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This is a Code question about Article 338, expect lots of Code cites. Any answer or challenge to answer MUST be well supported with Code cites, committee notes etc.

The allowed temperature of a conductor (60C, 75C, 90C) decides how many amps the conductor can carry. Different insulation types get different temperature ratings. For instance UF cable is rated 60C, but THWN-2 is rated 90C. NM cable is an "asterisk", allowed only 60C in practice, but the 90C figure can be used for certain calculations.

Article 338 is somewhat ambiguous about the thermal rating of SE cable indoors. Here's what it says:

Article 338: Type UF cable

338.10(B)(4) Installation Methods for Branch Circuits and Feeders.

(a) Interior Installations. In addition to the provisions of this article, Type SE service-entrance cable used for interior wiring shall comply with the installation requirements of Part II of Article 334, excluding 334.80.

Where installed in thermal insulation the ampacity shall be in accordance with the 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.

Article 334: Type NM cable

334.80 Ampacity. The ampacity of Types NM, NMC, and NMS cable shall be determined in accordance with 310.15. The allowable ampacity shall not exceed that of a 60°C rated conductor.

Article 334 is for "NM type" cable. 334.80 is the part of Article 334 which alwas limits NM cable to 60C thermal. Excluding that would mean SE is free to run at its normal thermal rating, which means you get to use 75C (if device terminations and any apparatus the cable goes through are good for 75C).


There's no question that SE cable surrounded by insulation is limited to 60C. However...

Notice how the end of the first paragraph (my bold) seems to conflict with the end of the second paragraph (my italic). One waives the 60C requirement and the other imposes it.

  • Is the bold phrase entirely redundant?
  • Or does the italic phrase only apply to the preceding sentence, and not to interior installations at large?

Note that the italic phrase was deleted in NEC 2008 and was re-added in NEC 2011.

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Just about all SE cable you use is not subject to the 60°C limit, unless it's limited by old or cheap terminations

The current (2020 and upcoming 2023) version of NEC 338.10(B)(4) part (a) reads as follows (informational notes omitted, 2023 moves them to the end of the part):

338.10(B)(4) Installation Methods for Branch Circuits and Feeders

(a) Interior Installations

(1) In addition to the provisions of this article, Type SE service-entrance cable used for interior wiring shall comply with the installation requirements of Part II of Article 334, excluding 334.80.

(2) Where more than two Type SE cables containing two or more current-carrying conductors in each cable are installed in contact with thermal insulation, caulk, or sealing foam without maintaining spacing between cables, the ampacity of each conductor shall be adjusted in accordance with Table 310.15(C)(1).

(3) 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.

The operative portion here is point 3, which reached its current form in 2017 with the addition of the "10AWG and smaller" restriction. Since SE cable, as a rule, is not even made in those small sizes, that obviates the perceived conflict between the 334.80 exclusion in point 1 and the text in 338.10(B)(4) part (a).

However, this means that we still have to worry about the 110.14(C)(1) termination temperature limit. This isn't an issue for new-build distribution equipment, which is pretty uniformly 60°C/75°C rated, but can be a problem with older panels/breakers (as both the panel and the breaker need to be rated for the higher termination temperature) and some 50A receptacles (generally speaking, cheaper ones -- check the markings on the receptacle to be sure).

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TLDR (thank goodness): SE cable is not limited to 60C unless it runs through insulation, and even that only applies for 2011-2014 code cycles.

This answer covers up to NEC 2011. ThreePhaseEel's answer picks up with NEC 2017.

The second sentence of paragraph 2 only applies to paragraph 2. We're sure, because this line has been battled over relentlessly.


The "Excluding 334.80" phrase is highly embattled - it was deleted in the 2008 code cycle and re-added in the next cycle, 2011, reasons here. So there is no doubt that language is there on purpose.

If paragraph 2 sentence 2 is standalone, the fought-over "Excluding" language is utterly pointless. Why would they debate and revise it?

But if paragraph 2's sentence 2 is only in context of sentence 1, then all the language makes sense.

Behind the curtain

We have access to the proposals and commentary on the matter.

As of 2005, the section was (in full):

(a) Interior Installations. In addition to the provisions of this article, Type SE service-entrance cable used for interior wiring shall comply with the installation requirements of Parts I and II of Article 334, excluding 334.80.

FPN: See 310.10 for temperature limitation of conductors.

The change was proposed in the 2008 code cycle by a cable manufacturer, General Cable.

Recommendation: Delete the phrase "excluding 334.80".

Substantiation: When Type SE conductors are used for interior wiring, as a replacement for Type NM cable, the ampacity of the conductors should be the same as permitted for NM cable since the insulations used are the same both NM and SE conductors.

This was accepted without note. So,

As of 2008, the section was (in full):

(a) Interior Installations. In addition to the provisions of this article, Type SE service-entrance cable used for interior wiring shall comply with the installation requirements of Part II of Article 334.

FPN: See 310.10 for temperature limitation of conductors.

.... deleting inclusion of part I, which is simply scope and definitions. Note that 334.80 is in Part II, so this brought 334.80 and its 60C limitation into force.

This change created a lot of excitement. This commentary was typical, and noted the proposer had a conflict of interest:

Recommendation: [revert]

Substantiation: SE cable has always had this exception. If the manufacturers have changed the insulation on the wire, it should reflect on the temperature/ampacity chart. This is just raising the cost of wire by having to use a larger size. Has the NEC been wrong for all these years?

The panel agreed, with a proviso:

Panel Meeting Action: Accept in Principle

Accept inserted text. plus Insert language: "Where installed in thermal insulation, the ampacity shall be in accordance with the 60°C (140°F) conductor temperature rating. The 90°C (194°F) rating shall be permitted to be used for ampacity adjustment and correction purposes, provided the final derated ampacity does not exceed that for a 60°C (140°F) rated conductor."

Panel Statement: The panel recognizes that SE cable is listed to 75C. The panel also recognizes that installation in thermal insulation can decrease the ampacity of a cable assembly.

Number Eligible to Vote: 14
Ballot Results: Affirmative: 10 Negative: 4

So, as of 2011, the section was (in full):

Note the restoration of the original language, and it has a new friend. Adds in italic.

(a) Interior Installations. In addition to the provisions of this article, Type SE service-entrance cable used for interior wiring shall comply with the installation requirements of Part II of Article 334, excluding 334.80.

Where installed in thermal insulation the ampacity shall be in accordance with the 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.

Informational Note No. 1: See 310.10 for temperature limitation of conductors.

Informational Note No. 2: For the installation of main power feeder conductors in dwelling units refer to 310.15(B)(7).

Note this second paragraph is totally new to NEC at this point.

In my opinion, the second paragraph is a concession to the cable manufacturer's concern about overheating SE cable.

The upshot is that it's perfectly clear from the rulemaking changes and the internal commentary that the purpose of the 2011 changes is to allow SE cable higher temperatures when not running inside insulation.

And this is why Code books get thicker.

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SE contains type RHW,XHHW, OR THWN (flame retard and moisture resistant) CONDUCTORS rated dry and damp locations above ground suitable exposure to sun. USE contains equivalent to RHW OR XHHW rated damp or wet location and direct burial. According to the NEC you can not use SE cable in an underground conduit. SE not rated for wet location..

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    Perhaps all true, but definitely not relevant to the specific question being asked. Answers need to answer the specific question being asked, not just be about the same general topic. – nobody Jun 15 at 12:23

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