5 ton AC unit not blowing cold during hottest part of the day

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Old 08-06-15, 04:15 PM
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5 ton AC unit not blowing cold during hottest part of the day

What is causing my 5 ton AC unit to stop blowing cold after it has been running for a while? I feel the return Freon line at the outside unit and it is not cold although the fan on the outside unit is running. I live in South Louisiana and it is very hot and muggy every day at this time of the year. The AC does not do this in the evening or at night only during the hottest part of the day (in the afternoon). Could it be low Freon? Do I need to get a larger unit? My house is 2600 ft square 2 story one AC unit for up and downstairs. I recently replaced the thermostat - it works fine. Any ideas would be greatly appreciated. It is an older Freon 22 unit.
 
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Old 08-06-15, 08:20 PM
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Is the small copper pipe almost too hot to hold or is it around 9 above outdoor temperature when it fails to cool?

When is the last time the outdoor coil was rinsed?

I would also see if the return air ducting is leaking in hot air.
 
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Old 08-07-15, 05:16 PM
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I rinsed the outside coil a couple weeks ago - used coil cleaner. I also cleaned the evaporator coil recently. The copper Freon return line does not get hot - it is ambient temp when it stops cooling. When it stops cooling I bump the thermostat up a degree so the unit cuts off - when it cuts back on it cools normally. I checked the return air box and it is tight. Thanks for your help! THe outside unit stays in the shade throughout the day. Any more ideas? Thanks!
 
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Old 08-07-15, 06:33 PM
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Any return air leaks?
Is the indoor unit in the attic?
 
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Old 08-08-15, 03:33 PM
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The indoor unit (evap coil) is in the second story attic with the return air in the second story ceiling. I have checked for leaks and found none in the return air. I am at a loss. As long as I keep the thermostat on 79 the AC unit cycles normally throughout the day. It is when I drop it down any cooler (78 or below) that it will run a long time and start blowing un-cooled air as if the compressor is not on even though the outside unit continues to run.
 
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Old 08-08-15, 03:44 PM
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A digital thermometer used at the intake grill, at the furnace intake, and at the supply air plenum may shed some light on the cause.
 
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