A coil freezing over


Old 03-04-04, 10:47 PM
Pendragon's Avatar
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A coil freezing over

OK, I'm stumped now.

For the last few days, the A coil in my a/c has frozen over and I can't figure out why. Here's the backstory..

A few days ago, the a/c wouldn't come on. I don't know about the heat, it wasn't cold enough for that.. Anyway, I didn't have time to figure it out before work, so I just turned it off. So the next day when I got a chance to check it out everything seemed ok (except for the not running part). So I just turned the breakers off for the inside and outside units, waiting a minute and turned them back on. Great, now the a/c works! I close the windows and go to work.

First problem, stepson isn't observant enough to realize that if the a/c is running, you need to close the window (in his room)!

I get home and you guessed it, the wife figures out that the a/c is just running and running and it's not getting any cooler, so she had turned it off. I pretty much figured it had froze over with all the humidity. So I take the cover off and left it to defrost overnight. Next morning I crank it up again and it's good.
Get home, and it's frozen solid again, only no windows left open and no one realized this time that it's been running all day but no blowing any air. So I've got to let it defrost again!

Now, I just don't know why it keeps freezing over, or what damage this might have caused to the system, having happened like, 3 days in a row now.

Any ideas?
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Old 03-05-04, 06:36 AM
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First is the air filter clean? The A coil clean? When you first turn it on, are turn just the blower on you get good airflow. The next thing is call a hvac tech. Most of the time frozen or ice on the A coil, your low on freon.He should look for the leak and fix it. Dont run it anymore . Just the fan is ok ED
Old 03-05-04, 06:52 AM
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You didn't say which brand A/C you have, but it really doesn't matter much anyway. Coils freeze because they are running below 32 degrees. When moisture laden air comes near a cold coil some of the moisture tends to condense like it does on a hot day on the outside of a glass containing a cold drink. When the coils are running below freezing the water first condenses and then becomes ices clogging the air passages through the coils. You end up with a big block of ice with the A frame coils in the middle. This whole sad situation usuallly happens because your A/C system is low in refrigerant. Due to the low refrigerant charge system pressures fall and so do the temperatures. Now it's also possible for other things to cause the same problems as you described, but when I'm faced with your kind of problem I check the system pressures first and go from there. I assume you don't have the equipment to check system pressures. Most likely you will have to get your friendly local A/C service man involved. The other things that can cause the same problem involve parts that requires breaking open the refrigerant line.
Old 03-05-04, 05:17 PM
Join Date: Nov 2002
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icing up

a common problem, usually due to a lack of air flow across the coil or not enough of a load.
If your low on refrigerant , you will have a high superheat. This is where the coil freezes on the bottom third only, then it starts to work it's way up...the suction line will be about ambient...not sweating... this is all starting from a clear clean evaporator coil, air filter and squirrel cage, all supply vents OPEN and all return vents OPEN! NO BLOCKAGES...and assuming the fan is continually running the whole time. You have to sit with the unit... you can't turn it on, and go to work, and figure it out later...attempt the repair upon return to figure this out...any set point below about 68 will freeze on most units.
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