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#59257 - 12/01/05 02:01 PM Grounded to the Water?!?!?  
slorch  Offline
Junior Member
Joined: Sep 2005
Posts: 6
Albany, NY USA
Please forgive the homeowner-type question. I'm a VDV installer, and I've already asked the pro electrician in the family:

My house was built in 2000, with a 200amp lateral-fed service. There is a stranded aluminum GEC running to the area where the water service enters the basement and a #6 copper running out to a buried rod.

That's reasonable. But wait. The water service is via plastic pipe and there is a compression fitting transition to copper 2 inches upstream of the ground clamp for the GEC. There's no way an electrician could miss the pipe being plastic.

I asked the family pro (industrial and motor control, high-volt, etc) about this. His answer was that "You're grounding to the water system, not the pipe, so it's fine".

I'm confused. I seems to be a violation of the NEC as I read it, and I was under the impression that water was not a particlarly good conductor, as compared to metal and earth. Can anyone explain the rationale behind this installation?


-Steve

Work Gear for Electricians and the Trades

#59258 - 12/01/05 04:02 PM Re: Grounded to the Water?!?!?  
Steve Miller  Offline
Member
Joined: Aug 2001
Posts: 325
Loudoun Cty, VA
I can't tell you anything about your place because I haven't seen it ... however ... here's a true story:
My house is built literally into a mountain. It's vintage ~1790. The well was dug (~285') into the mountain in 1973. When I moved in (1988) I replumbed the entire house in CPVC and PVC because the minerals in the water had rotted thru the copper to the point of constant pinholes in the type M copper (heavy wall). The copper was put in in 1973 along with the well. Every last piece is now plastic except a 12" nipple at the (gas) water heater in and out couplings due to the heat. In 1997 I tore out the old fuse box and put in a main breaker panel. The AHJ wanted a #6 to the water heater to ground the water itself. His argument was that there were so many minerals in the water that it became a good enough conductor to cause a problem. He told me that this was a common problem in the area. (Yes, I had the water checked by the county health dept and they declared it safe to drink). It was easier to comply than argue. In 2004 I did my neighbors house and the county still wanted this #6.


#59259 - 12/01/05 04:37 PM Re: Grounded to the Water?!?!?  
Roger  Offline
Member
Joined: May 2002
Posts: 1,716
N.C.
Slorch, I agree with the family pro, in your case the water pipe doesn't meet the criteria of being a Gounding Electrode and doesn't sound as though it is being used as such.

From the 99 NEC

Quote
250-50(a) Metal Underground Water Pipe A metal underground water pipe in direct contact with the earth for 10ft (305m) or more (including any metal well casing effectivly bonded to the pipe) and electrically continuous (or made electrically continuous by bonding around insulating joints or sections of insulating pipe) to the points of connection of the grounding electrode conductor and the bonding conductors.


Any Metalic Water Piping must be bonded though.

Quote
250.104 Bonding of Piping Systems and Exposed Structural Steel
(A) Metal Water Piping
The metal water piping system shall be bonded as required in (A)(1), (A)(2), or (A)(3) of this section. The bonding jumper(s) shall be installed in accordance with 250.64(A), (B), and (E). The points of attachment of the bonding jumper(s) shall be accessible.
(1) General Metal water piping system(s) installed in or attached to a building or structure shall be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor where of sufficient size, or to the one or more grounding electrodes used. The bonding jumper(s) shall be sized in accordance with Table 250.66 except as permitted in 250.104(A)(2) and (A)(3).


If I understand correctly, the installation is OK.


Roger



[This message has been edited by Roger (edited 12-01-2005).]


#59260 - 12/01/05 05:18 PM Re: Grounded to the Water?!?!?  
hbiss  Offline
Member
Joined: Dec 2003
Posts: 886
Hawthorne, NY USA
"You're grounding to the water system, not the pipe...

No, you are grounding the water system.

The wire is there to bond the copper system in the house to the service ground, not to provide a ground for the service as would be the case if there were a metallic water supply line.

And you need another ground rod. [Linked Image]

-Hal


#59261 - 12/01/05 05:21 PM Re: Grounded to the Water?!?!?  
sponge  Offline
Member
Joined: Feb 2003
Posts: 31
Quote
There is a stranded aluminum GEC running to the area where the water service enters the basement and a #6 copper running out to A buried rod
The water pipe doesn't meet the criteria of being a Gounding Electrode and doesn't sound as though it is being used as such... So, by code, shouldn't a 2nd ground rod have been installed in in this installation to acheive 25ohms or less?


#59262 - 12/01/05 05:23 PM Re: Grounded to the Water?!?!?  
sponge  Offline
Member
Joined: Feb 2003
Posts: 31
Hbiss - You beat me! J


#59263 - 12/01/05 05:42 PM Re: Grounded to the Water?!?!?  
iwire  Offline
Moderator
Joined: Jan 2003
Posts: 4,391
North Attleboro, MA USA
Plastic or metal water supplies he still needs two rods unless he can prove less than 25 ohms.


Bob Badger
Construction & Maintenance Electrician
Massachusetts

#59264 - 12/01/05 06:20 PM Re: Grounded to the Water?!?!?  
slorch  Offline
Junior Member
Joined: Sep 2005
Posts: 6
Albany, NY USA
Quote
The wire is there to bond the copper system in the house to the service ground, not to provide a ground for the service as would be the case if there were a metallic water supply line.

And you need another ground rod.


The fog is lifting a bit. I was assuming the system was setup to use the water line as the main electrode. It "looks" identical to such a system (AL conductor is connected to the panel's ground lug, while the #6 copper occupies a lug in the ground bar, no evidence of a 2nd rod, etc.). I assumed the #6 was for the required supplemental rod in such a system, when in fact it is the GEC.

So, if the bonding conductor is clamped on the "outboard" side of the meter, should the meter be jumpered to maintain continuity to the rest of the indoor plumbing? Right now it's plastic to compression fitting to copper w/AL clamped, then meter and remainder of indoor copper piping. No jumper over the meter.

In my defense, there is plenty of evidence of shoddy workmanship throughout the house, and with small children thrashing about, I'm wary. I've also been told I'm a little slow on the uptake... [Linked Image]


-Steve

#59265 - 12/01/05 08:58 PM Re: Grounded to the Water?!?!?  
Roger  Offline
Member
Joined: May 2002
Posts: 1,716
N.C.
Since we weren't there in 2000 when the service was inspected we don't know if the rod did infact meet 25 ohms or less, or if it didn't. [Linked Image]

Roger


#59266 - 12/02/05 04:29 PM Re: Grounded to the Water?!?!?  
makokiller  Offline
Member
Joined: Dec 2004
Posts: 51
millport, ny 14864
sounds like you are using a well and not a city water supply, so you should have 2 ground rods, and you also need to have #4 copper not #6..


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