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Old 04-24-2013, 03:51 PM   #16
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Originally Posted by ang1dust View Post
I have too much supply is 1 problem. From calculations i have over 2200cfm supply
i have
4 - 8 inch supply for bedrooms
1 - 6 inch for stair well
3 - 4 inch supply for 3 bathrooms
1 - 22x14 plenum going down to
2 - 8 inch split for the kitchen
1 - 8 inch for the dining room
1 - 8x11 inch for the living room (this is set up to be 8x16 wide but i cut it down becuse i ws getting no cooling up stairs and i put a 5 inch peice of sheet rock to cut it down but it blows about 25mph (i dont know the equivilnt of fpm) so downstiars gets so cold so fast) But it doesnt get cold nearly as bad during the day...If its over 92ish degrees outside i have to set my thermostat to 80, if its abour 98 it needs to be about 82, any higher it should be about 84 otherwise my AC runs for HOURS trying to get it down just half a degree....

so a quick explanation of this setup to give a visual
2 bedroom house, built on a square
there is a center to this house that it is bluit around so you can walk in a circle on both levels

the HVAC is in attic, it distributes horozontally to an T fashioned plenum that pushes air to the upstairs through an L fashion but the upstairs makes it a T pushing 4 8" and 2 4". This is all in the Attic and its return is upstairs and is about 90 feet long.

did i miss any details?

Your probably far closer to 1350, maybe 1430 CFM. Then you are to 2200 CFM.

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Old 04-24-2013, 03:55 PM   #17
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Turn on A/C. At a supply register with some what ow air flow. Hold up a tissue, walk away/move the tissue from the register until it stops moving from the registers air flow. mark that spot. Remove the air filter and return register grille. Repeat test and see if the tissue moves from air flow from that register at the spot it stopped at earlier. If it does, then you aren't moving anywhee close to the amount of air you thought.
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Old 04-24-2013, 05:25 PM   #18
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Your probably far closer to 1350, maybe 1430 CFM. Then you are to 2200 CFM.
could i ask you to break down your number based on the info i provided of my supply?
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Old 04-24-2013, 05:41 PM   #19
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8" max of 200 CFM per.
6" max of 70 CFM.
4" 30 to 40 CFM per.
8x11 500 to 550 CFM.


Did you try that test yet.
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Old 04-24-2013, 08:24 PM   #20
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8" max of 200 CFM per.
6" max of 70 CFM.
4" 30 to 40 CFM per.
8x11 500 to 550 CFM.

8 inch - 200x7 = 1400 (4 upstairs 3 downstairs)
6 inch - 70x1 = 70
4 inch - 30x3 = 90
8x11 - 8x11x1= 550

total = 2110 cfm

havent tried test, im not home yet i will tonight
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Old 04-24-2013, 08:30 PM   #21
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Thats the max they will carry(and not be noisy). Not what they are actually carrying in your system. Your 4 ton blower can't move that much air.
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Old 04-24-2013, 08:34 PM   #22
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Right thats why im saying my retrun is under powered to begin with and why i closed off the 8x11 hole - you see why i know my supply is too large for my system at 2200 ish?

Last edited by ang1dust; 04-24-2013 at 08:39 PM.
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Old 04-24-2013, 08:39 PM   #23
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Right thats why im saying my retrun is under powered to begin with and why i closed off the 8x11 hole

Its not that your return is causing all this trouble.

When you do that test. You will have removed .1" of resistance to air flow in your return. See if that makes a big difference or not.
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Old 04-24-2013, 08:46 PM   #24
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Ok ill try it and report back tonight or tomorrow
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Old 04-25-2013, 03:40 PM   #25
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Originally Posted by beenthere View Post
Turn on A/C. At a supply register with some what ow air flow. Hold up a tissue, walk away/move the tissue from the register until it stops moving from the registers air flow. mark that spot. Remove the air filter and return register grille. Repeat test and see if the tissue moves from air flow from that register at the spot it stopped at earlier. If it does, then you aren't moving anywhee close to the amount of air you thought.
So I am here at the house. I am attempting the tissue test but I must say, before the air turned on I dropped the tissue. It fell to the ground and on its way to the ground it floated about 2 feet away from the grill... I did it again and it dropped straight to the ground. I want to say this test is not going to be very accurate.
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Old 04-25-2013, 06:24 PM   #26
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there is no real scientific way to know if changing the filter setup will help. you may see turning vanes in return ducts and that is to direct the air in to the fan properly so it does not cavitate. doing your 2 filter setup may cause a weird turning effect and not direct the air properly into the fan and could unbalance it. depleting your cheqing account is more a matter of the unit having a worn compressor or low on freon or your house insulation/door seals/attic seal/windows/curtains/shade trees. all those make a huge difference. reducing "strain" won't make your AC cool better just save a bit of elec $$ on the motor. if your airflow was too low now the evap coil would freezeup and if it was way too high then water would blow off the coil and it would not drain properly and would whistle. doubt the 2 filter setup will change much but it makes for a good experiment.
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Old 04-25-2013, 06:25 PM   #27
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You hold it in the air stream, and watch it as I said. Dropping it won't tell you much, if anything.

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