86 Degree Ambient

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My guess is because it corresponds with an even metric number, 30 degree Celsius. Don't ask me where they got 30 degrees C from. :rolleyes:
 
Could be because a rise in temperature equals a rise in conductor resistance, which in turn lowers the current carrying capacity of that conductor and maybe 86 degrees is a temp at which the effect is unaccetable??? guessing
 
mdshunk said:
86 degrees Fahrenheit is exactly 30 degrees Celsius.

Next question; why 30?
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Echo...echo....echo...:grin:

My guess is because it corresponds with an even metric number, 30 degree Celsius. Don't ask me where they got 30 degrees C from. :rolleyes:
Click to expand...
 
I guess ones needs to have a better understanding of ambient
Heres a broad run on it
http://www.amptec.com/tempError.htm
Hey heres one from the old format found via Google (that lists other things)
&
forums.mikeholt.com/archive/index.php/t-66683.html

"Define ambient" I think this will define it here, note the 3rd and 4th listings.

Of course the reading is on U...:rolleyes:

Ok stike my thread ... I didn't answer 86?
 
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cadpoint said:
I guess ones needs to have a better understanding of ambient
Heres a broad run on it
http://www.amptec.com/tempError.htm
Hey heres one from the old format found via Google (that lists other things)
&
forums.mikeholt.com/archive/index.php/t-66683.html

"Define ambient" I think this will define it here, note the 3rd and 4th listings.

Of course the reading is on U...:rolleyes:

Ok stike my thread ... I didn't answer 86?
Click to expand...


I understand the definition of ambient. I'm just curious as to how the code came up with the temperature of 86 degrees as being the ambient.

Joe
 
I still think that is the temp when the conductor can no longer get rid of the heat to the surrounding atmosphere efficiently and the temp rise in the conductor ,.. resulting from the increased resistance ,..starts to degrade the insulation on said conductor.
 
joebell said:
Can anyone explain to me why the temp rating of 86 degree is the selected ambient temp. applied to table 310.16?
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infinity said:
My guess is because it corresponds with an even metric number, 30 degree Celsius. Don't ask me where they got 30 degrees C from.
Click to expand...
That's easy: because it corresponds with 86F. :cool:
 
M. D. said:
I still think that is the temp when the conductor can no longer get rid of the heat to the surrounding atmosphere efficiently and the temp rise in the conductor ,.. resulting from the increased resistance ,..starts to degrade the insulation on said conductor.
Click to expand...

It is my understanding that if I take a #12 THW conductor and load it to 25 amps (just an example I know the code allows a #12 at 20 amps) in an ambient of 86 degrees the temp of the conductor should be 167 degrees. If this 167 degree temp is exceeded then the insulation begins to break down.

I still don't understand the 86 degree rating

Joe
 
mdshunk said:
They probably picked 86 degrees the same way they picked 42 circuits. The SWAG method.
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Maybee they posted nubers on a dart board and threw a dart over there shoulder.

I thought that 42 circuit requirement was changed in this last code cycle?

Joe
 
I can't imagine that 86 was a random choice. Since 25C is generally accepted as room temperature, I would think that using 5C above room temperature is a sensible definition of ambient temperature. It would be interesting to know how this number was arrived at, though.
 
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