Step-down Transformer Ground Connection Point

[tom baker]

Grounding
The SDS must have a connection to a grounding electrode 250.30 (A) (5) has a very clear requirement on this, start with the first electrode and if you don't have one of the types listed, then its a made electrode
Bonding
The SDS must be bonded to metal water piping and structural metal 250.104 (D) has the details. Sometimes the grounding electrode connection can serve as the bonding connection see EX 1 and 2 to this section

 

[augie47]

You're right. I lost track of that as there were so many Art. 250 changes for 2011. It just moved and I remembered it as not being there. Foot in mouth.
Thats what I get for relying on memory. I looked it up in '05 and '08 and you are correct.

It looks like it may be my foot in mouth time. The exception to 250.52 has been removed in the '11 but so has the "5 ft wording". If I am reading the '11 correctly, you can use the water pipe for a grounding electrode connection at any point.

 

[david luchini]

It looks like it may be my foot in mouth time. The exception to 250.52 has been removed in the '11 but so has the "5 ft wording". If I am reading the '11 correctly, you can use the water pipe for a grounding electrode connection at any point.

I believe they have just moved those requirements rather than deleted them...See 250.68(C).

 

[iwire]

OK, I am officially lost on this.

 

[texie]

I believe they have just moved those requirements rather than deleted them...See 250.68(C).

Yes, that was my observation when I ate crow in my previous post. That said, I think it was allowed a one time to use piping as a GEC, but my cursory research back as far as the '96 edition says no. It just moved around over the cycles, especially in 2011 when a lot of changes were made. '96 is the oldest I have here in the office but I have older editions at home. I'll have to do some research further back for curiosity sake.

 

[augie47]

I believe they have just moved those requirements rather than deleted them...See 250.68(C).

Yes, that was my observation when I ate crow in my previous post. That said, I think it was allowed a one time to use piping as a GEC, but my cursory research back as far as the '96 edition says no. It just moved around over the cycles, especially in 2011 when a lot of changes were made. '96 is the oldest I have here in the office but I have older editions at home. I'll have to do some research further back for curiosity sake.

Double dog dang it ! I wish "they" would quit moving things !!! O.K., back to the original thinking.... IF there is a metal water pipe grounding electrode on the premises and no structural metal grounding, the pipe must be used as a grounding electrode for the SDS per 250.30(A)(7) and per 250.68(C) in the '11 Code the connection must be within 5 ft of the entry of the pipe. Do I have it correct ?

 

[david luchini]

Double dog dang it ! I wish "they" would quit moving things !!! O.K., back to the original thinking.... IF there is a metal water pipe grounding electrode on the premises and no structural metal grounding, the pipe must be used as a grounding electrode for the SDS per 250.30(A)(7) and per 250.68(C) in the '11 Code the connection must be within 5 ft of the entry of the pipe. Do I have it correct ?

I think you have it correct. :happyyes:

 

[texie]

Yes, that was my observation when I ate crow in my previous post. That said, I think it was allowed a one time to use piping as a GEC, but my cursory research back as far as the '96 edition says no. It just moved around over the cycles, especially in 2011 when a lot of changes were made. '96 is the oldest I have here in the office but I have older editions at home. I'll have to do some research further back for curiosity sake.

I checked previous editions and you could in fact use interior water piping as a GEC prior to the 1993 edition. The 5 foot rule was added in the 1996 NEC.