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 unless, as
gfretwell wrote, they "have the entire load of a residential service".
That would be, for instance, a feeder from a single residential service
disconnect to a panel. There can be no other connections to the service.
Originally 310.15-B-6 was only for residential service conductors.
Feeders were added *if* they carry the same load as the service
conductors (which is reasonable).
The feeders to your subpanels could not use 310.15-B-6.
"Diversity" allows the smaller service wire in 310.15-B-6. You don't
necessarily have diversity on a feeder.
..
| The original question implied you were using SE for branch circuit or
| regular feeder wiring.
I'm talking about feeds to sub-panels. Are they regular feeders?
yes
| Then you use the 60c column of 310.16.
| In past years you could use it at 75c. That changed a couple cycles
| ago. It was just reworded in the 2011 and 310.16 changed article
| number.
As far as I can tell from Googling it changed in 2008 and there was a
proposal (accepted in principle?) to change it back in 2011 unless the
cable was in thermal insulation in which case it would still be 60c.
I suppose this issue might be what made the contractor think you can't
use SER anymore; it isn't practical for the higher ampacities. Since
the new old house is in 2008 NEC territory I'll have to look at copper
SER (I'm guessing very expensive) or more likely go with conduit.
Dan Lanciani
ddl@danlan.*com
I'm not following what the change was.
I don't see a code specified temp rating for SE. I would think it then
can be used at the rating marked on the cable. It must be derated if
ambient will be higher (including thermal insulation).
There are further limits in 110.14-C-1 (does not apply service and
related feeder wires rated under 310.15-B-6 above).
For circuits rated 100A and less, generally the wire can only be used at
its 60C rating.
For circuits rated over 100A generally the wire can only be used at its
75C rating (if rated 75C or higher).
--
bud--