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Old 03-09-16, 05:06 PM   #17
jeff5may
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Join Date: Jan 2010
Location: elizabethtown, ky, USA
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I have found in past experiments that sucking the unwanted air from where it doesn't belong yields better overall comfort. In a setup like Jake is testing, this means drawing cold air in at the bottom (through a large pipe if possible) and exhausting it at higher velocity up high. With a tall, open space like he has, major stratification happens pretty much no matter what you do. The laminar flow towards the suction line causes the air circulator to siphon the coldest air from the room naturally. When it is blown at high speed up top, lots of mixing occurs before the cooler air has a chance to drop. When it does drop, the "not so hot" air stratifies, it pushes the coldest air down to siphon its way into the circulator. This effect was addressed in another thread, titled something like "Cool your whole house with your basement".

In the summer, this method works well, too. In Jake's case, this is less of a problem, since his vaulted ceiling naturally collects the warmest air. Two houses ago, I wasn't so lucky. The finished attic "master suite" was horribly sealed and insulated, and was a sauna on sunny summer afternoons. A 1 ton window air conditioner wouldn't keep it cool. The first summer in that place was awful. By July, we had the 1-ton window unit in one end wall and a 3/4 ton unit in the opposite end wall. Combined with a 3 ton central air unit, all three would be running the electric bill up in a hurry.

What I ended up doing in that house will sound crazy, but it did the trick, keeping the 1 ton unit from running most of the time. I installed a squirrel cage fan in the lone floor register, which fed off the central unit through an 8 inch circular duct. I sent the hot air downstairs, running it backwards through the duct. I used a rubbermaid container as a hood for the assembly, installing some 6 inch flex hoses that extended up towards the ridge. I ended up running the blower on low speed, so that when the central unit kicked on, it would blow some cold air past my hack. When it shut off, the cold air went right back downstairs, followed by the warm air from the ridge.

On those same hot days, after my rig was installed, you could literally walk up the stairway and feel the cool air pour out and stratify into the room. The top of the cool layer was right about where the 3/4 ton unit blew its cool air into the other end of the room, about chest level. Quite a learning experience for Mama and the kids. That floor vent octopus might not have looked right, but there was no arguing it worked from anyone.
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