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#1
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interior SER cable usage in 2008 NEC
My contractor's electrician mentioned that he thinks SER cable is no
longer allowed (or possibly no longer allowed to be run exposed) in interior residential applications under the 2008 NEC for, e.g., feeding sub-panels. Anybody know about this? If it is true there is going to be a lot of painful conduit work to get to the planned sub-panel locations in my new (very old) house... Dan Lanciani ddl@danlan.*com |
#2
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interior SER cable usage in 2008 NEC
"Dan Lanciani" ddl@danlan.*com wrote in message ... My contractor's electrician mentioned that he thinks SER cable is no longer allowed (or possibly no longer allowed to be run exposed) in interior residential applications under the 2008 NEC for, e.g., feeding sub-panels. Anybody know about this? If it is true there is going to be a lot of painful conduit work to get to the planned sub-panel locations in my new (very old) house... Dan Lanciani ddl@danlan.*com Apparently there is or was an older type of service entrance cable that had a rubber covering which is no longer allowed. Plastic or thermoset covered conductors are fine. Neutral has to be insulated, ground does not. Follow the installation rules for Romex |
#3
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interior SER cable usage in 2008 NEC
My contractor's electrician mentioned that he thinks SER cable is no
longer allowed (or possibly no longer allowed to be run exposed) in interior residential applications under the 2008 NEC for, e.g., feeding sub-panels. Anybody know about this? If it is true there is going to be a lot of painful conduit work to get to the planned sub-panel locations in my new (very old) house... *As far as I know it is still permitted. However the ampacity rating is not the same for interior circuits as it is for an electrical service. He would have to size the cable according to table 310.15(B)(16) in the 2011 code book and not by table 310.15(B)(7). A call to your local electrical inspector should clarify things. |
#4
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interior SER cable usage in 2008 NEC
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#6
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interior SER cable usage in 2008 NEC
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-- |
#7
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interior SER cable usage in 2008 NEC
On 2010-12-07, bud-- wrote:
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). 2008 NEC 338.10(B)(4)(a) says: 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. Article 334 is for NM cable, so this basically says that if you are using SER for interior branch circuits or feeders, you have to treat it like NM. In particular 334.80 limits the ampacity of NM to the 60 degree column. Earlier versions of 338.10(B)(4)(a) included a specific exemption from 334.80, but that got deleted in 2005 or 2008. Cheers, Wayne |
#8
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interior SER cable usage in 2008 NEC
Wayne Whitney wrote:
On 2010-12-07, bud-- wrote: 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). 2008 NEC 338.10(B)(4)(a) says: 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. Article 334 is for NM cable, so this basically says that if you are using SER for interior branch circuits or feeders, you have to treat it like NM. In particular 334.80 limits the ampacity of NM to the 60 degree column. I read that. Most of Part 2 is mechanical installation requirements. I would not call a 60C limit an installation requirement. Earlier versions of 338.10(B)(4)(a) included a specific exemption from 334.80, but that got deleted in 2005 or 2008. That certainly agrees with what you wrote above. -- bud-- |
#9
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interior SER cable usage in 2008 NEC
Wayne Whitney wrote:
Earlier versions of 338.10(B)(4)(a) included a specific exemption from 334.80, but that got deleted in 2005 or 2008. Cheers, Wayne I was curious why the change, so I looked it up. You are right - it was 2008. The argument was (interior use) "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." I guess the question then is why is SE allowed at a higher temperature rating outside. Looks like it has a 75 or 90C rating, depending on conductor insulation. Or 75C if not otherwise marked. -- bud-- |
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