10' tap rule

[mjmike]

If understanding the tap rule for 10', is it correct that the tapped conductor size does not depend at all on the feeder size or upstream feeder OCPD. Example: 500 kcmil feeder is tapped with 10' of #12 to a 20A enclosed circuit breaker.

Looks like wire size ratio does not come into play until you exceed 10'.

 

[david luchini]

If understanding the tap rule for 10', is it correct that the tapped conductor size does not depend at all on the feeder size or upstream feeder OCPD. Example: 500 kcmil feeder is tapped with 10' of #12 to a 20A enclosed circuit breaker.

Looks like wire size ratio does not come into play until you exceed 10'.

See 240.21(B)(1)(4)

 

[infinity]

10' is the maximum permitted length of the tap conductors under that rule. It also is required to be 10% or larger than the OCPD ahead of the feeder.

 

[chris kennedy]

It also is required to be 10% or larger than the OCPD ahead of the feeder.

Back that up please. I see nothing in 240.21(B)(1) that requires that.

 

[jaggedben]

Back that up please. I see nothing in 240.21(B)(1) that requires that.

David already cited the section above, but here's the text for you:

(4) For field installations, if the tap conductors leave the
enclosure or vault in which the tap is made, the
ampacity of the tap conductors is not less than one tenth
of the rating of the overcurrent device
protecting the feeder conductors.

 

[oldsparky52]

I guess it depends on whether the tapping conductor leaves the enclosure or not (as far as 10% size requirement).

 

[chris kennedy]

David already cited the section above, but here's the text for you:

Guess Rob's post was a typo.

 

[infinity]

Guess Rob's post was a typo.

Which part?

 

[chris kennedy]

My bad, I read "10% larger".

 

[infinity]

My bad, I read "10% larger".

 

[mjmike]

See 240.21(B)(1)(4)

Thanks, missed that.