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99k
10-01-2008, 04:45 AM
This is the second time this month where I went to install a water system and found the #4 ground wire from the panel to the copper water distribution line was purposely cut at the grounding clamp. Why would anyone want to do such a thing? In both instances, I noticed a lot of communications equipment in these mechanical areas ... is the issue possibly interference?

renaissanceEE
10-01-2008, 09:13 AM
If I were to hazard a guess that #4 to the plumbing was the old building ground. A new good grounding source was most likely created when the telcom/computer equipment was installed and the old cut at the clamp to stop any possible loops.

99k
10-01-2008, 09:47 AM
If I were to hazard a guess that #4 to the plumbing was the old building ground. A new good grounding source was most likely created when the telcom/computer equipment was installed and the old cut at the clamp to stop any possible loops.

In both cases, these homes were less than 10 years old. They appear to have had the proper grounds outside and the electrical panels were not upgraded. It would seem cutting a ground is going against code ... I thought it should be to two grounding rods and to the water line.
Please explain what you mean by creating a "loop"?

renaissanceEE
10-01-2008, 11:17 AM
loops is short for ground loops.
Having a good common ground source is is high importance when you have expensive electronics talking to each other over copper from distant ends of a building. You don't want that ground wire in twisted pair the shield in coax to be a different ground potentials at either end, it will shorten the life of the interface and cause on going problems.
When engineering telecom upgrades for the military it was standard practice even for a two room building to replace the building ground if the current was unknown or of low quality such as plumbing.

That being said this being a home "a lot of communications equipment in these mechanical areas" is mostly likely home electronics which were not installed by a telecom professional, so things like equipment life and reliability were not taken into account, and honestly not a major issue.

I would say your cut wire at ground clips to the plumbing was not related to the communication equipment.

Chris75
10-01-2008, 06:58 PM
If I were to hazard a guess that #4 to the plumbing was the old building ground. A new good grounding source was most likely created when the telcom/computer equipment was installed and the old cut at the clamp to stop any possible loops.

How on earth would a bonded metal pipe cause a ground loop? The only thing I see causing a loop is having the tel/catv grounding not bonded to the electrical grounding system.


To answer the OP's question, Probably a plumber that really didnt understand the function of the wire to begin with.
Are these city water supplies or well water in your area?

Chris75
10-01-2008, 07:01 PM
A new good grounding source was most likely created when the telcom/computer equipment was installed and the old cut at the clamp to stop any possible loops.

That would be a code violation, ALL grounding electrodes must be USED if present, and the water system would still need to be bonded even if not used as an electrode.

Billy_Bob
10-01-2008, 10:45 PM
I read somewhere that an electric company refused to connect the electric service if there was a cold water pipe ground. They would only connect the electric service with ground rod(s) being used as the service ground.

Perhaps this is a "new" trend to no longer use cold water pipe grounds?

I could see why this would be and that is the high cost of copper/metal and people replacing main underground water pipes with plastic, then there goes your ground. And if it is not this way now, then will likely be that way in the future (will replace with plastic).

I would suggest you document that the ground was disconnected before you did any work and it was not you who disconnected the ground. (CYA) Send copy to customer.

hj
10-02-2008, 07:22 AM
IN this area the water system must be grounded if it is metallic, AND also the gas system if there is one.

jadnashua
10-02-2008, 09:47 AM
In the desert, and in some types of soils, it is very hard to establish any decent ground so the more places you can attach and the larger the surface area contact you have, the better it will be.

While in the army in the desert, to make good grounds for communications, they'd pour salt then water down the ground around the ground stakes, otherwise, it was tough to establish decent communications and maintain safety.

Billy_Bob
10-02-2008, 09:47 AM
The way the electrician got around the electric company was to run a ground from the water pipe to one of the ground rods (not to panel). Then the electric company was happy.

This would avoid the situation of an energized water pipe system if underground pipe was replaced with plastic, the ground was lost to the ground rods from the panel, and there was a loose neutral.

Billy_Bob
10-02-2008, 09:49 AM
P.S. I agree all metal water pipes *should* be grounded.

99k
10-02-2008, 07:40 PM
Are these city water supplies or well water in your area?

In both instances the water supply was well water. In both instances the home was new enough that these appeared to be the original well tanks and so I don't think the plumber cut these grounds.

99k
10-02-2008, 07:59 PM
I read somewhere that an electric company refused to connect the electric service if there was a cold water pipe ground. They would only connect the electric service with ground rod(s) being used as the service ground.

Perhaps this is a "new" trend to no longer use cold water pipe grounds?

