Transformer grounding to water line

[Gategator37]

A transformer is located in the middle of a building, this transformer is being grounded with a #6 copper to a water line that is not located within 5 ft from the entrance of the building. According to 250.52 (A)(1) this is not legal right? Also, this #6 is ran through metal studs and up the wall to the water line...is this legal? I know that it is larger than a #8 so it does not have to be in a raceway, but can it be run through studs and up a wall?

 

[Pierre C Belarge]

See 250.30(A)(7) for the location of termination of the GEC. It is very specific.
Installing the GEC to a local water line is not permitted for Separately Derived Systems. One has to use the steel locally, or go back to within 5ft of where the water enters the building, if the water qualifies as an electrode. (is this an industrial location?)


Yes, one can install the GEC as you have explained, see Part III of Art 250.

 

[Gategator37]

As I was reading the code a little further it looks like 250.104(D)(1) allows the grounded conductor to be bonded to the metal water piping at the nearest available point, however, do a need a supplemental ground? This building is a remodel and has no exposed steel.

 

[Pierre C Belarge]

250.104 is BONDING of water and steel.
You are installing a Grounding Electrode Conductor in conjunction with a separately derived system. So, the reference is 250.30(A)(7), not 250.104.

I should mention, that:
250.30(A)(3) Grounding Electrode Conductor, Single Separately Derived System.
References within the paragraph, Section 250.30 (A)(7).

 

[Gategator37]

Thanks for your help I really appreciate it!

So if the water line is no where near this area and all of the steel is behind concrete what else could I ground to? Or do I need to go down 3 floors to the water, or somehow find steel in the building (I know its there, but not close).

 

[david luchini]

So if the water line is no where near this area and all of the steel is behind concrete what else could I ground to? Or do I need to go down 3 floors to the water, or somehow find steel in the building (I know its there, but not close).

The steel or water pipe are your only options, even if they are not very close to your transformer.

Only IF there is no water pipe electrode or structural steel electrode, are you allowed to use other types of electrodes, per 250.30(A)(7) Exc. No. 1.

 

[Pierre C Belarge]

Thanks for your help I really appreciate it!

So if the water line is no where near this area and all of the steel is behind concrete what else could I ground to? Or do I need to go down 3 floors to the water, or somehow find steel in the building (I know its there, but not close).

If you look at the first exception in 250.30(A)(7), you will see this:

Any of the other electrodes identified in 250.52(A) shall be used where the electrodes specified by 250.30(A)(7) are not available.

Since you mention that the water electrode is available (and the steel is not), you will need to install the GEC from the Separately Derived System all the way back to within 5ft of where the water electrode enters the building.
I know that this can be a burden, but it is the requirement.


You mention the steel is behind concrete. if you can show the steel meets the requirements of 250.52(A)(2), I would contact the Building Official and ask him if there is compliant way you can expose the steel and connect to it. It certainly cannot hurt to ask, and may save you a ton of stre$$.

 

[iwire]

250.104 is BONDING of water and steel.
You are installing a Grounding Electrode Conductor in conjunction with a separately derived system. So, the reference is 250.30(A)(7), not 250.104.

IMO 250.104(D) appllies as the transformer is required to be grounded and bonded.

250.104 Bonding of Piping Systems and Exposed Structural
Steel.

(D) Separately Derived Systems. Metal water piping systems
and structural metal that is interconnected to form a
building frame shall be bonded to separately derived systems
in accordance with (D)(1) through (D)(3).

(1) MetalWater 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.

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 and the water piping system
is in the area served.

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.


(2) Structural Metal. Where exposed structural metal that
is interconnected to form the building frame exists in the
area served by the separately derived system, it shall be
bonded to the grounded conductor of 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.

Exception No. 1: A separate bonding jumper to the building
structural metal shall not be required where the metal
frame of a building or structure is used as the grounding
electrode for the separately derived system.

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

(3) Common Grounding Electrode Conductor. Where a
common grounding electrode conductor is installed for
multiple separately derived systems as permitted by
250.30(A)(4), and exposed structural metal that is interconnected
to form the building frame or interior metal piping
exists in the area served by the separately derived system,
the metal piping and the structural metal member shall be
bonded to the common grounding electrode conductor.

Exception: A separate bonding jumper from each derived
system to metal water piping and to structural metal members
shall not be required where the metal water piping and
the structural metal members in the area served by the
separately derived system are bonded to the common
grounding electrode conductor

 

[david luchini]

IMO 250.104(D) appllies as the transformer is required to be grounded and bonded.

Bob, are you suggesting that 250.104(D) can be used instead of 250.30(A)?

The OP was asking about grounding the separately derived system. I'd agree that the piping & steel in the area of the SDS must be bonded per 250.104, but I feel the grounding electrode for the SDS must be as specified in 250.30(A). I think that was Pierre's point.

 

[iwire]

Bob, are you suggesting that 250.104(D) can be used instead of 250.30(A)?

Not at all, IMO both sections apply and both sections must be fully complied with.