TABLE 310.16 ampacity

[Don Gorham]

What is the reason the Mike Holt DVD series uses the 90deg c column for some wire ampacitys but then uses the 75deg c column for other ampacitys? I understand the 75deg c correlates to OCPD terminal ratings as the industry standard. During temp corrections are you starting with the 90deg c and then if the corrected temp is below the 75deg c use that ampacity? I just need to understand the code explanation.

 

[raider1]

Welcome to the forum.

The last sentence of 110.14(C) states "Conductors with temperature ratings higher than specified for terminations shall be permitted to be used for ampacity adjustment, correction, or both."

So you are permitted to use the ampacitys listed in the 90 degree column of 310.16 for ampacity adjusments, corrections or both, but the final ampacity to be used for the conductor can't exceed that listed in the column for the lowest temperature of the terminations the conductor will be used with.

Hope this helps.

Chris

 

[K2X]

I'm working through the same types of problems in class and was wondering where i could find the terminal temperature ratings on receptacles. I've been looking and can't find anything in writing. Thanks..

 

[iwire]

I'm working through the same types of problems in class and was wondering where i could find the terminal temperature ratings on receptacles. I've been looking and can't find anything in writing. Thanks..

60 C.

Look at 110.14

 

[infinity]

I'm working through the same types of problems in class and was wondering where i could find the terminal temperature ratings on receptacles. I've been looking and can't find anything in writing. Thanks..

They do make receptacles with a 75 degree C rating:

 

[Don Gorham]

OK so... as long as the final ampacity after corrections is not above the 75 deg c ampacity your good to use your corrected ampacity, except if there are no corrections to be made then use the 75 deg c column, as long as the terminal is listed for 75 deg c.

 

[iwire]

They do make receptacles with a 75 degree C rating:

Boy I would sure like to see a 50 amp or less straight blade receptacle rated 75C, I have my doubts any exist

OK so... as long as the final ampacity after corrections is not above the 75 deg c ampacity your good to use your corrected ampacity, except if there are no corrections to be made then use the 75 deg c column, as long as the terminal is listed for 75 deg c.

In order to use 75 C with the receptacle it would have to be marked 75 C, if the device rating is under 100 amps and is not marked you have to treat it as 60 C.

 

[infinity]

Boy I would sure like to see a 50 amp or less straight blade receptacle rated 75C, I have my doubts any exist



In order to use 75 C with the receptacle it would have to be marked 75 C, if the device rating is under 100 amps and is not marked you have to treat it as 60 C.

You might be right. This one lists an operating temperature limit of 75 degree C, continuous. Not to say that it's including the terminal rating but it does seem logical.

http://assets.twacomm.com/assets/pdf/18830.pdf

 

[suemarkp]

The last range receptacle I bought was marked 75C. But I've never seen anything smaller marked at 75C.

The other reason to use the 75C column would be wire that is in a wet area and was limited to 75C when wet (e.g. THWN). However, most newer wire is rated at 90C when wet (THWN-2).

 

[Howard Burger]

meaning of type coding

meaning of type coding

Don, when you're picking your wire, it might be helpful to know that the single H, on THWN for instance, indicates insulation suitable for 75C; HH has insulation suitable for 90C, and -2 indicates "conductor is permitted to be used at a continuous 90C operating temperature". This comes from Holt's Electrician's Exam Preparation, 1st ed.

 

[Don Gorham]

OK thanks, Don.