2011 Code Changes- Post your favorite and Discuss them

Status
Not open for further replies.

jumper

Senior Member
Has anyone looked in the 2011 NEC at Table 310.15(B)(3)(a) formerly known as 310.15(B)(2)(a). The heading of the Table apparently never got changed but look at the column "Number of Conductors" and its accompanying note.

It appears all the conductors in the raceway will count including the egc.

The footnote says see 310.15(B)(5) and(6), which states that the neutral in certain cases and the EGC are still omitted.

The change seems to merely clarify the fact that even though certain conductors may carry current at times, they may be omitted.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Looks like you are right about the note. Why did they rename the column from "Number of Current Carrying Conductors" to "Number of Conductors". They trying to save ink.:) They made it confusing.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
The other interesting thing is that some of the ampacities in the old 310.16- now 310.15(B)(16)- have changed. Most significant are the values of 14 & 12 at 60C. They are now 15 & 20 respectively down from 20 & 25. There are 13 other ampacity changes.
 

jetlag

Senior Member
I agree with you that it ends all arguments about it but I did not, and still do not see the need to prohibit what would be safe.
IF you have 2 MWBC and only 1 neutral , I dont think it is safe, if you load a MWBC on one side only it all goes to the neutral , if you load a second MWBC on the same phase as the first but no load on the other side, that load would also go to the same neutral and overload it . In other words when only one phase is being used 2 MWBC , both loads go to neutral.
 
Last edited:

jetlag

Senior Member
IF you have 2 MWBC and only 1 neutral , I dont think it is safe, if you load a MWBC on one side only it all goes to the neutral , if you load a second MWBC on the same phase as the first but no load on the other side, that load would also go to the same neutral and overload it . In other words when only one phase is being used 2 MWBC , both loads go to neutral.
I think I should reword this to make it more clear, lets say you run phase A ,phase B and a neutral to a MWBC, you run phase A and phase B to a second MWBC , but you use the same neutral as the the first MWBC . Now some one turns the loads on phase A only on both MWBC. Both loads will go to the one neutral :grin:
 

SmithBuilt

Senior Member
Location
Foothills of NC
The other interesting thing is that some of the ampacities in the old 310.16- now 310.15(B)(16)- have changed. Most significant are the values of 14 & 12 at 60C. They are now 15 & 20 respectively down from 20 & 25. There are 13 other ampacity changes.
I seen that. I don't understand that change. It will make a lot of work for us on hvac change outs though. When changing out some of the compressors we will now have to change the branch circuit wire to a larger size. I know that sounds simple, but on many homes it will be tough to get the wire from the panel to the disco. Especially the slab homes.
 

raider1

Senior Member
Staff member
Location
Logan, Utah
The footnote says see 310.15(B)(5) and(6), which states that the neutral in certain cases and the EGC are still omitted.

The change seems to merely clarify the fact that even though certain conductors may carry current at times, they may be omitted.
Looks like you are right about the note. Why did they rename the column from "Number of Current Carrying Conductors" to "Number of Conductors". They trying to save ink.:) They made it confusing.
Actually what this code change means is that all conductors in the raceway must be counted for the ampacity adjustments except for neutrals and EGC's in accordance with 310.15(B)(5) and (6).

This means if I pull in spare conductors for future connection then they must be counted for ampacity adjustments.

Chris
 

jumper

Senior Member
Actually what this code change means is that all conductors in the raceway must be counted for the ampacity adjustments except for neutrals and EGC's in accordance with 310.15(B)(5) and (6).

This means if I pull in spare conductors for future connection then they must be counted for ampacity adjustments.

Chris
Never thought of that, thanx.:)
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Actually what this code change means is that all conductors in the raceway must be counted for the ampacity adjustments except for neutrals and EGC's in accordance with 310.15(B)(5) and (6).

This means if I pull in spare conductors for future connection then they must be counted for ampacity adjustments.

Chris
You are the world's best head banger, for sure.

 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Last night I was with an ex-inspector who was in Phoenix Arizona with Mike Holt,
Keith Lofland and Jim Pauley. He said that they all agreed on art. 338.10(B)(4).

Here is how they see it. If se cable is run in an outside wall parallel to the stud and insulation is installed in the space then that would NOT constitute being run in insulation.

Here is what the code states for those who don't have the 2011 nec yet. The brown is the new wording.

(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, excluding 334.80.
Where installed in thermal insulation, the ampacity shall be in accordance with the 60?C (140?F) conductor temperature rating. The maximum conductor temperature rating shall be permitted to be used for ampacity adjustment and correction purposes, if the final derated ampacity does not exceed that for a 60?C (140?F) rated conductor.
 

George Stolz

Moderator
Staff member
Location
Windsor, CO NEC: 2017
Occupation
Service Manager
IF you have 2 MWBC and only 1 neutral , I dont think it is safe, if you load a MWBC on one side only it all goes to the neutral , if you load a second MWBC on the same phase as the first but no load on the other side, that load would also go to the same neutral and overload it . In other words when only one phase is being used 2 MWBC , both loads go to neutral.
Really! A #6 neutral serving a pair of 20A circuits is not safe?
 

tom baker

First Chief Moderator
Staff member
Here is another good change. Article 680 in the 2008 started this by req. GFCI to be in a readily accessible location for hydromassage. Now it will be for all GFCI. This may be an issue for vending machines etc.


Vending machines GFCIs are not required to be readily accessible. Only those GFCIs listed in 210.8 have to be readily accessible
 

jwelectric

Senior Member
Location
North Carolina
If se cable is run in an outside wall parallel to the stud and insulation is installed in the space then that would NOT constitute being run in insulation.
Dennis
Please don?t quote me on this but I think that the way NC is going to look at this requirement is as follows:
Back to back installation through an insulated wall see 60 degree column
Up an uninsulated wall through top plate into the attic space with cable being installed above the insulation see 60 degree column. ( the cable did pass through attic insulation)
Down the outside of an insulated wall under the building up inside an uninsulated wall see 75 degree column.

Should the cable pass through insulation even if it is just a fraction of an inch then see 60 degree column.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Mike, it seems you are saying what I said about running parallel to the studs in an insulated wall. I don't understand that reasoning- one side is next to wood so it is not in insulation-- that seems ridiculous. Of course, I think the whole 60C thing foe se is a bit much but consistent. So if se is allowed to run parallel in insulation then so should NM. :grin:
 

jwelectric

Senior Member
Location
North Carolina
Mike, it seems you are saying what I said about running parallel to the studs in an insulated wall. I don't understand that reasoning- one side is next to wood so it is not in insulation-- that seems ridiculous. Of course, I think the whole 60C thing foe se is a bit much but consistent. So if se is allowed to run parallel in insulation then so should NM. :grin:

No not quite.

If the SE or SE-R is in contact with insulation in any way then 60 degree column is to be used.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
No not quite.

If the SE or SE-R is in contact with insulation in any way then 60 degree column is to be used.

Okay I must have misunderstood this sentence. I read it as down an outside insulated wall... Not sure what else it means..:)

Down the outside of an insulated wall under the building up inside an uninsulated wall see 75 degree column.
 
Status
Not open for further replies.
Top