SER cable Temperature Rating

[wireman3736]

I have been told by a couple of electricians that at a code update course they recently went to they were told that SER cable has its ampacity rating based on the 60 deg column the same as NM cable, any thoughts.

 

[roger]

They are correct.

2008 338.10 (4) Installation Methods for Branch Circuits and Feeders.

(a) 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.

Roger

 

[Joe Villani]

I Agree

Compare Article 338.10 (B) (4) in both the 05 and 08 code.

The 08 code removes "excluding 334.80" which means the entire part 2 of article 334 must be complied with, including 334.80 which limits final ampacity of se cable to the 60 degree column.

Joe Villani

 

[mdshunk]

Also, in '05 they limited the temp to the type of insulation used in the SER, which wasn't always all that clear. I havn't seen any of the neoprene SER in quite a long time, so just making it the same as romex in '08 seemed quite reasonable.

 

[augie47]

and yet, 310.15(B)(6) remains unchanged so that 4/0 AL SER from your 200 amp outside service disconnect runs adjacent with your #2 AL SE to your heating system and it has a 75 amp ampacity

 

[Pierre C Belarge]

I have been told by a couple of electricians that at a code update course they recently went to they were told that SER cable has its ampacity rating based on the 60 deg column the same as NM cable, any thoughts.

That is true for installations when SE cable is used as a branch circuit or feeder.

If it is installed as a service conductor, you are not restricted to the 60C column for ampacity calculations of the cable/conductor.

 

[infinity]

This is one new code requirement that will surely bite a lot of guys in the butt. Using SE cable at 75 degrees has been a standard for a long time. I can see a lot of complaining when the inspectors start enforcing the 2008 NEC around here.

 

[wireman3736]

I guess now I know, Vermont hasn't adopted the 08 yet, usually between June and October they do. I do half my work in MA and the way I read there amendment for 334.80 is that the 60 deg requirement for nm is only when installed in thermal insulation, so I think I'm safe for the work I have done this year, definitely something to remember though.

 

[Dennis Alwon]

That is true for installations when SE cable is used as a branch circuit or feeder.

If it is installed as a service conductor, you are not restricted to the 60C column for ampacity calculations of the cable/conductor.

I am not sure I agree with that. If the service conductors are in the interior of the house I believe that art.338.10(B)(4) of the 2008 prohibits that use. At least it is arguable.

Also I learned why SE cable got rated at 60C. Apparently UL did a test on SE cable at 75C for 3 hours fully loaded and the cable failed. My question is when is se cable ever used at 100% of it's rating for 3 hours or more. Usually there is a 125% factor thrown in. Maybe ranges???? Unlikely tho---

 

[Pierre C Belarge]

Dennis
When one reads 338.10 Uses Permitted, it is broken down into 3 Subsections, (A), (B) and (C).

(A) pertains to SE cable as used for service installations.
(B) pertains to SE cable as used for Branch Circuits or Feeders.

Sub-Sub Section (4) Installation Methods for Branch Circuits and Feeders belong to Subsection (B), Branch Circuits or Feeders, not to Subsection (A) Service-Entrance Conductors.

The temperature limitations of 334 are applied in Sub-Sub Section (4).


One can also reference Table 310.15(B)(6).

 

[Dennis Alwon]

Dennis
When one reads 338.10 Uses Permitted, it is broken down into 3 Subsections, (A), (B) and (C).

(A) pertains to SE cable as used for service installations.
(B) pertains to SE cable as used for Branch Circuits or Feeders.

Sub-Sub Section (4) Installation Methods for Branch Circuits and Feeders belong to Subsection (B), Branch Circuits or Feeders, not to Subsection (A) Service-Entrance Conductors.

The temperature limitations of 334 are applied in Sub-Sub Section (4).


One can also reference Table 310.15(B)(6).

I do understand that Pierre but the article states:

In addition[/B] 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.

I believe the intent is how you interpret it but the words don't seem to be there to support it. The section is branch circuits and feeders but it says in addition it shall comply with req. of art. 334 when used interior. I think this needs better wording.

 

[iwire]

Dennis I think it is clear as it is, the section that says "used for interior wiring" only applies to SE used as "Branch Circuits and Feeders" inside the building.

It does not apply to branch circuits or feeders used outside, or service conductor either inside or outside. :smile:

 

[Smart $]

That is true for installations when SE cable is used as a branch circuit or feeder.

If it is installed as a service conductor, you are not restricted to the 60C column for ampacity calculations of the cable/conductor.

Let's not confuse "feeder" with "main feeder" as specified in 310.15(B)(6).

 

[POWER_PIG]

I am not sure I agree with that. If the service conductors are in the interior of the house I believe that art.338.10(B)(4) of the 2008 prohibits that use. At least it is arguable.

Also I learned why SE cable got rated at 60C. Apparently UL did a test on SE cable at 75C for 3 hours fully loaded and the cable failed. My question is when is se cable ever used at 100% of it's rating for 3 hours or more. Usually there is a 125% factor thrown in. Maybe ranges???? Unlikely tho---

Im confused now......is it not true that the temp. rating of a conductor is based on how hot the cable would be under a certain load? Say if a #8awg copper conductor is loaded to 50 amps, the wire would be 75deg. C.? And if loaded to 55amps would be heated up to 90deg.C? That would make sence to me that ser cable used for branch ckts or feeders would have to fall under the 60deg.C column because most interior branch ckt devices are only rated at 60deg.C at the terminals. If used as a service entrance cable, I believe we can agree that meter banks / panelboards/discs and the likes are suited for terminations at or above 75deg.C.