What causes an air conditioner's coils to freeze?
Question:
Answers:
Easiest to fix: dirt / dust preventing good air flow around coils. Not the most likely cause but easiest to fix.
Most common problem: Low on refrigerant. Once the ice starts it acts as a blanket making it easier to freeze up.
Run it in fan mode to melt the ice. Make sure it has somewhere to drain. Clean out / vacuum / blow out the coils inside and outside. Replace air filter. Clean & wipe down everything. If it still does it, make friends with an repair guy to recharge or repair.
It's over charged with refrigerant. You have use the valve on the low pressure side to let out the refrigerant until it reaches the appropriate level.
I thought you were talking about a car not house. However, despite the thumbs down, it could still be that it is overcharged.
low level of gas(134A) or another thing not enough air moving through the coil, like a filter stopped up usually one of these.
the fan that keeps the coils dry is burned up. It could also be that it is running constantly and is not kicking off. Turn it off for a while until it is unfrozen, then turn it back on and see if any of this happens. If ever thing else seems okay check the compressor or freon.
Slow airflow across the coils caused by a dirty filter or bad fan. Slow airflow across the coil caused by a dirty coil because the unit was operated without a filter. Low refrigerant charge allowing the refrigerant to evaporate too soon in the system cycle. Misadjusted Thermal Expansion Valve (if equipped) or other restriction in the liquid line (clogged filter/strainer) creating premature expansion. Misadjusted Evaporator Pressure Regulator (if equipped) allowing compressor to pump down evaporator to lower pressure than designed.
THERE MAY BE NOTHING WRONG WITH THE UNIT. IF YOU RUN THE AIR CONDITIONER, ESPECIALLY ON A HUMID DAY, THE EVAPORATOR COIL MAY ICE UP. IN NORMAL COOL, A COIL TEMPERATURE SENSING BULB TURNS OFF THE COMPRESSOR IF THE COIL GETS BELOW ABOUT 36 DEGREES F., PREVENTING FREEZING. IN MAX COOL, THAT FEATURE IS DISABLED. IF THE COIL ICES UP, SWITCH TO NORMAL COOL, THE COMPRESSOR WILL STOP BUT THE FAN WILL KEEP RUNNING. IN AN AIR CONDITIONER USING AN EXPANSION VALVE INSTEAD OF THE LESS EXPENSIVE CAPILLARY TUBE TO METER REFRIGERANT FLOW, THE TEMPERATURE SENSING BULB MODULATES THE EXPANSION VALVE FLOW TO CONTROL THE EVAPORATOR COIL TEMPERATURE, IT DOES NOT HAVE TO SHUT OFF THE COMPRESSOR.
Typically, an air conditioners coil will ice up when there is an inadequate air flow, due to dirty filters, Do not under any circumstances attempt to adjust the level of coolant as this gas is normally under high pressure and would instantly freeze your eyes or other parts of your body. If your filter is clean, and the unit is cycling (turning on and off) and you still have a freeze up, try the trick of turning it off for at least 30 minutes and then if it refreezes, contact a qualified service person with the proper guages to check the unit. They are not designed for the DIY groups to tinker with. They also have the potential to kill by electric shock. Good Luck!
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