water ground question

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Old 03-07-14, 05:30 PM
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water ground question

My electrician recently installed a new panel. He was not able to complete the entire installation in one day, he has to return next week to run the water ground back to the meter. There is a supplemental rod in place though....

Is this a safety or functionality concern until this is installed?
 
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Old 03-07-14, 06:19 PM
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If you mean a connection from the panel to the water pipe. It's not really called a ground. It's bonding. The ground rod(s), usually there are two, are the actual "ground."

It's required by Code (NEC 250.104(a)(1)) so it is a safety issue. Basically the idea is that all piping in the residence is at the same potential as equipment grounding conductor.
 
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Old 03-07-14, 06:56 PM
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So my electrician has left me in the lurch in an unsafe situation for a week?
 
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Old 03-07-14, 07:45 PM
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Hardly, the purpose of the electrodes is for high voltage events like a lightning strike. I would not sweat this for a week until they get back.
 
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Old 03-07-14, 08:08 PM
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Ardmi, the confusion is over the terminology. Is it a ground or is it a bond???

Normally a service entrance has two ground rods AND the service is also bonded to the water pipe. The ground rods are for lightning protection but the connection to the water pipe is to make sure that there is a low impedance ground path to the plumbing system (bond).

That way if a live wire came into contact with the plumbing it would trip the breaker and not be energized.

If the water pipe is being used as a ground then you'd need to be sure it is not plastic just outside the house. It is possible that there was a repair or splice made that you aren't aware of.

At any point if it's required by Code it should be addressed in a timely manner.
 
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Old 03-08-14, 06:55 AM
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two ground rods
Not all locations in the US require two ground rods installed. The only time we have needed to install two is where there is no water service in a building. The ground rod is supplemental to the water pipe bonding.
 
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Old 03-08-14, 10:09 AM
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My electrician recently installed a new panel. He was not able to complete the entire installation in one day, he has to return next week to run the water ground back to the meter.
Your incoming metal water supply pipe is the grounding electrode. Bonding that to the supply neutral creates the required low-impedance fault path. It should have been made first.

If a bond has been installed between one or two ground rods and the supply neutral, that will probably be OK for a short time. That connection, however, is supplemental to the bond to the water supply pipe.
 
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Old 03-08-14, 10:18 AM
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Your incoming metal water supply pipe is the grounding electrode. Bonding that to the supply neutral creates the required low-impedance fault path. It should have been made first.

If a bond has been installed between one or two ground rods and the supply neutral, that will probably be OK for a short time. That connection, however, is supplemental to the bond to the water supply pipe.
I just want to point out that for many many years only one or the other ground was required and not both. Most exsting homes probably have only one ground connection today.
 
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Old 03-08-14, 10:52 AM
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No problem if the electrician has to come back next week to install the connection (a grounding electrode conductor) to the water pipe.

Grounding electrodes include rods and the cold water pipe (if metal) exiting the house underground and re-bar for underground concrete foundation components but not gas pipes.

Today's code requires interconnecting (bonding) one water pipe (if metal) exiting the house underground, one re-bar (if any) and two 8' ground rods (and any other ground rods being used as grounds for equipment such as cable TV equipment). All of this is bonded to the panel neutral bus. The ground rod requirement is reduced to one if the rod achieves a 25 or fewer ohm impedance with the earth using specialized equipment for the purpose of making that measurement.

Bond: An essentially resistance free or impedance free electrical connection, in the sense that if A (a wire or piece of metal) is bonded to B and B is bonded to C then A is bonded to C. Size is relative to currents that may be involved, for example electronic components may be bonded to a chassis as ground with #22 wire while the typical bond from ground rod to panel is with #6 gauge copper wire.

Grounded: Having a low impedance connection with the ground or earth, by being or being bonded to a grounding electrode.

The (usually #6) water pipe ground wire is still needed to ground metal plumbing if the water pipe is plastic exiting the house. Here it is called a bonding jumper rather than a grounding electrode conductor. Two ground rods and, if any, one rebar will complete the requirements without the need to do an impedance test.
 

