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AC Frozen? Here’s How Long It’ll Take to Defrost

Here’s a problem you likely never anticipated: Ice on your HVAC in the middle of summer. It’s actually more common than you think!

When we’re running our AC units more often and at colder temperatures, they’re more likely to freeze up. If you notice something wrong with your AC, especially visible ice crystals, it’s time to take action. We’re here to help you defrost and get back to normal cooling ASAP.

How will I know if my AC is frozen?

Other than visible ice on any part of your HVAC unit, the next most obvious sign of a frozen AC unit is a lack of cool air. If you put your hand in front of your supply vents and you sense warm air coming out, you probably have ice somewhere in the system. 

You may also notice a hissing sound coming from the unit. If that’s the case, take steps immediately to prevent further damage. Your wallet will thank you later.

How to Defrost a Frozen AC Unit

Your AC will take anywhere from an hour to more than a day to completely defrost. It’s important to catch it early to prevent further damage to your unit—and, of course, so you’re without cool air for the shortest amount of time possible. 

Here’s your step-by-step defrosting guide.

Step 1: Turn OFF your AC.

We know, we know: It’s hot.  But frozen AC parts are bad news for the most expensive piece of your HVAC unit—the compressor. To avoid lasting damage and a hefty bill, turn your thermostat from COOL to OFF. This will start the defrosting process.

Step 2: Switch the fan to ON.

Turning the HVAC fan to ON will force it to blow warm air over any frozen coils—which will speed up the defrost process. Make sure it’s actually set to ON and not to AUTO. Automatic settings cause the fan to cycle—starting and stopping over and over again. You want continuous, non-stop airflow over the frozen areas. 

Step 3: Find the source.

Now it’s time for some investigative work. What caused your AC to freeze up in the first place? There are a few common culprits:

Dirty Air Filter

Clogged-up air filters essentially suffocate your HVAC unit. When warm air is restricted from the coils in your unit, the coils get too cold and eventually ice over. Replace air filters at least once a month to prevent an icy surprise.


Dirty Evaporator Coils

If your coils are dirty, the same process occurs. Dirt and grime covering the evaporator coils causes air restriction the same way dust does in your filter.

Leaking Refrigerant

If you spot a leak anywhere, that’s probably the cause of your ice problem. Low refrigerant levels cause drops in pressure, allowing moisture in the air to freeze around your HVAC coils. 

Despite what many homeowners may think, refrigerant doesn’t simply get “used up.” It doesn’t decrease over time, and it doesn’t evaporate during AC use. So if you’re low on refrigerant, there’s no doubt you have a leak. 

Note: Refrigerant is a hazardous chemical that should only be handled by licensed pros. Give us a call if you think you have a leak.

Problem Parts and Other Issues

A collapsed duct, weak blower, or closed valves might be causing your HVAC to freeze. AC units are also complex machines with a lot of other pieces and parts. Our Calgary HVAC pros can help to diagnose these less obvious problems.

Step 4: Monitor the situation.

As your HVAC unit thaws out, you might encounter some collateral damage. Overflowing drain pans and clogged condensation drains are a risk when this much water is coming off your AC. Put down some towels around the unit and watch for additional leaks to prevent water damage. 

Once your HVAC is completely clear of ice and all parts are dry, you can turn your AC back on. Monitor the unit for continued problems over the next several hours to a few days.

Step 5: Call us!

If changing the air filter solved your ice problem, you’re in luck! Now it’s time to keep your unit in top shape throughout the summer. Getting regular preventative maintenance and inspections can help catch issues early and prevent your AC (and your wallet) from freezing up.
Unfortunately replacing the air filter is the only thing you can do yourself. So if that didn’t work, it’s time to call us. All other issues are best diagnosed and treated by our team of Calgary HVAC professionals. We’re happy to help!

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