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#97117 01/23/06 10:12 PM
Joined: Jan 2006
Posts: 2
rjr1950 Offline OP
Junior Member
I was told that there are no wire terminations rated more than 75C degrees, and that this limits you to the temperature of the wire being used. Example - If I choose 2 aught THHN-2 from the table 310.16 the maximum ampacity would be 195 amps at 90C degrees, but because my termination was 75C degrees you would have to drop back to the 75C THHN conductor, which is rated at 175 amps. Is this correct?

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Joined: Jun 2004
Posts: 6
Junior Member
There is a variety of mechanical lugs and neutral bars listed in the Ilsco catalog as 90 degree temperature rating.

Joined: Jul 2004
Posts: 9,770
Likes: 14
You may have a little more trouble finding breakers and end use equipment with 90c terminations. You will be limited by the lowest rated termination on a conductor.

If you could start by using the 90c column there is no wiggle room for derating so the sharp pencil will come out.

Generally speaking you get limited at 75c.

Greg Fretwell
Joined: May 2003
Posts: 2,876
e57 Offline
If you dont mind, what type of terminations are you trying to get for 2/0? Most insulated for a few years or so have been 90C, and I cant remember ever seeing non insulated with under 90C. Unless were talking apples and oranges? As gfretwell mentioned devices, breakers and such are a different story.

Take a look at 110.14C... I believe this is the code you're reffering to? Then 310.16, with ambient tempature correction factor. And 310.15 after that... The wire size could change some more? [Linked Image]
Then a saving grace in 240.4B, via 240.6.

[This message has been edited by e57 (edited 01-24-2006).]

Mark Heller
"Well - I oughta....." -Jackie Gleason
Joined: Jul 2001
Posts: 599
JBD Offline

There is no UL Listed device termination rated at 90C. The rating of individual components such as a lug only is not the same as the overall rating of the device as required by 110.14(C).

I have always liked the Square D publication Wire Temperature Ratings and Terminations that discusses wires and terminations. "When terminations are inside equipment such as panelboards, motor control
centers, switchboards, enclosed circuit breakers, safety switches, etc., follow
the temperature rating identified on the equipment labeling instead of the rating
of the lug itself.

Joined: Feb 2002
Posts: 375
I am told that wire nuts are rated at 105 degrees.

So you run big wire from your equipment to a box using a wire nut change to a little wire. Do the same at the other end.

Poor practice but ...

Joined: Jun 2004
Posts: 6
Junior Member
The SQ D publication was a good one. As you say, it makes clear there is no distribution or utilization equipment 600v or less listed 90C.
Also helpful for me was the reference included to 110.40, 90C above 600V.

Joined: Jun 2004
Posts: 613
"I am told that wire nuts are rated at 105 degrees.
So you run big wire from your equipment to a box using a wire nut change to a little wire. Do the same at the other end.

Poor practice but ..."

George...Is this practice code compliant?

Would I have to increase the size of the EGC also as required by 250.122(B) for its entire length or just where the pigtails are tapped for device termination?


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