250.104(A), 250.104(A)(1)

[George Stolz]

Did someone say "gauntlet"?

1.) NEC Section/Paragraph: 250.104(A), 250.104(A)(1)
2.) Proposal Recommends: [revised text]
3.) Proposal:

Revise 250.104(A) as follows:

(A) Metal Water Piping. Where metal water piping systems do not meet the criteria for a grounding electrode as described in 250.52(A)(1), interior metal piping shall be bonded as required in (A)(1), (A)(2), or (A)(3) of this section. The bonding jumpers shall be installed in accordance with 250.64(A),(B), and (E). The points of attachment for the bonding jumpers shall be accessible.

Revise 250.104(A)(1) as follows:

(1) General. Interior metal water piping system(s) shall be bonded to any accessible point on the equipment bonding system. The bonding jumper shall be sized in accordance with 250.122, using the rating of the circuit that is likely to energize the piping system. If no such circuit exists, the bonding jumper shall not be smaller than 8 AWG copper.

4.) Substantiation: Under the 2005 NEC, interior metal water piping that does not qualify as a grounding electrode, extending ten feet beyond the structure, is still required to be sized for the service fault current that could not possibly energize the piping. Since the interior water piping would not be a grounding elecrode, there is no reason to bond to the service disconnecting means as currently required.
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Edit to lose my retarded comment. What the hell was I thinking about?

[ March 28, 2005, 07:43 AM: Message edited by: georgestolz ]

 

[hurk27]

Re: 250.104(A), 250.104(A)(1)

Gas piping can retain it's weirdness, we hardly touch that.

That outa get the CMP's rolling.

 

[charlie]

Re: 250.104(A), 250.104(A)(1)

Actually, the CMPs don't mind a little foolishness, it keeps them awake.

 

[George Stolz]

Re: 250.104(A), 250.104(A)(1)

Yeah yeah, yuck it up. I was tired. My toe hurt.

So am I on the right track or way off base?

 

[charlie]

Re: 250.104(A), 250.104(A)(1)

Does this mean that we now have to be serious?

If no such circuit exists, the bonding jumper shall not be smaller than 8 AWG copper.

What is the basis for the #8 as the minimum size and what would be the requirements to have its size increased?

 

[hurk27]

Re: 250.104(A), 250.104(A)(1)

Sorry George I thought it was part of the proposal?

[ March 28, 2005, 07:16 PM: Message edited by: hurk27 ]

 

[George Stolz]

Re: 250.104(A), 250.104(A)(1)

iwire, I'm flagging you down to read this too, if you haven't already.

Does this mean that we now have to be serious?

Not in the least. When you catch me with my fly down, expect an offhand remark as I zip up!

If an appliance is dropped into a sink, in order for a GFCI to trip before human contact the ground fault would need a path. This would be accomplished by bonding the water piping to the EGS.

I figure the max number of appliances that you would drop into a sink at any given time would be about forty amps worth. (The obvious stupidity of that statement is designed to evoke a response.)

 

[charlie]

Re: 250.104(A), 250.104(A)(1)

I am inclined to use #8 as the bonding conductor . . . period (yes, I know but I agree with you). The reasoning is that smaller conductors would be more fragile, larger ones would not be necessary for current carrying capacity since the larger circuit that may energize the piping system will be bonded. By the way, even with 40 amperes of fault current, a #14 wire would do nicely.

It would be well to question why metallic sewer piping is never required to be bonded since it is in contact with water in buildings just like the water piping system. OK, I know we don't use metallic drain pipes anymore but the point is still valid.

The only reason I can see for the CMP to reject this one is the possibility of a metallic water line being run to the building some time in the future. Since the Code rules are not based on the future, that would not be a valid reason.

 

[George Stolz]

Re: 250.104(A), 250.104(A)(1)

(1) General. Any accessible point on the interior metal water piping system(s) shall be bonded to any accessible point on the equipment bonding system. The bonding jumper shall be sized in accordance with 250.122, using the rating of the circuit that is likely to energize the piping system. If no such circuit exists, the bonding jumper shall not be smaller than 8 AWG copper.

