New A/C Unit Freezing Up.


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Old 05-07-12, 12:12 AM
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New A/C Unit Freezing Up.

History - House was built in 46, A/C was added a long time ago. Just replaced a 20 years old unit that was leaking. I have owned the house for 9 years and always operated the old unit the same as I am operating the new unit with no issues. I like my house cold, it is set to 68 for day and 65 at night, so that the upstairs is nice and cool. Return air system is not that good, have one upstairs and one down stairs in aprox 900 sq ft house. Again never had issue with old unit until it started to leak. New unit is same size as old unit, at lest that is what I was suppose to get. The new unit coil is bigger then the older unit was.

Problem - What is happing is that at night the unit will freeze up and I have to shut it off. We have allergies and do not like to have the windows open even on a cool spring night. It is 64 outside right now and the unit was freezing up. The other night did same thing and it was down to 60. I never had this issue with the old unit and do not have the issue with a window unit I still run in a bedroom to help with the upstairs, and the fact that I am now having to shut my whole house A/C down at night because of the freezing up. Heck back in college I would run that window unit in the winter when it was 45 outside.

So why is my new unit of 2 weeks freezing up on me? Is it overcharged? Is it low air flow?
 
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Old 05-07-12, 05:58 AM
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What do you mean 'freezing up' ? did you see ice somewhere ?
 
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Old 05-07-12, 09:52 AM
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Could be blower motor shutting off or could be dirty filter or a tad bit low on freon.
 
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Old 05-07-12, 02:39 PM
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If you're using a 1" allergen reduction filter, try something less dense. Also ensure that every vent is open.

Is the new unit the same size as the old one? If it's larger, your ductwork is probably undersized.

Low return air temperature can cause freezing - the lowest you should be setting it to is 68-70. (even that's very low)

Call the installer back to check the charge.
 
 

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