Disconnect for Transformer

[kiss]

I have to install several transformers in a building to either step up or step down the voltage 120/208-480 Volts or 480-120/208 Volts.
In these types of installations I am getting the feed from an existing panel and feeding the line side of the transformer from a circuit breaker. Do I need a disconnect (Fused or unfused) on the line or load side of the transformer? The load side of the transformer is going to a panel with a main breaker. Thanks.

 

[don_resqcapt19]

Re: Disconnect for Transformer

Transformers do not require disconnects. The do require overcurrent protection, but that does not have to be at or within sight of the transformer. The secondary conductors will require protection per 240.21.
Don

 

[pierre]

Re: Disconnect for Transformer

Just to elaborate on Don's post.
Transformers require overcurrent protection, but do not require a disconnect. The overcurrent protection is for the WINDINGS of the transformer, not the conductors on the supply side or the load side.

The CONDUCTORS for transformers will have their requirements found in 240.4, with secondary conductors specifically found in 240.4(F) and in 240.21(C)

[ March 08, 2005, 11:15 PM: Message edited by: pierre ]