Man fixing a air conditioning unit

What Can Cause Your Air Conditioning Unit to Freeze Up?

The air conditioner is a device that’s revolutionised interior climate control over the course of the last century.  The technology has proven invaluable in especially hot and humid climates, providing a means of removing the heat and moisture from an interior; but it’s also proven useful in cold ones, as it can act as a heater just as capably as it can act as a cooling system.

But in order to get the best from your air conditioner, it’s vital that you keep it in good condition via periodic maintenance.  It’s also worth learning to identify the tell-tale signs that might provide a clue that a failure is about to occur, and taking steps to prevent those failures.

One of the most common failures of an air conditioner is freeze up.  The symptoms of a freeze can be difficult to spot at first, but failing to take remedial action can cause the device to become irreversibly damaged.

In this article, let’s examine the problem, and consider what steps we might take to solve it.

What causes air conditioner freeze-up?

Air conditioner freeze-up is the result of a build-up of frost on the unit’s evaporator coil – the small heat-exchanging device which allows the air conditioner to do its work.  As warm air passes over the coil, the special coolant liquid inside expands, causing it to evaporate.  The heat energy is thereby transferred from the coil to another coil on the outside of the building, called the condenser coil.  The role of this set of coils is to disperse the heat outside of the building, before circulating back to the evaporator coils via a compressor.

The evaporator coils are the sharp end of the cooling system – they’re the part that actually cools down the air that the unit’s fans are blowing through the device.  If the air is particularly humid, then the result might be that water droplets settle onto the coil and begin to freeze.  This severely impacts the coil’s ability to properly function, as the frost will gradually impede the airflow through the tiny gaps in the evaporator coil.  Without proper airflow, the coil is next to useless.

What to look out for

There are several key giveaway signs which might suggest that your air conditioner is frozen.  Let’s consider them.

If the air conditioner suddenly becomes ineffective, then this might be as a result of frost forming on the evaporator coil.  Similarly, if you notice a sharp decrease in the flow of air from one side of the conditioner to the other, frost might be to blame.  We might also look out for signs of excess moisture – if there’s a large amount of condensation collecting within your unit, then be sure to check the coils for signs of frosty build-up.  When taking a closer inspection, you’ll want to be on the lookout for further signs of excessive condensation and icy-build up.  Once you’ve made sure that frost is to blame, don’t wait any longer; every moment that your air-conditioner is running will be causing it further damage – and it won’t be working properly, either.

Fortunately, the short-term solution is simple:  turn off the unit and allow the frost to fully melt.  Having done this, you’ll want to then call out a qualified engineer to inspect the system, and thereby prevent recurrences.  Sometimes, the cause of a breakdown can be complex; sometimes it might be something simple.

How can the problem be solved?

In order to prevent air conditioners from freezing up, we need to work out exactly what might have caused the problem in the first place.  Let’s take a look at some of the more common causes.

Airflow problems

If the warm air in your room can’t reach the evaporator coils, then problems are inevitable.  Not only will the air not be cooled, but the thermostat in the air conditioner will be reading a temperature that’s higher than it should be.  This means that it’ll decrease the temperature of the coil, which when the air is static will cause more condensation, and therefore more frost.

Often, this lack of airflow comes about because of a dirty air filter.  As an air conditioner runs, it’ll suck thousands of tiny particles from the air, which will collect in the filter.  This means that the air will be cleaner, but it’ll also gradually block the airflow.  Another potential cause of reduced airflow is a malfunctioning fan – so be sure to pay attention to the sound that the fans are making after you’ve thawed your machine, and make a note of any that aren’t properly spinning.

Other problems

A lack of airflow isn’t the only thing that might cause your coils to freeze up.  If the coils have become dirty or blocked up, then the air won’t a chance to get through, which will lead to the same problem.  If the temperature outdoors or the temperature you’ve set for night-time is really low, then frost might occur even when there’s adequate airflow.  While air conditioners are fabulously effective devices, they’re not miracle-workers, and shouldn’t be treated as such – even if you like to keep things frosty, be sure that you don’t drive yours so hard that the coils become actually frozen.

Of the things that must be handled by a professional engineer, a refrigerant leak is the most common.  You shouldn’t attempt to handle this problem yourself, as identifying and repairing leaks, and replenishing coolant levels, is a task that requires the right tools and expertise.

In conclusion

The air conditioner is an enormously useful piece of technology.  When they become frozen, however, they stop working properly.  It’s easy to thaw a frozen air conditioner – but preventing it from freezing again is a little trickier.  By looking out for the tell-tale signs we’ve looked at here, you should be able to work out the source of the problem – but if you can’t, don’t hesitate to bring in a professional.