Romex cable warm under heavy continuous use

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14ga wire is 2.53ohms per 1000ft, so it the total circuit length is 50ft, that is 0.1265ohms total. Ohms law says that P = I2 * R , so with 12A of current, 18.21W of heat is created in that wire at 25C (77F), resistance increases slightly with temperature, so let’s round it up to 20W of heat. Not a lot, but not nothing either.
 
Little Bill said:
Heinz 57 helps!:)
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For those of you who keep getting confused when to add 32 and when to subtract 32, I strongly recommend the +40/-40 method.
Take the temp you want to convert, add 40, multiply by either 5/9 or 9/5 depending on the conversion direction, then subtract 40.
This simplification is based on the fact that -40F and -40C are the same temperature.
 
GoldDigger said:
For those of you who keep getting confused when to add 32 and when to subtract 32, I strongly recommend the +40/-40 method.
Take the temp you want to convert, add 40, multiply by either 5/9 or 9/5 depending on the conversion direction, then subtract 40.
This simplification is based on the fact that -40F and -40C are the same temperature.
Click to expand...
I just google it 😜
Like "60c to f"Screenshot_20230813_214811_Chrome.jpg
 
GoldDigger said:
For those of you who keep getting confused when to add 32 and when to subtract 32, I strongly recommend the +40/-40 method.
Take the temp you want to convert, add 40, multiply by either 5/9 or 9/5 depending on the conversion direction, then subtract 40.
This simplification is based on the fact that -40F and -40C are the same temperature.
Click to expand...
I was referring to the Heinz57 helping with eating Crow!
Not talking about the conversion.
:D

For the conversion, I find it easier to just multiply by 1.8 and add 32 for C to F
 
Side note. At the large hospital that I retired from every year we had to perform an IR scan on the thousands of circuit breakers in the 12 story building. 20 amp GFCI bolt on circuit breakers always were slightly warmer then the other breakers and all breakers when loaded close to 80% ran several degrees warmer. All were in air conditioned fair size electrical rooms. Between normal & emergency power some rooms had over 400 circuit breakers. One thing the type NM cable ( romex ) appears warmest near panel. Is that cable bundled with several other cables? I believe this should not be a problem but would be better having a dedicated 12 guage copper cable feeding what is considered a continuous load ( due to 3 hours or more ). Did you perform voltage readings at panel main, at the 15 amp breaker & at feed at GFCI & output side ? They upgraded the insulation on romex back in the 1980's to a far superior yet thinner insulation on the conductors so you should have the newer style.
 
Jraef said:
14ga wire is 2.53ohms per 1000ft, so it the total circuit length is 50ft, that is 0.1265ohms total. Ohms law says that P = I2 * R , so with 12A of current, 18.21W of heat is created in that wire at 25C (77F), resistance increases slightly with temperature, so let’s round it up to 20W of heat. Not a lot, but not nothing either.
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That would be 20 watts per foot, right? Concentrate that to a small point like they do with a soldering iron and it is quite hot.

Bad connection on a terminal screw or in a wire nut is often less than 20 watts and look what that can end up doing.
 
Little Bill said:
For the conversion, I find it easier to just multiply by 1.8 and add 32 for C to F
Click to expand...
You can also do it in your head, maybe.
F to C works pretty well for relatively small numbers, the error gets worse with higher numbers but the result is still in the ball park.

C to F: Multiply by 2, then subtract 10%, then add 32.
example: 40C x 2 = 80, 80-10% = 72, 72+32 = 104F

F to C: Subtract 32, then add 10%, then divide by 2
example: 104F-32=72, 72+10% = 79, 79/2 = 39.5C
 
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