Dehumidifier Advice - General advice before buying a Dehumidifier

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For many people buying a dehumidifier can be confusing with so many makes and models available on the internet and in stores.


If you have never purchased a dehumidifier or never had the need for one you could be confused as to what is the best model for you. Generally you only get what you pay for, as the saying goes, and that can be true. However paying £200 for a dehumidifier when you can buy one costing £100 that apparently does the same job does not mean that the more expensive machine will do the job any better but the more expensive machine will probably have better build quality, extra features or operate in a quieter manner. However, the more you pay may result in a larger capacity machine which you may need depending on the size of room or house. It is no use buying a £99 dehumidifier that consumes 100 watts and expect it to deal with a large house or in a situation where there are several people in the house and where wet laundry is drying on radiators.


The old saying that you get what you pay for is true for dehumidifiers though a great value relatively low priced dehumidifier in my opinion is the DD122FW "Simple". This is a desiccant machine with manual controls and represents very good value and is great for smaller areas where temperatures are likely to be on the low side. Use the MEA10L if your home is generally above 16 deg C as this will be more economical to run

What size of machine should I buy?


Well most manufacturers and websites provide a guide or indication of the size or extraction capacity to suit a particular size of property. For example you will see within a product description that a certain machine for example is capable of dealing with a 3 bed room home while some will handle up to a 5 bed room home. Now this where you must be careful as there are compact homes, well heated and insulated and others that may be larger older style homes where individual rooms are much larger and where the building construction may be poor or where there is poor insulation or insufficient heating.


Therefore if you think that one dehumidifier may sort your problems out, and well it might, you may actually need more than one dehumidifier so do not believe that what you read about a dehumidifier will provide you with the definitive solution to your problems. I don't suggest that you should buy more than one dehumidifier when one will do, so in larger premises buy one dehumidifier and see the effect before considering a second one. Of course in large homes it may actually benefit you to buy two smaller dehumidifiers rather than one big one. A very good Dehumidifier for many homes is the EBAC 2650e that now comes with a 5-year warranty.


Dehumidifiers & Laundry


In so many homes that have condensation and mould you will find that laundry is often dried indoors and this is a major cause of the problem. If clothes are placed on radiators the moisture quickly evaporates from the clothes and finds its way to the cold areas such as a window or cold surface and then condenses back to a liquid. Of course using a dehumidifier can help with this situation and can help you dry laundry and the best way of drying laundry is to place the clothes on a rack and place the dehumidifier and the rack into a room and then close thee door and allow all of moisture from the clothes to be contained in that room that will eventually find its way into the dehumidifier.


Simply allowing clothes to dry on radiators in various rooms is asking for trouble even though a centrally positioned dehumidifier may be in use, as the moisture evaporates so quickly that the windows can attract moisture far more quickly than a dehumidifier due to the large surface areas of windows. If you do dry laundry in your home then you may require a dehumidifier with a greater extraction rate than you would normally require for a home where condensation exists but where no laundry is dried.
The best advice I can give you is simple - if you dry clothes inside the home then do it in one room along with the dehumidifier.


How do I use my Dehumidifier?


Generally you will place the dehumidifier in a central position, such as the hallway for whole house dehumidification but if you have a room or area that is problem area then you may wish to use the dehumidifier in that area to begin with. If you have an issue throughout the house then leave all internal doors open to allow the dehumidifier to circulate the air. Condensation in bed rooms - this can be an issue when people close their bed room doors at night and a dehumidifier can not deal with problem through a closed door. The only solution here is to open all bedroom doors fully in the morning and allow the dehumidifier to operate throughout the day to remove as much excess moisture as possible. Eventually you may find that bed room condensation levels will decrease over a period of time. Of course natural ventilation is beneficial so try to leave a window slightly open at night.


Dehumidifiers & Heat


As you may have noticed when looking for a dehumidifier, the manufacturers of refrigerated dehumidifiers may state that the machine will operate down to 2 or 3 degreed Celsius and therefore this more or less implies that no matter what the temperature you will always extract moisture. This is where I need to point out that lower the temperature in which the dehumidifier operates, the less the machine can extract. The reason for this is that the colder the air the less moisture the air can hold.


Therefore if you have a dehumidifier that tells you that its extraction rate is 16 litres per day at 32 deg C & 90% relative humidity it may only extract a couple of litres at 15 or 16 deg C and as the temperature drops further the less you may extract. So the bottom line here is do not expect too much from a refrigerated dehumidifier unless you are keeping a reasonable level of warmth within the area where it is operating. A good dehumidifier and warmth go hand in hand to achieve a good level of moisture removal.


Absorption / Desiccant Dehumidifiers or Refrigerated Dehumidifiers?


I have talked about the inefficiency & operation of refrigerated dehumidifiers at lower temperatures but there is an answer and that is to consider the use of an absorption or desiccant dehumidifier that works on a completely different principle. An absorption dehumidifier such as the Ruby Dry, DD122FW "Simple" , XDry / DD322 "Simple", has no compressor and is therefore lightweight. An absorption machine draws moist air into a slowly rotating disc impregnated with Zeolite. This disc absorbs the moisture and as it rotates heat is applied via a small fan motor and heating element and re-heats the moisture in the disc to a high temperature vapor. This vapour enters a condenser coil or radiator with the main fan blowing lower temperature air from the room over this condenser creating conditions where the vapour immediately condenses back to water and that water drains into the collection tank.


