310.15 (B)(16)

captainwireman

Senior Member
Location
USA, mostly.
I was asked about XHHW and since it is in both 75C and 90C, which one should he use?
What I always thought was:
XHHW in a dry location is OK for the 90C column.
XHHW-2 is OK for the 90C column under wet, damp, or dry conditions.
XHHW under wet or damp conditions must use the 75C column.

I never noticed this before and X wire is used a lot with the stuff I deal with. Do you think this could be expressed differently in the language since I could say "XHHW in the 90C column is an error because it is only acceptable under certain circumstances".
 

iwire

Moderator
Staff member
Location
Massachusetts
If all the terminations were rated 90 c you could use that value.

The other time you can use the 90C rating is for calculating the creating.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
XHHW is a 90? dry or 75? wet conductor. XHHW-2 is 90? in both wet and dry. {T310.104(A)}
 

iwire

Moderator
Staff member
Location
Massachusetts
XHHW is a 90? dry or 75? wet conductor. XHHW-2 is 90? in both wet and dry. {T310.104(A)}
Interesting.

Both plain old XHHW and XHHW-2 are listed under the 90 column.

Notice THWN is not listed in the 90 column.

IMO XHHW is 90 C wet conductor regardless of a -2.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Electrical Contractor
Interesting.

Both plain old XHHW and XHHW-2 are listed under the 90 column.

Notice THWN is not listed in the 90 column.

IMO XHHW is 90 C wet conductor regardless of a -2.

Is that the rule according to Bob, LOL, or do you think it is a misprint????
 

captainwireman

Senior Member
Location
USA, mostly.
I think we can agree that XHHW-2 is suitable for 90C in a wet location. My question goes back to why they have XHHW in the 90C column if it requires special conditions to be applicable (dry). Maybe there is no answer, in which case is a change to the code language applicable? Opinions?.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Electrical Contractor
There is no 310.13 in either the 2011 nor the 2014. Did you mean 310.10? That simply states that xhhw can be used in wet locations.

T310.15(B)(16) in the 2011 does show xxhw as 90C but it also shows it as 75C-- that's, IMO, because if it is used as wet then it must use the 75C rating
 

captainwireman

Senior Member
Location
USA, mostly.
For THHW or XHHW or any similar situations that may arise with new insulation types, I think it would be appropriate to have a note or indication to at least refer to 310.104(A) for clarification.
 
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