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Old 07-26-2011, 05:42 PM   #1
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Standard Size return Air (Cold Drop) Kits


The largest size I can find on the web is 25 x 10. Almost all of the return static loss occurs in my drop & filter and I would like to open it up. When I temporarily remove the blower door access panel, I get a major improvement in supply air flow, especially in our upstairs bedroom which is the hottest room in the house (SW corner) and at the end of the supply duct. Do I have to get a custom made drop? Thanks.

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Old 07-26-2011, 06:37 PM   #2
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Standard Size return Air (Cold Drop) Kits


You can get a custom made drop and boot or put one 10x25 on each side of the furnace.

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Old 07-26-2011, 06:47 PM   #3
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Standard Size return Air (Cold Drop) Kits


What size A/C do you have?
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Old 07-26-2011, 08:13 PM   #4
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Standard Size return Air (Cold Drop) Kits


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What size A/C do you have?
3.5 tons.
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Old 07-26-2011, 08:48 PM   #5
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Standard Size return Air (Cold Drop) Kits


Use vanes, and the 10X25 should work ok. Will work better if the return drop isn't on the blower's motor side.
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Old 07-26-2011, 09:07 PM   #6
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Standard Size return Air (Cold Drop) Kits


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Use vanes, and the 10X25 should work ok. Will work better if the return drop isn't on the blower's motor side.
Thanks Beenthere - you are always so helpful. I have a 10 x 25 drop now with a 16 x 25 filter. Can I install turning vanes myself?
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Old 07-26-2011, 09:44 PM   #7
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Standard Size return Air (Cold Drop) Kits


Yes, they are hard to install.
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Old 07-26-2011, 10:27 PM   #8
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Standard Size return Air (Cold Drop) Kits


You say that when you remove the access panel to the blower you get more supply on the second floor.You said major improvement did you not?
I think that I might want to encourage that.I would do Two 16x25 boots .One on each side.I would do whatever I could to find (create) more return air grilles from inside the home.I was going to suggest you get a 25x20x10 return air boot but I think two drops are a better answer.
It won't be too big but it will definetely allow you to have the upstairs improvement in supply.
I know more work but also more comfort and more ecconomical use of conditioned air.
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Old 07-27-2011, 06:24 AM   #9
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Standard Size return Air (Cold Drop) Kits


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Originally Posted by REP View Post
You say that when you remove the access panel to the blower you get more supply on the second floor.You said major improvement did you not?
I think that I might want to encourage that.I would do Two 16x25 boots .One on each side.I would do whatever I could to find (create) more return air grilles from inside the home.I was going to suggest you get a 25x20x10 return air boot but I think two drops are a better answer.
It won't be too big but it will definetely allow you to have the upstairs improvement in supply.
I know more work but also more comfort and more ecconomical use of conditioned air.
Yes, by shifting the available static pressure to the supply side, I can substantially increase supply flow. Right now I have (in round numbers) total static across fan of .5" wc with .25" supply and -.25" return. By flooding the return I now have close to .5" on the supply. Since pressure drop is proportional to velocity squared, I estimate I am getting about 40% more supply and it certainly feels like that is the case. The temp drop across the coil isn't changing very much down from 20 to 18 degrees. Not sure if this is bad with too much superheat going to compressor? I don't have room to do two drops so I have to enlarge the one I have. Almost all of my return static loss is in the drop and filter so I am not worried about the number of return grills or return duct. Of course, when I open up the drop to get more return air, I the return grills and/or return duct could become limiting.

Would I have to get these larger return drops custom made?

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