How to Set a Dehumidifier

How to Set a Dehumidifier

If you have always lived in a dry climate, you might not understand why people need dehumidifiers in their homes. You might not realize what dehumidifiers do. The thing is, above average humidity levels in the home can be extremely uncomfortable for people to live in and detrimental to our health, potentially aggravating allergies or other respiratory health problems.

In addition, high humidity will damage wooden furniture, curtains, clothes, musical instruments and other valuable items, not to speak of ruining dry food items like flour and rice.

What does a dehumidifier do?

A dehumidifier does what the word says: it takes the humidity out of a room. How does it do that? The workings of a dehumidifier are similar to that of an air conditioner, but where the air in a conditioner is cooled, down, the air in a humidifier is heated.

A dehumidifier has a fan that draws moist air in the room over a series of coils inside the dehumidifier: first the air moves over a refrigerated coil, and then a heated coil.  The refrigerated coil cools down the moist air sufficiently for it to condense into water droplets that are then collected in the bucket of the dehumidifier.

So how do you know when you need a dehumidifier? What is the ideal humidity level? The ideal relative humidity level should be somewhere between 30% – 50%. At humidity levels around 60% mildew and mold starts showing up on walls, clothes, curtains, in closets and in dark, unventilated places.

But there is another dead giveaway that you have a moisture problem in your home. Even before you notice any mildew growing, you’ll become aware of a distinctive, dank smell. To actually get an accurate gauge of the moisture levels in your house, get a hygrometer to check the relative humidity level in any room. You can buy a hygrometer cheaply at any hardware store.


You have to distinguish whether the room is moderately damp, very damp, wet or very wet. This will determine which level you set the dehumidifier at. You can find a chart here to help you.

Optimum humidity setting

Be careful to set the humidity level optimally. Setting your ideal humidity level too low could ware out the dehumidifier because it will be running continually. The Energy Star website explains that the volume of moisture or water vapor in the air is often referred to as Relative Humidity (RH), which is an indication of the amount of water vapor in the air when compared to the greatest quantity of water vapor the air can hold at that temperature.

According to Energy Star, the ideal RH level is usually between 30% and 50% in warm weather and between 30% to 40% in colder climates when you are running heaters.

Using a built-in humidistat or a hydrometer to determine the existing levels of humidity

Many dehumidifiers come with a built-in humidistat, a device that lets you set your desired RH for a room. When the room is at the preferred RH level, the dehumidifier will move on and off routinely to maintain the optimal humidity level.

If your dehumidifier doesn’t have a humidistat built-in, you can buy a hygrometer to gauge the relative humidity. The hygrometer will monitor RH levels continuously so you know when to switch the dehumidifier on and off.

Step by step, setting your dehumidifier

  1. Read through the manufacturer’s manual so you familiarize yourself with the workings of your dehumidifier.
  2. Use the hydrometer to measure the relative humidity level in the room you want to dehumidify.
  3. Make certain the dehumidifier is plugged into a grounded wall socket. Note whether your model automatically turns on when plugged in – if not, look for the “On” or “Power” button on the device.
  4. Next, search for a set of buttons or a dial labeled “Humidity Level”, “Dryness Setting,” or similar. Turn the dial in the direction that indicates increase in dryness to decrease the humidity or press the “Humidity Level” or similar button repeatedly until the display indicates the humidity level you want. Note: higher values indicate higher humidity levels.
  5. Now you need to set the speed of the fan, so search for a button that is named “Fan Speed”, “Power Level,” or something similar. Push the button to select the power level you prefer. Note: The higher the level, the faster the room dehumidifies but makes more noise and saps more energy.
  6. If your model allows for it, you can preset the time the dehumidifier should turn on. Look for a “Timer” button and press it repeatedly to choose the time you want it to start running.
  7. Allow the dehumidifier to run through several cycles. The first cycle will remove most of the excess moisture from the air; after that, the humidifier will ideally maintain the optimal level of humidity.
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