Clothes dryer

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Revision as of 05:40, 7 February 2007 by NT (talk | contribs) (FAQ & minor bits)
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Clothes line and Tumble dryer are the well known clothes drying options. Here a 3rd option is presented with advantages over tumble drying. This is a humidistatic dehumidifier in a large wardrobe, or walk-in wardrobe.


TD: tumble dryer

DH: dehumidifier

How it works

Clothes are taken out of the washer and put away in the wardrobe. And thats it, the end user need do nothing else.

Putting damp clothes in the wardrobe sets the dehumidifier running. The dehumidifier fans the air round, warms the space slightly, creates a dry climate and removes the moisture. The dehumidifier switches off when the clothes are dry.

Advantages & Disadvantages

Advantages compared to tumble dryer:

  • Takes up less space
  • Takes up no kitchen space
  • One less operation per load, since the clothes all go from washer to wardrobe, not via the dryer.
  • No dryer noise.
  • Much less energy consumption than a tumble dryer
  • Much lower run cost
  • Much less wear on clothes
  • Produces deionised water suitable for steam ironing, steam cleaning, batteries, etc


  • Heavier clothes such as winter coats can take many hours to fully dry. However this is rarely a disadvantage in reality. You would have to be a bit disorganised for this to be a problem.

Notes on Operation

Normally all clothes would be hanging.

Socks can be put in a plastic matrix on one side if this is preferred to a multi-bar hanger. Drawer dividers are used to create this matrix of miniature cubbyholes.

For items to be stacked, such as bedding, these can't be stacked when wet, but can be once dry. They can be put in the wardrobe on slatted or wire shelves to dry, or if preferred one can use extra large bedding hangers.

Some ventilation is recommended, clothes need at least some fresh air to dry fresh. Ventilation does not noticeably affect drying times.

Whole pillows of all types may be dried with this system. The pillow needs to be placed close to the air outlet on the dehumidifier, as pillows need forced airflow during drying to dry the centre of the fill sufficiently quickly.


The dehumidifier needs to be humidistatic, and preferably have a continuous drain connection. Higher power machines are not recommended.


Some personal experiences of this system:

1. I find a 400W compressor based dehumidifier will dry a load of washing this way in 60 minutes after a 1400RPM spin. Towels and thick denims may require longer.

2. I use a 200w dehumidifier in a walk-in room, and a 1000rpm washer. Clothes dry overnight. I tend to leave the door ajar so the clothes get fresh air, and this has no noticeable impact on drying times.

3. Unlike a tumble dryer, I get no lint from drying clothes. The drying room needs cleaning less often than other rooms. This means things that would wear down in a tumbler last better.

4. I was surprised by how low the condensate conductivity is. The water is actually purer than shop bought deionised water, so is good for all deionised water uses.


Dehumidifiers are protected by overtemperature cutouts on both compressor and fan, but it is still best not to permit clothes to cover the machine while in use. For large wardrobe spaces, the machine can be placed with no clothes above it. For furniture sized wardrobes, a shelf or rack over the dehumidifier can keep clothes off.

A high power machine in a small space is not recommended, as the warmth it produces may exceed the machine's ambient temperature ratings.


Don't the clothes dry stiff and rough?

No. Drying over a heat source causes this, but the closet dryer uses dry air rather than heat, and the problem does not occur.

Why does it use less energy than a tumble dryer?

The main use for energy in a TD is heat. A dehumidifier produces very little heat. Instead of heat the dh uses dried air to increase water evaporation from clothing.

But I thought condensing TDs just recirculate the heat, so very little is used?

Not exactly. Condensing dryers use cold water to condense the water vapour in the air path. This removes heat as well as water vapour. There is a desire to remove as much water as possible, but as little heat as possible, so a compromise is inevitable. This means that some of the heat is removed each time the air goes round. Consequently power consumption is lower than open circuit machines, but still not really low.

Don't dry clothes get damp when you put wet ones in with them?

When I put wet clothes in, I leave a 1" - 2" gap from the dry clothes so no damp transfer occurs. The air is dry during the drying process because the dh can remove damp much faster than the clothes evaporate it.

I have tried pushing wet clothes up against dry ones, and the amount of damp transmitted is small, such that the now dampened cloth dries out quickly even without the dh running. Perhaps the dry air acts to evaporate damp at the same time as damp is absorbed.

What are the costs & energy figures?

Dehumidifiers are popularly available in the £100 - £150 range new, and when found used are typically £30 - £60.

A 200w dehumidifier drying 3 loads of clothing may run for 25% of the time, thus consuming a mean power of 25% x 200w = 50w. With a fairly low spin speed machine like 1000rpm, the dh may be left running overnight, say 9 hours. 9 hours x 50w = 0.45kWh. At 10p/unit this is 4.5p.

On the other hand a 1.5kW tumble dryer might take 25 minutes to dry a load, or 75 minutes per 3 loads. 1.5 x 1.25 = 1.9kWh. At 10p/unit this is 19p, or about 4x the cost and energy use. 19p is not much, but for an average family it adds up to thousands of pounds over the years, and uses a lot of unnecessary energy.