I changed this to read "any point on the pipe is bonded to any point on the EGS." Just to clarify the lack of a 5' rule. Is this unnecessary?

It just seems like there's a problem that I'm not seeing here.

[ March 28, 2005, 09:33 PM: Message edited by: georgestolz ]

 

[charlie]

Re: 250.104(A), 250.104(A)(1)

OK, what do you think of this?

(1) General. Where installed in or attached to a building or structure, metal water piping system(s) that are not considered grounding electrodes shall be bonded to the service equipment enclosure, the grounded conductor at the service, the grounding electrode conductor, or to the one or more grounding electrodes used. The bonding jumper(s) shall not be smaller than 8 AWG copper and shall be sized in accordance with 250.122 using the rating of the circuit that may energize the piping system(s).

 

[shortcircuit2]

Re: 250.104(A), 250.104(A)(1)

Hey guys...your already rewriting the code But we haven't figured out why we have to size this bonding conductor for the metal water piping system at a size based on table 250.66

We are required to do the same for structural metal that is likely to be energized...250.104(C)

So, then we must also rewrite section 250.104(D) too...which deals with bonding metal water piping and structural metal to a separately derived systems?

Charlie...I too thought about a possible future reconnection of a street side metallic water pipe to the building or structure...a very unlikely situation.

IMO, the code does consider the future, 90.8(A) is a good example of that. Also a supplemental ground rod for a water pipe electrode is another example.

I've scanned through my books and none seem give a reason for this bonding, other than the possibility that the metal may become energized. I looked in code books back to 1978...

I think we need a better understanding of the reason behind this requirement to bond before we approach the CMP for a change.

shortcircuit2

 

[George Stolz]

Re: 250.104(A), 250.104(A)(1)

Originally posted by shortcircuit2:
Hey guys...your already rewriting the code But we haven't figured out why we have to size this bonding conductor for the metal water piping system at a size based on table 250.66

...I think we need a better understanding of the reason behind this requirement to bond before we approach the CMP for a change.

If someone can't come forward with an explanation, perhaps it's justifiable to submit a proposal to change this. As it sits, it seems excessive, IMO. If we are wrong, and the CMP is aware of the reason, won't that be made clear when they rule on the proposal? I thought a formal interpretation is kind of inherent in that.

We are required to do the same for structural metal that is likely to be energized...250.104(C)

So, then we must also rewrite section 250.104(D) too...which deals with bonding metal water piping and structural metal to a separately derived systems?

One step at a time!

I've scanned through my books and none seem give a reason for this bonding, other than the possibility that the metal may become energized. I looked in code books back to 1978...

I have no experience with lighting and metal structures. Will lightning seek out the metal frame of a building, if it is ungrounded? Perhaps this is the reasoning behind this? Just a thought.

Charlie, do you think it's necessary to have this bonding conductor connected as a grounding electrode? I think it would be sufficient to connect it to a subpanel, IMO.

Thanks for the continued attention to this, all.

 

[iwire]

Re: 250.104(A), 250.104(A)(1)

Originally posted by georgestolz:
iwire, I'm flagging you down to read this too, if you haven't already.

George I am happy you want my opinion.

I have not responded to this thread as I really do not understand the reasoning behind the requirement. I would hesitate to change the requirement without knowing why it was in the code in the first place.

Also I do not find it much of a hardship to use a 250.66 sized conductor.

I can not think of a time when this was an issue for us. The jobs we do always have a metal water main that must be used as an electrode.

Even if it is not metal all the way from the street it is metal for the run into the building.

 

[George Stolz]

Re: 250.104(A), 250.104(A)(1)

Originally posted by iwire:
I have not responded to this thread as I really do not understand the reasoning behind the requirement. I would hesitate to change the requirement without knowing why it was in the code in the first place.

Well, fools venture where angels fear to tread.

So does anyone see a function of this conductor, regardless of what the intent may have originally been, more than 25 years ago? My thought is, water piping should be guaranteed to be at zero volts, but the larger the service, the more outrageous it seems to be.

