Underperforming AC


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Old 08-02-11, 11:47 AM
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Underperforming AC

I have a similar problem... I live outside of Dallas,TX and it's been pretty warm lately. I just moved into this house that was built ~5 years ago and has 3 AC units. One of the units seems to be running all the time, but usually in the morning up and until around noon will keep the house at the set temperature of 77. However usually sometime after noon the temp will slowly begin to inch up to around 84-85. I initially had a HVAC guy out who tested it and thought the freon level and pressure readings at the compressor were appropriate and told me to clean the compressor which I did. However that didn't fix the problem. So I ended up deciding to call a different HVAC guy (b/c this last one couldn't seem to figure out the problem). The new guy came out and said he thought the freon level was a little low so he added 2 lbs of freon, but that didn't fix the problem either so I had another guy from the same firm come out and he said every thing checked out and the unit is too small for the area it is suppose to cool. However I have a problem with that diagnosis... the house is new and I'm pretty sure they would've checked for the appropriate HVAC sizing. Additionally last night I woke up in the middle of the night and the temp in the house was 84 still (outside temperature was about the same or maybe a little lower) and the unit was running but it was blowing air that was only mildly cool, definitely not cold. This morning at 7am it was still reading 82 in the house and about the same temp outside. Additionally whenever I go over to the condenser coil when it is running and put my hand above the fan the air doesn't feel very warm... rather just about the same as the surrounding air. Any ideas or suggestions on things I should check? Thanks
 
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Old 08-02-11, 11:57 AM
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Welcome to the forums

I moved your question into its own thread to increase visibility
 
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Old 08-02-11, 06:49 PM
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the compressor may not be starting every time. It may need a hard start. When you notice the unit is underperforming check the evap coil (inside coil) for ice. Check the large insulated copper line for ice (check both inside and outside) and feel how cool it is. Should be beer can cold. The small line should be outside temp to 10F higher than ambient outside temp. Make sure your filter is clean. Your run capacitor may be going out in the outside unit. Check for bulging or swelling.

There a whole bunch of things that potentially could be going on. The main thing would be that you apparently have not found a quality contractor yet.
 
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Old 08-02-11, 08:05 PM
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Bs new homes are almost never sized correctly maybe only 10% are correct.
 
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Old 08-03-11, 09:35 AM
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Thanks hvactechfw.

I've already recently replaced all the ceiling AC filters. The previous ones were dirty but not that bad. I'll check the temperature of the lines tonight.

Is there a way for me to check the run capacitor? I'm not familiar w/ what that is. thanks
 
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Old 08-03-11, 03:25 PM
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Cheaper to replace the capacitor than purchase a meter that will check its value.
 
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Old 08-03-11, 05:12 PM
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Where is the air handler? I am guessing it's in the attic in your area... Are there any duct that came undone, or insulation that not on the duct or came undone, or poor attic vent/air flow.

3 units in a home seems to be a large house? Are the others keeping up?
 
 

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