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Daves92gt 08-10-2012 04:32 PM

AC Froze up
Last night I found that my AC coil froze up. This happened about an hour after a storm where the outside temperature dropped rapidly from being about 80 to around 67 degrees with the thermostat set to 67. The system was just had a check up last month and nothing was wrong no leaks or anything like that. After I let it unthaw and turned it up to 70 it didn't have to cycle on again until this afternoon which its been working fine keeping the house at 70 degrees all day with no further freeze ups. Basically my question is could the extreme temperature drop with the low temp I had the furnace set at caused the freeze up? I've heard if it's not warm enough outside that can cause the coil temp to get below freezing. I just don't want to have to have someone come out and look at it again when it already was looked at last month if it was just because of the conditions. Like i said it hasn't frozen up again all day and the temp of the air coming out of the vent is between 50 to 51 which is right where it always sits about 20 degrees cooler than the return air. Air filter is new as well just changed at the start of the month.

Acomfort 08-10-2012 04:50 PM

Check your pressures

Marty S. 08-10-2012 05:22 PM

Yes low temps can cause freeze up. Not so much the 67 outdoor temp but combined with indoor temps in the 60's the pressure gets too low and falls below the freezing point.

turnermech 08-10-2012 06:17 PM

If everything was perfect with the system it should not have froze with the conditions you described, but you are getting close to the threashold of it. Sadly most systems are not installed perfect. How clean is your air filter? Might not take much to put it over the edge. An A/C probally maxes out at achiving 65 deg. inside temp and even that is hard to achive. you are nearing the range of refrigeration not A/c which IIRC classified at below 65 for medium temp refrigeration.

biggles 08-10-2012 06:28 PM

you have your liquid line during the warmer parts of that day but as the night temps drop so goes that condenser pressure and the LL starts to flash acting as if the unit is short.if it was 67F all day you won't run the AC so it is just a typical reaction any temperature below that stat setting is a chance to make ice and it starts back at the air handler...and travels on the insulated line right out to the compresor and can make it look like an igloo.just get in the habit of setting the temp up a little if that happen afgain or just do fan all night,or a cooling setbak if you have a programmable...70F day 75F-78F nights

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