250.52(a)(1)

[jxofaltrds]

When was the within 5' rule added? And why was it added.

Should say breaking.

 

[iwire]

My best guess was to prevent plumbers from getting blasted when they cut a pipe.

 

[charlie b]

My guess is to make sure the fact that there is a connection can be noticed by a plumber planning to work on the pipe. For the things in our world that are required to be "withing sight of" something, the NEC has set a limit of 50 feet. That is too far for a water pipe ground connection to have a chance of being noticed.

 

[M. D.]

Plastic plumbing devices and pipe . 5' is a reasonable length to maintain electrical continuity so the water pipe can be used as a conductor to interconnect electrodes .

from 2001 rop he wanted to increase it to 10 feet ,.Interesting panel language ,.. I thought the electrode was the 10' in contact with the earth??Shouldn't they have said the integrity of the connection to the grounding electrode.

do we have to maintain the continuity for the 5' even if we are not using it as a connection point for more electrodes ,..

SUBSTANTIATION: Where water piping enters the building in
a finished wall, as in a building using slab type construction, an
increase to 10 feet would allow the ground connection to be
made above the finished ceiling. If the 5 foot rule is enforced
and an access panel is provided in the middle of a living room or
office wall, it will likely be done away with after the inspection is
done. If access to the connection is important, this revision
would better assure that this need is met. The 5 foot seems to be
an arbitrary number to make the connection as close as practical.
PANEL ACTION: Reject.

PANEL STATEMENT: A length in excess of five feet will increase
the probability of impacting the integrity of the grounding
electrode.

NUMBER OF PANEL MEMBERS ELIGIBLE TO VOTE: 17
VOTE ON PANEL ACTION:
AFFIRMATIVE: 14
NEGATIVE: 3

 

[don_resqcapt19]

The rule first appeared in the 1993 code and was based on proposal 5-141 as found in the 1992 TDR (Technical Committee Report). The TCR is know called ROP (Report on Proposals).

Log # 2051 5-141- (250-81)): Accept in Principle
SUBMITTER: James H. Worden, Mark N. Shapiro, Port Huron, Ml RECOMMENDATION: Add after the first sentence:
Interior metal water piping is not to be used as a conductor to connect the required electrodes and their conductors together.
Ex. In industrial buildings where the entire length of the water pipe that is being used for the conductor is visible.
SUBSTANTIATION: Electricians do not have total control of the water piping system. Many unqualified persons may modify the water piping system. By al1owin~ the water pipe to serve as the only conductor, it may be possible to isolate the required grounding electrode conductors which is a hazardous condition. Sometimes this happens in concealed areas not visible on re-inspections.
PANEL ACTION: Accept in Principle
Change the new sentence as follows:
Interior metal water piping shall not be used as a conductor to interconnect the electrodes and the pounding electrode conductor.
Number existing "Exception No.1 and add new Exception No.2 as follows:
Exception No.2: In industrial and commercial buildings where conditions of maintenance and supervision assure that only qualified persons will service the installation and the entire length of the Interior metal water pipe that is being used for the conductor is visible.
PANEL STATEMENT: Panel believes the recommended change to 250-81 was too restrictive not to include industrial and commercial buildings but the Panel feels that supervision and maintenance is necessary for this provision.
The Panel solicits Public Comment on this proposal because it feels there may be other ways to assure a reliable continuity of interior metal water piping such as type of piping, size of piping, and locations other than commercial and industrial.
VOTE ON PANEL ACTION: Unanimously Affirmative.

 

[jxofaltrds]

Thanxs Don.

 

[jxofaltrds]

About objectionable current:

"When metallic water systems exist, the required grounding to the pipe allows some neutral current to return to the transformer through a neighbor's neutral and vice versa. For different reasons this current on the water system can be considered objectionable."

http://forums.mikeholt.com/showthread.php?t=56863