what degree table do you use sizing wire.

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paul.konifka

Member
Location
Albany NY
i have been having a conversation with some coworkers and we can not decide. i always had the rule of thumb 8awg was good for 40 amp and 6awg is good for 50 amps.

i have another coworker who insist you can use 8awg copper on a 50 amp and but we are fighting over the degree section.

when looking in the NEC table we are having different thoughts of what degree table to use. i always thought you had to use the 60 degree for romex unless your breaker was rated for 75 degree.

can some one shed light on that degree section you should look at
 

jwjrw

Senior Member
Romex and SER etc is 60*. It has nothing to do with 75* breaker rating
Thhn is 75* column


So if you have #8 romex it is 40a max ocp
If you have #8 Thhn it is 50a max ocp
 
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augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
In regard to Code references:
110.14 is the reference taking equipment terminations into account, but, as noted in Post #2, you have to keep the type cable being used in mind do to the limitations on NM (334.80) and SE (338.10) for example.
 

kwired

Electron manager
Location
NE Nebraska
i have been having a conversation with some coworkers and we can not decide. i always had the rule of thumb 8awg was good for 40 amp and 6awg is good for 50 amps.

i have another coworker who insist you can use 8awg copper on a 50 amp and but we are fighting over the degree section.

when looking in the NEC table we are having different thoughts of what degree table to use. i always thought you had to use the 60 degree for romex unless your breaker was rated for 75 degree.

can some one shed light on that degree section you should look at

Before your question can be answered several things need to be known.

type of conductor insulation

terminal temperature rating of devices conductor will be attached to

continuous or non continuous load

ambient temperature

number of conductors in raceway or cable that may require adjustment of ampacity


THHN is 90 deg column.

THHN must still use 60 or 75 degree column for terminal rating and is allowed to use 90 degree column for additional deration for ambient temp or number of conductors in raceway.
 

cpal

Senior Member
Location
MA
it would also be helpful to know the jurisdiction that the installation is covered by.

Th OP mentioned type NM The NEC limits NM to the 60 degree column

This language may not be applicable in all areas
 
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