Ice Crystal Snowflake in front of Portable Mobile Room Air Conditioner. 3d Rendering

Facing the cold, icy stare of a dehumidifier that’s frozen up? We’re here with answers. But first, it helps to understand how your dehumidifier works. When you know how a dehumidifier works, simple science can often explain why yours is freezing. If, while reading through this answer you find yourself wanting to start over with a new dehumidifier, we’ve got a short list of recommended dehumidifiers ready for you. 

To avoid confusion, it’s worth noting there are a few kinds of dehumidifiers. That said, if yours is freezing up there’s no need to waste time on the difference (you’re here for answers, right?). If you have icy buildup, that means it’s a refrigerant dehumidifier, the most common style found in musty basements and moist locations around the world. 

How your dehumidifier works:

  1. First, a compressor propels the fan to draw in air and activate the refrigerant in the coils. In most cases these are designed to cool air that’s above 65°F (or about 18°C). 
  2. Refrigerated coils then cool the humid air as it passes through. Just like with the water cycle, this causes warm air to contract and water to become droplets of condensation, which then drop into your dehumidifier’s water bucket. Isn’t science great? 
  3. Treated air then passes over warm coils, returning it to room temperature and sending it out into your home or business. 
  4. As your dehumidifier operates, a humidistat (or humidity control dial) works a lot like a thermostat to monitor humidity levels and control when the compressor starts and stops.

How to Clean Your Dehumidifier & Prevent it From Freezing Up

Anything that interrupts the process above can cause ice buildup. Fortunately, a few simple cleaning steps can easily prevent a dehumidifier from freezing up again. We’ll start with the easiest fixes first:  

First check the temperature

It takes a special dehumidifier to operate at colder temperatures

Operating temperature is the most common reason a dehumidifier freezes. If your unit is operating below the recommended level (usually 65°F), moisture freezes on the coil instead of draining into the bucket or hose. A coil that’s uniformly covered in ice or frost is your best indicator that temperature is your problem. If this is the case, solutions are simple. Try the following:

  • Move the dehumidifier to a warmer room
  • Elevate it to where there’s warmer air
  • Heat the air with a small space heater or blower aimed in the direction of the dehumidifier

If none of these are an option for you, there are a wide variety of dehumidifiers made specifically for colder locations. Some of these units come with defrosters, others don’t use refrigeration at all. If you need to control moisture in a cold, wet environment – this is an effective (if pricier) solution that could provide the comfort and peace of mind you’re looking for. 

Looking for a good space heater? Check out our updated guide to the Best Space Heaters for 2021.

Man changing water container in air dryer, dehumidifier, humidity indicator. Humid air at home. High quality photo

Still frozen? Check the airflow.

Outside of temperature, poor airflow can also cause a dehumidifier to freeze up.

Remember, the fan and filter work together to pull air (and only air) through the unit. Then, it passes through the coils and back into your home so that it’s drier, cooler, and more comfortable. This requires good airflow, which can be impeded by a variety of factors. 

Adjust the dehumidifier’s surroundings

If the ambient temperature of the room wasn’t the culprit, check the area around the unit. Slow or restricted airflow can lead to the coils freezing up. If your dehumidifier is too close to a wall or ceiling it could also be trapping excess dirt and dust. Most manufacturers recommend that you keep your dehumidifier at least 6 inches away from any walls or ceilings. 

Inspect the filter, then clean or replace it

Not everyone realizes that dehumidifiers typically come with either a washable or replaceable filter. Like the air filter in your car or air conditioner, these can get “gunked” up with dust, debris, and more. This reduces airflow and can cause a dehumidifier to freeze up.

  • Access the filter. Every model is a little different, look for a removable panel or pull-tab to slide the filter out.
  • Hold it up to the light. Can you see through? If not, cleaning or replacement could improve performance.
  • Wash or replace. Your dehumidifier should have a guide that explains how to clean or replace the filter. If it’s washable, you can usually place it in the sink (dirt side down) and spray away. If it’s replaceable, your owner’s manual should specify the size and type.

