metal water pipe bonding...why?

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shortcircuit2

Senior Member
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South of Bawstin
250.104(A)(1) requires the bonding jumper to a metal water pipe in single occupancy building to be sized according to table 250.66...

If the building were to be fed with service entrance conductors, lets say 500MCM copper, then the bonding jumper would be required to be 1/0 copper...

Now, if this building were to have a plastic water pipe feeding in from the street and the only electrode for the building were a couple of ground rods, which are allowed to have a maximum of #6 copper to these electrodes...

Then, what is the purpose of having the 1/0 bonding jumper to the water piping system?

shortcircuit2
 
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dillon3c

Senior Member
Re: metal water pipe bonding...why?

You know short circuit,
I posted a question in here a week ago that was on a Local Inspector Level test that I am taking.It was dealing with the same thing.

Question I posted in form was: Has anyone ever heard of the term (High and Dry Metalic Water System)..Never got a responce, so I deleted question..Come to find out from my Instructor,it's what you just discribed..

[ March 26, 2005, 10:01 PM: Message edited by: dillon3c ]
 
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dillon3c

Senior Member
Re: metal water pipe bonding...why?

Well the question on the test ask:

Is a high and dry metalic water system required to be bonded to the sevice equipment?
 
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shortcircuit2

Senior Member
Location
South of Bawstin
Re: metal water pipe bonding...why?

dillon...I'm not sure what a high and dry metalic water system is, maybe a sprinker system, but my answer would be yes to that test question.

250.104(A)(1) requires us to bond metal water piping systems installed in or attached to a building or structure and doesn't specify wet or dry, high or low...

shortcircuit2
 
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dillon3c

Senior Member
Re: metal water pipe bonding...why?

Yes, untill I got clairification on what it was, I also though sprinkler system..
 
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shortcircuit2

Senior Member
Location
South of Bawstin
Re: metal water pipe bonding...why?

dillon...your instructor refered to a interior water piping system that is fed from the street with plastic as a "High and Dry Metalic Water System" :confused:

I'll be talking to some of my plumber buddies about this one...

shortcircuit2
 
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dillon3c

Senior Member
Re: metal water pipe bonding...why?

Yep, got a brother thats a plumber too,But question is a preparation test question for the N. Carolina Department of Insurance Test.Outside of the State of NC,don't really know if anyone uses the term..
 
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buck33k

Senior Member
Location
Washington state and North Carolina
Re: metal water pipe bonding...why?

The #6 for bonding the water pipe in this case would seem to be adequate for lightning, but what if the piping were energized by the 500MCM on the load side of the service disconnect?

[ March 27, 2005, 11:35 AM: Message edited by: buck33k ]
 
charlie

charlie

Senior Member
Location
Indianapolis
Re: metal water pipe bonding...why?

Buck, that may be the reason but what about the gas piping system? The gas piping system is only required to be bonded with the same size wire as the grounding conductor of the circuit that would energize the pipe.
 
iwire

iwire

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Staff member
Location
Massachusetts
Re: metal water pipe bonding...why?

Originally posted by buck33k:
The #6 for bonding the water pipe in this case would seem to be adequate for lightning, but what if the piping were energized by the 500MCM on the load side of the service disconnect?
Click to expand...
Buck the question I have is how the heck could that happen?

If you have a house with a plastic water main but copper interior piping how in the world would it be energized by anything on the supply side of the service disconnect?

And if we say that it could happen then should we bond all metal (ducts, gas pipes, structural steel, etc.) with a conductor based on 250.66?
 
iwire

iwire

Moderator
Staff member
Location
Massachusetts
Re: metal water pipe bonding...why?

Originally posted by buck33k:
Bob
I referenced the LOAD side of the service disconnect in my post. That is, if the 500MCM continued from the service disconnect, through the building and on to a panel.
Click to expand...
Sorry Buck I misread your post. :eek:

The point I was trying to make still stands.

Normally all bonding is based on the amount of fault current likely to energize the metal.

So in your example one would think that the bonding would be based on the OCPD protecting the 500 Kcmil and table 250.122.

But 250.104(A)(1) requires the bonding jumper to a metal water pipe to be sized according to table 250.66 as if it is likely to be energized by the supply side of the service.

To me this is a head scratcher. :confused:

[ March 27, 2005, 02:43 PM: Message edited by: iwire ]
 
charlie

charlie

Senior Member
Location
Indianapolis
Re: metal water pipe bonding...why?

I am beginning to think that this would be a good proposal for the 2008 Code. Now, if someone will just pick up the gauntlet . . . :D
 
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shortcircuit2

Senior Member
Location
South of Bawstin
Re: metal water pipe bonding...why?

Could this bondings purpose be to discharge a static charge that may be imposed upon the metalic piping system produced during a common high voltage surge, such as lightning?

shortcircuit2
 
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mpd

Senior Member
Re: metal water pipe bonding...why?

look at 250.104 (2) in multiple occupancy buildings you could size that pipe bond in accordance with TA 250.122, which will be smaller than required by TA 250.66, serves the same purpose in a single family or multiple occupancy, in my opinion it is a load side bond.
 
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