Cold Air Return


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Old 11-01-08, 04:06 PM
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Cold Air Return

We did not have any cold air returns on our 2nd floor so we installed one on the ceiling at the top of the stairs and another high above in our master bedroom.

My thermostat is on the 1st floor and I have a bigger air return on the 1st floor underneath the stairs on the low side.

Last winter, if I set the temp to 67, the temps upstairs is usually 3 - 5 degrees warmer but this year the temp is the same as downstairs. Is it because of the two high air returns on the 2nd floor taking out the warm air when it rises?

Is this normal? Should I block the two returns on the 2nd floor during the winter to get the temps back to 70 - 72 when the thermostat is set to 67 on the 1st floor. I really dont want to set the thermostat to 70 just to make it 70 upstairs too. Please advise...Thank you!

During the summer, the returns on the 2nd floor removes all the hot air and helps cool the house very quickly.
 
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Old 11-03-08, 04:31 PM
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You are correct.

The upstairs returns are allowing all the air in the house to be circulated through the unit.

Blocking the upstairs returns in winter is totally up to you, what makes you comfortable.

However the unit may run longer with open returns upstairs.

IMO, add dampers to upstairs returns. Close down (to about 25% - not off) in winter, open in summer.
 
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Old 11-03-08, 06:49 PM
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Why would the unit run longer with open returns upstairs?
 
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Old 11-04-08, 04:19 AM
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Because the unit will be able to move (and condition) twice as much air.

Test it out.
 
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Old 11-04-08, 07:43 AM
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So are you saying if I close one or both vents on the 2nd floor, the unit wont run so long and hard?

One reason I added returns on the 2nd floor is because I was told by HVACs my furnace did not have enough return air causing the unit to run longer and harder. With more return air, I would think it would run more efficiently.

For now, I blocked the return at the top of the stairs as a test. I'm just afraid if I block them both on the 2nd floor, I would be back to where I was last year with the unit running harder and longer causing my electric bill to be much higher.

Please let me know if I am thinking incorrectly! Thank you!
 
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Old 11-04-08, 10:16 AM
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If you start closing returns and registers, the furnace temp across needs to be measured to make sure you aren't stressing the limits of the heat exchanger. Your ID plate on your furnace should give you a number that it should be running within acceptable range.
 
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Old 11-04-08, 02:42 PM
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I ment to say without open returns.

You want to have returns upstairs to move air around the house. But if you close them down a bit in winter more warm air will stay up there. Which was your original question.

As I said, what ever makes you comofrtable.

The furnace will run just as long and as often to keep the temp 68 or 70.
 
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Old 11-30-08, 08:14 PM
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I placed those magnet covers on both 2nd floor vents to fully cover it but the 2nd floor temp is still the same as the thermostat where last year it was 3 - 5 degrees warmer on the 2nd floor.

The 1st floor seems to be warmer than the 2nd floor. There are sections on the 1st floor with readings of 71 where the thermostat is at 68.

The only other difference I can think of is the room right below our master bedroom has two vents that I completely shut because we do not ever use those rooms and I did not want to warm a room that we do not use. Will the missing heat in the non-used room below our bedroom make up the difference? Can heat from that non-used room penetrate through the ceilings and through our bedroom floor warming it an extra 3 - 5 deg. That would be amazing!
 
 

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