Air Conditioner Ice Build-up

If you have air conditioner ice buildup on your evaporator coil or compressor unit, you may be wondering why this happens. Recall from my last blog that your central air consists of the evaporator coil and the compressor. The evaporator coil is the part of your “split” air conditioner that is attached to your furnace and cools warm inside air. In the summer, warm air in the house is “returned” to the furnace via the cold air return. The furnace blower motor blows that warm air over the evaporator coil which contains coolant. This process transfers the heat in the air into the coolant, and then the cooled air is forced through your house’s duct work. The compressor is the unit sitting on a pad outside. It sucks in the warmed coolant from the house and compresses it to make it hotter. Then a fan blows air over the condenser fins to transfer the heat in the coolant to the surrounding outside air.

Sometimes, something goes wrong and the coil, or even the compressor, can end up resembling an iceberg! Most coils are housed inside a case, so you might not see an ice build up until it becomes severe. But you will probably notice that your air is not as cool as it once was.

Ice buildup is a sign that something has gone wrong in the AC cycle which has caused the evaporator coils to become too cold. When the coils become too cold, the moisture in the relatively warm air in the vicinity of the coils condenses onto the coils and freezes. A side effect of frozen or frosty evaporator coils is that your compressor runs at a hotter temperature than it should and may burn out. Or, it may ice up too!

There are many reasons for air conditioner ice buildup in the evaporator coil and/or compressor. Common causes of evaporator coils becoming too cold and icing up include:

1. Blower motor not working. If the blower motor isn’t blowing warm house air across the evaporator coil, the coolant in the coil never warms but instead gets colder and colder.
2. Low coolant level. If the coolant level is low (probably due to a leak or under filling), when it expands as part of the AC cycle when it enters the evaporator coil, it cools off too much.
3. Overcharged unit. If there’s too much coolant it the system, it can also cause ice (as well as ruin the compressor).
4. Dirty air filter. A dirty air filter decreases the airflow across the coil,which basically has the same effect as blower motor not working. )
5. Running the system when it is too cold (below 60 degrees or so) outside. Your air conditioner just wasn’t built for that!
6. Restriction in the coil
7. Faulty metering device (aka expansion valve). This controls the amount of coolant coming into the evaporator coils.
8. Improper sizing of equipment. If your system is too large or too small (i.e. the “tonnage” of your system, or how much heat it can remove in an hour), this negatively impacts its operation.

What should you do if you notice air conditioner ice buildup? First, turn off your air conditioner and let the ice melt away. Then, check for dirty air filters, blockages in the ducting, or debris buildup in and around the compressor. If none of those are causing the problem, then it might be time to have KJ Thomas Mechanical out to diagnose the problem. We have over 30 years of experience installing and servicing heating and air conditioning systems and can help you keep your system running well. Call us at 303-435-8141, or schedule online.