How Does a Dehumidifier Work?

How Does a Dehumidifier Work?

A Dehumidifier installed to help prevent further damage.
The source of the water damage is from the homeowners dehumidifier.

As a Water Damage Restoration Company, This Is Asked All The Time

Dehumidifiers reduce the humidity level in your home by drawing the room air through the appliance and removing the moisture. The level of humidity reduction is regulated by the humidistat or by a control board with a sensor. When the humidistat or sensor detects a need to reduce the moisture in the air, 120 volts of alternating current is sent to the compressor and the fan motor.

The compressor is part of a sealed refrigerant system that compresses the refrigerant in gas form and pumps it through a set of condenser coils where the gas becomes a hot liquid. The coils dissipate the heat as the liquid travels through them. Once the refrigerant has passed through the condenser coils and the capillary tube, it travels to the evaporator coils as the refrigerant liquid enters these coils it expands into a gas which makes the coils cold. The gas flows through the coils to a suction line attached to the compressor. The compressor will then pump the gas back into the condenser coils where it once again becomes a liquid and the cycle continues.

At the same time the fan motor rotates a blade to draw the rooms humid air into the appliance where it condenses on the cold evaporator coils. The condensation accumulates on the evaporator and drips into a bucket or is diverted through a hose to a floor drain. The cooler air from the evaporator is heated as it passes through the condenser coils and is returned to the room.

Water vapor reaching its fail point on the window

This process continues until enough moisture has been removed from the air to satisfy the setting on the humidistat or the control board. Most dehumidifier models are equipped with a safety switch that will prevent the appliance from running if the bucket is full. If you suspect the dehumidifier should be running when it’s not, the buckets safety switch may be defective. 

You can use an ohmmeter to test the switch for continuity to help determine if the switch is functioning or not. Both the condenser and evaporator coils need proper airflow for the dehumidifier to work efficiently.

Over time these coils can collect dust dirt and debris so it’s a good idea to clean the coils regularly. Just be careful not to bend the fins. If you hear the dehumidifier running but no air is being exhausted, then it’s likely that the fan motor has failed and will need to be replaced.

If your model is equipped with an air filter, the filter will need to be cleaned from time to time to prevent frost from building up on the evaporator coils. Most standard dehumidifier models require the room temperature to remain above 65 degrees Fahrenheit for the appliance to work properly. As lower temperatures can cause the evaporator coils to frost over.

If the temperature in your home regularly drops below 65 degrees, you will need to obtain a model that is specifically designated for lower temperature operation. A&R Environmental uses custom made to our industry dehumidifiers for all water damage and mold remediation jobs. These dehumidifiers contain modifications to the conventional refrigeration system that result in cooling the process airstream to a significantly lower temperature, using various energy exchange systems. Visit our website to see a dehumidifier in action on a water mitigation job.

Dew Point…? What’s That? What’s the Humidity Outside?

Dew Point…? What’s That? What’s the Humidity Outside?

Sweating outside on a humid day.

Everyday learning. Trying to spread the wealth of knowledge one blog at a time.

Let’s take a couple minutes to explore the difference between relative humidity and dew point. Relative humidity, despite its name, is not a good measure of how humid it is outside. Rather, dew point is a much more accurate representation of how humid most people would describe it feels outside. The big difference between the two is how much moisture the air can hold.

When the temperature is 55 degrees, the relative amount of moisture the air can hold (relative humidity), is much smaller than the amount of moisture or water vapor the air mass at 95 degrees can hold. The relative humidity of 55 degrees of 50 percent, is a much smaller amount of water vapor or moisture in the air, than a 50 percent relative humidity at 95 degrees. Even though the RH is the same it’s considerably more moisture when the temperature is 95 degrees.

When you look at the measure of how much moisture we’re talking about, dew point is the value we often refer to. So a 37 degree dew point is what you get with a temperature of 55 and a relative humidity of 50%. While a dew point gets up to 74 by the time you have a temperature of 95 with a 50% relative humidity.

Water vapor reaching its fail point on the window

This is roughly a subjective scale on how most people would describe a given dew point to feel outside. Generally speaking, a dew point below 60 feels pretty comfortable and dry to most people. When the dew point starts climbing through the 60’s, the humidity becomes increasingly noticeable. As the dew point climbs through the 70’s, the humidity feels downright unbearable outside.

So the next time somebody asks you how humid it is outside remember, relative humidity is a relatively poor measure of how humid it is. Dew point is a much more accurate representation of what the humidity feels like when you step outdoors.