upstairs fells warm


Old 09-26-07, 02:37 PM
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Join Date: Jun 2007
Posts: 10
upstairs fells warm

Good day to all. I live in New Orleans and replaced both outside units and downstair air handler about 8 months ago. Both outside condensor units was stolen. About 2 months ago before moving back in, I reinstalled both outside units. Everything has been working fine untill about a week ago. Upstairs is starting to feel extremly warm to my family. The upstairs unit runs inside and outside and the lines are cold and sweating. At night it cools to a comfort but not cold. The unit also cuts on and off during the night only. The thermostat reads about 75-80 on a 84degree day and about 68-70 during the night but it never feels like it. It use to make you get under the blankets but now on top with almost nothing on. Filter was not too dirty but I changed anyway. I also went into the attic and checked the lines running into the air handler. The line is very cold. Just luke to cool air coming out of vents when I put my hands by them. I feel no restriction because the blower is blowing the air strong like it should be. I read a couple of forums and will note that there is no ice at the valves of the condensor unit. It feels and look the same as the downstairs unit about 2-3 foot next to it. Any suggestions would be greatly appreciated. I also swap the thermostat with down stairs. Downstairs still cold, upstairs no change. HELP!!!!
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Old 09-26-07, 02:44 PM
Join Date: Feb 2006
Location: USA
Posts: 929
Sounds to me like you have a duct problem. Most likely a return air duct is introducing warm dry air from your attic into the air handler, but don't rule out the ducts to the rooms.

Any chance the A/C was sized incorrectly when it was replaced?
Old 09-26-07, 03:47 PM
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Join Date: Jun 2007
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Hi mdtaylor. Thanks for the reply. I did upgrade upstairs a 1/2 ton more. The tech said this was ok to do after he look at my furnace to see if the pistons needed to be changed. I have a 3 ton goodman outside and a 2.5 ruud in the attic. The piston size in the ruud is 65. I also noticed just now in the attic since the house is quite a whishing - hissing sound like fluid or air going through the smaller line. I thought I heard a leak but notice the whole line was doing it after walking with my ears by it for about 15 feet. Any suggestions and THANKS!!!!
Old 09-26-07, 07:26 PM
airman.1994's Avatar
Join Date: Dec 2005
Location: VA
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Id say their is your problem. 3 ton outdoor with a 2.5 indoor. Not removing heat. Id start here and the duct.
Old 09-26-07, 08:37 PM
Ed Imeduc's Avatar
Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 18,389

Might check and see what the temp drop is over the coil at the coil. Next did they vaccum the system real good when it was open. Could be contaminate's and noncondensables are in it.
Old 09-27-07, 05:56 AM
Join Date: Oct 2005
Location: USA
Posts: 1,076
I'd have to agree, evaporator is 1/2 ton too small and it's flooded with freon. In such cases the coil cannot pick up heat. The cooling process works best when freon changes state from liquid to gas. If you measured superheat, I'd bet it's almost zero.

As far as noises, was the system purged with nitrogen? Was a deep vacuum pulled? Were the filter/driers changed?

It is possible (but not recommended) to get a 1/2 ton system mismatch (condenser too large) to work, but both an expansion valve and proper air flow are an absolute must.
Old 10-08-07, 02:01 PM
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Join Date: Jun 2007
Posts: 10
Thanks to all for your help. See a/c whishing sound next forum for an update.......

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