How Does a Dehumidifier Work?

Every summer when the humidity has gone through the roof, a dehumidifier will be there absorbing all the excessive moisture. It is a very important appliance that you will find in every household. Have you ever wonder how a dehumidifier would magically draw in buck load of water from damp air? What is the secret behind this water bending technology? How does the dehumidifier know how long it should run or when to stop? All shall be revealed here.


How Do Refrigeration Dehumidifier Works?

Refrigeration dehumidifiers work on the same basis as a refrigerator or air conditioner. When active, the wet air will be drawn inwards to the ‘refrigerated’ coil that freezes the air. The cold air that passes over the coolant pipes will form water droplets that drip into the bucket. The now dry air will be heated and dispersed as mists through the hot compressor unit. The entire mechanical refrigeration cycle will continue until the bucket is full (via a plastic float) or a humidity point is reached. Refrigeration dehumidifiers are safe, very effective, and consume less energy at high temperatures. The downside is it can be costly to maintain and is less effective when operating below 45% relative humidity level.

How Do Desiccant Dehumidifiers Works?

Desiccant dehumidifiers uses moisture absorption that reduces humidity by absorbing water molecules. It is similar to desiccant packets or silica gel found in food and clothes. The damp air is pulled in to dehumidifier’s rotating wheel via the electric motor fan. The rotating wheel (typically made with Zeolite) will then absorb all moisture from the passing air. The small air duct underneath will heat up the air and push the dry air out. Desiccant dehumidifiers are safe, very quiet, and use less energy at lower temperatures. It is the more sensible and economical choice than a refrigeration based dehumidifier.

How Does a Thermoelectric Dehumidifier Works?

Peltier AKA Thermoelectric dehumidifiers convert energy into a temperature difference and vice versa. Typically made of only four parts: A Peltier module, a fan, a smaller cold side heat sink, and a larger hot side heat sink. It starts off with the fan pulling damp air into the back of the dehumidifier. When electricity runs through the Peltier elements sandwiched between the two heat sinks, one side of the module gets heat up while the other side cools down. The air will travel pass the hot and cold sink that condenses moisture to the reservoir through before exhausting the dry, warm air. The entire cycle is called thermo-electric or Peltier effect and can be found in most mini dehumidifiers. The biggest advantage with thermoelectric dehumidifiers is they are very quiet, even more so than a desiccant unit. Peltier dehumidifiers are also portable, durable, easy to maintain, and inexpensive as it has little moving parts. The disadvantage is of course the limited capacity in absorbing surrounding moisture. Because of that, Peltier dehumidifiers are only meant for table, bedside or wardrobe use rather than the entire room. It will not work in a harsh environment like below freezing weather or high humidity over 50-70%.

What is Ionic Membrane Dehumidifier?

The Micro-size dehumidifier, Ionic membranes is not a common dehumidifier that can be found in the market. It is often used in appliances like CCTV, IP camera, electrical panel, cabinet, display lighting, and industrial areas. Ionic membranes are usually made of solid polymer electrolyte (SPE) membrane at only a few millimeters thick. Ionic Membrane is maintenance-free, uses low power, completely silent, and vibration-free. It does not have a collection tray as there is no water collected. On the flip side, because it has no moving parts, it can only remove moisture from enclosures therefore it will not improve home air quality.

Do I Need a Dehumidifier?

A hygrometer is very useful to determine if a room has excessive moisture, but there are ways to do the check without relying on one. First, confirm if the air quality in your home feels stale, dry, and uncomfortable to breathe. Next, scent any unpleasant, musty odor that lingers around the house. Lastly, spot any mold patches that are constantly growing on the wall, floor, and ceiling. If you check all three lists, a dehumidifier is urgently needed.

Which Types of Dehumidifier Should I Go For?

Go with a Mechanical/ refrigeration dehumidifier because it is the popular type with plenty of availability. It is arguably the most effective type on its moisture capturing ar normal temperature. A desiccant dehumidifier would also be a good option for the bedroom due to its silent operation. It is also very energy efficient at low temperatures and rarely freezes up. So if you are comparing many different models at this stage, focus on the points below instead.

  • Capacity (pints): In other words, it measures how much water can be removed in 24 hours. You will typically find dehumidifier in 30-pints, 50-pints, or 70-pints category. The higher the numbers, the faster and larger the room size a dehumidifier would be able to cover.
  • Wattage: The higher the wattage, the higher the power usage in a dehumidifier. A mini dehumidifier would only use 20 watts of power compared with a mid-range model that use 50 watts of energy. So rather than focus on a model with the least wattage consumption, go with the same category models in terms of dehumidifying. Remember, less power usage equals cheaper electricity bills.
  • Functionality: Since most dehumidifiers work identically to each other, look out for these functions when choosing one. Low-temperature operation with auto defrosts, auto restart during an outage, and auto shut-down when the bucket is full. Digital display with humidistats, 24-hour timer, and filter check are important features to have as well.

There are three common types of dehumidifiers in the market. A mechanical/ refrigeration, absorption/ desiccant, and thermoelectric. By keeping the humidity level in a room not more than 50 percent, a dehumidifier will reduce the number of molds, mildew, and other microbes growth. It will also make the air much more breathable, free from allergies and musty mold smell. As for non-health benefits, it will protect your household items from rust and decay due to excessive moisture. You can learn more about the benefits of dehumidifier here.

How Does a Dehumidifier Works?

A dehumidifier will suck damp air in a room, extracts the moisture out, and blows back out the dry air. In typical fashion, dehumidifiers can be broken down into four component parts: a fan compressor, cooling coils, plastic reservoir, and reheater. The front reservoir collects the dripping water through condensation. At back, there will be a gravity drainage pump that can be used to pumps water straight to a floor drain underneath the device. Advanced models have a built-in pump internal motor that draws the water straight out of the dehumidifier. With either of the continuous drainage option active, you do not have to rely on the removable bucket to collect water and empty it when it's full. The reheated air will be exhausted back to the room and the whole dehumidification cycle repeat itself. All full-sized dehumidifier will have a humidistat that measures the relative humidity (RH). You can program the humidity level between 30 to 50 percent and the dehumidifier will run until the desired point is achieved.



Max Fernandez

A loving father and a dedicated reviewer for airfuji.com with more than 1000 air purifiers under his belt. Max Fernandez is also one of the million patients currently suffering from asthma. Feel free to nudge him if you have any questions.