Temperature Column

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Yes but you can use the 90C for de-rating. So basically after de-rating the rating of the wire cannot be used if larger than the 60C rating. The 60C column is the weak link.

For example, if after de-rating a conductor from the 90C column it is rated 50 amps but if the cable is rated 40 amps under the 60C column then the rating cannot be used higher than the 40 amps
 
Basically with NM and UF your termination temp rating is always 60C so the base size is never less than the 60 column. If there is ambient temperature corrections or bundling adjustments required in an application you can start those adjustments from the 90C column if it is NM-B or UF-B rated cable, which all of it has been since mid to late 1980's
 
Dennis Alwon said:
Yes but you can use the 90C for de-rating. So basically after de-rating the rating of the wire cannot be used if larger than the 60C rating. The 60C column is the weak link.

For example, if after de-rating a conductor from the 90C column it is rated 50 amps but if the cable is rated 40 amps under the 60C column then the rating cannot be used higher than the 40 amps
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Yup I just found out about that recently . Thanks
 
Tulsa Electrician said:
You mean NM. Artical 334
334.80
334.112
Informational note. The most common used is NM-B.
We call it Romex all the time as long as we know where to look.

Also review 334.116 Sheath.
Good info.
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Nice little interesting piece of information that was in my NFPA online NEC edition that I subscribe to.

Nonmetallic-sheathed cable was first recognized in the 1928 NEC as a substitute for concealed knob-and-tube wiring (Article 394) and open wiring on insulators (Article 398). The original advantages of nonmetallic- sheathed cable over knob-and-tube wiring were that the outer sheath provided continuous protection in addition to the insulation applied to the conductors; the cable was easily fished in partitions of finished buildings; no insulating supports were required; and only one hole needed to be bored, and that hole could accommodate more than one cable passing through a wood cross member.
 
Cool
 

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Tulsa Electrician said:
You mean NM. Artical 334
334.80
334.112
Informational note. The most common used is NM-B.
We call it Romex all the time as long as we know where to look.

Also review 334.116 Sheath.
Good info.
Click to expand...
I believe NM-B came out in about 1984. Wasn't long after and all NM sheathed cable produced from then on was type NM-B. NEC eventually required it to be NM-B. Regular NM is still covered by code in order to deal with existing installations, but new installations are required to use NM-B.
 
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