Service cable SEU & SER

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jbelectric777

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For everyone who uses the NEC and is subject to inspection, pass this on to a fellow installer, it may save a lot of trouble and $$$$$. Type SEU & SER usually used in dwellings has to be de rated if used for non dwelling service entrance. An example is 4/0 aluminum and a 200 amp breaker in a dwelling cant be used for a commercial office building because a 4/0 aluminum isnt rated for it. It happened today to a nice guy I know, his plans that went through my review passed because the architect (or his sub contracting engineer) knew the rules exception for dwellings, now he has to change either 5 breakers or all the SER his electricians already installed. Its not such a big deal to me in theory as most of you would agree but its code, and at the end of the day the bottom line is someone fooged up!, and I cant cover for em... Always be sure to read your plans and not assume you think you know if your not sure, and if your not sure call your boss or even your local inspector, thats what he's there for..... I hope this helps someone from not running into the same problem, and if it was ever discussed before here then good and take it as a simple reminder....... I hope everyones Thanksgiving was a good one! And Merry Christmas and a Happy, safe new year to everyone if I dont get in the forum before the holidays.....
 
What is the load served?? 4/0 al is 180amps next size up? 200 amp,.. as long as the connected load is less than 180 you would be good to go ,.. yes?
 
I think by derating he was intending to mean the difference between 310.16 and the dwelling section 310.15 B 2 ?
 
M. D. said:
What is the load served?? 4/0 al is 180amps next size up? 200 amp,.. as long as the connected load is less than 180 you would be good to go ,.. yes?
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If you are using the 2008 NEC then SE cable is limited to the 60 degree column of 310.16 so therefore 4/0 AL SER is good for 150 amps.

Chris
 
nakulak said:
I think by derating he was intending to mean the difference between 310.16 and the dwelling section 310.15 B 2 ?
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I agree.

What the original poster is talking about is the fact that you can't use Table 310.15(B)(6) for non-dwelling main power feeders or service entrance conductors.

Chris
 
a little help from the Ma. guys

a little help from the Ma. guys

Huuuray for the Mass code ,.....I think:-?

334.80. Delete the second paragraph and revise the first paragraph to read as follows:
334.80 Ampacity. Type NM, NMC, and NMS cable shall have conductors rated at 90/C (194/F).
Where installed in thermal insulation, the ampacity of conductors shall be that of 60/C (140/F)
conductors. The ampacity of Types NM, NMC, and NMS cable installed in cable tray shall be
determined in accordance with 392.11.
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So, if it is not in thermal insulation and I am in Massachusetts the 75 degree column would be O.K. to use ?
 
jbelectric777 said:
For everyone who uses the NEC and is subject to An example is 4/0 aluminum and a 200 amp breaker in a dwelling cant be used for a commercial office building because a 4/0 aluminum isnt rated for it.
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Even SER that is not marked is rated for at least 75 Deg C. So I dont get it. It should have passed 4/0 Alum 75 Deg C. 180 amps next size overcurrent protection 200 amps table 310.16

As far as the 08 sending you to 334.80 that is only for branch circuits and feeders. Not service entrance cable being used as service entrance conductors
 
david said:
Even SER that is not marked is rated for at least 75 Deg C.
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Unless it falls under the venue of 338.10(B)(4)
david said:
So I dont get it. It should have passed 4/0 Alum 75 Deg C. 180 amps next size overcurrent protection 200 amps table 310.16
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If it were in a 75? allowable situation AND the load didn't exceed 180 amps.
david said:
As far as the 08 sending you to 334.80 that is only for branch circuits and feeders. Not service entrance cable being used as service entrance conductors
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The OP stated SER so I assume the was OCP ahead of it, if so it would be a feeder.
 
david said:
Even SER that is not marked is rated for at least 75 Deg C. So I dont get it.
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There are times that ser is only rated 60C NOT 75C. See art. 338.10(B)(4)(a). Take particular note of the comment addressing Part II of art. 334--- specifically 334.80
 
Dennis Alwon said:
There are times that ser is only rated 60C NOT 75C. See art. 338.10(B)(4)(a). Take particular note of the comment addressing Part II of art. 334--- specifically 334.80
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Dennis, or anyone else , I'm curious about your take on the Massachusetts revision of 334.80?
It does not seem to recognize the 60 degree limitation placed on NM cable , unless it is installed in thermal insulation .

334.80. Delete the second paragraph and revise the first paragraph to read as follows:

334.80 Ampacity. Type NM, NMC, and NMS cable shall have conductors rated at 90/C (194/F).
Where installed in thermal insulation, the ampacity of conductors shall be that of 60/C (140/F)
conductors. The ampacity of Types NM, NMC, and NMS cable installed in cable tray shall be
determined in accordance with 392.11.
Click to expand...
 
M. D. said:
Dennis, or anyone else , I'm curious about your take on the Massachusetts revision of 334.80?
It does not seem to recognize the 60 degree limitation placed on NM cable , unless it is installed in thermal insulation .
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I agree with your take on it. I believe Bob has brought this up in the past. I am hoping there will be a change in the 2011 that will follow this thinking for the NEC.
 
Dennis Alwon said:
I agree with your take on it. I believe Bob has brought this up in the past. I am hoping there will be a change in the 2011 that will follow this thinking for the NEC.
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the language of 334.80 did not significantly change in the ROP,
 
OK, so if I followed this correctly, for a dwelling, I can still run 4/0 AL SE to the socket and to a disco. But into the house from the disco I now need to run a larger cable due to the 60 degree rating now imposed on the feeder?

How would the above fit into the part about not needing to be larger than the SE conductors?

I may not be the sharpest marble, but changes like this don't make sense to me. In my experience I have not seen an issue with 4/0 SER being used with a 200 amp service. How often would it be loaded that highly anyway?
 
jimport said:
How would the above fit into the part about not needing to be larger than the SE conductors?
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I believe you are referring to art. 215.2(A)(3)

215.2(A)(3) Individual Dwelling Unit or Mobile Home Conductors. Feeder conductors for individual dwelling units or mobile homes need not be larger than service conductors. Paragraph 310.15(B)(6) shall be permitted to be used for conductor size.
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There are issues with this article since it does not tell us what larger means. Larger size wire or larger ampacity. It does not state ampacity so can we compare wire sizes that are copper vs alum. I think not. I believe this art. should be change to "larger ampacity". This would clear things up.

If you look at art. 310.15(B)(6) you will see that over the years the wording changed from larger conductor to larger ampacity. I believe that is the intent of art. 215.(B)(3).
 
Dennis,

My point was the two sections seem to contradict each other. Article 215 seems to negate the need to upsize the wire, while 334 seems to say I must due to the 60 degree column.

In my interpretation larger would mean in regards to more ampacity.
 
jimport said:
Dennis,

My point was the two sections seem to contradict each other. Article 215 seems to negate the need to upsize the wire, while 334 seems to say I must due to the 60 degree column.

In my interpretation larger would mean in regards to more ampacity.
Click to expand...

Well than a 4/0 aluminum SER would have a smaller ampacity than 3/0 alumin. in conduit based on the need to drop to 60C for the SER (in most cases). And I agree a change is needed.
 
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