SER Cable Ratings

[circus12]

Guys,
Re: 2008 NEC-I am in a standoff with the local AHJ concerning sizing for SER unit feeders from the meter to the individual unit panels. Project is residential apt. townhomes, 4,5 and 6 units per building. Stick frame, slab on grade. Service is 120/240V/1Ph. I was planning to use Table 310-15(B)(6) to size my 200A feeders as I have in the past. The AHJ is stating that I must now follow the 2008 revisions in Art. 338.10(B) and size the SER unit feeder accordingly as the SER is now considered 'interior wiring'. I can understand this if I were using the SER to feed a range, heater, dryer etc within the unit but I am at a loss to see the feeder from the meter as interior wiring. My understanding of interior wiring is that wiring which does not leave that particular unit. Has anyone else run across this ? Jurisdiction is in North Carolina although that should not make a difference.
Thanks,
circus12

 

[raider1]

You can still use Table 310.15(B)(6) for the main power feeder for each dwelling unit.

There has been a lot of confusion as to how to deal with SER cable in the 2008 NEC.

There was one change and one clarification to the 2008 NEC that deal with SER cable.

The clarification was that the main power feeder must be a single feeder and carry the entire load for the dwelling unit. This is located in the text of 310.15(B)(6).

And the change was 338.10(B)(4)(a) now requires that when you use SER as interior wiring you must meet ALL the requirements of part II of 334 including 334.80 which limits the SER cable to the 60 degree column of Table 310.16.

Again a main power feeder to a dwelling unit can be sized from Table 310.15(B)(6).

Chris

 

[Jljohnson]

310.15(B)6 is quite clear as to EXACTLY what is considered a "feeder" and your application clearly fits the bill. I am with you on this one and believe the inspector to be misunderstanding the code. I suggest that you ask him to re-read the section that I mentioned and re-evaluate his position.
good luck,

 

[cpal]

310.15(B)6 is quite clear as to EXACTLY what is considered a "feeder" and your application clearly fits the bill. I am with you on this one and believe the inspector to be misunderstanding the code. I suggest that you ask him to re-read the section that I mentioned and re-evaluate his position.
good luck,

A mini pole (of sorts)

Table 310.15(B) (6) lists USE amongst the permissable insulkations for the enhanced ampacities.

Can that insulation be brought into the building without restriction??

 

[raider1]

A mini pole (of sorts)

Table 310.15(B) (6) lists USE amongst the permissable insulkations for the enhanced ampacities.

Can that insulation be brought into the building without restriction??

USE is not permitted for interior wiring, take a look at 338.12(B)(1)

Chris

 

[cpal]

USE is not permitted for interior wiring, take a look at 338.12(B)(1)

Chris

If 338.12 (B) modifies 310.15(B) (6) then why does 338.10 (4) (a) not?? Just asking!!

 

[raider1]

If 338.12 (B) modifies 310.15(B) (6) then why does 338.10 (4) (a) not?? Just asking!!

338.12 does not modify 310.15(B)(6) it prohibits the use of USE as an interior wiring method.

310.15(B)(6) is an ampacity table. If you meet the requirements of that table you can use that ampacity for the conductors.

338.10(B)(4)(a) requires that when you use SER cable for interior wiring then you must also meet the requirements of Part II of 334.

334.80 requires that we use the 60 degree column to determine ampacity. Because Table 310.15(B)(6) does not have a 60 degree column we can use the ampacity listed in that table, provided that we meet the requirements to use that table.

Chris

 

[cpal]

Chris I donot disagree with your argument.
but I do not see where the omision of a 60 degree col in table 310.15(B)(6), holds water.

334.80 requires that we use the 60 degree column to determine ampacity. Because Table 310.15(B)(6) does not have a 60 degree column we can use the ampacity listed in that table, provided that we meet the requirements to use that table.Chris

Why could one not say
310.15(B)(6) does not have a 60 degree col so in that case 334.10(4)(a) omits the use of that table for interior use??

 

[Pierre C Belarge]

310.15(B)(6) Permits the size of the wiring method to be as per the table. The table is specific as to the Cable Types and the Conductor Types that are permitted.

SE cable, Art 338 is more specific with regards as to the wiring process.
Such as the temperature rating (ampacity) of SE cable when used for interior wiring or exterior wiring.
If the SE cable is used for interior wiring, regardless if it is a feeder or branch circuit [338.10(B)(4)(b), which references 334.80], then one is restricted to ampacity of the cable as per 310.16, 60C column. This may limit one as to what size SE cable to use.

 

[cpal]

310.15(B)(6) Permits the size of the wiring method to be as per the table. The table is specific as to the Cable Types and the Conductor Types that are permitted.

SE cable, Art 338 is more specific with regards as to the wiring process.
Such as the temperature rating (ampacity) of SE cable when used for interior wiring or exterior wiring.
If the SE cable is used for interior wiring, regardless if it is a feeder or branch circuit [338.10(B)(4)(b), which references 334.80], then one is restricted to ampacity of the cable as per 310.16, 60C column. This may limit one as to what size SE cable to use.

So Pierre do I understand that you feel a No 4 Cu SER is not allowed to supply a 100A unit panel in a multi family?

 

[raider1]

Why could one not say
310.15(B)(6) does not have a 60 degree col so in that case 334.10(4)(a) omits the use of that table for interior use??

Then we could never use Table 310.15(B)(6) for a main power feeder that feeds a panel inside of the building.

