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
This may be of no help, but . . .
----------------------
338.12(B)(1) and (2) Service-Entrance Cable: Type USE - Uses Not Permitted Type USE (URD) cable is not permitted for interior wiring of branch circuits and feeders originating and terminating within the same building. However, Type USE cable is permitted for aboveground installations where USE cable emerges from the ground and is terminated in an enclosure at a location acceptable to the Authority Having Jurisdiction, either inside or outside, and the cable is protected in accordance with 300.5(D). This amendment will continue to allow the generally accepted practice of installing continuous runs of USE cable without splicing, terminating in the first enclosure either outside or inside of a building, when the cable in enclosed in a suitable raceway This also applies to the indoor portion of an underground run of USE cable that originates at an indoor panelboard near an outside wall of a structure. 342.30 Intermediate Metal conduit: Type IMC - Securing and Supporting 344.30 Rigid Metal Conduit: Type RMC - Securing and Supporting 352.30 Rigid Polyvinyl Chloride Conduit: Type PVC - Securing and Supporting 355.30 Reinforced Thermosetting Resin Conduit: Type RTRC - Securing and Supporting 358.30 Electrical Metallic Tubing: Type EMT - Securing and Supporting These raceways shall be secured and supported in accordance with subsections (A) and (B) to .30 of their respective articles. New subsection (C) is not adopted. This amendment will continue to allow raceways up to 3' in length to be unsupported between enclosures and secured by the enclosures, and shall be deemed in compliance with 300.11(A).----------------------------------------------------------------------------
---------------
What it means is not quite clear to me. (-:
Bobby G.
*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.
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.
In article , snipped-for-privacy@aol.com writes: | On 6 Dec 2010 22:12:35 GMT, ddl@danlan.*com (Dan Lanciani) wrote: | | >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 | | 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.
The original question implied you were using SE for branch circuit or regular feeder wiring. 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. Main feeders or Service entrances that have the entire load of a residential service can still use 310.15(B)(6)
In article , snipped-for-privacy@aol.com 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.| 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?
| 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
. 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. .
yes
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).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
I read that. Most of Part 2 is mechanical installation requirements. I would not call a 60C limit an installation requirement.
That certainly agrees with what you wrote above.
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.
In article , snipped-for-privacy@isp.com (bud--) writes: | Dan Lanciani wrote: | > In article , snipped-for-privacy@aol.com 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
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.