The advantage of this type of dehumidifier is that it is lightweight and efficient across a wide temperature range but is likely to be more cost effective below 16 deg C. Will it cost more to run? On the face of it yes, but as it gets the job done more quickly it will run for less time and when compared to a refrigerated dehumidifier working at low temperature. The refrigerated machine will still be running long after the absorption machine has got rid of the condensation so the bottom line here is increased efficiency with little if any increase in running costs. Be aware that absorption dehumidifiers will increase the air temperature as these machines run between around 350 to 700 watts depending on the model and mode of operation.  I would not suggest the use of domestic desiccant dehumidifier in a very dusty environment.


Which type to buy?


Desiccant if below 16 deg C otherwise use a compressor model such as the MEA10L for smaller area or the Ebac 2650e for a larger home as these will prove more economical to run. However, using a desiccant dehumidifier at warmer temperatures is not a problem. Many people are quite happy to use a desiccant machine at any temperature simply due to the fact that they are lighter in weight and therefore easier to handle, produce heat that maybe a benefit to them plus they can be quieter (on low fan speed). Just keep in mind that they can be less economical to operate when compared to a compressor model at higher temperatures.

Humidistat Accuracy - please be aware that the humidistat’s on many desiccant machines including the Ruby Dry, the DD122FW "Simple" and the DD322FW "Simple are not that accurate and therefore humidity levels can go above & below the actual setting on the machine. Using a thermo-hygrometer will help you set your desiccant dehumidifier to the correct level is suggested. Generally the rotary humidistat on the DD122FW "Simple & the DD322FW "Simple" will be around +/- 6% of where you set the rotary dial. With a Ruby Dry if you set the control to 60% the machine will actually control humidity to between 45 & 55% which is generally ideal. Setting the Ruby Dry to 40 or 50% may well be totally unnecessary and wasteful of electricity.

You really require a thermo-hygrometer so that you can trim the dehumidifier control to a suitable humidity level particularly with respect to the EcoAir DD122FW & DD322FW "Simple" desiccant dehumidifiers. Of course a degree of manual intervention is often required when you feel that your humidity is under control. 

Air Filtration


With all dehumidifiers you must maintain the cleanliness of the air filters. Failure to do so can result in premature failure and reduced performance. Check filters every 4 to 6 weeks. If you are considering buying a desiccant dehumidifier and you may have a dusty environment then consider the Ruby Dry Dehumidifier as this dehumidifier is also fitted with carbon impregnated secondary filter. Forget the carbon business as this filter is there to protect the machine and this filter must be kept clean - very important.


Sound Levels


With all dehumidifiers we try to show the sound level or decibel level to give an indication of how loud a dehumidifier may be. However, the decibel levels can not really give you an accurate idea of what you will hear and sometimes it’s not all about decibel level as you can have 2 pieces of music both at the same level but one you hate but the other you like. Most dehumidifiers operate in the region of 37 to 46 decibels so you have to understand that no dehumidifier is silent and if you are close enough to a machine it will probably bother you. So how do you minimise the sound, well for a start place the dehumidifier in the hallway or on a landing, use the machine during the day when you may be out at work or when there are other sounds to be heard.


For those of you who have never heard a dehumidifier I can try and describe the sound. First of all you have a compressor just like you have on your refrigerator and so the sound of a dehumidifier compressor is similar to the fridge compressor but at a lower level. Then you have a fan usually with adjustable speeds or automatic speed control so add this fan sound to the sound from the compressor and you have a busy sounding piece of equipment. It should not be a mechanical racket but you will be conscious of motors running plus the sound of air being emitted from the machine. Unless you have a particularly damp issue the dehumidifier after a period of use should spend more time off than on.


If the machine is in the hall and you are in your lounge then that’s fine but if you are sat next to the dehumidifier then that’s a different story. A number of refrigerated dehumidifiers now use a compressor called a rotary compressor and these are generally on the quieter side compared to reciprocating compressors still found in some makes of dehumidifier, but at times there is little to choose between them.  I have mentioned Desiccant dehumidifiers and some of these can be quieter on their minimum speed than refrigerated dehumidifiers but as they move quite a considerable amount of air the sound level can be quite high when they are operating on high fan speed but once humidity is brought under control they should spend more time on low speed so sound levels are not really an issue. The quietest desiccant dehumidifier on low speed is the Ruby Dry.


Should I use it at night? Yes you could do if it does not disturb sleep, so use the dehumidifier in the hallway if possible but don’t necessarily have it on the landing area with all bed room doors open and expect to have silence.  


I believe a dehumidifier is in your home to do a job and that is to prevent condensation and mould and therefore you either put up with some additional sound or continue to have a damp problem and do remember that a dehumidifier should not run non-stop as the built in humidity controller will turn the compressor or heater in the case of the desiccant machines on and off according to the humidity levels. Do keep in mind that some dehumidifiers, particularly desiccant dehumidifiers, will continue to run the fan even though dehumidification has stopped though if the fan is set to low speed, noise intrusion should not be an issue.


Using a dehumidifier in winter - click this link for advice on dehumidifier in cold weather.


We hope that this information will help you make the correct decision when it comes to purchasing your dehumidifier and we will try to help you further by adding additional information to this page.