Can I eliminate two returns without causing big problems?


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Old 08-18-08, 10:30 PM
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Can I eliminate two returns without causing big problems?

I have one zone in my house where I have 4 bedrooms and 3 baths and a long hallway. The air handler is up in the attic and each room has a separate return and supply.

The problem is that the air handler is located in the middle right above a bathroom. At first I did not know why that bathroom has such low ceiling (6') when the rest of the rooms are at 8'. I removed the sheet rock and could see what is going on, I did a sketch below to illustrate:

http://i173.photobucket.com/albums/w...pub/acduct.jpg

Since the return connections are off to one side, the returns from the other side has to find a way to go all the way around. All the ducts are sheet metal with sprayed foam insulation except the blue section is a "coiled" duct about 16" in diameter that goes below the air handler and back up to connect to the opposing side. I checked and there is no room in the attic to pass the coil any other way. I think this is why it was done this way and then a low drop ceiling was put in.

My question is, do I really need 6 returns for that zone? If I eliminate the coiled duct I could get rid of the drop ceiling but I will be eliminating two returns. Is that ok?

What other options do I have? If I cannot eliminate it, can I fabricate some rectangular sheet metal duct to closely "hug" the bottom of the air handler, to have a very wide duct but minimal height so at least I can increase the ceiling to 7'?

Any thoughts or suggestions would be greatly appreciated.
 
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Old 08-19-08, 07:39 AM
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Hello there.

Some pros will be able to give you some more ideas, but my first thought is it is not a good idea to pull those two returns. You need a specific volume of air to be pulled across the A/C coil and whatnot in your air handler for the system to function and for maximum efficiency. Additonally, you want to be pulling hot air from those rooms while giving the fresh cool air at the same time.
 
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Old 08-19-08, 08:27 PM
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I understand. So if I close off two returns, I might be restricting flow to the coil and cause problems.

I wonder if there is a way to determine what volume or flow rate the coil needs and just back track what flow I have going in just to see if currently it is within design specifications, and more importantly if I close off two supplies, how much air it would be off by, and from there, may be I can determine if a new return in a hallway may be able to compensate.

Are there "AC tech" that does just analysis and no selling? I just talked to another one today and he is again just a salesman.
 
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Old 08-20-08, 07:00 AM
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Look around Better Business Bureau, ask friends, etc. for contractor recommendations. It can be hard, but at some point you should find more of a technician instead of just a salesman.
 
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Old 08-20-08, 09:27 AM
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Air Conditioning Repair

Rather than lower th ceiling that much square duct should have been med in the first place to get maximum headroom the last time I saw a 6 foot ceiling was in an old farm house you will need some professional help as you are going to need to calculate the size duct you need for your system if you down load this Ductulator you can type in your info and it will give you the required duct sizes just remember you need at least 400 cfm for every ton of cooling this unit provides
 
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Old 08-20-08, 08:52 PM
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Don't close those returns, return duct is important. Your 7' design should work. make sure your duct(area) size is same as the 16' coiled one.
 
 

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