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Article 422.13

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Djelite

Senior Member
Location
Ny
Occupation
Electrician
I was looking at Mike Holts book and came across this.Why is this calculation on mike holts book a 10awg and not a 12 awg?
 

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Djelite

Senior Member
Location
Ny
Occupation
Electrician
Dennis Alwon said:
Also #12 is limited to 20 amps except for a few instances. 240.4(D)
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Thats true but i don’t think that applies to this question. It makes complete sense now that you explained it , no further info was given so 60 degrees must be used. Thank you
 
infinity

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Djelite said:
I was looking at Mike Holts book and came across this.Why is this calculation on mike holts book a 10awg and not a 12 awg?
Click to expand...
#12 is limited to 20 amps by 240.4(D) for a water heater regardless of wiring method. Even if you had a 75° C wiring method like MC cable you're still limited to 20 amps even though for #12 AWG at 75° C the ampacity is 25 amps.

240.4(D) Small Conductors.
Unless specifically permitted in 240.4(E) or (G), the overcurrent protection shall not exceed that required by (D)(1) through (D)(7) after any correction factors for ambient temperature and number of conductors have been applied.
240.4(D)(5) 12 AWG Copper.
20 amperes
Click to expand...
 
Dennis Alwon

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Djelite said:
Thats true but i don’t think that applies to this question. It makes complete sense now that you explained it , no further info was given so 60 degrees must be used. Thank you
Click to expand...
Why doesn't it apply to this question? What, in this question, makes you think that it doesn't apply.
 
kwired

kwired

Electron manager
Location
NE Nebraska
Occupation
EC
Djelite said:
Thats true but i don’t think that applies to this question. It makes complete sense now that you explained it , no further info was given so 60 degrees must be used. Thank you
Click to expand...
Still end up with 10 AWG being required because of 240.4(D), even when 75 C ampacity table is allowed to be used.

sorry didn't read all posts before replying.
 
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