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Old 05-03-2012, 11:00 AM   #1
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Ac and upstairs


I have an AC unit that according to the home inspector when I bought the house is slightly to small for my house. After living in this house for over 2 years now I think I know why he said that. Its an old unit so we are just going to let it run out its life span and get a bigger one in the future.

Anyway, the upstairs of the house is always about 5 or more degrees warmer than downstairs. We only have 1 thermostat and it is located downstairs so it makes sense I guess. Is there anything I can do to keep the up stairs cooler without freezing the downstairs or paying a million in the electric bill? We have a split unit and the second part is in the attic with the main part being outside. Our 8 month old daughters room is always the hottest room in the house!

Edit: all the air vents are in the ceiling, upstairs and downstairs.


Last edited by nikeman; 05-03-2012 at 11:41 AM.
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Old 05-03-2012, 12:20 PM   #2
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Ac and upstairs


The quick and cheap way to handle this common problme is to block/close downstair vents (say 50%) and force more air go upstair. but do not block too much, it will hurt your A/C system. If just your daughter's room is hot, install another vent with a much bigger duct into her room. and do not close her room door or block the return air vent.

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Old 05-03-2012, 12:29 PM   #3
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Ac and upstairs


Move your thermostat upstairs, it actually must be close to where you sleep if only one is installed per house.

Do not worry about downstairs, cold air will be there anyway.

Last edited by sqslist; 05-03-2012 at 12:32 PM.
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Old 05-03-2012, 12:48 PM   #4
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The master bedroom is downstairs and the stat is right outside the door. I will try closing the vents partially since moving the stat sounds expensive.
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Old 05-03-2012, 01:10 PM   #5
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Ac and upstairs


vent the attic any load there in the summer is considered a load onto the system.do you have a return vent on the hallway wall up on 2nd floor if not it is getting pulled to the 1st floor vent...the more you can cycle the air on any AC system the more comfortable it will be...do not relocate stat .... work the air ...starve the 1st to push the air to 2nd...where is the air handler n the hottest of days the insultaed line at the furnace should be like a beer cold and the thin copper line out of the condenser should be warm if super hot condenser is dirty...shut off power /stat and wash with hose(lightly don't blast the fins) inside out especially 5" from the bottom.....selaing duct is a added trick...
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Old 05-03-2012, 01:30 PM   #6
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Ac and upstairs


Check and make sure you do not have any ductwork leaks, and if you do, seal them. Also, make sure the ductwork is well insulated, and the attic is well vented to reduce the attic temperature the AC unit is operating in.

If the unit is too small, you may want to buy a mini-split system or a window unit to add to the cooling power upstairs, and help balance out the temps in the house some.
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Old 05-03-2012, 03:12 PM   #7
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I have a return with air filter downstairs in the wall and one upstairs in the ceiling over the hallway. Will partially closing vents down stairs work even with a split system? All the vents are in the ceiling so I assume they are not connected to each other in any way. I saw a thing called a register booster but that would be a pita to have a wire running down the wall to plug into an outlet. The entire upstairs is hot but my daughters room is slightly hotter all the time. The attic is pretty well insulated from the tiny space I can get access to and looks to be insulated all the way across. Both upstairs bedrooms have crawl spaces for storage and when we open one of those doors it's like opening an oven on really hot days. I will get a picture in there. I think that there should be more insulation then there is and that might be I biggest problem area.
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Old 05-03-2012, 04:08 PM   #8
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Can be a pin in your butt to do. But, run larger supplies to your upstairs areas. Your system probably isn't too small, but your duct system probably is. Might want to check into making the return for upstairs larger, this will help increase air flow. Not just the return grille, but the duct also.
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Old 05-03-2012, 05:15 PM   #9
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Quote:
Originally Posted by beenthere
Can be a pin in your butt to do. But, run larger supplies to your upstairs areas. Your system probably isn't too small, but your duct system probably is. Might want to check into making the return for upstairs larger, this will help increase air flow. Not just the return grille, but the duct also.
Sounds expensive to me. Going to see how it goes closing off some downstairs vents partially. A few of the vents down stairs are already closed or almost closed though. Thinking one vent per room downstairs should be good.
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Old 05-03-2012, 05:39 PM   #10
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Also. Our attic is very small and can only be accessed through a small opening in the 2nd bedroom. The air supplier is right by the opening and the ductwork and PVC pipes take up the majority of the space. I can see all the way across the top of the house from there though, I just can't get up there. When I need new shingles on the roof I will have them vent it also. That won't be for a long time though since the shingles are only about 13 years old.
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Old 05-03-2012, 07:07 PM   #11
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This is a very common problem. Almost every house has this problem even some of them have 2 A/Cs. Anyway, here are your options: Close downstair vents, move t-stats, install larger duct and vents and returns for upstair, also make sure you have good insulation in the attic, install roof fan to bring down attic temp, deal with west side sun problem, etc....
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Old 05-03-2012, 07:14 PM   #12
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You can't simply install bigger ducts and expect the system to work properly. It's called cfm and static pressure which directly affects saturation, evaporation, temp drop and possible liquid returning to the compressor.

Only if the ducts are too small already and the system has a high static pressure will there be any wiggle room and even if so it'll more than likely only be one duct being up sized to the next size and that's it. And that's if it's on the supply side that you have a high static pressure.

If you want bigger ducts, you need a bigger system altogether. You can't just upsize the system without a manual J determining if the existing one is too small.
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Old 05-03-2012, 08:09 PM   #13
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I closed 3 vents completely downstairs and closed a couple partially. I do feel an increase in airflow coming out upstairs already so that's a good thing. The babies room is on the west side of the house so it's funny you mention "west side heat". So far so good, I'm going to see how it works out over a few days. It's supposed to be 90 degrees tomorrow so that's a good test.
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Old 05-03-2012, 09:12 PM   #14
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Quote:
Originally Posted by Doc Holliday View Post
You can't simply install bigger ducts and expect the system to work properly. It's called cfm and static pressure which directly affects saturation, evaporation, temp drop and possible liquid returning to the compressor.

Only if the ducts are too small already and the system has a high static pressure will there be any wiggle room and even if so it'll more than likely only be one duct being up sized to the next size and that's it. And that's if it's on the supply side that you have a high static pressure.

If you want bigger ducts, you need a bigger system altogether. You can't just upsize the system without a manual J determining if the existing one is too small.

The part I high lited in red, is not true.
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Old 05-03-2012, 09:13 PM   #15
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Ac and upstairs


Quote:
Originally Posted by nikeman View Post
I closed 3 vents completely downstairs and closed a couple partially. I do feel an increase in airflow coming out upstairs already so that's a good thing. The babies room is on the west side of the house so it's funny you mention "west side heat". So far so good, I'm going to see how it works out over a few days. It's supposed to be 90 degrees tomorrow so that's a good test.

Good luck.

closing off registers decrease total air flow though.

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