Grounding Electrodes, 1959 v 2008 vs 2014

[rruelas123]

Hoping to find a couple of advisory interpretations regarding a project we are designing.

In a recent survey of a existing building with (2) electrical services (1 at 400A 208/120 3phase, 4 wire from 1959 and a second at 800A 480/277, 3phase 4 wire from 2009) we discovered the following regarding the grounding electrodes currently in use.

The 1959 service only has a visible connection to a 3/4" cold water pipe within the same room approximately 5 inches above the concrete slab. Our plumbing engineer in reviewing the existing drawings does believe this cold water pipe does travel under or perhaps within the existing slab for at least 10' before rising up again and connecting to a existing sink. Per the 1959 NEC 250.81 a "metallic underground water piping system, either local or supplying a community shall always be used as the grounding electrode where such a piping system is available". The 1959 code does not distinguish that the metallic underground water pipe has to be the water service pipe, nor does is state as the current code does that it has to be in direct contact with earth. That said, by the letter of the 1959 code, we believe this grounding electrode to be in compliance with the code it was installed under.

The 2009 service only has a visible connection to a abandoned 3" water pipe in the same room approximately 10" above where this pipe rises above the slab. This 3" water pipe was the the main water service to the building, but around the same time the 2009 electrical service went in, this pipe was capped in the building and cut off from the city main supply in the street approximately 150' away. In effect, this pipe is no longer a water pipe as it is abandoned and does not supply water to the building, it is only a empty pipe in the ground. During this same renovation project, a new water service was brought into the building approximately 200' away in a new building addition at the time.

Our current renovation project involves removing the underground branch pipe that the 1959 service is utilizing as a GE (grounding electrode). I explained to the owner and architect, that if we remove that underground pipe, we now need to provide a new GE and a new GEC, and since there is a new water service we would need to take that GEC to the water service and utilize the main water service as the GE. Of course the prospect of adding several thousand dollars to the project is not going over well. One of there responses was "why can we just not go to the abandoned 3" water main that the 2009 service is connected to".

Based on our interpenetration, the 3" abandoned water service is not a Grounding Electrode as it is not a water pipe anymore as it is not connected to the building water system, nor is it connected to the city water main and under current code, we can not connect the 1959 service to it. Additionally our interpenetration is that the 2009 Electrical service is currently in violation. We believe it to be in violation, as there is a underground water pipe (the main water service) in direct connection with the earth present in the building (although 200' away in another portion of the building) and that the 2009 service should be utilizing that pipe as a GE since it is present.

In summary, we believe that if the current metal water pipe under slab that the 1959 service is connected to is removed, we are required to run a GEC 200' to the main water service and that the use of any other metal water pipe under slab will not satisfy 250.62 of the 2014 (current edition in effect in this jurisdiction) code as there is no guarantee a under slab (or in slab) metallic water pipe is in "direct contact with earth". Additionally we believe the 2009 service should be disconnected from the abandoned 3" pipe and a new GEC also ran to the main water service. Based on the above does anyone have a different interpenetration to offer? Is there something we are not considering that would allow us to not run 200' of GEC to the building water service?

Any feedback is appreciated.

rruelas123
engineer

 

[roger]

Simple fix would be to change the new water service to plastic or install a dielectric union so it does not meet the requirement of being a GE and simply drive a couple of rods.

Roger

 

[jmellc]

Get Inspections involved and get a ruling from them. You can argue with the customer for a month and not change their minds. Present to them what Inspections requires and let them take it or leave it.

 

[rruelas123]

If I had some sort of inspector to go to for a ruling I would. However, the type of project this is falls under a statewide government agency where no local AHJ has authority. Even at the state level, the governing body does not have inspectors to make this type of judgement call, the onus is on the design team for compliance with code and all interpretations.

My original post was in effort to gain opinion on whether our interpenetration is valid, or if anyone else has run into a similar situation or has a different opinion for interpenetration of the code that may open up other options for compliance.

Thanks

 

[ActionDave]

If I had some sort of inspector to go to for a ruling I would. However, the type of project this is falls under a statewide government agency where no local AHJ has authority. Even at the state level, the governing body does not have inspectors to make this type of judgement call, the onus is on the design team for compliance with code and all interpretations.

My original post was in effort to gain opinion on whether our interpenetration is valid, or if anyone else has run into a similar situation or has a different opinion for interpenetration of the code that may open up other options for compliance.

Thanks

I agree with Roger.

 

[kwired]

Simple fix would be to change the new water service to plastic or install a dielectric union so it does not meet the requirement of being a GE and simply drive a couple of rods.

Roger

Placement of the dielectric union can be critical to determining if you still have a "metal underground water pipe" electrode or not, but otherwise yes.

The abandoned 3 inch water pipe is no longer a 250.52(A)(1) electrode, but can still be used as 250.52(A)(5) electrode (rods and pipes).

 

[don_resqcapt19]

The abandoned water pipe is a 250.52(A)(8) electrode and can still be used as a grounding electrode. The real issue is that since there is a 250.52(A)(1) electrode available, it must be used. Apply Rogger's idea to eliminate the 250.52(A)(1) electrode and use the abandoned water pipe as your electrode. It does not appear that an (A)(8) electrode requires a supplemental electrode like an (A)(1) would.

 

[roger]

Placement of the dielectric union can be critical to determining if you still have a "metal underground water pipe" electrode or not, but otherwise yes.

Of course it does, I think that goes without saying and is the reason I stated "so it does not meet the requirement of being a GE".

Roger

 

[tom baker]

Regardless of what grounding electrodes you use, you'll need a common grounding electrode between services, see 250.58

 

[kwired]

Of course it does, I think that goes without saying and is the reason I stated "so it does not meet the requirement of being a GE".

Roger

But it basically means the dielectric union needs to be outside the structure, if any part of that pipe enters the structure and is continuous for at least 10 feet in earth - 250.50 plus 250.52(A)(1) says you must use it as an electrode.

 

[roger]

But it basically means the dielectric union needs to be outside the structure, if any part of that pipe enters the structure and is continuous for at least 10 feet in earth - 250.50 plus 250.52(A)(1) says you must use it as an electrode.

So what's your point that hasn't already been stated?

Roger

 

[kwired]

So what's your point that hasn't already been stated?

Roger

Well it started out as the dielectric union approach not being as simple as it may sound. I guess the non metallic supply line isn't normally so simple either. Simple concept, yes, but not necessarily so simple to install.