Dehumidifier Freezing Up (Even Icing Up): 4 Common Causes & Fixes

“My dehumidifier is freezing up. Why is my dehumidifier icing up? How to fix it (quickly)?”

Dehumidifier freezing up is not all that uncommon. In our experience, more than 20% of homeowners experience this problem and less than 30% really know how to fix it. That’s why we will go step by step to explain why the dehumidifier is freezing up and how you can repair it yourself.

As you might imagine, dehumidifier icing up is not normal. In order to stop your dehumidifier from freezing up, you have to:

1. Diagnose why the dehumidifier is icing up. Culprits are too low room temperature, humidity sensor issue (frozen dehumidifier coil), or airflow issues (broken blower fan, dirty filters).
2. Fix the culprit. This may involve moving a dehumidifier to a warmer room, replacing the humidity sensor, changing filters, or replacing a blower fan.

Seems quite straightforward, right? Fixing a dehumidifier icing up is, however, not a piece of cake.

To help everybody out, we will list the 4 most common reasons why this happens and how to fix them. Every one of these culprits can be fixed, and we’ll show you how.

In short, a dehumidifier can be frozen up because:

• Temperature of the room is too low (below 65°F). This is the most common reason for dehumidifier freezing up in the basement since basements usually have a lower temperature than the rest of the house.
• Blower fan or fan itself isn’t working as it should. To prevent any dehumidifier from freezing up, you should sustain adequate airflow over the cold condensation coils. Without this airflow, the water on the coils will not drip to the water tank; instead, it will freeze on the coils.
• Faulty humidity sensor (or temperature sensor).
• Dirty filters. Restriction in airflow leads to dehumidifier freezing up.

In order to understand what is causing a dehumidifier icing up, however, let’s first get acquainted with how a dehumidifier works:

How Does A Dehumidifier Work And Why It Freezes Over?

A dehumidifier is an HVAC device that:

• Reduces the indoor humidity levels. Relative humidity levels should be anywhere between 30% and 50%.
• Does not include temperature. This seems a bit redundant to mention but it’s vital in understanding how a dehumidifier works.

In the most basic sense, a dehumidifier that is not freezing up uses a condensation process to suck moisture out of the indoor air. Here is the step-by-step of how the dehumidifier works (we will also note what goes wrong when the dehumidifier is icing up):

1. Dehumidifier fan sucks the air into the dehumidifier and generates airflow. Without a properly working fan, the dehumidifier could ice up.
2. That airflow passes over cold coils. Because the coils are so much colder than the incoming air, the moisture in the air will condensate on the cold coils. Of course, if the incoming air is not sufficiently warm (above 65°F), it won’t warm the cold coil sufficiently, the cold coil will become cooler and cooler, and eventually freeze over.
3. Now colder but drier air has to be warmed again to room temperature. That’s why it is passed over hot coils.
4. Dehumidifier fan expells the drier but same-temperature air into your home.

As you can see, we have already touched on the main culprits that cause dehumidifiers to freeze up. Let’s look at exactly what these are and how to unfreeze your dehumidifier:

1. Room Temperature Is Too Low (Coils Freeze Over)

Cold coils are the most important part of any dehumidifier. They are cooled via a refrigeration process involving a gas-liquid refrigerant and compressor.

These coils are continuously cooled via the refrigerant. Why don’t they eventually freeze over? Well, because the incoming air from your home is continuously warming them up, a temperature balance is struck.

During this process, of course, the humidity in the air is condensed on these coils are the condensate water is dripping into the water tank located at the bottom of the dehumidifier.

Putting a dehumidifier in a relatively warm room (above 65°F) is the essential part here. If, however, the temperature of the air surrounding the dehumidifier is below 65°F, the incoming air will not be sufficient to cool the cold coils adequately. The temperature balance that is struck might be below freezing point, and, voila, we get ice formation on the coils.

Solution: Just put a dehumidifier in a warmer room. Since dehumidifiers cannot effectively work in below 65°F rooms, moving it is an easy albeit not very satisfactory solution.

You probably need a dehumidifier in the room you put it in (Example: High humidity basement). Nonetheless, if you move it to a room nearby, the dehumidifier will still suck the high moisture air from a room where you have access to humidity levels, extract the moisture, and return the dry air back.

If the freezing happened due to low room temperature, you shouldn’t see this icing up in a warmer above 65°F room.

2. Blower Fan Or Fan Issue (Airflow Restriction Leading To Dehumidifier Freezing Up)

As have learned from how dehumidifiers work, you need a constant supply of warmer air that heats up the cold coils. If the incoming air is too cold, you will have a freezing problem; that was covered under #1 cause.

The same icing problem can happen if you have a restriction in airflow. Every dehumidifier has a fan that provides this airflow, and every fan is powered by a motor fan (or blower fan). If the motor or the fan itself is damaged, resulting in lower or no RPMs, lower or no airflow, you will see that the condensation on the cold coils will slowly but steadily be freezing over.

Once the coil gets covered with ice, you will (if you don’t shut the dehumidifier off) see that a dehumidifier icing up from the bottom as well.

The problem is a faulty fan motor or a problem with the blades (bent blades, for example).

Solution: Replace the fan motor. This is easier said than done. For fan motor replacement, you will probably need professional help. The key is to check which motor you need (voltage, amps, model); HVAC professionals know these things the best.

If the icing is happening due to problems with the fan itself, you can try to fix the fan. In many cases, however, you will have to replace the fan together with the fan motor.

3. Faulty Humidity Or Temperature Sensor Icing Up Your Dehumidifier

Every dehumidifier has an anti-frost or auto-deicing mode. That’s actually telling of how often a dehumidifier can freeze up. This mode is switched on when the humidity or temperature sensors tell it to switch on.

Needless to say, if something is wrong with these sensors, the anti-frost mode doesn’t switch on, and you are left with a dehumidifier icing up continuously.

Solution: It’s really hard to check if the humidity sensor and temperature sensor work as they should. An experienced HVAC professional will usually role out all other potential causes for a dehumidifier icing up before suspecting these sensors.

A professional help here is very useful. If you truly suspect that you have a misbehaving sensor, the only solution is to replace it. After the sensor replacement, the dehumidifier should automatically go into auto-deicing mode without a problem and you shouldn’t see ice building up in the dehumidifier anymore.

4. Dirty Filters Restricting Airflow And Causing Dehumidifier To Freeze Up

As we have explained in the #2 cause (when a fan or fan motor is damaged or not working at all), the restriction of airflow will lead to a dehumidifier icing up.

Dehumidifier’s air filters filter out air particulates. However, if they are dirty (very dirty, actually), they can restrict airflow so much that the dehumidifier starts icing up. Note: A little dirt in the filters won’t restrict airflow sufficiently to lead to icing up. The filters have to be really packed with dirt, dust, etc.

Solution: Just change the dehumidifier air filters. This is the easiest fix that can lead to the airflow normalization and prevent the dehumidifier from icing up again.

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All in all, some of these problems you can fix yourself, for others you will require professional help. Nonetheless, it is useful to understand why dehumidifiers build up ice and what potential solutions can defrost your dehumidifier.