De-rating in free air

[Darryl Cirel]

I am looking at the Tri-plex wire listings and see that the ampacities are listed for 40 degree C and NO Sun.
I have de-rated wire based on how many inches off the roof, but never in free air for being in the sun.
Where can I find those calculations or formula??
Darryl

 

[Smart $]

Welcome to the forum :thumbsup:

Please cite the specific table which states "NO sun" in the NEC. AFAIK, there is none.

If this is part of a compliance with listing, and the listing ampacity table says "no sun", you'll have to contact the manufacturer. Aside from that, if it does say no sun, and you intend to use "in sunlight", the cable will have to be marked as Sunlight Resistant.

 

[iwire]

I am looking at the Tri-plex wire listings and see that the ampacities are listed for 40 degree C and NO Sun.
I have de-rated wire based on how many inches off the roof, but never in free air for being in the sun.
Where can I find those calculations or formula??
Darryl

I am curious what kind of triplex you have.

Most is not listed.

 

[Julius Right]

I think the same as Smart $, of course. However, if you would afford a bit more complicate calculation you could follow IEC 60287-1-2-ch. 2.2.1.2 Cables directly exposed to solar radiation [you?ll need the cable details-as diameter of conductor and above different layers ?or you may ?build? the cable according IEC 60502-1 or 2.]
Neher&McGrath in ?The Calculation of the Temperature Rise and Load Capability of Cable Systems? also recommends ?it may be desirable to consider the effect of solar radiation...and the effect of wind..? formula 47B.