Buying Guide – Dehumidifiers Selection and Operation

There are many reasons that you may need to use a home Dehumidifier including both comfort and to reduce the growth of mold. In this HowTo we will cover some of the features that can help you make your purchase decision and cover some of the operation and maintenance considerations.

How Does a Dehumidifier work?

Dehumidifiers work on the principle of condensation of air moisture on cold surfaces. Everyone has taken a cold drink out of their refrigerator on a worm humid day.  When you retrieve the soda its outside surface is dry but as it sits in the warm air water that is trapped in the room air comes into contact with the metallic surface of the soda can. When this happens the water in the air condensates and water droplets are formed.

This is exactly how a Dehumidifier works. A coil that is filled with a Freon type coolant is pumped into a coil and then a fan that sits in front of that coil forces room air across the cold surface of the coil. When the water in the air builds up it forms droplets that are then collected and stored in a tank or tray below the dehumidifier.

What are some of the features you can look for?

Most dehumidifiers will have a few basic common features.

• A run time setting that will set how often the Dehumidifier will cycle or turn on.
• A front Warning Light  that shows the tank is full.
• An Automatic Shutoff when the tank is full.
• Automatic Defrost if the cooling coils Ice Up.
• Easy to clean filter screen or front grill to remove room dust that accumulates durring operation.
• Drain Plug on water tank so you can route the water collected to a sink or waste line reducing your need to empty the tank every few days.

Basic Operation

• Install your Dehumidifier in a location that can get good air flow. The fan inside the dehumidifier needs to circulate the rooms moist air through its system to remove the water vapor.

• Run the Dehumidifier on the “VERY DRY” or Highest setting for the first few days of operation. This will remove water that is in rugs and furniture. Once the bulk of moisture is removed you can then lower the setting to 50% and then adjust as needed to provide comfort and performance.

• In basements it is important to seal your basement walls with a moisture barrier paint “Drylock is one” this will reduce your need to run your Dehumidifier but it will probably not eliminate it totally. If you have a sump pump you should cover the top as possible to reduce evaporation.

• Remove Fish Tanks and House Plants: Large Fish Tanks or a large number of house plants will fill the room air with evaporated water. It is important to place these items in an area of your home that has good ventilation or reduce the water that is evaporated from them with lids or other devices.

•  Run your Dehumidifier at 70F or above. When you run your dehumidifier in a room that is cooler there is a higher likelihood that the coils will freeze up. If this happens you should turn off your dehumidifier and let the frost melt.

Cleaning is very important… You should empty the water that is in your dehumidifier often if not every day then every couple days. Water that sits in your tank can grow harmful bacteria. If your tank or the coils get moldy then you should use a strong bleach to clean all of the surfaces before you continue using it. Dirt and Dust is another problem because dust is sucked through the fan of the dehumidifier it will accumulate on the internal parts and coil. This will reduce the performance of your dehumidifier so you must change filters and remove dust every couple weeks or months as necessary in your location.

Energy Efficiency

Dehumidifiers can be very expensive to run but there are times that you must have one. You should always check the Energy Star information for both the average price and the running time they expect. Energy Star ratings are not based on Continuous Use of some appliance such as dehumidifiers and air conditioners so read the tag closely. For this reason you should take the steps to remove the possibility of water vapor entering your home by use of vapor barriers when installing insulation and by the use of special paints that can reduce vapor from passing through your walls. As we said above basement concrete walls can be painted with drylock but you may also want to add a plastic vapor barrier and drywall the area. Check our Howtos on Mold Abatement.

More Information

There are many reasons that you should get a professional to help you with your purchase. Treating the symptoms is not always the best way to cure a problem and it might just be that your home is built over a spring or has a high water table. This would mean that other methods need to be used to cure your wet basement problem. If water actually pools or your carpets feel wet then you definitely have a serious problem. If you smell or see mold then you should always get an expert to give you advice.

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