Why is My Air Conditioner Frozen?

Why is your air conditioner frozen? Good question. Picture this: it’s a blazing hot summer day and your air conditioner just doesn’t seem to be working right. Oh, you can hear it working away, but your home just doesn’t seem to be cooling down. You go outside and — to your astonishment — your outdoor unit is covered in ice.

What’s going on?

This strange situation occurs when your air conditioner’s evaporator coil (a key component in your HVAC system, responsible for transferring heat from the inside of your home to the outside) malfunctions.

Without going into a physics lesson on the Joule Thomson Effect, let’s just say that when the evaporator coil is cooling more than it should, it will mostly probably freeze up.

Consistent malfunctioning of your evaporator coil can end up costly repairs, so it is important to diagnose the problem and fix it as soon as possible. Below are some possible reasons this is happening:

  • Poor airflow: Anything that restricts the airflow over the coil’s surface will adversely affect the balance of your system and cause icing. Primary culprits include dirty filters, a damaged blower motor and dirt buildup on the coil.
  • Lack of refrigerant: Leaks or insufficient levels of refrigerant can make the cold coil too cold and allow moisture in the air to freeze and accumulate, causing icing.
  • Poor temperature control: Bad thermostats or setting your thermostat too low can cause your air conditioner to run constantly, which may eventually drop the temperature of the condenser below the freezing point, causing icing. Running your air conditioner in temperatures below 60 degrees can also cause this problem.

If your air conditioner freezes up, do the following:

  1. Turn off the system and let it completely defrost.
  2. Change your filters and clean any dirt or obstructions you can see.
  3. Make sure furniture, curtains, etc. are not blocking your floor registers.
  4. Call a trusted HVAC professional: and have them do a thorough inspection of your system. Proper maintenance is critical to a healthy air conditioning system, and little money spent on maintenance will save you a good deal of money in the long run.
Air conditioner frozen inside

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