Mechanical Ground...

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1793

1793

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Louisville, Kentucky
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I have a two wire outlet that I would like to establish a mechanical ground. There is a copper cold water line very close by. What if any safety issues are posed by using a grounding clamp on this COLD water line to make a ground?
 
Re: Mechanical Ground...

250.52 Grounding Electrodes.
(A) Electrodes Permitted for Grounding.
. . . Interior metal water piping located more than 1.52 m (5 ft) from the point of entrance to the building shall not be used as a part of the grounding electrode system or as a conductor to interconnect electrodes that are part of the grounding electrode system.
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Re: Mechanical Ground...

Right Al. That is alloed per 250.130:
(C) Nongrounding Receptacle Replacement or Branch Circuit Extensions. The equipment grounding conductor of a grounding-type receptacle or a branch-circuit extension shall be permitted to be connected to any of the following:
(1) Any accessible point on the grounding electrode system as described in 250.50
(2) Any accessible point on the grounding electrode conductor
(3) The equipment grounding terminal bar within the enclosure where the branch circuit for the receptacle or branch circuit originates
(4) For grounded systems, the grounded service conductor within the service equipment enclosure
(5) For ungrounded systems, the grounding terminal bar within the service equipment enclosure
FPN: See 406.3(D) for the use of a ground-fault circuit-interrupting type of receptacle.

There is a danger in bonding to the metal pipe past 5 feet into the building. Why not use a GFCI as allowed in 406.3(D)? Unless its a time and materials job, of course.
 
Re: Mechanical Ground...

Tom; thanks for the advise. The outlet in question is set for a computer. This is why I'm looking for the ground. What is the safety issue using a COLD water line past the five feet. This is an old house in copper.
 
Re: Mechanical Ground...

The hazard would be if someone were to put a chunk of pvc pipe in replacement of your copper pipe somewhere down stream then you would have no ground.
 
Re: Mechanical Ground...

Play this out with me. If a chunk of pvc were installed ahead of the clamp and the ground is lost to the outlet and for the sake of what ifs, and the ground wire becomes energized, would the water system then become hazardous?
 
Re: Mechanical Ground...

Originally posted by 1793:
If a chunk of pvc were installed ahead of the clamp and the ground is lost to the outlet and for the sake of what ifs, and the ground wire becomes energized, would the water system then become hazardous?
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1793 It makes no difference that it is the cold water pipe, the hot water pipes should be bonded in someway also.

None of this changes the fact the NEC does think that using the water pipe as a equipment grounding conductor further than 5' from the point of entrance is hazardous.

The answer to your question is yes, all the copper pipe on the clamp side of the PVC would become live.

So say you are standing in your shower, the copper feeding the water valves would be at 120 volts to ground. The cast iron drains would be at 0 volts to ground.

When you try to adjust the water you become a conductor.

[ July 28, 2004, 06:25 PM: Message edited by: iwire ]
 
Re: Mechanical Ground...

This was my concern when the question was raised to me. I do appreciate the chance to think out loud and confirm my thoughts.
 
Re: Mechanical Ground...

what your trying to do is use a bonded pipe as the ground not grounding the pipe.Your kinda using the system in reverse order.Please don't enough kids have been killed already.
I don't even like the 5 foot rule

[ July 28, 2004, 07:56 PM: Message edited by: jimwalker ]
 
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