I could see why this would be and that is the high cost of copper/metal and people replacing main underground water pipes with plastic, then there goes your ground. And if it is not this way now, then will likely be that way in the future (will replace with plastic).

I would suggest you document that the ground was disconnected before you did any work and it was not you who disconnected the ground. (CYA) Send copy to customer.

As far as I'm aware, copper (or metal) pipes should be grounded regardless of whether the incoming line from a well (usually 1" poly) or is city water (typically 3/4" min. copper). In this last house I verified the grounding rods where present outside and reconnected the ground at the water line.

Chris75
10-02-2008, 09:25 PM
Its this simple, we (electricians) must bond the water piping system and all available grounding electrodes. Its really not hard to understand, if the water system leaves the house with 10' or more in metal underground piping, then it must be used as an electrode.

Billy_Bob
10-02-2008, 11:18 PM
In the desert, and in some types of soils, it is very hard to establish any decent ground so the more places you can attach and the larger the surface area contact you have, the better it will be.

While in the army in the desert, to make good grounds for communications, they'd pour salt then water down the ground around the ground stakes, otherwise, it was tough to establish decent communications and maintain safety.

I saw this done at a mountain top satellite/microwave station. Very rocky up there, 5 ground rods driven and interconnected, plus a saltwater drip system from a couple of 50 gallon drums. They would have to cart water up there every so often to keep the drip lines going (and would add salt).

99k
10-03-2008, 03:51 AM
Its this simple, we (electricians) must bond the water piping system and all available grounding electrodes. Its really not hard to understand, if the water system leaves the house with 10' or more in metal underground piping, then it must be used as an electrode.

If the system does not have 10' or more of underground metal piping, should it be disconnected? Is there anything adverse that would cause someone to want to cut the ground at the piping?

99k
10-03-2008, 04:00 AM
That would be a code violation, ALL grounding electrodes must be USED if present, and the water system would still need to be bonded even if not used as an electrode.

Could you please explain the theory of bonding the water system to the electrodes. I imagined this was done as a safety issue to protect the occupant if somehow a stray voltage entered into the water system piping (i.e. HW heater, frayed wire against a pipe, etc).

220/221
10-03-2008, 03:09 PM
Usually when I see bond/ground wires cut, there is a piece missing and has been stolen for scrap.

Sometimes the plumbers will disconnect when working on fittings by the clamp and don't reconnect..

We are required to bond the metal piping and structure to keep it from becoming energized in a fault condition. Ironicly, a neutral fault can end up energizing the piping, using it as a "return" path.

pudge565
10-05-2008, 07:45 PM
If I were to hazard a guess that #4 to the plumbing was the old building ground. A new good grounding source was most likely created when the telcom/computer equipment was installed and the old cut at the clamp to stop any possible loops.


NEC requires that the water pipe be used as a grounding electrode if it is matal and extends into the ground at least 10'. I will look up the section on Tuesday when I go back to tech.

Billy_Bob
10-06-2008, 04:55 AM
NEC requires that the water pipe be used as a grounding electrode if it is matal and extends into the ground at least 10'. I will look up the section on Tuesday when I go back to tech.

In Oregon, we have "amendments" to the NEC. One amendment says "...water pipe shall not be used unless the metal underground water pipe has been verified..."

Full text of amendment...

From Oregon Amended Language, 2008 NEC...

250.52 Grounding Electrodes...
...
(B) Not Permitted for Use as Grounding Electrodes...
...
(3) In existing electrical installations, when a service change or upgrade occurs, an existing metal underground water pipe shall not be used unless the metal underground water pipe has been verified as suitable for continued use as a grounding electrode. An existing metal underground water pipe shall be bonded to the new grounding electrode system as required by 250.104(A).

Above from...
http://www.cbs.state.or.us/external/bcd/notices/Adopted_Rules/20080401_amend_918-305_pr.pdf

pudge565
10-07-2008, 07:34 PM
Ah yes I forgot about amendments. I also forgot to look up the code today will do it tomorrow.

AcidWater
10-23-2008, 07:24 PM
Is there any NEC rule that gives the maximum length of 4AWG grounding conductor wire that may be run from the panel to the location of the grounding electrode?
***

Does the code now or in the past, allow the copper piping system to be used as part of the grounding conductor from the electric panel to the grounding electrode?

ie:
Panel box
4AWG wire to nearest point of copper pipe (say 12 feet away)
copper pipe runs thru house to well pump
near the pump, 4AWG wire from pipe goes into the wall penetration used by the well pipes
presumably to either a buried electrode, a metal well casing, or possibly down to be buried in the concrete foundation.