Dehumidifiers
Dehumidifiers come in a range of types and models with a wide variety of features. It is important to understand the purpose of each of these features and to decide which of these will be of benefit to you in your home.
5. Laundry mode
7. Timer
8. Ioniser
11. Hot gas defrost
12. Mildew guard
13. Casters
14. Watts
16. Dry it inside
17. Size
19. Noise level
The traditional model has a compressor and works the same way as a refrigerator. Refrigerant is pumped around a series of pipes causing some pipes to be very cold and some to be hot. A fan blows the incoming air over the cold coil causing the moisture in the air to condense and freeze on the pipes. Then the dry air is blown past the hot pipes and is warmed up. At a regular interval the system is reversed so the pipes defrost and the water is collected in the tank for disposal. While it is defrosting the dehumidifier is not dehumidifying.
A desiccant dehumidifier works differently. It has a round disk that is made of zeolite that rotates slowly and also vibrates. As it vibrates water molecules in the air condense onto the disk. The disk is also rotating. At the top of the disk the moist air is blown by a fan and moisture is removed. At the bottom of the disk warm air is blown past the disk and the water is blown off the disk and is collected in the tank. The air that is expelled into the room is warmer than the inlet air by 10 to 15 degrees
Why? Both units are efficient. The compressor units dehumidify for part of the time and defrost for part of the time. Because of the compressor they are noisier. The desiccant units dehumidify all of the time they are on and they are quieter since the fan is the only part that creates noise. The desiccant units consume on average approximately the same amount of electricity as a compressor type dehumidifier.
A regular compressor dehumidifier will operate in the 5 to 30 degree C range. The warmer the weather the faster the dehumidifier will collect moisture. When a compressor type dehumidifier is defrosting it uses the ambient temperature to melt the ice on the coils. In the case of some dehumidifiers like the Mitsubishi models they have a hot gas defrost so will operate down to just above 0 degrees C.
Desiccant dehumidifiers operate on a different system with the wheel being dried out using hot air so again will operate down to just above 0 degrees C.
Why? If the dehumidifier is to be used in an unheated area such as a garage or caravan it is important that the unit will operate at temperatures that are as low as possible.
The capacity of each model is defined as the number of litres of moisture that can be removed in a 24 hour period at 30 degrees centigrade and 80% humidity.
Why? The capacity of the machine will dictate the amount of water that it is possible to remove during a day. The bigger the capacity the faster the humidity will be reduced. As a rule the higher capacity of the machine the larger the unit is. So there is a trade off between the capacity of the machine and the size of the unit.
Each humidifier has a tank that collects the moisture when it is removed from the air. Some models have tanks that have a cover that stops water spilling out when you take them out to be emptied.
Why? The bigger the tank the fewer times it has to be emptied in a day but the heavier the tank is when it is full.
The laundry mode increases the fan speed so that the air in the room and is drier so that the laundry will dry faster allowing less time for moisture in the air to encourage mould growth.
Why? If you are hanging your laundry indoors or have a shower room with poor ventilation the laundry mode can be very helpful to get rid of excess moisture quickly.
There are louvres that rotate and distribute the dried air to the front and top of the machine so the air is spread around the room more evenly.
Why? The louvres distribute the air more widely around the room so there are fewer dead spaces where there is no air movement.
The humidifier can be set to come on for a set period of time of say 1, 2, 4 or 8 hours.
Why? If you want the dehumidifier to run for a set period of time you can set the timer so you know when it will shut off.
An ioniser will generate negative ions that are blown into the air. Air in an enclosed space will gradually become positively charged resulting in static electricity discharge when you touch something metal like a radiator and the positively charged air will suspend dust particles in the air. When negative ions are added static electricity is dissipated and the dust will fall to the ground. It is like being at the sea side.
Why? It cleans the air and reduces static electricity in your home.
Dehumidifiers have a very basic filter that will remove large particles from the air to stop the particles being sucked into the workings of the machine and causing them to eventually clog the machine. Some models coat this filter with nano silver (very small particles). This kills any bacteria or viruses that are drawn into the machine and cleans the air that is expelled back into the room.
Why? Cleans the air in the room and kills bacteria and viruses so stopping the fan distributing them.
A manual control is basically a knob that turns that will go from low to high and continuous operation. The higher the setting the more moisture is removed and the lower the humidity in the room. The manual control machines are usually the basic units and have one fan speed.
The electronic control units are more sophisticated units that can offer more operating options. The first option is either a pre set humidity level of 40, 50,60, and 70% level or in some units there is a variable setting. There is also the option of a timer that will turn the unit off after 2, 4 or 8 hours. Most units have one fan speed but some of the desiccant units have up to 3 fan speeds for faster drying.
Why? The units with manual controls are basic machines that do the job. The units with electronic controls offer more options such as more fan speeds.
With a regular compressor dehumidifier it will not defrost at low temperatures. With the more advanced models like the Mitsubishi E16VX the hot gas defrost allows it to operate and defrost at just above 0 degrees.
Why? Useful in unheated areas where it is important to keep the humidity low, protecting against mould and moisture damage.
The Mitsubishi model has a system called Mildew Guard. This is an automatic function that the unit will operate intermittently for 2 to 4 hours a day. The length of time the unit operates will depend on the humidity in the room and the setting of the machine.
Why? This is an automatic function that will keep the humidity level in your room at a desired level and will protect you and your property.
Most dehumidifiers have castors to allow for easy movement of the unit. They can be quite heavy and castors can be very useful if you are moving the unit around to different areas.
Why? Dehumidifiers are reasonably heavy units so castors can be very useful and save your back.
The wattage specificed against each unit is an indicator of what the running costs of the unit will be. The thing to remember about the 2 different types of dehumidifier is that the compressor type has a lower watt rating but only dries the air for part of the operting time, the rest of the time it is defrosting. On the other hand when the desiccant units are on they are dehumidifying.
Why? Gives an idea of the comparison of the running cost of the different units.
When there is a power cut some dehumidifiers will not restart. It is important that the dehumidifier restarts after a power cut if the unit is to be used in a property that is not inhabited all the time for example a caravan, boat or second home.
Why? If there is a power cut you do not have to worry about the dehumidifier not restarting.
The Mitsubishi dehumidifier has a feature that will dry the interior of the machine so that mould and bacteria will not build up in the machine.
Why? Dehumidifiers can have a lot of water passing through them and it is possible for mildew to develop in the machine. By having the machine dry itself out, this greatly reduces the growth of mildew in the machine.
The size of your dehumidifier is important since it may be used in the living area of your home. Always check to see if you have an area in the middle of your home to place the dehumidifier where the air movement will not be restricted.
Why? The dehumidifier will be there for a long time so you don’t want it to be in the way.
Most dehumidifiers come with a continuous drainage option. If you can locate your dehumidifier close to a drain the unit will empty into the drain saving you the effort of emptying the unit up to several times a day.
Why? Saves time emptying the unit as well as eliminating the risk of spilling the water while you are emptying the unit.
Both the desiccant and the Mitsubishi models are quieter to operate than the regular compressor models.
