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Best product to "seal" access panel in hvac duct?

7K views 33 replies 3 participants last post by  Doc Holliday 
#1 ·
What would be a good weatherstrip type of product to seal up an access panel in a square duct? This panel would be opened and closed here and there so it cannot be permanent. Something that will keep air and temps within the duct. Thanks for any help. -Mike
 
#2 ·
If you have an actual hvac access panel (they are made in 6" x 6", 8" x 8" and 10" x 10" and I think 12" x 12") than the only sealing you need to do is around the rim. You can use foil tape or hardcast mastick. Between the removeable door and the rim that is cut into the duct and will remain there is already a seal and in the door itself is insulation.
 
#9 ·
Thanks. No links to the original two pics?

My main goal is to create a bypass where I can block off airflow to my first floor and redirect it to the basement. I thought the best way to do that would be a door that when open stands up straight and cuts off airflow so it all comes out the opening that remained when it was lifted. Not sure if that will be possible unless I make my own.
 
#10 ·
Okay, now we're getting somewhere. Redirecting air would be adding a duct line (to your basement) and using dampers to balance the air internally. What a damper is is a door that sits directly in the duct, right at the plenum, that you can close or open, cutting off air flow to certain areas while forcing the air (in greater velocity) elsewhere. You can slightly close it off or close it off all the way.

Do you have a duct running to your basement now? Why not simply run a duct straight off of the plenum to the basement? Are you trying to tie into a duct line or the plenum or is this line to the basement already there and you simply need more air through it?
 
#13 ·
I know about dampers, but they won't work exactly how I need them to since they are more like a throttlebody. I need a diverter. I could use a damper and an access panel in conjunction, but I've had trouble finding rectangular dampers.

This is the main trunk line to my first floor. It runs along the ceiling of my basement and is 12x18. I want to heat and cool my basement using this line. So I need to completely cut off airflow to the basement when not using it so that I can heat and cool the first floor without leaking air into the basement. I also need to able to completely or mostly block off air from going to the first floor while sending air to the basement.

If I just added another line to my basement then the air would still be shooting upstairs. Plus I'm also adding another "door" for the return.
 
#17 ·
Hey, no problem. That's why we're here.

The flex line, right where they take off from the metal trunk line, is where the dampers go. You can find them in each size for each flex duct.

Is there already a flex line going to the basement or not? I have a feeling all you're really going to have to do is add one run to the basement from the trunk line and then, if the air flow is not strong enough, add dampers to balance the air.
 
#19 ·
Why do you need to shut off all of the air to the first floor, when you want heat in the basement?

As Doc said, a separate line for the basement. plus add a damper in the trunk that goes to the first floor, and one in the trunk that goes to the basement. open and close them as needed.

You could also then, add a zoning panel and use motorized dampers, that opened and closed automatically by thermostat control.
 
#20 ·
I want full control. If I'm heating the basement I don't want to have to heat the first floor. There are times when the basement may be cold and upstairs is hot. Right now it's 75 on my first floor and about 50 in my basement.

And as mentioned earlier, I would love to put a damper in the main trunk, but can't find any that are 12x18. Plus the door would still need to be there because I'll have to seal off the basement sometimes. Adding a line from the trunk is just adding extra work and cost for the same final product.
 
#22 ·
Sorry for the crap pics, Photobucket changed the res plus I think they were blurry to begin with.

Left side trunk is the return. Right side is the supply. I would like to put the register before the flex lines split off before the i-beam. The return would have to be as far as possible from the register I imagine so over in the left corner.
 
#24 ·
12X18 would need to be made up by a shop. Local fab shops can make one for you. Same with your door idea.

Zoning it would make it so that each floor is controlled independent of the other. While more money and work up front. Its no work when you want to use the room.
 
#26 ·
Though there is a damper that is like blinds where the slats rotate. I would need to put one in the bottom of the duct and one in the duct. I'm sure they don't have an airtight seal though.

I was thinking if the duct is say 18 inches wide on the bottom. I could cut a 16.5x16.5 hole and then put maybe a 17 and 3/4" door in there with rigid or soft foam around it to form somewhat of a seal when it is upright. Maybe use a magnet in the duct to hold it open. i would still have a lip in the bottom of the duct to screw the door down to. maybe with wing nuts or something. It will be a pain to open and close, but since it's just the basement, temps don't normally call for heat or ac.

Also was thinking I could make the hole longer, maybe 17x24 or whatever to keep the backpressure down. Don't know how to calc it, but I'm sure the system blows stronger to get air upstairs through multiple lines than it would to just blow out the main duct 10 feet from the handler. So maybe making the hole bigger would keep stress off the sytem and cool/heat down there faster.

Thoughts/ideas?
 
#27 ·
Are you going to do the same with the return? If your going to put all the air to that basement room, then you need to have as much return as you have supply.
 
#29 ·
Yuppers, I'd zone the system. Probably have to reconfigure the ducts to accomodate but that's the best (and most importantly design specific) method to heat/cool one area and not the other if that's what you're wanting to do.

Two or three, even up to four thermostats for one sysem.
 
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