310.15 (B)(16)

[captainwireman]

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]

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.

 

[John120/240]

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.

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

 

[augie47]

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.

??

 

[iwire]

??

Posting from a smart phone with auto correct.

It was supposed to say derating.

 

[captainwireman]

Are you saying XHHW in a wet location can use the 90C table for applying derating factors? A little confused.
I do hate anything smaller than a keyboard :lol:

 

[Dennis Alwon]

IMO, if xhhw is used in wet location then you may only use the 75C. Dry and damp are good for 90C

 

[iwire]

IMO, if xhhw is used in wet location then you may only use the 75C. Dry and damp are good for 90C

Both XHHW and XHHW-2 are listed in the 90C column and 'XHHW' has a 'W' so that applies to wet locations as well.

This is a different situation than THWN/THHN.

 

[infinity]

XHHW is a 90? dry or 75? wet conductor. XHHW-2 is 90? in both wet and dry. {T310.104(A)}

 

[iwire]

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]

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????

 

[ActionDave]

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

I agree. It's not a typo. They are both 90 degree conductors.

You do need xhhw-2 to use 90 degree in wet areas though. 310.13 says plain xhhw is 75 degree in wet locations

 

[iwire]

Is that the rule according to Bob, LOL,

No it is simply what the table (Table 310.15(B)(16) shows in my 2011 NEC. It is also what the designation says as far as I know

XHHW = Two 'H' means 90C, a 'W' means wet.

or do you think it is a misprint????

I think there is a mistake in 310.13.

 

[iwire]

I agree. It's not a typo. They are both 90 degree conductors.

You do need xhhw-2 to use 90 degree in wet areas though. 310.13 says plain xhhw is 75 degree in wet locations

Rutrow.

Just went looking at my fresh 2014 and there is no 310.13.

 

[iwire]

Heading out on a date with the wife, see you guys later.

 

[captainwireman]

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]

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

 

[infinity]

Did anyone besides Bob look at T310.104(A)? I'm confused about the confusion.

 

[Dennis Alwon]

Did anyone besides Bob look at T310.104(A)? I'm confused about the confusion.

Yes I did - that why I made the comment on my first post in this thread

 

[captainwireman]

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.