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Dan Lanciani

In article , (bud--) writes:
| Dan Lanciani wrote:
| In article , writes:
| | On 7 Dec 2010 06:45:24 GMT, ddl@danlan.*com (Dan Lanciani) wrote:
| |
| | | The only thing that happened was the plugged the loophole that let you
| | | use SE cable at the 75c ampacity indoors. I think that actually
| | | happened in 2002 or 2005 tho.
| | | In 2011 they massaged the language but it really did not change.
| | | SE/SER can be used inside but at the 60c ampacity.
| |
| | So #2 SER aluminum is down to 75A? I think this is a fairly big change
| | because not long ago there were debates about whether the "service and
| | feeders" exception let you go to 100A as opposed to being limited to the
| | 75c ampacity of 90A. Looks like now you would need 1/0 for 100A @ 60c and
| | (wow) 350kcmil for 200A. I don't think the catalog I was looking at even
| | has SER that big. With 75c rated conductors in conduit and 75c rated
| | breaker terminals/enclosure can you still use the 75c ampacity indoors?
| | If so, maybe conduit doesn't look so bad after all.

| |
| | Dan Lanciani
| | ddl@danlan.*com
| |
| |
| | You are confusing 310.15(B)(6) with 310.16.
|
| No, I was just commenting that the clarification that you cannot use
| 310.15(B)(6) for sub-panel feeds (something that was done a lot and often
| debated here) combined with the newer 60c limitation makes for a rather
| substantial practical change. For example, my house (not the new old one)
| has a 400A panel feeding a 200A sub and 2 100A subs with 4/0 and 2 AL SER
| respectively. All installed by a licensed electrician, inspected and
| approved. By the new rules those cables look terribly undersized and
| should be 350kcmil and 1/0.
| .
| Far as I know you could *never* use 310.15-B-6 for feeders

Honestly I don't want to start a long debate (especially because this
has been covered here extensively in the past) but for whatever reasons
(call it widespread misinterpretation of the code) it was used and
approved frequently. If you Google some of the discussions on the
latest change you will see some people are still using it. In many
(but not all) cases the 310.15-B-6 numbers weren't all that much
bigger than the 75c ratings, e.g., IIRC, 125A vs. 120A for AL 1/0
which in conjunction with the next-standard-sized breaker might have
contributed to the confusion. But I'm just speculating wildly.

| I'm not following what the change was.

As the 2008 NEC you have to use the 60c ampacity for indoor SE applications.
This can make for some pretty big conductors. The change was made by analogy
to NM cable, but I'm not sure that makes a lot of sense. Historically NM
cable had 60c conductors and I thought limiting it to 60c even after NM-B
went to higher-temperature conductors was in the nature of reverse
grandfathering. I really don't understand if the feeling is that you simply
cannot have a plastic cable usable at 75c or if different materials would
allow for it. Regardless, I think this is a significant change and makes
conduit atractive in cases where SER would have been the obvious choice
before.

Dan Lanciani
ddl@danlan.*com