View Full Version : Need help sealing duct box
09-02-2006, 01:15 PM
After crawling around in the attic recently, I felt cool air around the duct unit and figured I had leaks in the ducts. Well, it turns out it's worse than that. I'm no expert on what these things are called, but the big box attached to the furnace and blower with all the ducts running out of it wasn't sealed properly. On the bottom of the box is a gap almost 1" wide at one point that was left completely open and air is just pumping out of it. It's almost too big to try to put mastic and tape over it. I went to Home Depot to get some expandable foam to put in it but the "expert" there said that would make the unit sweat, plus I'm worried about how hot the unit may get in the winter. Expandable foam is combustible above 240F. This was a poor installation job and I'm ticked I'm just now finding it after almost 7 years. No telling how much this has cost me. Can anyone recommend the best way to fix this disaster?
09-02-2006, 01:31 PM
Not sure how that "expert" figure foam would make the unit sweat, it is an insulator not a conductor, therefore could not possibly sweat.
I would not reccomend using foam being that it is combustible and you dont want it getting on your blower or coil or anything else when it expands.
The right way to fix this would be to have a contractor come out and remove the whole "box" and seal it then securely fasten it to the air handler. And if the box is incorrectly sized or built you may need a new one made altogether. At the same time all of the connections where the round ducts come off of the box could be sealed properly as well (because they most likely are not now). Even if it costs you more doing it the right way, you will probably make your money back in the long run with energy savings, and have peace of mind knowing that you are not losing money into cooling your attic!
09-02-2006, 01:31 PM
I think you need more than just the gap sealed.
Hard to tell from the picture, but that looks like the connection between the furnace and the evaperator coil.
It also looks like the evaperator coil is very badly out of level, so it is sloped back away from the drains.
It looks like that emergency drain pan under the coil has water in it, possibly due to the coil being so out of level that condensate water overflows the back of the coils internal drain pan and leaks into the emergency pan.
Any time that sheet metal drain pan under the coil has water in it, you have a problem. With everything working normally, there should never be any water in it.
You need to get a competent contractor out there to have a look at the situation and correct it.
09-02-2006, 01:58 PM
Thanks guys for the quick response. There's no water in the tray, the photo just makes it look that way. We've never seen any water in it. I'm sorry, I don't know if that's the evaporator coil or not, but it is connected to the furnace. The line from the outside A/C unit comes into that box. And yes, it is out of level. I've been able to seal some of the ducts around their connections but that gap is the main problem. Any ideas how much a proper repair would cost? Thanks again for the quick responses and help.
09-02-2006, 02:39 PM
The coil should connect to the furnace just fine when it is all leveled up right. We cant really discuss price here but I would guess at paying maybe a days labor roughly, and some materials for sealing and screwing it all together. Also may take 2 techs to do the job of leveling it up, one to hold it in place while another secures it, also may take a couple of guys up there just to move it around. Probably not going to be a hard fix, but its really impossible to guess without surveying it in person.
09-03-2006, 03:26 PM
We managed to shove enough sealant in the gap and cover with enough tape to completely close off the gap until we can get a contractor out for a proper fix. I can't believe what a tremendous difference it made in the cooling effect in the house. For the first time ever in this house, we can now feel positive air pressure in the house. Before, you really couldn't feel the air moving around in the house that much, but now you can and the difference is night and day. Hopefully this will reduce our energy bills and substantially lower the dust content in the house as well. I'm still sick about the wasted money in energy bills I've spent in the last 7 years.
09-03-2006, 04:04 PM
[QUOTE]Originally posted by chainring
. I went to Home Depot to get some expandable foam to put in it but the "expert" there said that would make the unit sweat,
Don't believe the "expert" stock boy at the Depot. I hope you put metal across under the tape.Big difference a little sealing will make...
09-03-2006, 10:01 PM
for a jury rig that will do just fine. i would get it fixed right when you can afford it. you don't want any of your friends making fun of that mess.
09-04-2006, 03:21 AM
just mastik over it and be done, that is one poopy install, i would contact whoever did that.
09-04-2006, 10:16 AM
Have someone atleast look at it to make sure your coil is not going to flood out your attic. You have more air flow over the coil which means more condensate may be formed. Better to be safe than sorry. And he may see something else that could drasticly help. Call for a seasonal preventive maintenance and they give it a good once over.
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