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Old 07-13-2011, 10:21 PM   #1
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Upstairs Cooling Problems


We have a 3200 square foot home and have been having issues since we moved in. First, the house was originally wired up to a 4 ton unit that heated and cooled the whole house. Later, someone added a 3 ton unit for the downstairs. The 3 ton unit uses flex duct in the crawl to heat and cool. This unit blows great and heats and cools quick. The 4 ton unit that use to do the whole house has what I think is flex duct running throughout the house. It is hard/impossible to see this ductwork because of the way it was set up and it doesn't run through the attic upstairs. So we have vents at the ceiling of our downstairs, and vents at the floor of our upstairs that all come from the 4 ton unit setup. I blocked off the ceiling vents downstairs (because the 3 ton unit takes care of downstairs and has registers in the floor.) using magnets and simply closing them. The air coming out of both downstairs unit and upstairs unit is around 60 degrees in the summer. The difference is in the air pressure. Downstairs (3 ton) blows very hard and is awesome. Upstairs the air doesn't blow hard at all in some spots and average in others. I decided to add a return air to the upstairs unit because it was pulling from a small wall cavity and it was like a kink in a hose, the unit wasn't getting enough return air. So I designed a steel box in the attic and connected all of my returns to it, and then did the same where they go into the furnace. This helped very slightly... We also decided to have a company insulate the attic just recently to bring us up to a R45 which is what the region calls for. They used a new fiberwool insulation. Our 4 ton unit used to run all day and still couldn't get the temps down upstairs until 3 in the morning! Now, the temps are lower than they were, but our unit still runs all day trying to keep it at 76 in the summer. I am lost as to what the hell is going on. If it is my ductwork, wouldn't I have to start tearing up the ceiling to access it? And why can't my house cool itself down upstairs? Should I install an attic fan or two up in the attic? I'm just very frustrated with this situation because that 4 ton unit should be able to do the job up there. My 3 ton unit blows so much harder! HELP!

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Old 07-13-2011, 10:36 PM   #2
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Upstairs Cooling Problems


- to fix your problem you need to do load calculation so your system will be balanced for these 2 units
- better insulation and air circulation in the attic.

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Old 07-13-2011, 10:39 PM   #3
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Upstairs Cooling Problems


Well we have just added the insulation, so that shouldn't be the issue. We have 18 vents in the attic. But they are just the mesh ones. Do you think I should install some automatic attic fans on t-stats? I think I have a lot of leaking coming from somewhere because it should be blowing a lot harder than it does out of those vents upstairs. How do I get the test that you talked about done? And how much does it cost?
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Old 07-13-2011, 10:43 PM   #4
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Upstairs Cooling Problems


http://www.hvaccomputer.com/
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Old 07-13-2011, 10:53 PM   #5
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Upstairs Cooling Problems


This is my setup
Upstairs Cooling Problems-hvac.jpg
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Old 07-13-2011, 11:02 PM   #6
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If I start talking about things now I'll be assuming. We need numbers to help better.
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Old 07-13-2011, 11:05 PM   #7
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Upstairs Cooling Problems


so i need numbers using that calculator progam? I am not very HVAC savy, so I dunno how well I can help you help me haha. It is really weird because my unit looks like it doesn't use flex duct upstairs, but when I got into the attic via closet I saw a flex duct feeding a downstairs ceiling register. But I felt cold air around it as well. I bet it is all messed up but I feel like the only way to get to it is to tear open the dry wall and start fixing it one at a time which will be basically tearing up my entire house!
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Old 07-13-2011, 11:25 PM   #8
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Old 07-13-2011, 11:27 PM   #9
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Upstairs Cooling Problems-house-demensions.jpg
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Old 07-14-2011, 04:36 AM   #10
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Upstairs Cooling Problems


Remove blower panel of 4 ton unit. By pass safety switch, run fan, see if air blows out better. If so, you still have a return problem.
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Old 07-14-2011, 10:38 AM   #11
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What do you mean by by pass the safety switch?
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Old 07-14-2011, 11:07 AM   #12
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Upstairs Cooling Problems


Most systems have a switch that prevents the system from running if a panel cover is off. You may have to have someone hold it in or jump the switches' terminals to keep it running.
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Old 07-14-2011, 06:10 PM   #13
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Upstairs Cooling Problems


my air blows very very slightly better with the cover of the return blower off. But it isn't a huge difference. It is 81 outside but only 80 upstairs with ac blowing and set at 75. it has been running almost all day. the temp coming out of the vents is 59. I just don't get it... I don't know what is going on. We even added a return duct to the furnace and everything. I put paper up to the returns and it sticks to the vent. It just seems like it is working really hard just to cool it and it can't catch up or something. We just had the attic insulated so I don't know why this is happening. Can anyone else help?
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Old 07-14-2011, 06:48 PM   #14
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Upstairs Cooling Problems


Sounds like the supply is under sized then. Anyway to run an additional duct for the supply. To perhaps the fartherest rooms.
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Old 07-14-2011, 07:47 PM   #15
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Upstairs Cooling Problems


Looks like Delta T is 16.....low

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