The other cost that is hard to quantify is the wear on clothes caused by tumble dryers. The amount of lint these machines produce suggests that they might be a major cause of clothing wear. But in the absence of any hard figures we are left guessing. Perhaps a bit more idea could be obtained by measuring the lint removed from clothes per time period by a tumble dryer.

How much noise does a dehumidifier make?

Inevitably it depends on the model, but noise is not generally a problem with the lower power (200w) units. One of mine makes a little more noise than a fridge, since it is a refrigeration circuit plus a quiet low power fan. With the door closed it is not audible, with door open it is. The older one is quieter, and I have sometimes walked next to it in a quiet room without noticing it was running.

This does not mean there are no noisy models out there, but they are designed for use amid daily living, and are quieter than tumble dryers. An advantage of buying a used machine is you can see for yourself if its quiet.

Larger dehumidifiers such as used to dry out new buildings are another matter, and are ill suited to domestic use.

What about used dehumidifiers?

They are few and far between. If buying used, you may have to scan the paper and wait months to find one.

They are also not the simplest to check. Refrigeration systems can fail while looking and sounding normal, so like most used items there is an element of risk there.

Used machines may lack a piped drain facility, or may come without the connector for it. This only matters if you plan to plumb it in so you never need empty it.

One thing you must always do

A dehumidifier should be left standing for 24hrs the right way up before use. This is because it may be tipped over during transport, or by the person or shop you bought it from. Tipping causes compressor lubricant to leave the compressor, and it takes time for this to drain back in. Running a dh that has just been tipped may kill it.

What about clothes wear?

Wear shows most on collars, sleeve ends, the bottom edges of trousers, and as bobbling on jumpers.

Repeated bending, bumping into things and rubbing all cause wear. Static electricity is also known to be a significant cause of wear, especially for woollens. Tumble dryers do a fair amount of all of these. The closet dryer does none, as the clothes do not move during drying.

Is it really safe to have clothes waving about above a heat source?

Clothes do not move during drying. High power dehumidifiers that would blow clothes around are not recommended. The airflow is less than a breeze, it is not noticeable.

Low power dehumidifiers such as 200w machines do not produce much warmth, and nothing in them runs hot enough to ignite anything. Even if the fan vent is 3/4 blocked there is no cause of fire.

Both compressor and fan must be protected by an overheat cutout to avoid signficant legal liability for the manufacturer, and to ensure the product runs reliably. Thus all domestic dehumidifiers have these features built in.

Clothes are porous, and even wrapping a blanket around a dehumidifier will not stop the airflow. It will reduce it, but not stop it.

Despite all this, multiple layers of safety are always a good thing, as in the real world things do go wrong now & then. It is therefore recommended to be totally safe that clothes are not hung over the dehumidifier.

What if I don't want the whole family's clothes in one wardrobe?

The favoured incarnation is a dryer and wardrobe in one, but it can just be used as a dryer if preferred, with dry clothes being moved to personal wardrobes elsewhere.

Can I use desiccant instead?

No, desiccants do not have anywhere near the rate of water absorption needed.

How come leaving the door ajar makes little difference?

First there is no significant heat build up in the drying cupboard, so an open door does not change the drying temperature noticeably.

Secondly, the rate at which even a basic dehumidifier removes water vapour from the air is greater than the rate at which water vapour diffuses from a room interior into the cupboard, so low RH is maintained either way.

The difference it makes is that a limited amount of water vapour is removed from the room air when the door is left ajar.

Why aren't these systems on sale?

At present the method is more or less unheard of. Given its advantages and the current worries about energy I expect it might become a popular system in time.

There is also nothing much to sell, as its just a dehumidifier in a big wardrobe. Wardrobe manufacturers could make a concealed dehumidifier compartment with vents and tubes for air circulation, but this will only happen once there is market demand.

I run a laundry, can I use this system?

Yes, and you can say goodbye to most of your dryer running/fuel costs. But there are some caveats.

  • Drying cycle takes longer than TDs. OTOH you can dry a large amount of loads at once.
  • A relatively high power dehumidifier is needed for a roomful of clothing.
  • When sizing your dehumidifier, bear in mind that dh ratings are normally given at 30C, and extraction rate is much lower at 20C.
  • No powerful wiring or plumbing is needed to run the dh, just plug it into a mains socket.
  • A ceiling fan is needed to get airflow all round a packed room, and can be used on its own in summer.
  • High power dehumidifiers in a fanned room need a guard over them to keep fallen clothes off. The guard should be fine enough to be effective against all clothing items.
  • Items to be dried should be hung up, either on rods or hangers, which takes longer than bundling into a TD. A quicker alternative for some types of item might be layered wire racks, but this would inevitably cause a good deal of creasing.
  • If you need fast drying, a room heated to 30C gives optimum drying speed, and uses less fuel than tumble drying.
  • If you use a mix of TDs and a drying room, you could arrange for heat lost from the TDs to warm the room.
  • How well the washers remove residual water from clothing has a major effect on drying time. This depends of course on drum diameter, spin speed and spin time.

What if I'm not sure?

You can talk to us at news:uk.d-i-y

Or you could try it and see. If you like it, you stand to save thousands, and if you don't like it, you wasted the cost of the machine. That's not a bad bet.

See Also

Keywords: tumble dryer tumble drier clothes clothing laundry design kitchen layout planning plan wardrobe