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?
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.
Re: Grounded to the Water?!?!? #59259 12/01/0503:37 PM12/01/0503:37 PM
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
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.
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.
[This message has been edited by Roger (edited 12-01-2005).]
Re: Grounded to the Water?!?!? #59260 12/01/0504:18 PM12/01/0504:18 PM
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?
Re: Grounded to the Water?!?!? #59262 12/01/0504:23 PM12/01/0504:23 PM
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...
Re: Grounded to the Water?!?!? #59265 12/01/0507:58 PM12/01/0507:58 PM