 

[iwire]

Re: 250.104(A), 250.104(A)(1)

Originally posted by georgestolz:
Well, fools venture where angels fear to tread.

We now return to our regularly scheduled program. )

 

[George Stolz]

Re: 250.104(A), 250.104(A)(1)

The open utility neutral is a good argument. Do you think it would be more appropriate to drop the #8 and leave bonding out completely?

In my "clumsy" analogy above, the appliances would have needed a two wire cord to make use of the fault path the water piping could provide. Given the amount of PEX and porcelain sinks, it would diminish the effectiveness of that path even more.

Leaving it out is a strong option.

 

[shortcircuit2]

Re: 250.104(A), 250.104(A)(1)

I don't think leaving the bond out altogether on metal water piping systems is a good idea IMO. I do think as an alternative the AHJ should permit the metal water piping system to be bonded in accordance with 250.104(B)

As for the lost neutral theory...I think that bonding would be the lessor of the 2 evils...meaning there would likely be a greater chance of the piping to become energized from a fault.

Well, as for having ungrounded wiring systems in a dwelling...we all know that will never happen.

Now, as Iwire described, a 3/0 bonding connection in the large buildings he works on is nothing to worry about, and there is more likely a chance of the metal piping systems being exposed to large fault currents.

Most of the time its not a problem to run the 1/0 bond to the water pipe in a dwelling either...I was just wondering why...It seems like it is oversized in the installation I described in my 1st post.

I think this bonding rule will probably stay unchanged, its been in the code for a long time. There are some codes that seem to apply more appropriately to certain installations than to others.

shortcircuit2

 

[iwire]

Re: 250.104(A), 250.104(A)(1)

Originally posted by shortcircuit2:
I don't think leaving the bond out altogether on metal water piping systems is a good idea IMO.

As Charlie pointed out we do not have to bond the cast iron (still widely used in commercial) drain pipes.

Why is a supply line likely to be energized but a waste line is not.

The most likely source to energize a water supply system would be an appliance connected to it. IMO

Why not treat it like a gas pipe where the EGC to the appliance may be the bonding means?

 

[George Stolz]

Re: 250.104(A), 250.104(A)(1)

Originally posted by iwire:
The most likely source to energize a water supply system would be an appliance connected to it. IMO

Why not treat it like a gas pipe where the EGC to the appliance may be the bonding means?

I'm warming up to this idea. I have a residential background, so I see things small scale. Are there any changes for huge services that would affect this?

I think leaving it out is sounding better and better. Shortcircuit, sell me on keeping it.

 

[shortcircuit2]

Re: 250.104(A), 250.104(A)(1)

Lets see now...that waste line would be subject to 250.104(B) if it were likely to be energized and I'm not sure how this would happen. How about those new automatic flush urinals? What voltage is connected to that photoeye control?

The waste pipes must interconnect with the metal supply pipes or building metal through their supporting means somewhere in the building.

The metal water piping is addressed by the code because it has been assumed for years to be connected to the street metal water pipe electrode. It is important to have zero potential between metal piping system(s), other metal piping, structural metal, and the buildings grounding electrode system.

My theory...it is important to have the metal water piping system bonded to have it a the same potential because people physically come in contact with the metal parts of the system(s). This is a good reason not to treat it like a gas piping system.

My theory...the gas company doesn't want their piping system used as an electrode because of the explosive nature of natural gas. But the interior piping system must be bonded to prevent a potential difference if it were energized.

I think that the one phenomenon that is the reason that bonding will always be important is lightning. The potential voltage difference between a buildings wiring, metal piping and metal structural components would be enormous if bonding between each were not present. If a building were to suffer a stroke of lightning without intersystem bonding the damage would be extensive.

But...in the single family dwelling, as addressed in my original post, the oversized bonding jumper to the interior metal piping system, that is fed street side with plastic piping, seems a little overkill.

Maybe an exception to 250.104(A) allowing the AHJ to allow bonding in accordance with 250.104(B) under conditions where the building is fed with plastic water pipe.

shortcircuit2