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Old 07-11-2011, 10:53 PM   #1
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Lennox 12ACB48 - Help


Hello,

I recently purchased a home with a Lennox 12ACB48 unit. The unit would not cool very well so the sellers had it serviced and freon was added and fan motor replaced I believe. Vent temps went from mid 70s to 59-64 around the house. Today it was very hot outside (Houston TX) and the unit stopped cooling. It was blowing 84 out of most vents and the compressor was blowing somewhat cool air out the top. I turned the thermostat off and back on after a few minutes and everything seems to be fine for now.

Can anyone help me with what is going on? My uncle a competent engineer came over and put gauges on the system and they were OK he said. I have a service call scheldued with my home warranty, but I trust this site way more than any tech from the home warranty company.

Any ideas as to what is going on?

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Old 07-12-2011, 06:54 AM   #2
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Lennox 12ACB48 - Help


Have them test the strength of the capacitor for the compressor. May be weak and causing it to overheat. May have got lucky and it cooled off/reset when you stopped it.

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Old 07-12-2011, 10:18 AM   #3
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anything else i should ask them to do to make sure they dont tell me nothing is wrong as the syste is working fine now?
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Old 07-12-2011, 05:24 PM   #4
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Coil in the attic was very dirty and needs to be cleaned. Coudl this have caused it? I did change the filters to the 3m ones, maybe this cause it to be way too restrictive. I have changed back to the cheap filter until we clean the coil.
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Old 07-12-2011, 05:42 PM   #5
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If the coil is very dirty it will freezeup from a lack of airflow. Usually takes 4 or more hours to defrost so your shutting it off for a "few minutes" to reset it does not make sense. Get it cleaned and use a Merv 7 or 8 filter and hopefully everything will be OK.

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Old 07-12-2011, 05:51 PM   #6
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It took several hours for me to realize it was not cooling, I was asleep. I believe the compressor cut off and then me cycling the switch the few hours after i noticed it caused it to come back on. Does that make sense? So it probably did have several hours to thaw out.

I purchased the 3m filters with a MERV11 rating, I assume a MERV 7 or 8 is preferred because it is less restrictive?
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Old 07-12-2011, 06:03 PM   #7
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Yep.... Preferably Merv 8.
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Old 07-12-2011, 06:50 PM   #8
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Thanks,

Anything else I can do to get this thing maintained better?
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Old 07-12-2011, 06:55 PM   #9
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Flush the outdoor coil with a garden hose and sprayer once a month. Have the freon checked once a year. Use window blinds/drapes/shades and shade trees to lessen the load on it. Seal up the attic hatch and door gaskets so they don't leak air in/out.
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Old 07-12-2011, 06:55 PM   #10
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Quote:
Originally Posted by yuri View Post
Flush the outdoor coil with a garden hose and sprayer once a month. Have the freon checked once a year. Use window blinds/drapes/shades and shade trees to lessen the load on it. Seal up the attic hatch and door gaskets so they don't leak air in/out.

Flush outside coil from the outside in?
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Old 07-12-2011, 07:08 PM   #11
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Yes. You may have a double 2 layer coil with it being a larger 4 ton unit. Best way to clean them is from the inside out and then outside in but it takes a tech to remove the condensor fan and reinstall it w/o damaging the wiring or creating rattles.
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Old 07-13-2011, 10:33 AM   #12
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Don't use a pressure washer (just in case)
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Old 08-26-2011, 08:13 PM   #13
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OK So the tech came about a month ago and said the coil was dirty and it needed to be cleaned. I let him clean it (very very dirty) and the system ran fine for about a month now and it just did the same thing again. Fan running, but compressor not and not cooling. I shut the system off and sprayed it with a water hose and waited about 10 minutes and low and behold it is cooling again right now.
What could this be?
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Old 08-26-2011, 08:39 PM   #14
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I would bet good money that the txv screen is dirty. You would need the tech to come out again to diagnose this.
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Old 08-26-2011, 08:40 PM   #15
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Could be low on charge,txv not working correctly,weak capacitor, compressor internal relief opening....
Not much you can check without the right tools.

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