[R-390] Re: Can someone tell me...

[Tisha Hayes]

Remember to derate the current handling capability of a conductor if it is
bundled. Many of the published ratings for conductors vary because of the
application they are placed into.

Wiring in conduit, wiring in trays or bundles. Applications like
communications, audio, industrial control, etc.. each have their own
de-rating standards. You could go through NEC to see the closest fit for
your application, unfortunately most of the NEC standards do not list
specifications for wiring smaller than 18 AWG.

You will also have I2R losses based upon wire gauge and this is dependent
upon the length of a run. Usually the bigger limiting factor is with heat
losses (and where that heat goes), in bundles with other conductors, the
entire bundle heats up. There is not much shown on the temperature rating of
the different insulation types (PVC, teflon, kapton, kynar) or the
environmental conditions (existing temperatures in the area where the wiring
is located). There are dozens of tables that do not cross-reference well
into other tables, I would suggest being very conservative with current
ratings and when in doubt, go with a larger wire gauge.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.qth.net/pipermail/r-390/attachments/20090104/2a846d79/attachment.htm