Again 310.15(B)(6) Permits the use of a specific ampacity given to a conductor provided that we meet the requirements of that section. This Table modifies the general ampacitys given in 310.15 due to load diversification of a residential service or main power feeder.

334.80 states "The ampacity of Types NM, NMC and NMS cable shall be determined in accordance with 310.15." So provided that we meet the requirements of 310.15(B)(6) we can use that ampacity Table, if not we must use 310.15(B) which uses Tables 310.16 through 310.19.

Chris

 

[cpal]

Then we could never use Table 310.15(B)(6) for a main power feeder that feeds a panel inside of the building.
Chris

Why would the lack a 60 deg col impact the application of this table in matters other than SER ?

Again 310.15(B)(6) Permits the use of a specific ampacity given to a conductor provided that we meet the requirements of that section. This Table modifies the general ampacitys given in 310.15 due to load diversification of a residential service or main power feeder.
Chris

I agree in part this table was produced from utility data (as I understand it) as applied to reidential distribution.

334.80 states "The ampacity of Types NM, NMC and NMS cable shall be determined in accordance with 310.15." So provided that we meet the requirements of 310.15(B)(6) we can use that ampacity Table, if not we must use 310.15(B) which uses Tables 310.16 through 310.19.
Chris

I like your lline of thought on this one but the second sentence limits the ampacity of the SE Cable (interior use) to "a" 60 degree col. and again table (B) (6) does not have such a column. also the firrst sentence of 334.80 directs the ampacity application of NM to 310.15 in general but we all agree that NM when used for interior use is limited to a ampacity that does not elevate the insulations temperature beyound 140 degree F. Use of table 310.15(B) (6) would (or could) elevate the temperature of a SE insulation to at least 75 degree C.

Just pickin you brain (thanks)

 

[raider1]

Why would the lack a 60 deg col impact the application of this table in matters other than SER ?

You are correct, I should have stated that we could never use SER cable as a main power feeder to an interior panel.

I like your lline of thought on this one but the second sentence limits the ampacity of the SE Cable (interior use) to "a" 60 degree col. and again table (B) (6) does not have such a column. also the firrst sentence of 334.80 directs the ampacity application of NM to 310.15 in general but we all agree that NM when used for interior use is limited to a ampacity that does not elevate the insulations temperature beyound 140 degree F. Use of table 310.15(B) (6) would (or could) elevate the temperature of a SE insulation to at least 75 degree C.

Just pickin you brain (thanks)

You can pick my brain but you won't find much.

Chris

 

[Pierre C Belarge]

Then we could never use Table 310.15(B)(6) for a main power feeder that feeds a panel inside of the building.

Again 310.15(B)(6) Permits the use of a specific ampacity given to a conductor provided that we meet the requirements of that section. This Table modifies the general ampacitys given in 310.15 due to load diversification of a residential service or main power feeder.

334.80 states "The ampacity of Types NM, NMC and NMS cable shall be determined in accordance with 310.15." So provided that we meet the requirements of 310.15(B)(6) we can use that ampacity Table, if not we must use 310.15(B) which uses Tables 310.16 through 310.19.

Chris

I am not sure if you are disagreeing with me or not.

My Stance:
One cannot use the rating of Table 310.15(B)(6) for SE cable if, the SE cable is installed in the interior of a building.
Section 310.15(B)(6) is a general rule, with specific wiring methods/conductors that are spelled out.

Section 338.10(B)(4)(b) is specific in referencing 334.80, without stating there is an exception for Main Power Feeders. The CMPs were aware of this issue, and did not provide for an exception.

Here is the substantiation to the proposal sent in to change this.

CMP's
"Substantiation:
When Type SE conductor 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 ar the same both NM and SE conductors."


There is no exclusion for Main Power Feeders.

 

[Pierre C Belarge]

So Pierre do I understand that you feel a No 4 Cu SER is not allowed to supply a 100A unit panel in a multi family?

If it is installed in the interior of a building, one cannot use Table 310.15(B)(6) for ampacity values, one has to use Table 310.16, 60C column for the final value.

 

[circus12]

SER vs NM conductor insulation

SER vs NM conductor insulation

Here's a variable to think about. Suppose the SER cable is aluminum and contains conductors with XHHW or XHHW-2 insulation? Would that not move us out of the 60 Degree column?

 

[cpal]

Here's a variable to think about. Suppose the SER cable is aluminum and contains conductors with XHHW or XHHW-2 insulation? Would that not move us out of the 60 Degree column?

all the SER we are diuscussing has those types of insulated conductors.

The Al SER is no different from the "copper"?? Ser insulation wise

 

[A/A Fuel GTX]

If it is installed in the interior of a building, one cannot use Table 310.15(B)(6) for ampacity values, one has to use Table 310.16, 60C column for the final value.

Im confused.......A feeder is run in the interior of a building and 310.15(B)(6) applies........Correct:-?. When talking about branch circuits, I understand we must use 310.16.

 

[electricmanscott]

If it is installed in the interior of a building, one cannot use Table 310.15(B)(6) for ampacity values, one has to use Table 310.16, 60C column for the final value.

I've been saying this for a year and a half and nobody has agreed with me.

I've also ignored myself and run 4/0 al ser to feed 200 amp panels from meter mains.

 

[A/A Fuel GTX]

I've also ignored myself and run 4/0 al ser to feed 200 amp panels from meter mains.

And I have run #2 AL SER for many 100A condo MLO panels from distant meter packs......