Do I need a sperate disconnect for this xformer?

[rookie4now]

We're setting a 3P 480/208 transformer. There is a 3P panel on the load side feeding 2 circuits. Do we need a disconnect between the xformer and the panel? I thin 450.3(B) Note 2 allows the panel to be the disconnect because there are less than 6 circuits.

 

[tom baker]

There are new rules in the 2011 NEC for transformer disconnects - what cycle are you on and where is the disconnect located - is it within sight of the transformer?

 

[rookie4now]

There are new rules in the 2011 NEC for transformer disconnects - what cycle are you on and where is the disconnect located - is it within sight of the transformer?

2008 NEC. Transformer inside building within line of sight of the primary disconnect and also the distribution panel on the load side of the transformer. Just out of curiosity, what difference does line of sight make? I didn't see any reference to that in 450.3(B).

Thanks

 

[augie47]

408.36 I believe will require the panel to have a main since the panel is not actually a "service panel" so the exception would not apply. (If you have to add a disconnect for any reason (see below), that disconnect can serve as the panel "main".

Also 240.21(C) might require a disconnect depending on the length of the tap.

Keep in mind, with transformers you must meet the rules in Art 450 as well as Art 240 (and 408, etc)

 

[david luchini]

We're setting a 3P 480/208 transformer. There is a 3P panel on the load side feeding 2 circuits. Do we need a disconnect between the xformer and the panel? I thin 450.3(B) Note 2 allows the panel to be the disconnect because there are less than 6 circuits.

I think you are asking if you can use a main lugs panel with 2 feeder circuit breakers on the secondary side of a transformer, with the 2 circuit breakers in the panel being the secondary overcurrent protection allowed by 450.3(B) Note 2.

The answer is no, not because of 450.3(B), but because of 408.36. You need to protect the panelboard with AN overcurrent device located within or at any point on the supply side of the transformer.

 

[rookie4now]

I think you are asking if you can use a main lugs panel with 2 feeder circuit breakers on the secondary side of a transformer, with the 2 circuit breakers in the panel being the secondary overcurrent protection allowed by 450.3(B) Note 2.

The answer is no, not because of 450.3(B), but because of 408.36. You need to protect the panelboard with AN overcurrent device located within or at any point on the supply side of the transformer.

Will a back-fed breaker in the panel handle that?

 

[augie47]

sure.. if you meet all the other rules (240.21, etc)... & . don't forget 408.36(D)