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Residential Romex #12 or #14 jacket temps

1K views 13 replies 7 participants last post by  Yoyizit 
#1 ·
Those of you with IR meters, have you ever checked this?

I'm looking for data like
#14 copper
amb temp = 22C
current = 10A
jacket temp = ?C

or

#12 copper
amb temp = 30C
current = 15A
jacket temp = ?C

TIA
 
#4 ·
An IR thermometer won't be accurate enough to make this measurement. The temperature difference will be very small, and since the cable jacket has different emissivity than whatever the surroundings are, the error due to emissivity difference will make the actual temperature difference indistinguishable.
 
#5 · (Edited)
I put 25A through #14 copper once and it went about 2F above ambient as measured with a precision thermistor placed under the jacket. I haven't checked this value against the Neher-Mcgrath equation.

I'm trying to make sense of passing 30A through #12 in an HVAC setup without unduly shortening the life of the Romex insulation. Every 9C increase halves the life and 30A instead of 20A is a (30/20)^2 = 2.3x increase in insulation temp rise above ambient from whatever the 20A temp is.

For those philosophers on this forum - with the time on my hands I am trying to make sense of every decision I have ever made in my whole life, and it's not so easy! :laughing:
Life is lived forward and understood backward.
 
#9 ·
.

I'm trying to make sense of passing 30A through #12 in an HVAC setup without unduly shortening the life of the Romex insulation.
Hey silly, 30A would never be allowed to flow through #12 AWG in an HVAC scenario, you know why? because the motor contains thermal overloads that would shut the motor off before it reached that amperage. :)

in simple terms, the motor is the load, so if the motor can't physically draw more than 25 amps, I guess the wire is pretty safe.
 
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