# Attaching plenum to furnace.



## hartkem (Oct 4, 2008)

I have my Trane XR90 wired and gas hooked up and I am ready to start the ductwork. Being this is my first install I am somewhat confused on how to install a plenum to the furnace. I am using a downflow in the horizontal configuration in the attic. On the inlet side there is a 1/2" or so flange that it looks like I could use sheet metal screws to attach a plenum. In order to do this the size of the plenum would have to fit around the flange exactly. Is this correct or is there a better more common way. Also I wasn't going to install an A/C coil but I may be changing my mind so I can add a/c later easier. The supply air side doesn't even have a flange. The metal is just bent at a 90 degree angle at the bottom and is completely flat. How can you attach a plenum to this? If you could somehow put a screw in from the inside of the plenum you cold go into the 90 degree bend of the metal. I think that if I were to install a coil on the furnance the outlet of the coil has a flange like the inlet air side. Is the furnace not intended to but used without a coil? Thats for your help


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## Sin (Nov 10, 2008)

Yes you use sheet metal screws to attach plenum. It should also be a good fit. I purchased a plenum at Menards 50 bucks maybe other home centers will carry them. These plenums you then cut to fit. Leave a little room for adding these. S-Cleats. They come in a long stick that you cut to fit. 

http://www.audubonsupply.com/browse.cfm/2,156.html

They'll add a little support and beef up the sheet metal a little. That top cleat on that page is for fitting a run of two square ducts together. This shows what the plenum will look like. You'll need to cut to fit.

http://www.audubonsupply.com/browse.cfm/2,155.html

http://www.ductworks.net/xcart/home.php?cat=82&sort=price&sort_direction=1

Also used those s-cleats to attach inlet side. 
Not familiar with AC coils. Good luck. That working with sheet metal
was the only hard part of installation. Wear some good gloves when working with sheet metal.


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## 1610 CUB (Jul 19, 2008)

hartkem said:


> I am using a downflow in the horizontal configuration in the attic.


I don't think you can do that?!:no:


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## hvaclover (Oct 2, 2008)

_ could be wrong but I think a dedicated down flow cannot be used in the horizontal position. Did you check the *instructions*​ or did somebody just tell you it was OK?​_


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## RippySkippy (Feb 9, 2007)

1610 CUB said:


> I don't think you can do that?!:no:


Sure he can....http://www.advancedenergyconcepts.com/documents/XR90FURN-01.pdfhttp://www.gotrane.com/Commercial/Uploads/Pdf/1112/tux_c.pdf and http://www.tranesystems.com/residential/products/furnaces/XR90-Furnaces#


OP you might see if you can get the A coil cabinet and install it at this time rather than having to re-do your tin work later. 

I don' know the name of the item, but when I installed my furnace, I had a local shop make a bellow (sheet metal connectors on each side of a flexible section in the middle) that goes on each end of the air handler to isolate it from the rest of the duct work, and it provided a bit of give when installing everything.


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## 1610 CUB (Jul 19, 2008)

All I see at the web sight is up flow/horizontal and down flow/horizontal. Nothing said about no upside down down flow! Check your model number and make sure


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## hartkem (Oct 4, 2008)

Yes the downflow can be used in horizontal. I have already went through the steps to convert it so the condesation drain flows correctly. I wish I had more experience with the S cleat and drive cleat. How close does the size of the plenum have to be to the size of the furnace outlet?


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