Transformer Taps ?

[Davebones]

We have an 112kva , 480v to 120-208v transformer . The secondary wires feed to a wire trough 15ft away . There the secondary wires there have three taps that each feed up to a 225 amp main breaker panel above the trough . Is this not a violation of the transformer taps rules ? ( Can;t tap a tap ? ) We need to add another panel and if I understand the tap rules we have to come from the transformer terminal's to do this . This was done originally around 1984 . We are a manufacturing facility but this setup is in the office area ...

 

[david luchini]

Yes, sounds like a violation of 240.21(C). I don't know what the Code said about it in 1984.

 

[EC Dan]

Would be a violation of 240.21(C)(6)(2) in NEC 2017. Similar wording in NEC 1981 in 240.21 Exception 8e. Note that this isn't necessarily an example of the "can't tap a tap" rule described in 240.21, since it sounds like the three taps are all on the same conductors.

 

[kwired]

Can't tap a tap isn't direct code language, but wording in all the different tap rules one can sort of come up with this saying because essentially you can't tap a tap.

Yes I think what was there was never code compliant.

 

[jim dungar]

Yes, sounds like a violation of 240.21(C). I don't know what the Code said about it in 1984.

That type of installation was allowed and was typical back in the 80s.

 

[Davebones]

I was curious and just found some original drawings . It's actually drawn that way on the blueprints . We have three transformers set up's like that . Transformer to wire trough then tapped up to each panel .