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-   -   How to patch around a 2" x 4" hole in back of furnace (http://www.diychatroom.com/f17/how-patch-around-2-x-4-hole-back-furnace-114656/)

darlingm 08-20-2011 12:37 AM

How to patch around a 2" x 4" hole in back of furnace
 
First time doing anything with a furnace. I can't imagine this is typical, but there's a hole in the back of my furnace that's around 2" x 4", but I haven't measured to be exact. It's in the basement, and luckily I can easily get to each side. A bunch of air leaks out of it when the A/C runs (and I assume heat would also). Looks like a long time ago, someone tried patching it with some type of spray foam.

What's the proper way to plug this leak? I do have quite a bit of Great Stuff around for other projects, but I'm thinking that wouldn't do much better than this black stuff did.

Thank you so much - I think plugging this one leak alone will save a lot of energy every month.

http://img189.imageshack.us/img189/1...0819231140.jpg

gregzoll 08-20-2011 01:24 AM

A piece of sheet metal works. Just have to secure with screws, then tape the seams.

JJboy 08-20-2011 02:00 AM

Quote:

Originally Posted by gregzoll (Post 711207)
A piece of sheet metal works. Just have to secure with screws, then tape the seams.

after doing all, you can use mastic for the final finish.:thumbsup:

gregzoll 08-20-2011 02:29 AM

Yes, that way works also.

beenthere 08-20-2011 06:50 AM

Thumb dumb. No worry of screws going where you don't wan t them to be.

concretemasonry 08-20-2011 08:08 AM

You are really not be losing warm or cold air, but not controlling the flow as much as you want because the basement is still in the livable space.

Dick

kb3ca 08-20-2011 08:24 AM

A piece of sheet metal and some of that shinny silver refrigeration tape (available at HD). Don't use screws.

REP 08-20-2011 05:13 PM

What I would do is use a piece of sheetmetal cut out so as to cover most of that hole.I perssonally do not like to have sheet metal touch those copper lines because of vibration either digging into the copper or creating harmonics.That said I would actually seal what ever leak there will be with thunb gum.
As for the sheetmetal with or without screws it dosen't matter as long as you are very carefull not to punture the copper lines or the coil that they are attached to. I would use small 1/2 inch zip screws and RTV on the sheet metal to form a gasket.
What you are lookingt at are the suction line (the big line covered with black foam) and the liquid line attached to where I assume the metering orfice is located.(that big brass nut)
Making sure the existing metal is scraped and clean before attaching the sheetmetal patch is also important.
Good luck

darlingm 08-20-2011 06:53 PM

Thanks for everyone's responses. I'm going to go the route of sheet metal without screws. REP, also thanks, because vibrations/harmonics would drive us nuts!

Few follow-up questions.

Since looking at it a bit more today, I've noticed the liquid line is dripping water at a slow rate when the A/C is blowing. It seems to be leaking at that yellow'ish nut.

1 - Is the liquid running through that line just water, or does it contain freon?

2 - What's the best way to stop that leak?

3 - Haven't worked with thumb gum before. If I cut the sheet metal so it blocks most of the hole but doesn't touch either line, would Fire Block Great Stuff be just as good to use as thumb gum? I already have that, but could buy thumb gum if that was better. I'm sure a consideration is how easy whatever I do is to remove, if it needs to be some day. Not sure how removable thumb gum & Great Stuff area.

If I cut the sheet metal so it blocks most of the hole but doesn't touch either line,

beenthere 08-20-2011 08:22 PM

Don't use great stuff, it won't come off easy. thumb dumb it.

Missouri Bound 08-20-2011 09:52 PM

What you are probably seeing is the pipe sweating, the suction line would be cold, and condense. If you cut a piece of sheet metal in half, and install it from the inside, it will naturally be held against the furnace. A little mastic or perhaps duct seal around the pipe may work. It should be dry when you apply it.

REP 08-21-2011 01:02 PM

First what is running in those lines is freon.In through the small line and out in the large line.
Second the moisture you see feel on the brass nut is water that has condensed on the coil that the lines are connected to.
That is not a "leak" it is what happens when hot humid air hits something that is cold (i.e. that a/c coil)
Thum gum is like a piece of clay or a very dense play dough.It won't be any good for holding that small piece of sheetmetal to the metal plenum,but it will be able to fill the small gap between the copper lines and that small piece of metal.That is why If I did it I would use screws to hold that small piece of sheetmetal to the plenum.
Good Luck

hvaclover 08-21-2011 10:06 PM

I am a little concerned about that yellow coloration on the LL nut holding the piston. Is that leak trace dye?

hvaclover 08-21-2011 10:12 PM

I don't think that is a good idea. There is enough air coming out that line set hole to make a difference in other part s of the home

hvaclover 08-21-2011 10:16 PM

Quote:

Originally Posted by REP (Post 712180)
First what is running in those lines is freon.In through the small line and out in the large line.
Second the moisture you see feel on the brass nut is water that has condensed on the coil that the lines are connected to.
That is not a "leak" it is what happens when hot humid air hits something that is cold (i.e. that a/c coil)
Thum gum is like a piece of clay or a very dense play dough.It won't be any good for holding that small piece of sheetmetal to the metal plenum,but it will be able to fill the small gap between the copper lines and that small piece of metal.That is why If I did it I would use screws to hold that small piece of sheetmetal to the plenum.
Good Luck

Rep you are right. Thumb Gum is not made to close openings that size. Only used for sealing the line set opening of the line set in to the plenum.


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