J Box fills and de-rating

[shaz]

When it comes to fills, both for boxes and conduits, NEC appears to consider "eddy currents" as a far greater effect than temperature variances.

In regards to boxes, the count includes "yolks/clamps/hickeys etc." yet it ignors the type of devices such as dimmers etc. that account for heat buid-up. The wire specifications are clearly dependent on temperature fluctuations!

In viewing a rather stuffed Junction box where all wires are connected with "wire nuts". Are the wire nuts devices - no! As far as I understand it is a termination point for some device hanging out there, and it will increase temperature within the enclosure, but that is not under consideration or the fact that the wing nuts also displace the available space (volume).... Can someone please explain NEC reasoning to me?

Shaz.

 

[charlie]

Re: J Box fills and de-rating

The Code is set up as a minimum standard. If a box is not large enough, shame on you if you don't get a larger one when the electrical work is being done. It seems to me that (most of the time) contractors will use boxes that are larger than needed to take care of those problems.

If you feel like this is a pervasive problem, I highly recommend that you take advantage of the newest part of this forum, "Proposals for the 2008 NEC".