered: 11/26/06
Posts: 341
Loc: Texas
Why do you want a 400A panel in the garage, and will your local POCO even let you put one that big on your garage?
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#174202 - 01/28/08 10:07 PM Re: Upgrade [Re: ITO]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9045
Loc: Estero,Fl,usa
I see no reason why you need more than the 4 wire feeder. The water pipe is bonded to the ground rods via the EGC in the feeder.
_________________________
Greg Fretwell

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#174248 - 01/30/08 01:05 AM Re: Upgrade [Re: gfretwell]
u2slow Offline
Member

Registered: 09/18/03
Posts: 198
Loc: Salt Spring, BC, Canada
 Originally Posted By: gfretwell
I see no reason why you need more than the 4 wire feeder. The water pipe is bonded to the ground rods via the EGC in the feeder.


I agree. I did exactly the same install on my house a couple years ago - just with a 200A main and 100A existing in the house. That satisfied the inspector.

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#174254 - 01/30/08 07:33 AM Re: Upgrade [Re: u2slow]
JValdes Offline
Member

Registered: 06/03/07
Posts: 308
Loc: South Carolina
That is why I posted the question. I too assumed that the EGC and EMT would allow for a four wire feeder to the 200 amp sub panel. But I am getting conflicting advise on this matter. Several members at the Mike Holt forum have indicated that I need a bonding conductor seperate from the feeder to the sub panel, to go all the way to the house unbroken and connected to the water line at the house. Just as if the new service was at the house. I have also been advised that I can go with a three wire feeder since I am using EMT. I am going to contact the inspector and see what he requires. thanks for your feedback fellow forum members.......John

ps....400 amp service is needed for the new testing facility that will be in the garage.

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#174258 - 01/30/08 01:56 PM Re: Upgrade [Re: JValdes]
LK Offline

Member

Registered: 01/21/03
Posts: 1721
Loc: New Jersey
The way I see it the main panel at the garage will need a GEC going unbroken back to the water meter.

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#174259 - 01/30/08 02:09 PM Re: Upgrade [Re: LK]
u2slow Offline
Member

Registered: 09/18/03
Posts: 198
Loc: Salt Spring, BC, Canada
Its going to bubble down to what the inspector wants to see.

What my inspector said was he is no longer considering the water supply as a ground. It simply needs to be bonded along with the gas supply.

That said, I do not have water or gas in the garage area. They are contained to the house where it is served by the existing panel. So that may be a factor.

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#174274 - 01/30/08 07:29 PM Re: Upgrade [Re: u2slow]
Active 1 Offline
Member

Registered: 02/22/03
Posts: 684
Loc: Grayslake IL, USA
Like LK said if it's an attached garage.

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#174282 - 01/30/08 10:44 PM Re: Upgrade [Re: Active 1]
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9045
Loc: Estero,Fl,usa
I suppose it gets down to what 250.64(C) exception means
 Quote:
Exception: Sections of busbars shall be permitted to be connected together to form a grounding electrode conductor
.

It doesn't say "busbars in the same enclosure"
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Greg Fretwell

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#174286 - 01/31/08 03:48 AM Re: Upgrade [Re: LK]
SteveFehr Offline
Member

Registered: 03/19/05
Posts: 1192
Loc: Chesapeake, VA
 Originally Posted By: LK
The way I see it the main panel at the garage will need a GEC going unbroken back to the water meter.
Unbroken, OR spliced via busbars or exothermic welds. Routing the GEC through the existing panel's busbar is acceptable per 250.64. In this case, the ground between the two panels is an GEC and must be a discrete wire sized IAW 250.66.

That said, the GEC is still required to be as short and straight as possible*, so the AHJ may feel routing through the old panel is unnecessarily circuitous and may require a more direct connection between the new panel and ground. In this case, the connection between the two panels is no longer a GEC, but merely an EGC, and EMT is acceptable if properly bonded.

* 250.4(A)(1) became stricter about this in NEC 2008.

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