waterilne grounding towhhouses

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UncleRico

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Two townhomes(common wall between them),seperate electric services on far ends.The water comes in on the far side of one townhouse,branches off to a water meter for house number one,then continues over to second home through cieling joists to a second water meter.
My friend is doing a service upgrade on the second home. He asked me if he has to run a ground wire through both homes to where the water comes in to the building.I said yes,but his inspector said he can ground where it comes in to the second home.I think the inspector is wrong.What should my friend do?(by the way the water pipeing is bonded through the hot water heater)


Any comments?
 
Re: waterilne grounding towhhouses

He should provide some other grounding electrode (maybe a ground rod). 250.52 states that metal water pipe shall not be used as a grounding electrode if located more than 5' from the point of entrance to the building.

He should also provide a second ground electrode unless he can verify one ground rod meets 250.56.

Steve
 
Re: waterilne grounding towhhouses

Steve, what about 250-50(99NEC) where it states that "if available" on the premises, an underground metallic water pipe shall be used as a grounding electrode? And thus the GEC connection to the pipe shall be within 5' of the pipe entering the building. :confused:


steve
 
Re: waterilne grounding towhhouses

It also says "water piping located more than 5' from the entrance to the building shall not be used...." So the water pipe is not really "available" as a grounding electrode.

Although a ground wire could be ran into the other townhome and attached within 5' of the entrance, the connection would not be "accessible" (see 250.68(A) of the 2002 code). I also would not want to rely on a grounding electrode conductor that runs through someone else's basement.

Even it the water pipe were used as a grounding electrode, another electrode would have to be provided. See 250.53 (D)(2).
 
Re: waterilne grounding towhhouses

Steve, I'm not under the '02 Code, so I don't know the wording of it(if different than the '99). Would convenient vs. available have any bearing here? :confused: Or does the '02 clearly state "available"?


steve

[ April 21, 2004, 02:29 PM: Message edited by: stamcon ]
 
Re: waterilne grounding towhhouses

No matter how inconvenient he will have to get back to the original grounding electrode system.

All grounding electrodes used must be bonded together.

250.58 Common Grounding Electrode.
 
Re: waterilne grounding towhhouses

Originally posted by iwire:
No matter how inconvenient he will have to get back to the original grounding electrode system.
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Not if there is a fire wall between the 2 buildings, since the fire wall creates two buildings, bonding of the electrodes together is desirable but not requird by Code.
 
Re: waterilne grounding towhhouses

By erikmartin: then continues over to second home through ceiling joists to a second water meter.
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This is a very bad water pipe setup as this very reason is why we can't run service conductors through another building. What happen's if this home owner decides to remodel his side of the building and this pipe is in the way. If he own's it and there is no easement granted then he would have every right to cut this pipe and remove it. The plumbing AHJ should not have allowed this. Each unit should be treated as a separate building with separate utility's to each unit. We just had this problem in a around town here and this question came up at our IAEI metting.
 
Re: waterilne grounding towhhouses

Originally posted by iaspiretowire:
Not if there is a fire wall between the 2 buildings, since the fire wall creates two buildings, bonding of the electrodes together is desirable but not required by Code.
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I would talk to the AHJ on that before I counted on it.

250.50 Grounding Electrode System.
If available on the premises at each building or structure served, each item in 250.52(A)(1) through (A)(6) shall be bonded together to form the grounding electrode system. Where none of these electrodes are available, one or more of the electrodes specified in 250.52(A)(4) through (A)(7) shall be installed and used.
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It may be two buildings but it is one structure, the AHJ might say the water line is unavailable but I doubt it if it was available for the other service.

No matter what the decision on the grounding, the new service will have to be bonded to the water line but luckily the bonding can be done at any point on the water line.
 
Re: waterilne grounding towhhouses

I think there is some grey area here, and he will have to do whatever the AHJ wants. Personally, I would not let anyone rely on a water pipe in another person's basement to be the grounding electrode condutor.

Even if the water pipe is used as the grounding electrode, a supplementary electrode has to be provided. If you can prove the "supplementary" electrode has less than 25 ohms to ground, why not just call it the primary. Then if the AHJ insists on using the water pipe as an electrode, it could be a supplementary electorde.

Steve
 
Re: waterilne grounding towhhouses

This is a little off subject, but my grandparents house had the shutoff and meter for their water service in the basement of the neighbor's house. Two completly separate houses!! As far as I know, it's still that way.

Steve

[ April 22, 2004, 12:01 PM: Message edited by: steve66 ]
 
Re: waterilne grounding towhhouses

Steve to me it has more to do with keeping the grounding systems at the same potential.

You are in the kitchen of the unit with the new service you are using the sink and you touch the the refrigerator.

I would want to be darn sure that the plumbing is at the same potential as the EGC running to the refrigerator.

I guess as long as you do proper bonding of the water pipes at the new service it will be fine, but I do not think you can say that the water line is unavailable.

As you said a talk to the AHJ is in order. :)
 
Re: waterilne grounding towhhouses

Here is another variation: on my way from Florida back to Mass, I did a job in Richmond (EMF problem). Though there were a bunch of miswired circuits (cut neutrals, grab one from another circuit, etc.) the main magnetic field was from the circulation of neutral current on building steel between the two services to this commercial steel building.

The service I was dealing with had no bond to the copper water pipes, but it bonded to the steel, and had several ground rods bonded together. (The local electrician assumed that the other service was bonded to the water pipe where it entered the long building).

Curiously, the experienced electrical company owner said that grounding to the water pipe was a requirement in residential but not in commercial! He was an intelligent guy, too. I disagreed, but realized that the building steel was bonding back to the other service and water pipe where it entered the building.

Since I was not there as an inspector, I was dealing with the fact that when two services are bonded to the same building steel, there will be a parallel path for neutral through the building steel to the neutral in the other service and back to the Tformer. Even with one service shut off, there was current from the other service through the steel to the service neutral for the shut off service.

The only remedy for the magnetic field problem I could see was to balance the loads as much as possible in both service load panels. Thus reducing neutral current. Any other ideas?

Karl
 
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