Is it legal (NEC/Canada) to drill a drain hole in the bottom of a PVC weatherproof electrical box, when used in a wet location?
If so, what size is recommended to drain the water out and keep the wasps out (or avoid other issues)?
For the rest of the seal, is it common to silicone the entire seal between cover and box? Or do you typically seal the top and sides, but not the bottom? Is this a matter of code or good practice?
An instruction manual for a motion sensor reads "If not installed on a weatherproof box or if an adaptor plate was used, caulk the wall plate and mounting surface with silicone." I note, based on an answer below, that the silicone recommendation does not apply, and the opposite is recommended, when mounting on a PVC weatherproof box.
Best Answer
Yes, and you'll want a 1/8" hole
This is governed by NEC 314.15:
I would not seal the rest of the box though; the idea with normal weatherproof electrical enclosures is to provide a rough seal to keep bulk moisture, bugs, and such out, while having enough air movement to prevent any pressure differentials across the seal from driving moisture in through the slightest imperfections. (The drain hole helps with this as well, although you'll want to keep an eye on it as spiders can be particularly pesky hole-pluggers.)