Dehumidifiers - Frequently Asked Questions

How do I know if I need a dehumidifier?

For comfort conditions room humidity should be anywhere between 40% & 60% rH (relative humidity).  A sign of excess moisture is condensation on the windows inside the room; the room may also feel very stuffy (although this can vary from person to person).  The best way to identify if a dehumidifier is needed is to obtain a thermo-hygrometer which will measure the humidity in the room.

You can find them on the AWC: http://www.airandwatercentre.com/thermohygrometer-shows-temp-humidity-297-details/

 

What size dehumidifier do I need for my room?

This is a not a simple to answer as there are many variables.  The size of the dehumidifier is dependent on how much moisture there is in the room for example if there is a excessive amount of moisture in the room then a larger machine would be needed and vice versa.

 

Can one dehumidifier do a whole house or would I need one unit in every room which is affected?

Depending on how damp the area is some dehumidifiers can quite happily do a whole house. If there is one area which is badly affected then it would be best to place a dehumidifier there first to get the problem under control and then move to a more centralised location once the problem is sorted. If the dehumidifier is placed centrally then internal doors will need to be open to allow air to move and damp air will always migrate to dry places.

 

What’s the difference between a compressor dehumidifier and a desiccant/silica gel unit?

A compressor dehumidifier uses refrigerant to create cold coils (very similar to fridges & freezers) upon which moisture from the air is condensed. This condensation then runs from the coils into the water tank at the bottom of the unit. A desiccant or silica gel dehumidifier uses a moisture absorbent material which when saturated is heated up and the moisture is released into the tank. Also desiccant/silica gel dehumidifiers aren’t affected by temperature so they can be used in low temperatures but due to the way that the material is heated up to be reused they do have a higher power consumption than compressor machines.

 

What is the difference between desiccant and silica gel?

There really is not much difference between desiccant and silica gel material. They will both absorb moisture but the main difference is that desiccant can hold and extract more moisture than silica gel.

 

Does the desiccant/silica gel inside the dehumidifier have to be replaced?

No, the material within the dehumidifier is constantly recycled. When the material is saturated with moisture it is then heated up, the moisture falls into the tank and then the material is re-used.

 

Can a dehumidifier be used in a bathroom?

As long as the dehumidifier has an IP rating it can be used in a bathroom. An IP rating is basically a rating stating how well a unit is protected against objects. The two wall mounted dehumidifiers both have an IP rating of IPX1 which means that they are protected against vertically falling drops of water (condensation). They would need to be installed out of the way of the shower, bath and any taps.

 

I need a dehumidifier for my cellar/basement, what would you recommend?

If the cellar/basement has no heating then the recommended dehumidifier would be the 10 litre desiccant unit as it can operate in low temperatures down to 1°C and can be set for continuous drain. If wanting a more powerful unit with a higher extraction rate then would recommend the 20 litre dehumidifier again which can also be set for continuous drain.

 

I have a holiday home which needs a dehumidifier what can you recommend?

The best dehumidifier for this use would be a unit which has an auto restart, this means that if the unit is left unattended and there is a power cut the dehumidifier will re-start in its original setting rather than going to standby.

 

I want to use a dehumidifier in my garage with my cars, which one would be best?

The best type of dehumidifier to use in a garage would be a desiccant or silica gel unit. This type of dehumidifier can be used in areas which might not have any heating and can operate down to a temperature of 1°C. The 3 desiccant/silica gel units that would be suitable are: The 7 litre desiccant dehumidifier, the Ruby Dry dehumidifier (which is a silica gel unit and will extract 6 litres of moisture a day) or the 10 litre desiccant dehumidifier.

 

My house has been flooded and I need to dry it out, which unit would be best?

For drying out a house it would be best to go for a larger unit, anything from 20 litres extraction upwards. The larger units are more industrial looking but are far more effective compared to a smaller domestic unit. We would also recommend getting the air flowing in the house so the use of a large fan, such as the 18inch high velocity fan, will get the air moving and aid in drying out the house.

 

I want to use a dehumidifier to help dry out my washing, can this be done?

All dehumidifiers can be used to help dry clothes but there are a few machines which actually have a laundry mode on them. A laundry mode will leave the dehumidifier on in full power continuously and will dry clothes as quickly as possible. The dehumidifiers that have this option are:  The wall mounted dehumidifiers, 7 litre desiccant dehumidifier and the 10 litre desiccant dehumidifier.

 

I have very limited space and would prefer a wall mounted dehumidifier, is there such a thing?

There is a wall mounted dehumidifier; it comes in a 12 litre or 14 litre versions.  Both units have a digital display allowing the humidity to be set and can also be set for continuous drainage.

 

I don’t want to be emptying the water tank all the time what can you recommend?

The majority of dehumidifiers have the option to be set up for continuous drainage. This means that a hose can be fitted to the unit which will then drain away any moisture which is extracted.

I need a dehumidifier which is lightweight, which would be best?

A lightweight dehumidifier would be a desiccant or silica gel model. The reason that these units are lightweight is due to the fact that they don’t have a compressor inside them and just have a moisture absorbing material.

 

I want to be able to control the amount of moisture that is removed, what unit would be best?

The best dehumidifiers would be one which has a humidistat built in as this will allow you to set the humidity level you would like to maintain and the unit will then switch on and off according to the setting. For more accurate control it would be best to go for a dehumidifier which has digital controls rather than a rotary control as the digital display will let you see what the room’s current humidity is and see what humidity you are setting.

 

Are all dehumidifiers noisy, are there any quiet units?

Desiccant or silica gel dehumidifiers are the quietest as they do not have a compressor inside them so the only audible sound would be the fan.

A compressor sounds very much like a fridge when it’s on and has a slight humming noise when the compressor starts up.  

Do you sell a dehumidifier that doesn’t have to use power?

All dehumidifiers require an electrical supply to be able to extract moisture from the atmosphere.  

An alternative product we sell is Superdry which is a onetime use calcium chloride desiccant moisture absorber. These moisture absorbers come in a range of sizes from a small sachet to long poles suitable for hanging. Superdry can be used in areas from small storage spaces up to large containers. They on average last about 6-8 weeks and have to be replaced when full.

 

What’s the cost of running a dehumidifier?

This will vary depending on the type of dehumidifier and how much power it uses. A desiccant dehumidifier will use more power than a compressor type as it has to heat up the moisture material within it to be re-used again.

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