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AC System Freezing Up: How You Can Fix It The First Try

Frozen AC System

Is your air conditioner freezing up? It can be surprising to see a chunk of ice sitting on your outdoor AC system, especially in the middle of summer. But sometimes you can’t even see the ice on the exterior of the unit.

While you may think something like this during the hottest days of the year is impossible, an air conditioning unit freezing in the summertime is something that happens frequently.

If you fear you’re experiencing a frozen air conditioner, continue reading to hear what causes it, what to do if you’re experiencing a frozen AC system, and how you can prevent or keep something like this from happening again.

What Causes an Air Conditioner to Freeze?

To understand how an AC unit can start freezing up, you first need to understand the basics of how central air conditioning systems work. And it all starts with your evaporator coils.

This key air conditioning component is full of extremely cold refrigerant. When the coils are activated, the refrigerant will need warm air to blow across them. This cools your air and keeps the coils at a warm enough temperature that they do not freeze. The indoor coil removes heat from the inside air, and then will transfer it using the refrigerant to the outdoor coil which pushes the heat to the outside. The system is actually pulling heat from your indoor air and transferring the extra heat outside. This is why if you ever put your hand over the fan running on your outdoor unit the air feels noticeably hot.

However, if something in the air conditioner malfunctions, the whole system gets disrupted. If something prohibits the warm air from blowing over the coils, this causes the evaporator coil to allow the refrigerant to cool too much, causing it to fall below freezing and ice over. Or if the refrigerant pressure is wrong inside the coils, then your system’s coils can become too cold and can quickly freeze up. And that can leave you with a frozen AC.

What To Do if You Find Ice on your Outdoor AC Unit

If you believe you are experiencing a frozen outdoor AC, there are some simple steps you can take in order to get things back up and running again.

Step 1) Thaw

Make every effort to avoid using the AC while the evaporator coils are frozen. Running the AC with frozen coils strains the AC compressor. Go to your electrical breaker and turn off the power to your AC unit. This will keep the system from freezing up even more and begin to let the ice thaw. The AC compressor is the most expensive component in your air conditioning unit. The strain could damage this incredibly valuable part and set you up for a costly air conditioning repair service call. 

Even if it’s blistering hot outside, it could take a whole day for the ice to completely thaw away. Don’t be tempted to break up the ice with a heavy object or sharp tool. This easily damages components so much so you’ll need to replace multiple parts, which can add up financially, or worse be forced to replace the system altogether.

Step 2) Dry

Once the ice is completely melted away, you need to dry the evaporator coils. You can use some paper towels, or let the parts dry out in the sun if in direct sunlight. Restore the power to your system and turn the blower on. Run inside and set your thermostat to only run the blower or fan, depending on the model of the thermostat you have. This circulates air around and through the coils to dry them quickly. Once the coils are dried thoroughly, your system should resume operating normally.

Now that you know what to do if you ever encounter a frozen air conditioner, let’s talk about how you can keep this from happening.

How to Prevent a Frozen Air Conditioning System

It’s important to recognize this is preventable. Take these measures to keep your HVAC system from freezing over.

Change Your Air Filter

The leading cause of a frozen HVAC system is a dirty air filter. The air filter cleans the air circulated into your home. As your AC system runs throughout the summer, the filter catches dirt, pollen, dust, and other allergens. This can restrict airflow and could lead the HVAC coils to freeze. Typically, we recommend you check your filter monthly. Change it as needed. For most folks, this is one to every three months. Filter changes vary based on factors, such as:

  • The type of filter you have
  • If you have children or pets in the home
  • If you live in a high-pollen count area
  • Whether a smoker lives in the home
  • If someone with asthma, allergies, COPD or congestive heart conditions lives in the home 

Schedule Regular Maintenance

It is just good practice to have an annual air conditioning maintenance service call. The professional HVAC technicians at ARS/Rescue Rooter ensure all of the following are checked and cleared for your system to run properly for the summer ahead:

  • Inspect coolant levels and pressure to ensure your system runs at peak efficiency
  • Calibrate thermostat(s) and check proper cycle and temperature to improve comfort and control
  • Inspect and tighten wiring, contacts, capacitors and relays to avoid expensive repairs
  • Ensure the evaporator coil is clean
  • Ensure the condensate drain is clear
  • Inspect and clean the condenser
  • Inspect the outdoor disconnect switch
  • Inspect the condenser fan motor and blades; lubricate if needed
  • Check compressor amps at startup
  • Carry out additional safety and efficiency checks

It’s also safe to avoid handling coolant chemicals since they can be toxic. Leave it to our technicians and keep yourself away from handling them if possible. 

Have an HVAC Airflow Inspection

Obstructed airflow can keep the coils from properly cooling and lead to a frozen AC unit. Similar to a clogged filter, blocked vent returns and registers prevent adequate airflow to and from the system. This causes your system to work harder without a way to release the cooled or heated air.

Another good practice is to walk around your home and check that indoor air vents and registers are clear from any obstructions. If you fear you’re experiencing weak airflow through your vents, your ductwork may be to blame. In some cases, the ductwork is installed well but the wrong size for your house or the capacity. Or there’s a duct leak or a section of ductwork has collapsed somewhere within your walls.

Clean Evaporator Coils

The condensate lines drain excess moisture from your HVAC system. If there’s a clog in the line, the water becomes stuck and the excess water freezes. And that frozen water in your lines could leave you with frozen HVAC coils too. This causes your system to struggle or not work at all.

Check the Forecast

Are summer temperatures expected to drop at night? A good rule to remember is when the outdoor air temperatures dip, you should turn your air conditioner off. Icing can occur if you’re running your outdoor AC on cooler nights. A special ambient temperature control installed can help prevent your unit from running in cooler weather.

A Frozen AC is Avoidable

While it can be frustrating to find a frozen AC system as a homeowner, the problems that cause this are preventable. It’s important to not neglect regular maintenance and tune-ups on your air conditioner each year. Hiring a professional HVAC service team, like ARS/Rescue Rooter, or taking advantage of maintenance service plans, can help keep your system running strong all year long and save you money.

Find our nearest location to schedule service online or over the phone. We’re standing by for any emergency air conditioning service -- including a freezing AC unit.

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