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#214584 - 12/23/14 11:53 AM service grounding for two attached buildings?
cgw Offline
Member

Registered: 07/29/04
Posts: 133
Loc: Rochester NY
Two buildings connected for about 10 corner to corner. Service laterals to each from a single pad mounted transformer. 120/240V-1 Ph. Multi family with separate meters at the buildings. Essentially the two buildings are separate buildings except that they share a water service (the water service & meter is in one and the copper water main runs to the other)
Should just the one building service ground be connected to the underground water service?

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#214585 - 12/23/14 12:02 PM Re: service grounding for two attached buildings? [Re: cgw]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6785
Loc: Brick, NJ USA
Sounds like there are two (2) electrical services. Two (2) main disconnects, 1 at each, or the good old six switch rule at each. So each has to be grounded at the respective first means of disconnect to the water, steel, rods, etc.
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John

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#214587 - 12/23/14 01:55 PM Re: service grounding for two attached buildings? [Re: cgw]
cgw Offline
Member

Registered: 07/29/04
Posts: 133
Loc: Rochester NY
Yes. Two services/two main disconnects (1 each). But only one water.
Just ground the other one to a ground rod only. I don't think both should be connected to the water?

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#214588 - 12/23/14 02:15 PM Re: service grounding for two attached buildings? [Re: cgw]
shortcircuit Offline
Member

Registered: 06/27/04
Posts: 608
Loc: massachusetts
I would say since the building is connected that the 2nd service grounding electrode conductor should be connected to the waterpipe within 5ft of its entry to the structure...250.50 + 250.68(C)(1)

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#214589 - 12/23/14 03:06 PM Re: service grounding for two attached buildings? [Re: cgw]
cgw Offline
Member

Registered: 07/29/04
Posts: 133
Loc: Rochester NY
I hear you but that is the same as connecting the ground for the two services together. Is this OK?

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#214591 - 12/23/14 05:08 PM Re: service grounding for two attached buildings? [Re: cgw]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6785
Loc: Brick, NJ USA
IF you have water pipe that is in contact with the earth, it must be connected to the grounding electrode system.

Think about this....a bunch of structures all connected with metallic water services; all tied into a metallic water 'main' in the street. That equates to many services all connected to what in actuality is a 'common electrode'!
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#214594 - 12/23/14 11:00 PM Re: service grounding for two attached buildings? [Re: cgw]
gfretwell Offline

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Registered: 07/20/04
Posts: 9012
Loc: Estero,Fl,usa
You certainly want all of the grounding electrodes bonded together and the water pipe is as good a way as any. Does the pipe run underground between buildings? Connect the second service to the water pipe within 5' of it's entrance to that building. You still need another electrode in both buildings. Water pipes can not be the only electrode.
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#214595 - 12/24/14 05:04 AM Re: service grounding for two attached buildings? [Re: cgw]
shortcircuit Offline
Member

Registered: 06/27/04
Posts: 608
Loc: massachusetts
On second thought cgw...if the building you are working in has a true Fire Wall separating the structures, they are considered separate buildings and each would need its own grounding electrode system. You would still need to BOND the water pipe system in the 2nd building. (if it were metal)

The fact that you have 2 services to the building must have been allowed because of Fire Wall separation?

I say you are allowed to ground to the water pipe in the 2nd building but not required. Better ask the AHJ what he thinks also.

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#214601 - 12/24/14 11:09 AM Re: service grounding for two attached buildings? [Re: cgw]
Scott35 Offline

Broom Pusher and
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Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
I agree with John and Greg: there are Two Separate Services, therefore each Service requires a Grounding Electrode System.

Since there is a Metallic Water Line with minimum 10 feet direct contact with the Earth, this Metallic Pipe must be included in the Grounding Electrode System.

In addition, per 250.53(D)(2), the Cold Water Electrode must be supplemented by at least (1) additional Electrode (typically driven rods or "Ufer").

Quote:


(the water service & meter is in one and the copper water main runs to the other)



This may require the Grounding Electrode Conductors bonding to the Cold Water Line at the same location (i.e.: both terminate within 5 feet of entrance to the Building), unless the Cold Water Line entering the "Other Building" (the Building without the Water Meter) could be figured as if it was coming in from the Street (min. 10 feet contact with Earth).

Sounds to me that the GEC from both Services will need to Terminate at the same location on the Cold Water Line (within 5 feet from entrance to the Building).
There will only need to be (1) Supplemental Electrode(s) to the Cold Water.

Does this sound right??? dunno

--Scott (EE)
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

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#214604 - 12/24/14 03:12 PM Re: service grounding for two attached buildings? [Re: cgw]
HotLine1 Offline

Member

Registered: 04/03/02
Posts: 6785
Loc: Brick, NJ USA
Scott:
As I 'see' the OPs layout; two (2) electric services, and one (1) water meter, with metallic water pipe to the second structure.

A GEC to the street side of the water pipe, with a jumper around the water meter bonds all the metallic water piping, both within that structure, and over to the adjacent structure. A GEC on the water pipe in the second structure would bond that service to the GE, along with whatever additional GEs the OP cares to install.

I see no reason to run the GEC from the second location back to the street side of the water meter.

Agree? Or debate?
_________________________
John

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