Central A/C blows air on the 3rd floor, but barely on 2nd and 1st.


Hi,
My central air unit is on the 3rd floor. When it's on, the air flow on the 3rd is tremendous and it becomes cold in a second. At the same time, the air is barely coming out on the 2nd and the 1st floors. The ducts are old, but I inspected the parts that are accessible and they seem to be intact. What could be the problem here and what should I try next?
Many thanks in advance,
Aaron
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Check for closed dampers. If they are open, check for broken ducts, or perhaps close the ducts partially on the 3rd floor to redirect some of the air to the floors below.
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Mikepier wrote:

I second that!
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Moe Jones
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On a somewhat unrelated note, I heard that if one is not careful and closes twoo many vents, it can burn out the A/C unit. Is that true?
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No, but it can be hard on the blower motor.
s
On a somewhat unrelated note, I heard that if one is not careful and closes twoo many vents, it can burn out the A/C unit. Is that true?
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Steve Barker DLT wrote:

Hard on the compressor as well. With less airflow passing through the equipment, the evaporator will become flooded with liquid, hence the compressor may blow out.
--
Zyp



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Aaron Fude wrote:

Not burn up the A/C but if you do close off too much air flow you could cause your A/C to ice up and cause the refrigerant to flood back to your compressor and knock out the compressor valves.
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My furnace/AC is in the basement - where it belongs! :-)
Anyway, every season I rebalance the ducts so that more cool air goes to 2nd floor during the cooling season and more hot air goes to the first floor during heating season. Cold air sinks, hot air rises.
Partially close some of the upper vents to force more air downstairs, but keep in mind that whatever cool air comes out of the upper vents will also add to the cooling of the lower floors as it sinks.
The ideal case would be electric dampers tied to a central controller which takes input from three thermostats and continuously balances the system as the air rises and falls.
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More details would be helpful-- had the unit been ok and this problem suddenly occur, has it been this way all along, or did you just move in this summer? What are the ducts-- flex, ductboard or sheet metal? You say that you checked the accessable ducts. If there is a problem with them, you can almost bet it will be where they are least accessable. Murphy's Law! Larry
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