Ice or frost on your HVAC unit isn't always a sign of a problem. When temperatures dip below freezing – which they do most winters around here – ice is par for the course. Moisture in the air condenses on your unit, then freezes in the cold air.
If your outside AC unit is frozen, this isn't normal. Here's a very simplified explanation for what's happening: Your AC is freezing up because something in the system is causing your refrigerant temperatures to drop.
Outdoor cooling units are built to endure these harsh winter weather conditions, which eliminates the need for a cover. Moisture (water) can freeze the air conditioner's condenser coils, which can cause damage over time. However, there is no way to keep moisture out 100% of the time.
Thaw Out Your AC
To thaw the ice out, first, you need to turn the AC's thermostat off and turn the fan on. Leave the fan on for a few hours to allow the unit to fully defrost. In some cases, it may thaw out after an hour. In other, more extreme cases, you may need to leave the fan on for a full 24 hours.
As it turns out, frost formation is a strange but normal occurrence for any air conditioning unit. The culprit lies with the refrigeration process itself — as your air conditioner extracts heat from indoor air, the surrounding moisture condenses and a small portion of it freezes on the coils.
It just means that the air around your compressor is warm and that your compressor is working hard to keep things cool inside your system. The frost is not a sign of a leak, and won't cause any damage to the unit by itself. As long as your regular maintenance is done, you should be in the clear.
1st Step: Turn Your HVAC Unit Off.
Even if it's sweltering outside, you still need to turn OFF your air conditioner! Running a frozen air conditioner will wear out parts much faster, and could overheat your unit. Worn parts are bad news for the most expensive piece of your HVAC unit—the compressor.
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.
An outside air conditioner unit cover is available commercially. If you do not have a ready-made vinyl or plastic cover, a piece of plywood will also do. It will protect the air conditioner from falling ice, keep debris and leaves away, and, at the same time, allow the unit to breathe.
Frozen Coils: Running an air conditioner in cold weather can cause the evaporator coils to freeze. This happens because the refrigerant inside the coils can drop below freezing, leading to ice buildup. Frozen coils can restrict airflow and reduce the system's efficiency, eventually causing damage.
The fact of the matter is that it isn't necessary to cover your air conditioner for winter or cold weather, or at any other time in the spring, summer, or fall. The outdoor unit is designed for outdoor installation and can withstand even extreme weather, including rain, high wind speeds, snow, winter storms, and ice.
What Can Cause a Frozen Compressor? A clogged air filter that's limiting the amount of air that's moving over the cooling coil. Insufficient refrigerant or too much refrigerant that are causing icy buildup while destroying your compressor. A broken blower motor that's not funneling warm air over the cooling coil.
The temperature will need to go below -50 degrees for Freon to freeze. If the temperature outside during the winter is higher than that, you can expect the refrigerant to maintain its shape.
The short answer is YES. You can safely pour water on your unit, though warm water is preferable to very hot water.
Don't worry though, it's actually much more common than you think! Very cold refrigerant coils + moisture in the air = ice. When you're running your AC unit more often and at colder temperatures, like you do in the middle of summer, they're more likely to freeze up.
If you have the ability to wait, switch off the fan, and your unit can thaw on its own. Note that this will take at least a few hours. Run hot or even cool water from your garden hose over the unit to melt ice. Never try to chip away ice with anything sharp, as this could damage your equipment.
Low Refrigerant Levels
An AC unit needs a certain amount of refrigerant – a chemical agent – to ensure proper cooling performance. When the refrigerant levels fall below the needed amount, it throws off the balance and causes your air conditioner to freeze.
Air conditioners may be cooling systems but they are not meant to freeze up. It is not part of their design. If it happens, then the cooling system is not working as intended. It will not be able to cool down the house as well as it should.
Then, change the fan setting from 'auto' to 'on. ' The fan will slowly defrost the system. Once your air conditioner is ice-free, you can turn it back on and reset the fan to auto (This may take an hour or more).
When the filter becomes dirty, this can block airflow and cause the evaporator coil to get too cold, which can lead to a frozen AC unit. As a general rule of thumb, many HVAC professionals recommend replacing the air filter every 90 days.
AC coils freeze for a variety of reasons—the most common, though, is lack of airflow. Dirty air filters or problems with your ductwork can cause weak airflow, which hinders your equipment and its ability to keep coils warm and running properly. Temperatures drop and the AC coils freeze.
Control lines accumulate moisture from condensate during normal operation of the compressed air system. In cold temperatures, air compressor control lines can quickly freeze up, with adverse effects on system performance.
Warmer temperatures can cause the moisture in the freezer to settle on walls and shelves, forming frost. Air drafts from vents or open doors can also contribute to frosting, as they bring extra humidity into the freezer.