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Discussion Starter #1
I'm wanting to finish my partial basement (300 sq.ft.) to make an extra den living space, but have some low ductwork that I need to move in order to get the right ceiling height.

As you can see in the photos, there are two ducts dropping down from a cold air return that connect to the unit. What I want to do is patch the current connections and take the duct from the front of the return, go straight off the return into the crawl space on the left, follow along the framing in the crawl space, exit in the joists above the bottom of the stairs, and run an elbow down and into the top of the return in the unit (see photos and follow the red line to get an idea of what I am saying). This would be my ideal situation as all ductwork would then be in the joists.

My second option would be to run an elbow at the current unit connection up into the joists and run the ductwork across and through the joists (through each triangle section support) and into the side of the return following its current path. This is less ideal as I would at least have a soffit near the unit where the elbows are...but the ducts would at least be up in the joists.

Any problems with either option? Also, why do they have two ducts coming off of one return going into the unit? Can I use only one duct with either above option? Thanks.



 

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from your pics.. I can't see any reason as to why you can't move it to the end. As to why they used 2 .. They needed that much air .. If you only use 1 you will have to use a larger pipe . If your return has a divider...You will have to use 2 or take out the divider
 

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There is a science to duckwork. Go get a copy of ACCA's Manual D from your library and you will see what I mean.

Here's my thoughts:

Option 1: If I understand correctly, you can do that but adding another elbow or two will increase the static pressure of your return somewhat.

Option 2: Would be the same straight shot but in fact reduct your static pressure (good). But I am not sure you can pass the same sized ducts through those joists, at least I can't tell from here.

Whatever you do be sure to have the same cross sectional area of those two ducts (or more). Whoever designed your system clearly needed that volume of air.
 

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Discussion Starter #4
Thanks for the posts. The duct will fit throught the joists (see duct in first pic at top left). I might patch some metal on the side of the return since there is currently only the silver cardboard of the return on the sides and run the two 6" ducts out the side following the same path as now, but drop them into the top of the unit...if you imagine a rectangle, currently the path follows the right and bottom sides of the rectangle where the new path would follow the top and left sides of the rectangle.

Thoughts?
 

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Can't really imagine what you are describing. A diagram, or scanned written diagram, or mock up of your photos helps a bunch.

Regardless, if you can pass both ducts thru your joists that sounds like the preferred approach as you have little risk of increasing your static pressure.
 

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Discussion Starter #6
Can't really imagine what you are describing. A diagram, or scanned written diagram, or mock up of your photos helps a bunch.

Regardless, if you can pass both ducts thru your joists that sounds like the preferred approach as you have little risk of increasing your static pressure.
Thanks again for the post...here's a diagram of what I mean. The only issue I can forsee would be the return is not totally encased in metal (silver cardboard-like material on sides), so I would have to tac on some for the connection on the side of the return (where the red duct path meets the return in diagram) or also replace the entire return with a full sheet metal return. Thoughts?

 

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Okay, I understand you return sides are not sheet metal but perhaps duct board. Yes, just replace those sections with sheet metal. You may be able to just slide the sheet metal over the duct board. Get a bucket of duct mastic to seal all the small leaks and odd edges that may leak. Can't think of any other issues.
 

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Discussion Starter #8
Just wanted to thank you for the responses...I was able to move the duct work this weekend. I used two collars and connected directly to the ductboard with U181 tape to seal any leaks. Photos are below.

 
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