Transformer Grounding

[RUWired]

The installer did not install the GEC for the transformer to either the steel or the water, he used ground rods.

.

Pierre, lets say that the water and steel are not closely available (because its installed outside) as an electrode and the rods were installed to meet 250.(A)7.

Article 250.104(D) is still required to be intalled.

Rick

 

[Pierre C Belarge]

Pierre, lets say that the water and steel are not closely available (because its installed outside) as an electrode and the rods were installed to meet 250.(A)7.

Article 250.104(D) is still required to be intalled.

Rick

250.30(A)(7) does not allow for the fact the water is far from the SDS. What if the Transformer was up on the second floor of a building and 500 feet horizontally across. It would still be required.

 

[Pierre C Belarge]

Pierre, are you claiming that you can actually stop thinking about this stuff at night? I wish I could develope this skill!

I am studying for a meeting I have with the State representative, engineers, management company, local building official, electrical contractor, and the EC. I wrote (as a consultant) a document that the engineer states is holding up the job and creating a hardship for the property owner.
The meeting is to see if the State will give a variance to allow the installation. The EC on the job is not the original installer.
The original installer came from out of state, did not file, did not have inspections and really messed the job up. It is the installation of a generator, firepump and related wiring with a remote service which is separate from the building building service. I cannot provide pictures, maybe later.

So, in answer to your question, NO.

 

[RUWired]

250.30(A)(7) does not allow for the fact the water is far from the SDS. What if the Transformer was up on the second floor of a building and 500 feet horizontally across. It would still be required.

It would be required if the building steel and water were not in the area. In your OP your suggesting the EC go to the water within 5'. I'm saying not required if water is available closer. If the closest is 5' from the building, than i agree with you.

Rick

 

[Smart $]

It would be required if the building steel and water were not in the area. In your OP your suggesting the EC go to the water within 5'. I'm saying not required if water is available closer. If the closest is 5' from the building, than i agree with you.

Rick

I'm quite certain Pierre's mention of 5' is regarding the maximum distance from the waterline's entry into the building to the GEC's connection thereto.

 

[RUWired]

The problem with on-line posting is we're not on the job site to visually see the proximity of the water line to the transformer.

That being said, the most important object is to insure continunity of the new SDS's equipment to the water line in this case.

Whether the GEC is connected to the water electrode within 5' of the building or its connected to the water in close proximity and a rod electrode is used in conjunction with the bonding of the water, is more the point.

Rick

 

[Pierre C Belarge]

It would be required if the building steel and water were not in the area. In your OP your suggesting the EC go to the water within 5'. I'm saying not required if water is available closer. If the closest is 5' from the building, than i agree with you.

Rick

I disagree with this part of your post.
See 250.30(A)(7)(1). Metal water pipe grounding electrode as psecified in 250.52(A)(1).
.52(A)(1) states the water pipe within 5' of entry to the building.

The use of water pipe further in the building than 5' allows for the chance that the water pipe may not be continuous for many reasons, such as maintenance of the piping system over time, therefore the piping system would not be complete back to the electrode.

 

[hurk27]

Pierre

Why can't the exception to 250.52(A)(1) be allowed?

Exception: In industrial and commercial buildings or structures where conditions of maintenance and supervision ensure that only qualified persons service the installation, interior metal water piping located more than 1.52 m (5 ft) from the point of entrance to the building shall be permitted as a part of the grounding electrode system or as a conductor to interconnect electrodes that are part of the grounding electrode system, provided that the entire length, other than short sections passing perpendicular through walls, floors, or ceilings, of the interior metal water pipe that is being used for the conductor is exposed.

 

[Pierre C Belarge]

Pierre

Why can't the exception to 250.52(A)(1) be allowed?

I am absolutely for that in the proper locations.
I guess it would be a call by the AHJ.
I can vouch for this building as not being maintained by any qualified individuals though.

 

[tryinghard]

Just because it is currently an ungrounded system does not necessarily mean it should remain ungrounded, maybe it never did qualify or maybe its evolved past the initial need, these are worthy questions for the client/owner.

Essentially the grounding and bonding are the same and all the more critical to detect faults (250.4(B) & 250.21). If the water pipe is an electrode and not bonded this needs to be done anyway. 250.30(B)(2) simply refers back to (A)(7) that stresses a water or structure metal frame electrode that is ?near as practical?, if neither meet this criteria then another can be used but they still must bond to any other electrode on the system.

 

[Smart $]

I disagree with this part of your post.
See 250.30(A)(7)(1). Metal water pipe grounding electrode as psecified in 250.52(A)(1).
.52(A)(1) states the water pipe within 5' of entry to the building.

The use of water pipe further in the building than 5' allows for the chance that the water pipe may not be continuous for many reasons, such as maintenance of the piping system over time, therefore the piping system would not be complete back to the electrode.

I initially thought the same thing... but didn't post after rereading the "specifics".

Pierre, please reread 250.52(A)(1) in this sense: It does not say you cannot use exterior metal water piping. It only says you can't use interior water piping past 5' from its entry.

PS: It appears this is all going to change in the 2011 NEC.

 

[tryinghard]

...Article 250.104(D) is still required to be intalled...

Rick you have a valid point regarding bonding the water pipe with this ungrounded SDS. If other electrodes are installed and not bonded as a system a water pipe may not be an effective fault current path. In this particular case I understand the water does not have a GEC at/to the service.

In light of 250.30(B), 250.4(B), 250.21, & 250.104; (30(A)(7) includes a FPN) but how can the water pipe be an effective fault path downstream from the ungrounded SDS?

 

[Smart $]

... but how can the water pipe be an effective fault path downstream from the ungrounded SDS?

Ground fault detection supposed to "handle" the first ground fault (i.e. very little ground fault current due to isolation, but path parts are kept near ground potential if adequately bonded). Grounding becomes more effective (and needs to be adequately sized) as a current path in the event of a simultaneous second ground fault.

But then again... a water-supply pipe electrode and bonding thereto really isn't for fault current... it's for a ground reference.

 

[tryinghard]

Ground fault detection supposed to "handle" the first ground fault (i.e. very little ground fault current due to isolation, but path parts are kept near ground potential if adequately bonded). Grounding becomes more effective (and needs to be adequately sized) as a current path in the event of a simultaneous second ground fault.

But then again... a water-supply pipe electrode and bonding thereto really isn't for fault current... it's for a ground reference.

annunciation/alarming requires effective paths as well as phase short allowance, my point with the water pipe is it may not be an adequate path in this case meaning a fault could remain on it while another faults to metal frame or ??. Ouch if this would happen the phase short could happen with human touch!