Tap ampacity

[Smart $]

OK, so then augie47's suggestion of using 90C splices to transition a #6 conductor to a #4 conductor for the 75C OCPD terminals would be NEC-compliant for the example in the OP?

It would be as long as the transition does not occur in a 75°C-rated equipment enclosure. Nothing in the enclosure is permitted to exceed 75°C.

 

[wwhitney]

The #6 would have to terminate in an overcurrent protective device. That device or terminals would be 75C

So you see splices as terminations? Some other respondents don't.

Cheers, Wayne

 

[wwhitney]

It would be as long as the transition does not occur in a 75°C-rated equipment enclosure. Nothing in the enclosure is permitted to exceed 75°C.

Can you provide a reference for this? That enclosures have temperature ratings, and/or that an equipment enclosure that contains 75C terminations can't also contain 90C terminations.

Thanks,
Wayne

 

[Smart $]

Can you provide a reference for this? That enclosures have temperature ratings, and/or that an equipment enclosure that contains 75C terminations can't also contain 90C terminations.

Thanks,
Wayne

Code-wise... 110.14


Industry-wise... http://www2.schneider-electric.com/...7/en_US/Wire Terminations 0110DB9901R2-02.pdf
(see the diagram on page 4 in particular)

 

[Dennis Alwon]

So you see splices as terminations? Some other respondents don't.

Cheers, Wayne

I didn't say that. I said at one end the wire may be tapped- at the disconnect- but at the other end it would have to terminate on a breaker or lugs. NO? Those terminals are 75C thus reducing the #6 ampacity

 

[wwhitney]

I didn't say that. I said at one end the wire may be tapped- at the disconnect- but at the other end it would have to terminate on a breaker or lugs. NO? Those terminals are 75C thus reducing the #6 ampacity

So if the splice isn't a termination, one end of the conductor is the #6 at the tap, the other end of the conductor is the #4 terminating at the OCPD. The splice in the middle is just a splice, not a termination.

Cheers, Wayne

 

[wwhitney]

Code-wise... 110.14


Industry-wise... http://www2.schneider-electric.com/...7/en_US/Wire Terminations 0110DB9901R2-02.pdf
(see the diagram on page 4 in particular)

Thanks for the references. I don't see anything in 110.14 that says an enclosure will have a temperature rating, or that a single enclosure can't contain both 75C and 90C equipment. So I don't see any issue in ordering a panelboard with an oversized enclosure, using the free space to mount some 90C splice blocks, and feeding the panel with 90C conductors, spliced at the block to larger 75C conductors to terminate on the panelboard OCPD. If you disagree, what part of 110.14 would you cite?

Cheers,
Wayne

 

[Dennis Alwon]

So if the splice isn't a termination, one end of the conductor is the #6 at the tap, the other end of the conductor is the #4 terminating at the OCPD. The splice in the middle is just a splice, not a termination.

Cheers, Wayne

I'm sorry I thought we were still talking about #6 the entire way. I agree you can splice the #6 as long as the connectors that are used for splices are rated 90C. I believe many wirenuts are rated 105°.

 

[Smart $]

Thanks for the references. I don't see anything in 110.14 that says an enclosure will have a temperature rating, or that a single enclosure can't contain both 75C and 90C equipment. So I don't see any issue in ordering a panelboard with an oversized enclosure, using the free space to mount some 90C splice blocks, and feeding the panel with 90C conductors, spliced at the block to larger 75C conductors to terminate on the panelboard OCPD. If you disagree, what part of 110.14 would you cite?

Cheers,
Wayne

Since we are talking about #6 and not more than 100A, I'd reference 110.14(C)(1)(a)(3)...

(3) Conductors with higher temperature ratings if the equipment
is listed and identified for use with such conductors.

Your equipment (as a unit) is not listed and identified for use with 90°C-rated conductors.

You have to reduce the "equipment" to a simple splice or tap with no distribution control or utilization devices within the enclosure. Code does not specifically state this but it is an accepted practice.

 

[wwhitney]

Your equipment is not listed and identified for use with 90°C-rated conductors.

Which equipment? A 90C splice method is being used. The panelboard is being fed with conductors at their 75C ampacity. To my knowledge, the enclosure doesn't have a temperature rating.

Cheers, Wayne

 

[charlie b]

Since we are talking about #6 and not more than 100A, I'd reference 110.14(C)(1)(a)(3)...

(3) Conductors with higher temperature ratings if the equipment
is listed and identified for use with such conductors.

Your equipment (as a unit) is not listed and identified for use with 90°C-rated conductors.
You have to reduce the "equipment" to a simple splice or tap with no distribution control or utilization devices within the enclosure. Code does not specifically state this but it is an accepted practice.

You quoted sub paragraph (3), but you did not also quote the upstream sub paragraph (a). The first words under (a) are "termination provisions." So the "listed and identified" part is not talking about the enclosure or anything else within the enclosure. When it mentions "equipment," it is only talking about the termination provisions.

 

[Smart $]

Which equipment? A 90C splice method is being used. The panelboard is being fed with conductors at their 75C ampacity. To my knowledge, the enclosure doesn't have a temperature rating.

Cheers, Wayne

The enclosure doesn't have a temperature rating, but technically I believe panelboards are listed in combination with an enclosure.

The panelboard contains equipment, the breakers, which are likely rated for 40°C ambient with an allowable 30°C temperature rise. The panelboard in combination with its enclosure is tested to provide the environment to not exceed that rating when continuously loaded to 80%. I forget how the 5°C difference weighs into it. All the same, industry practice requires that nothing within the enclosure exceed 75°C. As you have already established, the 90°C-rated #6 splice with the #4 will exceed 75°C.

 

[Smart $]

You quoted sub paragraph (3), but you did not also quote the upstream sub paragraph (a). The first words under (a) are "termination provisions." So the "listed and identified" part is not talking about the enclosure or anything else within the enclosure. When it mentions "equipment," it is only talking about the termination provisions.

As far as I can tell, it is not talking about listed components, e.g. panelboard, not the breaker within the panelboard. That is, we must go by the panelboard L&I, not the breaker L&I.

 

[wwhitney]

The enclosure doesn't have a temperature rating, but technically I believe panelboards are listed in combination with an enclosure.

If that's true, and if the listing specifies no equipment exceeding 75C in the enclosure, then I'll agree that the scenario I described would be an NEC violation of 110.3(B). But I'm skeptical.

Regardless, I don't see the 110.14 violation. I also don't see what difference using a different enclosure for the 90C splice makes, from a practical point of view. It doesn't guarantee greater thermal separation.

Cheers, Wayne

 

[Smart $]

If that's true, and if the listing specifies no equipment exceeding 75C in the enclosure, then I'll agree that the scenario I described would be an NEC violation of 110.3(B). But I'm skeptical.

Regardless, I don't see the 110.14 violation. I also don't see what difference using a different enclosure for the 90C splice makes, from a practical point of view. It doesn't guarantee greater thermal separation.

You should know by now, NEC rules are intended to be impractical. :lol: