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OT: Plugged AC drain revisited

Hi All, Yesterday I finally bit the bullet and cut into the wall where I suspect the problem with my AC drain was. Found out that, as I suspected, the 'techs' putting in my DirecTV drilled right into it, and then when I put in the expanding foam insulation, it filled the hole and the drain pipe! Replaced the old 90 with a six inch sweep, so that part is done.

BUT, I now know to no longer use expanding foam, the hard way. I had been real careful cutting the drywall so that I could just replace it in the hole, and had replaced a lot of the blown in insulation with some sections of 2" styrofoam, but then filled in the gaps with the expanding foam. After I put the drywall back in place, the expanding foam pushed it back out again. Now I will have to cut a LARGER hole and go by a small piece of drywall to path it.

So, lesson learned. No longer will I use expanding foam to fill in voids!

Charlie

Reply to
Charlie E.
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Does filling dead airspace with anything really provde better insulation?

Reply to
W8CCW

Yes, if said space is more than about 1/2" or 1cm wide - because it's not "dead" at that point, it sets up delightful circulating currents. And that's not even getting into actual leaks through the membranes. The point of most insulation is to trap small pockets of air so they cannot circulate, and types which block air movement better typically work better than types which let air flow freely through (fiberglass is notorious for flowing a bit too freely.)

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Reply to
Ecnerwal

Air is a much poorer heat conductor than most other substances. So theoretically, a dead airspace should be a good insulator.

But air supports convection currents. And that's how most of the heat is lost through dead air spaces. So the job of most insulating mediums is to minimize convection while containing the greatest volume of trapped air.

--
Paul Hovnanian     mailto:Paul@Hovnanian.com
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A physicist is an atom's way of knowing about atoms.
                -- George Wald
Reply to
Paul Hovnanian P.E.

Yes. If the gap being filled is wider than about 6mm, the air in the gap will convect, and transfer more heat than it would if the convection were slowed or stopped by some kind of low density filling.

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman

A nice drywall trick I learned helps to fix it easier.

Tilt the keyhole saw at an angle, so it will cut at a a cone shape angle, with the apex of the cone inside the wall. That way, when you paste the circular piece back in with polyfilla, it won't need extra support. Tilt a weight against the plug until the mud hardens. On a ceiling, cut cone shape backwards, so the round piece can't fall out. Pull the plug downwards with a couple of drywall screws to set into the m= ud.

Another way is to cut a piece out, then slide in a few strips of wood into the opening. The strips should be a few inches longer than the hole is wide.

Screw into the wood through the untouched wall to hold it in place. Put the cut out portion of drywall back into the hole and screw it into the same strips. Make sure the screw heads are slightly below the surface before applying polyfilla and sanding block.

mike

Reply to
m II

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