310.15 (B)(16)

fmtjfw

Senior Member
UL White book 2013

UL White book 2013

ZKST Thermoset-insulated wire

XHH ? Indicates a single conductor having a cross-linked synthetic polymer insulation with no overall covering provided, rated 90?C dry.
XHHW ? Indicates a single conductor with the same description as Type XHH, except that it is rated 90?C dry, 75?C wet.
XHHW-2 ? Indicates a single conductor with the same description as Type XHH, except that it is rated 90?C dry, 90?C wet.
 

iwire

Moderator
Staff member
Location
Massachusetts
ZKST Thermoset-insulated wire

XHH ? Indicates a single conductor having a cross-linked synthetic polymer insulation with no overall covering provided, rated 90?C dry.
XHHW ? Indicates a single conductor with the same description as Type XHH, except that it is rated 90?C dry, 75?C wet.
XHHW-2 ? Indicates a single conductor with the same description as Type XHH, except that it is rated 90?C dry, 90?C wet.

Well that pretty much screws my opinion :D

Still have issues with way XHHW without -2 is in the 90 C. Column
 

captainwireman

Senior Member
Location
USA, mostly.
Seems the question keeps getting missed.

What the X wire is made of and what conditions it is approved for is already known and a given. I got it.

Also it is understood that ampacity derating factors 310.15(B)(2)(a), 310.15(B)(3)(a), and 310.15(B)(3)(c) if applicable are chosen from the 90C table, then the larger derated load is applied to the 75C column if the load is continuous.

The issue goes to Iwires last statement.

"Still have issues with way XHHW without -2 is in the 90 C. Column"

It seems to be a constant other places in the code when a particular situation does not apply in all circumstances there is a note, exception, highlight, or asterisk.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Electrical Contractor
Well that pretty much screws my opinion :D

Still have issues with way XHHW without -2 is in the 90 C. Column
That is because it can be used in the 90C column if it is not in wet location. I don't know how else they can explain it in the table.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
That is because it can be used in the 90C column if it is not in wet location. I don't know how else they can explain it in the table.
I agree, it needs to be in both columns because the difference depending on the location in which it's installed. The inclusion in both tables makes you inquire further as to why it's included in both columns which eventually leads you to 310.104(A).
 

captainwireman

Senior Member
Location
USA, mostly.
Yep, well you should know, I guess.

I always use XHHW-2 so this never came up. Interesting.

Digging into this calculation further, situation with all the following variables:

XHHW
continuous load
ambient temp correction
75C lugs

Larger of these two:
Ampacity of XHHW from 75C column x 1.25 then pick wire size from 75C
Temp correction / ampacity rating from 90C column then pick wire size from 90C

Choose the larger wire size for calculation.

This is how I would do this. Is this correct?
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Electrical Contractor
I believe it is moot also as most wiring today will be -2 so it is not an issue. I guess it could be with existing installs????? I have never heard of anyone getting tagged for this but surely it must have happened somewhere
 

ActionDave

Moderator
Staff member
Location
Durango, CO, 10 h 20 min without traffic from wing
Occupation
wire pulling grunt
XHHW
continuous load
ambient temp correction
75C lugs

Larger of these two:
Ampacity of XHHW from 75C column x 1.25 then pick wire size from 75C
Temp correction / ampacity rating from 90C column then pick wire size from 90C

Choose the larger wire size for calculation.

This is how I would do this. Is this correct?
That's what I do.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Electrical Contractor
Yep, well you should know, I guess.

I always use XHHW-2 so this never came up. Interesting.

Digging into this calculation further, situation with all the following variables:

XHHW
continuous load
ambient temp correction
75C lugs

Larger of these two:
Ampacity of XHHW from 75C column x 1.25 then pick wire size from 75C
Temp correction / ampacity rating from 90C column then pick wire size from 90C

Choose the larger wire size for calculation.

This is how I would do this. Is this correct?

If you mean you are in a wet location then I disagree otherwise you are correct
 

xformer

Senior Member
Location
Dallas, Tx
Table 310.15B16...

Table 310.15B16...

I think this post is a great example of what so many of us don't understand. 310.15B16 is just an ampacity table for conductors (under certain conditions) .... Therefore you can have the same conductor listed under different temps. One must Apply 310.104 to the conductor insulation for field installation condition before going to look at 310.15B16
 

captainwireman

Senior Member
Location
USA, mostly.
I could cite a half dozen or so instruction references and none of them would say "start with 310.104". Truly 310.15(B)(16) is probably the most referenced but least understood code section, even by the instructors.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Just thought of something, I pretty sure you don't have to use the temp correction for xhhw under 2014.
You still have to do the temperature corrections for XHHW, but you don't have to add the temperature adder shown in Table 310.15(B)(3)(c) if you are using XHHW conductors.
310.15(B)(3)(c) Raceways and Cables Exposed to Sunlight on Rooftops.
Where raceways or cables are exposed to direct sunlight on or above rooftops, the adjustments shown in Table 310.15(B)(3)(c) shall be added to the outdoor temperature to determine the applicable ambient temperature for application of the correction factors in Table 310.15(B)(2)(a) or Table 310.15(B)(2)(b).

Exception: Type XHHW-2 insulated conductors shall not be subject to this ampacity adjustment.
 
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