SE cable ampacity

[Electromatic]

Do people here think that SE cable laying in/on loose fiberglass insulation for part of a run is subject to the 60° ampacity limitation? I'm on the 2014 NEC. They've revised the SE rating rules several times. I'm curious if it changed any in 2017 and/or 2020.

 

[wwhitney]

For the 2014 NEC, I would think you'd want to install a barrier (1x running board?) between the SE cable and the top of the loose fiberglass so that the cable is not "in" the insulation. The relevant texts:

2014 338.10(4)(a) in part:

Where installed in thermal insulation, the ampacity shall be in accordance with 60°C (140°F) conductor temperature rating. The maximum conductor temperature rating shall be permitted to be used for ampacity adjustment and correction purposes, if the final derated ampacity does not exceed that
for a 60°C (140°F) rated conductor.

2017 338.10(4)(a) in part:

For Type SE cable with ungrounded conductor sizes 10 AWG and smaller, where installed in thermal insulation, the ampacity shall be in accordance with 60°C (140°F) conductor temperature rating. The maximum conductor temperature rating shall be permitted to be used for ampacity adjustment and correction purposes, if the final derated ampacity does not exceed that for a 60°C (140°F) rated conductor

Cheers, Wayne

 

[Electromatic]

Interesting: So in 2017, any SE larger than #10 can ignore the 60° insulation rule?

 

[petersonra]

I don't see how being "on" top of the insulation is "in" the insulation.

 

[wwhitney]

I don't see how being "on" top of the insulation is "in" the insulation.

Agreed, but the OP said "in/on". I could see the weight of the cable causing it to sink into the insulation between supports. Basically you want to be able to see the top of the cable and not have it covered with insulation.

Cheers, Wayne