Using Water Pipe Exception

[George Stolz]

If you wanted to use the exception to 250.52(A)(1) in a commercial establishment, a couple of questions:

1. Can the excepted water pipe pass horizontally through a hard lid (say, 30' of pipe concealed)?

2. If not, why not?

3. What are "conditions of maintenance and supervision" in this case? Is that qualified plumbers or electricians?

They may seem like stupid questions, but I would like some answers.

Thanks in advance,

 

[benaround]

George,

#1 I would say NEC says no, I would also say it does happen

#2 An Inspector can't see if for example non-metalic devices were used in

that 30' area, making the GEC useless or uselesser. If it just goes thru a

2x4 wall he can see it is ok.

#3 That's a good question, I don't know if it is spelled out anywhere. To me

it means that on site people work to the spec's of on site management type

that require things be done right. It may mean something way different to

others.

 

[jwelectric]

George
Read 250.104(D)(1) Exceptions
Maybe this will help clear up a few things

 

[George Stolz]

Frank, thanks for the response.

Mike, no, it actually opens doors to more questions.

I am working in a private airplane hangar. The center portion of the building is high ceiling hangar. The periphery is smaller rooms, kitchens, etc.

The service is literally on the opposite side of the building from the water pipe. So, someone's inclination was to use the portion of the metal piping on the closer side of the service, and use the exception to 250.52(A)(1). Since most of the building's smaller rooms have hard lid (only three have dropped ceilings), I thought it would be better to use the building steel as a common electrode, and forget pulling a conductor from the service to the water pipe (directly) altogether. There is an underground conduit running from the service to the electrical room for a GEC.

A short jumper from the water pipe to the building steel in the water room would connect the metal water piping system to the GES. Another bonding jumper (or GEC) to the ground ring, and there is a small conduit for the GEC from the Ufer to the service.

Mike, forcing me to look at that section this morning, has introduced a large ball of wax for me.

The chase: We are planning on running a GEC from the SDSs in the Electrical Room to the building steel in that area. Do I need to run a seperate bonding jumper to the water pipe in the Electrical Room area? As in, a bonding jumper from the SDS common grounding busbar to the water pipe in the area, despite already having the water pipe connected to the GES from the originating system?

 

[jwelectric]

It sounds like you have already bonded the building steel to the service Grounding Electrode System and to the metal water pipe.
The SDS is also bonded to the building steel for the connection to the GES thereby it is bonded to the water piping.

Edited to add;

3. What are "conditions of maintenance and supervision" in this case? Is that qualified plumbers or electricians?

I would think that the NEC is for electrical installations so it would be for the electrician and not the plumber.

 

[George Stolz]

It sounds like you have already bonded the building steel to the service Grounding Electrode System and to the metal water pipe.
The SDS is also bonded to the building steel for the connection to the GES thereby it is bonded to the water piping.

But doesn't seem to be what .104 is asking for:

250.104(D)(1) Metal Water Piping System(s). The grounded conductor of each separately derived system shall be bonded to the nearest available point of the metal water piping system(s) in the area served by each separately derived system...

What does this mean?

As far as qualified personnel go, I agree - but what electrician is going to oversee plumbing repairs, was my half-hearted thought. It's just an odd concept, I could very well be being thick-headed on that.

 

[jwelectric]

The grounding electrode for the service includes the following, the building steel and the metal water pipe electrode. These items are bonded together and make the grounding electrode for the service.

The exceptions state that if the building steel or the water pipe is the grounding electrode for the SDS then bonding is not required. Being that both are bonded together to make the electrode for the service the use of either would include both if used for the electrode for the SDS and bonding of the other would not be required in my opinion.

In other words the building steel and water pipe are both one grounding electrode so to hit one would be to hit both.

 

[George Stolz]

Mike, that sounds reasonable, but I'm not seeing how the exception's helping me out here. For the record, I would like to discuss both the wording of the sections and what's commonly practiced in the field, for both are new ground to me.

250.104(D)(1) Metal Water Piping System(s). The grounded conductor of each separately derived system shall be bonded to the nearest available point of the metal water piping system(s) in the area served by each separately derived system. This connection shall be made at the same point on the separately derived system where the grounding electrode conductor is connected. Each bonding jumper shall be sized in accordance with Table 250.66 based on the largest ungrounded conductor of the separately derived system.

This seems to say to me, connect to a very close pipe to the SDS.

Exception No. 1: A separate bonding jumper to the metal water piping system shall not be required where the metal water piping system is used as the grounding electrode for the separately derived system.

250.30(A)(7) orders me to connect to the nearest of either building steel or metal water pipe grounding electrode (250.52(A)(1)-defined, Grade-A electrode). So, if I use the building steel as my electrode for the SDS, then I have not complied with the exact wording of the section - have I?

Wouldn't it make more sense to say "where the metal water pipe is already connected to the GES" for this exception?

Exception No. 2: A separate water piping bonding jumper shall not be required where the metal frame of a building or structure is used as the grounding electrode for a separately derived system and is bonded to the metal water piping in the area served by the separately derived system.

The "in the area served" language is killing this for me. This is probably the exception you were referring to, and it would sit well for me, if it weren't for the "in the area" mumbo-jumbo.

What does that mean?

 

[jwelectric]

Maybe they are talking about area 51. :grin: lol :grin:
I think that it is pretty close to where you live.