Last edited by AllanJ; 03-08-14 at 11:19 AM.
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Old 03-08-14, 12:13 PM
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Today's code requires interconnecting (bonding) one water pipe (if metal) exiting the house underground, one re-bar (if any) and two 8' ground rods (and any other ground rods being used as grounds for equipment such as cable TV equipment).
AFAIK, the current NEC requires what it always has: A low-impedance path to earth for faults.

All of this is bonded to the panel neutral bus.
To establish the Grounding Electrode Conductor, conductors to sources of a low-impedance path, including but not limited to the metal cold-water supply and driven rods, are bonded to the supply neutral. This may or may not occur at a neutral bus bar.

The ground rod requirement is reduced to one if the rod achieves a 25 or fewer ohm impedance with the earth using specialized equipment for the purpose of making that measurement.
The 25ohm-or-less impedance is a handy measurement that many jurisdictions use as the test for meeting the actual requirement for a low-impedance path. Some jurisdictions require a lower value.

Bottom line? All codes is local. The NEC is a model code. It has no force or authority until and unless it is adopted, in whole or in part, by the authority having jurisdiction. Not infrequently, local jurisdictions adopt a model code as part of a regulatory framework that interprets or amends provisions of the model code.

Knowing, understanding, interpreting and meeting all of this is part of the skill set that your electrician brings to the job.
 
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Old 03-13-14, 01:15 PM
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They finally came out and ran the water ground. Thing is, the water meter is on the opposite side of the basement than the service enterance. So they ran the water ground back to the panel in EMT.... its an 80' run.

Is that length a bad thing?
 
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Old 03-13-14, 01:40 PM
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Other then they would have to bond the EMT to the ground wire, which is kind of a hassle. Are you sure it is not PVC?
 
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Old 03-13-14, 01:49 PM
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Its in emt for sure. In fact it was insulated wire they used.... and where the connections are at the water meter etc they stripped all the insulation off.... so inside the conduit, its still insulated.

Also passed electrical inspection like this?

I noticed that the connector they used where the conduit connected to the panel looked like a standard locknut/setscrew connector you would see on a box but it had what looked like a grounding screw on the locknut on the inside of the panel...
 
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Old 03-13-14, 02:06 PM
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If it passed inspection, then I would assume that it is OK.

it had what looked like a grounding screw on the locknut on the inside of the panel
That sounds like a bonding bushing. This sounds correct.
 
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Old 03-13-14, 04:12 PM
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You do not have any choice about the 80' run between breaker panel and water pipe.

One water pipe (if metal) exiting the house underground must be included in your grounding electrode system.

Plumbing cannot be part of a grounding electrode conductor, for example if a pipe runs from near the panel to near where the cold water pipe exits, you may not connect a short #6 or whatever wire from the service neutral to the pipe near the panel and connect another short #6 wire from the pipe near where the main cold water pipe exits, past the water meter and to the exiting pipe and call this a proper grounding electrode system.
 

Last edited by AllanJ; 03-13-14 at 04:31 PM.
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Old 03-13-14, 04:21 PM
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The connection to the water line needs to be within 5' of where it enters the house whether it is 5', 80' or more from the panel.
 
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Old 03-13-14, 04:23 PM
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Is the water ground or the ground rod considered the primary? I know one is supplemental correct?
 
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Old 03-13-14, 04:24 PM
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The rod is supplemental to the water.
 
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Old 03-13-14, 05:28 PM
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it had what looked like a grounding screw on the locknut on the inside of the panel

That sounds like a bonding bushing. This sounds correct.
I'd call that a grounding locknut. Did it look something like this?

T&B 108 1-IN GROUNDING LOCKNUT | Gordon Electric Supply, Inc.
 
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Old 03-13-14, 05:50 PM
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indeed, grounding locknut... never saw one before. Not sure how it would be used with the water ground and the panel though... is that like double bonding? (all metal conduit system)
 
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