Check to see if the fan and coils are dirty

A screwdriver and a vacuum cleaner could be all you need 

If you’ve checked the temperature and taken care of the filter but your dehumidifier is still freezing, your next step is to clean out the inside of the unit. The filter is often the first line of defense when it comes to dirt and debris, but fine particles can still work their way inside. This can cripple your air flow, hurt performance, and contribute to your freezing problem.  

Getting access to your dehumidifier’s insides will be a little different for every model, but in most cases – all it requires is a pair of hands and a Philips screwdriver to remove the outer casing. Be sure to unplug your dehumidifier first. Once inside, it should be easy to see where dirt is causing a problem. 

As you inspect the inside of your dehumidifier, ask a couple questions: 

  • Is the fan unobstructed? Or is it caked in dust and barely able to turn? 
  • Are the condenser coils free from dirt and dust? Or are they covered in crud?  

How to clean out your dehumidifier fan and coils

Your vacuum’s crevice attachment can really come in handy here. If the dirt and dust is bad, a wet rag is also a tried and true way to get into the cracks between coils. Remember, this thing is built to handle moisture. You won’t hurt it with a little water, just keep it away from any sensors and control panels. Notice the filthy black water when you ring out the rag? That’s progress. 

Dehumidifier with touch panel, humidity indicator, uv lamp, air ionizer, water container works in apartment while people relaxing. Modern devices against dampness

When temperature and airflow aren’t the cause

More technical dehumidifier repair could be required

If temperature and airflow aren’t at fault, you could have a problem with either your humidistat or refrigerant. When this is the case, you’re exiting the realm of “everyday maintenance” and might consider a quote for professional repair, a DIY fix, or replacing the unit altogether. 

Your humidistat could be damaged

As we covered earlier, a humidistat works a lot like a thermostat to gauge humidity, and regulate the compressor. If you’re operating above the recommended temperature and your dehumidifier is still frozen, your humidity control might be faulty. If it’s not being read correctly, the compressor will stay on which can freeze and damage the coils. 

Tip: The easiest way to check humidity control functionality is to turn the controls and listen for the *CLICK*. It can also be tested with a multimeter, if you have one. 

Your refrigerant might be low

The coils in your dehumidifier rely on refrigerant to cool the air. If the refrigerant is low, the resulting pressure change causes the temperature to drop. This not only damages the coils themselves, but can also cause your dehumidifier to freeze up. 

Frequently asked questions about dehumidifiers freezing up

How do I keep my dehumidifier from freezing?

To prevent your dehumidifier from freezing up, consider these key factors and components:

  • Temperature: Is your unit operating at the recommended temperature? Most conventional dehumidifiers run best at 65°F (or about 18°C).
  • Airflow: Ensure that your dehumidifier is always getting appropriate airflow. A number of factors can influence airflow ranging from positioning in the room to the condition of your fan and filters. 
  • If your humidity controller (called a humidistat) is broken or faulty, it can cause your compressor to work overtime, which can quickly freeze your dehumidifier. Prevent damage with regular maintenance and by following the manufacturer’s operating instructions. 
  • Refrigerant: If your dehumidifier is low on refrigerant, the resulting pressure and temperature drop can quickly lead to ice buildup and damage. Avoid coil damage to prevent leaks by regularly inspecting and cleaning your dehumidifier. 

What happens when a dehumidifier freezes up?

When a dehumidifier freezes up, the water in the air doesn’t successfully condense and drop into the retention bucket. Instead, it sits on the refrigerated coils and freezes there. This eventually creates a buildup that can shut down the entire unit and damage components.

How many years do dehumidifiers last?

The average dehumidifier can last up to 10 years, or even longer. To make the most of yours, regular maintenance is all it takes. Just clean the filter, fans, and coils from time – and don’t forget to empty the bucket. 

The Bottom Line: Simple Maintenance Goes A Long Way

By now, you understand how a conventional dehumidifier works, which factors could cause it to freeze up, and how to fix it. Your dehumidifier should operate flawlessly when it’s within the recommended temperature range and free from dirt, debris, and nearby obstructions. 

Fortunately, preventing freeze-ups and ensuring long-term functionality comes down to simple, periodic maintenance. The best part? It usually only requires a sink, a vacuum, a screwdriver, and a rag. 

We hope this guide made it easy to bring fresh, dry air back to your home or business.