Yet Another SDS violation

[lile001]

There are several transformers in a building I am working on that don't seem to be properly grounded.

In each case, they have installed a primary wire with a ground wire, "properly" sized according to table 250.122 taking into account the primary circuit breaker. (Ooops - common mistake!)

This same ground wire attaches to the case of the transformer, then also attaches to the XO terminal of the secondary.

Of course this violates the code because the primary wire doesn't comply with table 260.66, which would generally require a heavier wire for the secondary of a 480:208 transformer.

Now, in fixing this, we'd like to take a wire complying with 250.66 from the XO terminal to the nearest building steel.

My question is, must the primary ground wire be disconnected from the XO terminal, or is it allowed to remain in place?

 

[roger]

Actually, there is no real violation, only an omission of a properly sized GEC on the secondary side.

All existing conductors and connections can remain in place, just add the GEC

Roger

 

[augie47]

If you are talking about theb "primary" wire being the one feeding the transformer, then 250.122 IS the corrrect method for sizing that EqGr conductor.
Beyond that, I agree with Roger. add a GEC based on 250.66 & the transformer "secondary" conductors.

 

[benaround]

lile, If the primary EGC is being used for the SBJ it may not be sized right.

Side note: If I was getting paid to fix this situation, I would go with a more

standard method just to CYA , jmo.

 

[don_resqcapt19]

It is my opinion that the reason the transformer needs grounding electrode conductor sized per Table 250.66 is not a technical reason...only a code rule. Assuming that the transformers are in the same building as OCPDs for the primary feeders, what real purpose does a larger grounding electrode conductor serve?

 

[RUWired]

Now, in fixing this, we'd like to take a wire complying with 250.66 from the XO terminal to the nearest building steel.

Keeping in mind that the lug must be rated for the amount of wire going into it. A lot of people try to jam the neutral and all the grounds together.