Why Is My Dehumidifier Blowing Cold Air?

If you’re familiar with dehumidifiers, you’ll know that they blow hot, dry air. It’s not an ideal scenario considering that dehumidifiers are typically run during the hot season when you need a way to cool the home. In an ideal world, you’d want the dehumidifier to blow cold, dry air to help keep the home at a comfortable level.

However, that’s never the case. All dehumidifiers, usually working, produce hot, dry air. Indeed, the only dehumidifiers that produce cool air under normal circumstances are air conditioners!

So, when you wake up one day and find that your dehumidifier is producing cold air, there’s likely a problem. Let’s find out what it could be and how to address the issue.

How Dehumidifiers Work

Maybe we should first explain why a standard dehumidifier produces hot, dry air and not cold, dry air.

Dehumidifiers are appliances designed to extract excess moisture from the atmosphere. Excessively humid conditions can compromise indoor air quality. In addition, they create the perfect breeding ground for mold and other fungi. Most fungi cause diseases. Many bacteria and viruses also thrive in warm, humid conditions.

Excessive moisture can cause rotting in the attic and crawl space, thus compromising your home’s structural integrity. The dampness can also damage your wall paint, wallpaper, and your books and paper documents.

Dehumidifiers draw the moist air from your home, extract the moisture, and return dry air into your home. Meanwhile, the extracted moisture is condensed into water and drainage away, usually manually or continuously, into a sink or drain hole.

However, keep in mind that dehumidifiers are typically used when it’s scorching-hot indoors during the summer season. Therefore, the moist air entering the dehumidifier usually also contains a lot of heat. Depending on your geographic location and the time of the year, the air in our home can be as much as 90˚F. Some areas are up to 100˚F hot during the peak of summer – against a recommended 64˚F for ideal indoor comfort (according to the World Health Organization).

As the hot, humid air passes through the dehumidifier and moisture is extracted, the refrigerant typically extracts some heat, too (though not as much as an air conditioner).

Unfortunately, unlike air conditioners, dehumidifiers don’t have a mechanism to eliminate the collected heat. A standard air conditioner will have a condenser unit outside to help dump the heat outside the house. But dehumidifiers don’t.

As such, the heat is usually returned to the air re-entering the home. This process is accomplished at a special section of the dehumidifier known as the re-heater. This is why any standard dehumidifier will blow hot, dry air rather than cold, dry air.

Why Your Dehumidifier is Blowing Cold Air

If your dehumidifier is blowing cold air, it’s operating out of the norm, which means something is wrong somewhere. The following are three common causes and what you can do to remedy the situation.

The compressor is not working (for compressor dehumidifiers)

As we’ve seen, an ordinarily functioning compressor dehumidifier produces heat. Therefore, if the appliance isn’t producing heat, something may be wrong. Since the compressor unit is the heart of the compressor dehumidifier, it is the first place you should look whenever your dehumidifier begins to produce cold air.

The compressor unit in a dehumidifier performs almost the same function as in an air conditioner, except that it focuses more on removing moisture rather than heat in dehumidifiers. When it receives moisture-laden refrigerant from the condenser coils, it compresses the gaseous refrigerant and thus raises its temperature. Raising the temperature of the refrigerant forces heat and moisture absorbed from your home to exit the refrigerant.

In air conditioners, the heat is released to the cooler outdoors. However, in dehumidifiers, it’s held in a re-heater and later reintroduced to return air.  

A broken compressor may fail to circulate refrigerant, compromising the entire process. This can manifest in colder air at the outlet vent.

Why? Because the warm air entering the dehumidifier from your home will still pass through the cold condenser coils, resulting in a temperature drop. However, since refrigerant cycling is compromised, the heat may not be reintroduced to air returning from your home.

Of course, this can only go on for so long before the entire system breaks down. If there’s a refrigerant leak, for instance, the condenser coils may soon become warm too.

The reheating system has failed

We’ve mentioned the dehumidifier’s reheating system severally. If it fails or malfunctions, the air coming into your home from the dehumidifier may also be cold rather than warm.

The way the reheat system works is a little complex. But, generally, it involves a unique device that can hold and release heat on demand. During the dehumidification process, heat is naturally removed from return air. It’s a natural process. Refrigerant naturally absorbs heat when exposed to warm conditions.

However, unlike air conditioners with a mechanism to dispose of the collected heat, the dehumidifier isn’t designed to dispose of heat. Therefore, it needs a way to hold the heat temporarily before returning it to your home. Otherwise, the heat loitering around that unit may compromise even the dehumidification process. That’s where the reheat system comes in handy.

However, the reheat system can fail too. Typically, the system comprises a heat exchanger, which helps to transfer heat between two fluids. Unfortunately, heat exchangers can get damaged, crack, or even rust. When this happens, their ability to pass heat from one area to the next is compromised.

In the case of a dehumidifier, the exchanger may not hold any heat from return air or pass over the heat to supply air. Ultimately, this will result in cold supply air. However, this, too, can only go on for so long before the dehumidifier breaks down.  

The unit has iced up

Finally, the dehumidifier can also produce cold air on the supply end when the unit is iced up. The term “iced up,” as the name suggests, means when the condenser coils and other internal components of the dehumidifier are covered in ice.

When this happens, the warm air from your home may not even enter the dehumidifier in the first place. Or, if it does, it may do so in tiny quantities. Instead, the cold breeze you’re feeling is likely to result from the fan blowing across the ice. When air is passed across the ice at speed, it creates a very cold breeze.

The dehumidifier can become iced up for several reasons. For once, a refrigerant leak can cause the system to become too cold and ultimately freeze up. Why? Because refrigeration systems such as a dehumidifier rely on the heat extracted from your home to prevent freezing.

Another reason your dehumidifier may ice up is the buildup of dirt. When there’s a dirt buildup, supply air is constricted. This effectively restricts the amount of warmth inside the dehumidifier. As we’ve seen above, reduced warmth inside a refrigeration system always causes icy conditions and, ultimately, freezing.

Get Professional Help Immediately

The biggest problem with dehumidifiers blowing cold air isn’t even about the cold air. Instead, it’s the imminent risk. All three issues discussed above can damage your dehumidifier within hours rather than days. Whether it’s a damaged compressor, failed heat exchanger, or frozen internal components, it only takes a few hours for the entire dehumidifier to fail – necessitating costly repairs, or worse, replacement.

Therefore, if you notice that your dehumidifier is producing cold air rather than warm air, it’s vital that you shut it down right away and call an HVAC professional to diagnose and fix the problem.