Is this a feeder tap

[petersonra]

A fully protected conductor feeds a control panel to a disconnect switch.

A tap on the line side of the disconnect switch provides power to a lighting transformer.

My contention is that this is a feeder tap IAW 240.21 and thus as long as it is less than 10 feet long and does not leave the enclosure that it can be any size that is protected at its ampacity downstream.

A customer is claiming the ampacity of the such a tap must be at least 10% of the OCPD feeding it. The rule seems quite clear to me. But, maybe I am missing something.

Incidentally, in rereading this section, there seems to be a gray area in it. If the tap is longer than 10 feet even if it does not leave the box it appears it would not qualify under this section and would have to meet one of the other tap rules. Am I reading ti correctly?

Just curious, what rules are there for branch circuit taps? There don't appear to be any similar provisions.

 

[infinity]

Are your tap conductors 10' or less and leaving the enclosure? If so, you need to comply with 240.21(B)(1) which is as you've stated the 10% rule. If they do not leave the enclosure or a vault then the 10% provision doesn't apply but the 10' provision does.

 

[don_resqcapt19]

Bob,
Unless the lighting trasformer is in the disconnect enclosure, the 10% rule applies. If this disconnect is an open disconnect within a larger panel that also contains the transformer, then the 10% does not apply. In both cases the 10' limit applies.

 

[petersonra]

Are your tap conductors 10' or less and leaving the enclosure? If so, you need to comply with 240.21(B)(1) which is as you've stated the 10% rule. If they do not leave the enclosure or a vault then the 10% provision doesn't apply but the 10' provision does.

That's my thoughts on the matter as well.

Bob,
Unless the lighting trasformer is in the disconnect enclosure, the 10% rule applies. If this disconnect is an open disconnect within a larger panel that also contains the transformer, then the 10% does not apply. In both cases the 10' limit applies.

The lighting transformer is in a separate enclosure but contained within the enclosure the main disconnect is in that the feeder terminates at.