250.104(d) ?

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ibew441dc

Senior Member
I had a question asked to me that got me thinking.

Heres my first attempt to keep it as simple as possible.

If i have a delta/wye transformer and the primary EGC is sized large enough to satisfy the required size of metal water pipe or structural metal bonding jumper required by 250.104(D)1&2 , and the primary EGC is bonded to the GES which is bonded to metal water pipe and structural metal, Would it be permitted to use the primary EGC as my bonding jumper required by 250.104(D)?

(sorry for the run on sentence, I hope I got my question clear enough)

Thanks
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Yes, if it's large enough for the new secondary ampacity. It often isn't with step-down transformers.
 

iwire

Moderator
Staff member
Location
Massachusetts
I think it is up for interpretation by the local AHJ.

Notice that 250.104(D)(1) requires the water pipe bond to be "nearest available point of the metal water piping system(s) in the area served by each separately derived system"

Once you factor in the exceptions to 250.104(D)(2) it gets really convoluted.

I would talk to the AHJ before counting on anything.
 

benaround

Senior Member
Location
Arizona
daniel, Are you trying to use the primary EGC as the GEC of the seperately

derived system? IMO, this can only be done following 250.30(3)(ex.#2).
 

ibew441dc

Senior Member
benaround said:
daniel, Are you trying to use the primary EGC as the GEC of the seperately

derived system? IMO, this can only be done following 250.30(3)(ex.#2).


In the original scenario i was not trying to illustrate using the primary EGC as the GEC.
(just looking at possibilities of satisfying bonding requirements for water pipe & structural metal)
 

ibew441dc

Senior Member
iwire said:
I think it is up for interpretation by the local AHJ.

Notice that 250.104(D)(1) requires the water pipe bond to be "nearest available point of the metal water piping system(s) in the area served by each separately derived system"

Once you factor in the exceptions to 250.104(D)(2) it gets really convoluted.

I would talk to the AHJ before counting on anything.

The response you gave me is similar to the one I gave when the question was originally presented to me.
 

ibew441dc

Senior Member
LarryFine said:
Yes, if it's large enough for the new secondary ampacity. It often isn't with step-down transformers.


The possibility of installing an oversized EGC on the primary was discussed due to the fact that it was the easiest and closest to the metal water pipe and structural steel.
 
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