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Old 08-21-2010, 11:11 PM   #1
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Thermostat Placement and Blower Speed


Okay I am new to this forum but have been trying to understand how to most efficiently run my 2 A/C units and I don't think I have figured anything out.

My House:
  • Built 2004
  • 2100sq ft two story
  • 2 story foyer
  • Both return ducts in 2 story foyer, the 2nd floor overlooks the foyer so 2nd floor vents outside of bedroom actual cool the foyer.
  • downstairs a/c unit is smaller than upstairs
  • Live in Las Vegas Summer daily temps 110.
1. The thermostat placement has always bugged me but never been able to understand if there is a better place. There is 1 thermostat on each floor. BUT they are in the 2 story foyer, so 1 on the 1st floor, the 2nd straight above it on the 2nd floor just outside the master bedroom. My thought has always been the upstairs one is measuring temp when cool air drops to the 1st floor.
  • Would it make sense to move 2nd floor thermostat onto opposite all INSIDE the master bedroom?
  • The 1st floor thermostat is in the foyer as well, but should be cooling the downstairs area not the foyer, so 2nd floor runs and runs and cools 1st floor thermostat to turn off, then foyer is cool but rst of 1st floor is hot. Should that be moved as well?
2. Not sure if all systems work this way but when I close a vent the pressure in other rooms is greater, so that's how you balance it out. BUT if I wanted to move the 1st floor thermostat then I need more airflow into the other 1st floor rooms (family room and kitchen area), so I close the vents in the foyer. But when I do that the closed vents whistle which I cannot deal with that sound. Any way to stop the whistling vents?

3. How do I know if my system is running the way it should? Of course in the extreme heat it runs all the time, maybe 8+ hours/day. I only have it set to 78 and night and 80 in the day. When would I need a freon charge? anything I should check?

4. I have been reading about blower settings and thinking about checking the 1st floor unit for which wire is hooked up. My manual talks about checking temp differences first and how important it is. Does this only matter if you are turning the blower speed down? If I set them to high would it matter?


Thanks for reading, just have been trying to figure out this system since I moved in 3 years ago. Any help would be appreciated.

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Old 08-22-2010, 04:57 AM   #2
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Thermostat Placement and Blower Speed


Just move the first floor thermostat. Leave the second floor where it is.

Wait until the first floor thermostat is moved and has the first floor conditioned for a couple days before trying to balance the system any more.

In LV your blower should be running on high speed. You don't have much humidity.

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Old 08-22-2010, 09:51 AM   #3
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Thermostat Placement and Blower Speed


Okay that all makes sense but any idea how to stop the 1st floor vents from whistling? It's like mo matter what the pressure is closing even 1 vent in the foyer it whistles.
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Old 08-22-2010, 11:34 AM   #4
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Thermostat Placement and Blower Speed


Sounds like an undersized duct/distribution system.

After moving the thermostat. Open all registers. And see if you need to close any.

Will probably need to add one or 2. May be able to slow the blower to stop it. May not.
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Old 08-22-2010, 03:37 PM   #5
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Thermostat Placement and Blower Speed


Okay working on moving the Tstat today, but trying to make sure it will work in the fmaily room. the only Issue is for some reason th family room vent does not work like the rest, if I close other vents it should push more air to the other rooms, but the family room vent stays even. Its not pushing much air out at all.

Is there something else I am missing?
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Old 08-22-2010, 03:43 PM   #6
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Thermostat Placement and Blower Speed


The thermostat should be near a return.

Air takes the path of least resistance. So your family room vent apparently is a more restrictive path. And the air goes to other registers/vents instead.
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Old 08-23-2010, 01:10 PM   #7
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Thermostat Placement and Blower Speed


The AC requires 400CFM per ton for operation, if you can get the model number of the unit you can google the installation or service manual for the unit. If you do not have the proper tools for measure of the static pressure you can use .6"wc to .8"wc and check the chart to see if high delivers that amount or more. High CFM will cause the noises your speaking of as well as poor humidity removal.

Kevins
owner operator
lennoxoemparts

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