OCPD for Secondary of Transformers

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EMCelec

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Okay...so I have been reading about secondary OCPD for transformers and there is alot of info in these Forums.

I would like to get some clarification ....

If I have a 480/277 Panel in a electric room with a breaker feeding the primary of the transformer, transformer hanging in the ceiling 10' feet away, and the secondary feeding a 208/120v Panel on the other side of the room and it is more than 25' away do I need to insert a disconnecting means in between the secondary side of xfmr and the low voltage panel; though the panel has a main breaker.

Does the 10' or 25' tap rule for xfmr's apply? Or is this not a tap?
Any help on this issue would be appreciated.

When do I need to have a disconnect on the secondary side of the xfmr? When it is out of sight? or more than a certain footage?
 
I moved this to a new thread of its own, since it is not a continuation of the thread into which it was originally placed.
 
There is a 10 foot rule that has some restrictions, and there is a 25 foot rule that has more restrictions. But the basic rule starts at 240.21, with the statement that you have to protect every conductor against overcurrent, and the protective device has to be at the place where the conductor gets its current supply, unless one of the rules that follow can be applied.

So yes, if the secondary conductors are longer than 25 feet, you do need an overcurrent device close to the transformer. And it has to be more than just a disconnecting means, it has to provide overcurrent protection. Being in the same room means nothing, and being in or out of sight means nothing. Length of the secondary conductors is all that matters.

I would not call this a "tap." I use that word only when a smaller wire is connected to a larger wire, and is being protected not at the point of connection but at an overcurrent device at its load end.
 
I agree with Charlie b, but might add that, IMHO, this would fall under 240.21(C)(3) as "transformer secondary conductors" and the 25 ft rule is for industrial (I did not see in your OP what type occupancy).
Also note under 240.21(C) that the "next size up" rule from 240.4(B) does not apply.
 
Thanks for the replys....This is in a private Hospital.
240.21C (6) Secondary conductors Not over 25' Long
 
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