ampacity of #8 THHN in EMT

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Sierrasparky

Sierrasparky

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Location
USA
Occupation
Electrician ,contractor
Hey can you put #8 THHN on a 50 amp breaker for a single residential Range outlet. ( 120/240v )
I know it must be # 6 if NM wire is used.
I have a disagreement with a fellow Electrician.
 
Certainly you can, see Table 310.16, 75deg and if needed 240.4

Roger
 
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As long as the terminals are 75 degree rated there should be no problem. After all how often does a range even pull it's full amp rating? you would need all 4 burners and the oven on at the same time.
 
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acrwc10 said:
As long as the terminals are 75 degree rated there should be no problem. After all how often does a range even pull it's full amp rating? you would need all 4 burners and the oven on at the same time.
Click to expand...


Thanksgiving and Xmas dinner come to mind. Sunday family gatherings also.
 
My theory is you must wire to the nameplate rating of the unit just as you would a heat strip. This theory is Generally ignored. My boss in Lee County told me "Don't go there" but could not give me a code reference. I passed many ranges in the maga homes that should have been on 60 amp ckts because I was told to.
 
How about 220.55? That allows you to treat a range branch circuit the same way yoo do for the Service calculation. See all the little caveats in Note 4 to that table. To require a branch circuit over 50A would need a range sized > 22KW (see Note 1).
 
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acrwc10 said:
As long as the terminals are 75 degree rated there should be no problem. After all how often does a range even pull it's full amp rating? you would need all 4 burners and the oven on at the same time.
Click to expand...

Yes you can but has nothing to do with the 4 burners and oven. #8 thhn is good for 50 amps at 75. The 4 burners might keep going for over 3 hours but the oven has thermastat that will be cycling on and off.
As for romex he is limited to 40 amps.
If nobody ever used all 4 burners they would not be there.
What you have is a romex man that might not even have a code book. Help him out by showing him 310.16 and point out that romex is 60 degree. But first make a free lunch bet.
 
acrwc10 said:
As long as the terminals are 75 degree rated there should be no problem. After all how often does a range even pull it's full amp rating? you would need all 4 burners and the oven on at the same time.
Click to expand...

Even then it would rarely pull a full load. Most ovens have an upper and a lower element that are rarely on at the same time. You broil with the upper, and bake with the lower. Preheat and self clean are about the only times they would both be on at the same time.
 
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