I don't have my 2014 code book yet. I have been told that table 310.15 (B) (7) is not in there any more. That's the single phase dwelling service and feeder size table. It allowed us to use 4/0 aluminum SER for a 200 amp breaker panel. Does this mean that we will be forced to use 250 SER for these dwellings now? My inspector said there is going to be an IAEI meeting next month and they will be addressing this issue. He did say that 4/0 would still be allowed except where it passes through insulation. What will be the article that address this issue, and how is it allowed or not allowed? He doesn't know how this will shake out yet. Am I missing something? Thanks.
310.15 (B)(7) going away?
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It's replaced by a formula. I believe for single family 120/240v services you can reduce the circular mils by up to 17%. I quickly did the math and believe you still are ok with 4/0 al or 2/0 cu on a 200a service.
What they did for single family dwellings 100-400 amps, where the conductors carry the entire load of the service, is to allow an 83% factor. So a 200 amp service conductor may be rated 200 * .83= 166 amps. Then use 310.15(B)(16). So if you have a 75C rated install you could use 2/0 copper (175 amps) or 4/0 alum (180 amps). The problem is if you use ser and have to use the 60C rating then you need 250 Kcm alum
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What was their reasoning for changing this. That's ridiculous.Dennis Alwon said:
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Is that the correct phrase? Or is it like the old way where if "the conductors carry the entire load of the dwelling unit..."?
The difference being each apartment in a multi-family house is considered a dwelling unit and that's why we were always able to get away with using #2Al for 100A instead of limiting it to 90A like in any other situation.
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Just to make things more complicated
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I agree... they keep changing things that have no problems to begin with...
It was cut and dry... no gray areas.. but the CMP saw it differently.. :no::no:
I have not heard of any services busting out in flames using the old table... not even the dreaded SE ones..
:laughing:
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It's gonna over complicate generator installations thats for sure. I don't even think the load terminals in a 200 amp switch are rated for 250sDIYer4Life said:Just to make things more complicated
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You shouldn't need to use 250's.
Only if you are using SER cable that goes thru enough insulation to make you use the 60 degree column.
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So unless they start selling 250kcmil SEU (they have it in SER, but i can't find it in SEU) , it would seem the death of SE service risers....? :blink:~CS~
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Steve, just pull the insulation out!!!
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No, you don't need it in SEU because there is very little chance of running the service riser in insulation.
If you install an outside disconnect and then run SER from that disconnect thru the house to the panel, then you have to be mindful of the insulation or else you will have to upsize to 250.
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I think i'll most likely be confused until the 2014 update DIY'er
when does MH put that out anyways?
~CS~
when does MH put that out anyways?
~CS~
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iirc, it's the romex/raceway deal honestly
~CS~
~CS~
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It's not about romex or raceways. In the 2008 they made you use the 60 degree column for SE cable instead of the 75 degree column like we were always able to do.
In the 2011 they reversed themselves and allow you to use the 75 degree column again as long as the SE cable isn't in contact with insulation.
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I'm sure we've not seen the last of the changes for this !
Time to start writing those code change proposals for the 2017 NEC !!!
Time to start writing those code change proposals for the 2017 NEC !!!
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