SE cable used for branch circuits

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JohnJ0906

JohnJ0906

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Baltimore, MD
I noticed a change in article 338 (SE cable)
338.10(B)(4)(a) interior instalations In addition to the provisions of this article, Type SE service entrance cable used for interior wiring shall comply with the instalation requirements of Parts I and II of article 334, excluding 334.80

This is the text from the '05. The parts in red are deleted in the '08 NEC. Part I in 334 is definitions, so that doesn't really affect anything. However 334.80 is the section that restricts the ampacity of NM to the 60? column.

I guess that we can no longer use the 75? column when using SE cable for feeders and circuits, which was a reason for using this instead of romex.
 
This came up before and I wondered if this was an error or an intentional omission. When the NEC adds things it is obvious because of the highlight but when they drop words there is nothing to denote the change. I find that curious.
 
I just read the sections and my interpretation of it is that the the installation requirements from 334 are to be followed. Drilling holes, support.. 334.80 applies to NM, NMS, NMC. No mention of SE is made there. I'm not going to use the 60deg column for SE any time soon : )
 
Since I originally posted this, I have received the '08 Handbook. According to the (non enforceable) commentary to this section, we will be restricted to the 60? column for ampacity, when using SE cable as branch circuit wiring.

Evidently, this was a deliberate change.
 
More info from the ROP


7-88 Log #2639 NEC-P07 Final Action: Accept
(338.10(B)(4)(a))
____________________________________________________________
Submitter: James M. Daly, General Cable

Recommendation: Delete the phrase ?excluding 334.80? and change the
comma after ?Article 334? to a period.

Substantiation: When Type SE conductors are used for interior wiring, as a
replacement for Type NM cable, 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.

Panel Meeting Action: Accept

Panel Statement: This action will modify the action taken on Proposal 7-84.

Number Eligible to Vote: 14

Ballot Results: Affirmative: 14
____________________________________________________________
Click to expand...

7-89 Log #3124 NEC-P07 Final Action: Accept
(338.10(B)(4)(a))
____________________________________________________________
Submitter: Truman C. Surbrook, Michigan State University

Recommendation: Delete the reference to Part 1 of Article 334 with the
sentence to read as follows:
(a) Interior Installation. 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 s I and II of Article 334, excluding 334.80.

Substantiation: There is nothing in Article 334, Part I that applies to Type SE
cable.

Panel Meeting Action: Accept

Panel Statement: The action on this proposal is modified by the panel actions
taken on Proposals 7-88 and 7-90 and modifies the panel action on
Proposal 7-84.

Number Eligible to Vote: 14

Ballot Results: Affirmative: 14
___________________________
Click to expand...

7-90 Log #3349 NEC-P07 Final Action: Accept
(338.10(B)(4)a.)
____________________________________________________________
Submitter: Frederic P. Hartwell, Hartwell Electrical Services, Inc. / Rep.
Massachusetts Electrical Code Advisory Committee

Recommendation: Delete the phrase ?excluding 334.80?.

Substantiation: This is a companion proposal to one submitted to correct
the requirements in 334.80 so the 60?C starting point only applies, but always
applies, to cables run embedded in thermal insulation. Ironically, this wiring
method is the very one that NEMA selected in the 1987 cycle to study the
affects of thermal insulation, and those affects proved a dramatic decrease in
ampacity when this wiring ran through insulation. The present NEC wording
that eliminates the 60?C column ampacity calculation recreates the very hazard
documented in the NEMA testing. The solution is to apply 334.80 to SE cable
applications, but first, to correct 334.80 (see companion proposal) so the 60?C
start point only applies where the cable runs through thermal insulation.

Panel Meeting Action: Accept

Panel Statement: The action on this proposal modifies the action taken on Proposal 7-84.

Number Eligible to Vote: 14

Ballot Results: Affirmative: 14
____________________________________________________________
Click to expand...
 
Thank you Bob.


To be honest, this is a rather annoying change, to me. :mad: A big reason for us to use SE cable rather than NM was the ability to use the 75? column for ampacity.

Oh well. :roll:
 
I think this one is going to surprise a LOT of ECs around here.

I think perhaps I will bring it up at the code change seminar I am attending Tuesday, if the instructor doesn't.
 
Bob, are you saying the intention of the change is to size SER off the 60deg column?

James M. Daly "since the insulations used are the same both
NM and SE conductors."

Not sure what he's smoking...
 
wireman71 said:
Bob, are you saying the intention of the change is to size SER off the 60deg column?

James M. Daly "since the insulations used are the same both
NM and SE conductors."

Not sure what he's smoking...
Click to expand...

Yes, that is what is being said in the 2008 NEC. You must use the 60C column when sizing conductors for SE cable when the cable is used for branch circuits. It would be the same rule for NM cable. You may use the 90 C for derating.
 
wireman71 said:
Bob, are you saying the intention of the change is to size SER off the 60deg column?
Click to expand...

Yes, exactly that, when used for branch circuits and feeders as mentioned in 338.(B)(4).

When used as service conductors size it as we always have.
 
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If you take this change in conjuction with the changes to 310.15(B)(6) then you have a complete change of how the typcial house in my area is wired.

For example it is common in my area to supply a large home with a 320 amp meter/main with 2 200 amp breakers and 2 4/0 Aluminum SER cables to two separate panels in the home.

Now with the change to 310.15(B)(6) because there is not a singel main power feeder I can not use Table 310.15(B)(6) and must use Table 310.16. So if I use the same feeder conductors I must now protect them with a 150 amp breaker.

Chris
 
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