My second electical question of the morning…
What’s the best way to air seal an electrical box (outlet, switch, etc) in existing construction? I’ve got rocklath (plaster) walls, if it matters. I have some of those foam gaskets but, those aren’t really made for gang boxes, switches, etc.
Should I caulk on the inside or foam it on the inside of the box? Will that make later renovations harder? Do I need high-temp caulk or foam if I do that?
Thanks!
Replies
bump.
Please don't foam up the inside of the box. The NEC fill is based on having air in there to let heat dissipate. The wires will get a lot hotter than their design value. I've had to dig foam out of boxes, no fun.
Pull the plate and fill between the outside of the plaster ring and the drywall with drywall mud or whatever. When that's hard, you can use a thin piece of that peel and stick urethane foam weatherstripping all around if you really want to, but there'll be very little left for it to do.
-- J.S.
Well, you could pull all the devices out so you could get at the back inside of the box and reach in there and plug any holes with that grey electrician's putty. Comes in a plastic wrapped bar about the size and shape of an lod balck board eraser.
that grey electrician's putty
I believe the technical term is "monkey sh!t."
From WWII navy.
If there are holes in the box (or between the box and adjacent plaster) you can poke the "straw" through them and fill the area around the box. Be sure to use low-expansion foam so you don't bust the wall open.
You can also get some electrician's putty (similar to plumber's putty but non-conducting and safe for plastic) and use that to plug holes in the box, pack around the wires as they enter the box, etc. Be sure to cut power while you do this.
happy?
I ended up using Dynaflex 230 caulking across the small gap between the box and wall. A little caulk got in the box, but I doubt that's conductive. I used the foam cutouts for everything else, which I can't see doing much if its not sealed to the DW. The switchplate probably doesn't make a good compression fit.