XFMR Grounding Electrode

[Sparky5150]

Does the code prevent you from routing the grounding electrode conductor with the feeder to the XFMR?

I have a new 30 kva XFMR in a new room of existing bldg. that has no exposed steel or metal water piping.
I may have to route electrode back to the main electrical room and rather than providing a separate conduit for the electrode I wondered if it can be ran with the feeder conductors since it is a long run above existing ceiling tiles.

Thanks as always for your input!

 

[jumper]

I cannot find a code section disallowing it. I have not done an install like this so this is my first search, I may have missed something.

Since you mention conduit, if it is metallic, 250.64(E) may be a player in this scenario.

 

[ActionDave]

I have never thought of doing this either. I took a look at 250.30 and 250.64 and could not find anything that says you can't.

 

[Smart $]

Note Code makes no considerations for exposed vs. concealed structural metal. If there is structural metal closer than running all the way back to the MDP you have to use it.

Are you certain there is not any available in the above-ceiling-tile space?

What Code cycle are you on? There has been some changes through cycles which will or will not permit you to run a combination GEC/EGC... but there has never been a prohibition of running both in same conduit (or using conduit as the EGC).

 

[augie47]

I agree with Derek in that 250.64(E) may pose a problem.

 

[Smart $]

I agree with Derek in that 250.64(E) may pose a problem.

How so?

 

[jumper]

How so?

I brought that up because of the bonding rules for "choke effect" when a GEC in in metallic conduit.

I am not saying it applies I merely wanted the OP to see if it applies.

 

[ADub]

XFMR Grounding Electrode

Look at 250.30(a)(4) exception no. 2

Also 250.64(e) is easily taken care of with a simple bonding bushing if it's needed. And honestly if you utilize the article I referenced you might not even need it since your metallic raceway is terminated to the service equipment.

Sent from my iPhone using Tapatalk

 

[Sparky5150]

Note Code makes no considerations for exposed vs. concealed structural metal. If there is structural metal closer than running all the way back to the MDP you have to use it.

Are you certain there is not any available in the above-ceiling-tile space?

What Code cycle are you on? There has been some changes through cycles which will or will not permit you to run a combination GEC/EGC... but there has never been a prohibition of running both in same conduit (or using conduit as the EGC).

We are in the 2014 NEC.
Thanks for your input.

 

[Smart $]

We are in the 2014 NEC.
Thanks for your input.

Okay... see 250.121 Exception.

However, it's still as I said. If you have closer structural metal or water pipe electrode, either exposed or concealed, you have to use it according to Code. If you believe it is too difficult, contact your AHJ before running a GEC all the way back to main. That'd be a bummer if he red flagged because you didn't use nearest. Also note that any other electrode in the GES can also be used under 250.30(A)(4) Exception No. 1, and the AHJ may interpret 'nearest' to include one of those as the alternative.

 

[don_resqcapt19]

Look at 250.30(a)(4) exception no. 2

Also 250.64(e) is easily taken care of with a simple bonding bushing if it's needed. And honestly if you utilize the article I referenced you might not even need it since your metallic raceway is terminated to the service equipment.

Sent from my iPhone using Tapatalk

Often the size of the required GEC and the size of the lug on the grounding bushing prevents compliance with that section.

 

[Smart $]

Often the size of the required GEC and the size of the lug on the grounding bushing prevents compliance with that section.

The conduit is typically bonded to the enclosure per 250.64(E), which points to 250.92(B) and ensured by 250.92(B)(2) through (B)(4). In many cases, only a bonding-type locknut is all that is required.

 

[don_resqcapt19]

The conduit is typically bonded to the enclosure per 250.64(E), which points to 250.92(B) and ensured by 250.92(B)(2) through (B)(4). In many cases, only a bonding-type locknut is all that is required.

That varies from AHJ to AHJ, and typically at some point a GEC exits a conduit without being in an enclosure.

 

[ADub]

Often the size of the required GEC and the size of the lug on the grounding bushing prevents compliance with that section.

I agree and have found that to be true in my installs but the op mentioned a very small transformer that will have a very small GEC so I figured it would work for him.

 

[Smart $]

That varies from AHJ to AHJ, and typically at some point a GEC exits a conduit without being in an enclosure.

The Code is the Code. I not my fault if an AHJ interprets it differently.

And here it is being run in the same conduit as the feeder... so not the case.

 

[Sparky5150]

Okay... see 250.121 Exception.

However, it's still as I said. If you have closer structural metal or water pipe electrode, either exposed or concealed, you have to use it according to Code. If you believe it is too difficult, contact your AHJ before running a GEC all the way back to main. That'd be a bummer if he red flagged because you didn't use nearest. Also note that any other electrode in the GES can also be used under 250.30(A)(4) Exception No. 1, and the AHJ may interpret 'nearest' to include one of those as the alternative.

I believe the bldg. engineer is requesting the 400 foot run back to the main with the feeder.
Are you saying the code requires we connect to the closest GEC/available steel? This is an existing hospital facility.

Can you install a bare electrode conductor?

Thanks,

Sparky

 

[ADub]

XFMR Grounding Electrode

I believe the words are "near as practical" and "preferably". Imo 230.4(a)(4) exception 2 pretty much releases you from 230.4(a)(4) 1 and 2


Sent from my iPhone using Tapatalk

 

[Smart $]

...
Are you saying the code requires we connect to the closest GEC/available steel?

Here's the actual requirement of 250.30(A)...

(4) Grounding Electrode. The grounding electrode shall​

be as near as practicable to, and preferably in the same area​

as, the grounding electrode conductor connection to the​

system. The grounding electrode shall be the nearest of one​

of the following:​

(1) Metal water pipe grounding electrode as specified in​

250.52(A)(1)​

(2) Structural metal grounding electrode as specified in​

250.52(A)(2)​

Exception No. 1: Any of the other electrodes identified in​

250.52(A) shall be used if the electrodes specified by​

250.30(A)(4) are not available.​

Exception No. 2 to (1) and (2): If a separately derived​

system originates in listed equipment suitable for use as​

service equipment, the grounding electrode used for the​

service or feeder equipment shall be permitted as the​

grounding electrode for the separately derived system.​

Informational Note No. 1: See 250.104(D) for bonding​

requirements for interior metal water piping in the area​

served by separately derived systems.​

Informational Note No. 2: See 250.50 and 250.58 for requirements​

for bonding all electrodes together if located at​

the same building or structure.​

This is an existing hospital facility.

Has no bearing on the matter.

Can you install a bare electrode conductor?

Yes AFAIK(CR)

 

[Sparky5150]

Thanks for your attention to this Smart $!
As well as everyone else who contributed!