Here at Meaco, we have great conversations with our customers all the time. We’re commonly asked questions about desiccant dehumidifiers, so we thought we’d put this handy guide together.
How Does A Desiccant Dehumidifier Work?
A desiccant based dehumidifier draws the air in from the room over a filter and passes it over a rotating wheel. This wheel is full of a material called Zeolite which absorbs the excess water out of the air. When the wheel is saturated it needs to be regenerated. A heater in the base of the dehumidifier blows warm, dry air over the Zeolite to force the moisture out of the wheel. The Zeolite is now ready to dry again and the warm, wet air from the wheel hits a metal surface which ensures the excess moisture condenses and the water drips into the internal tank. The heat used during the drying process is mixed with the dry air to ensure that the air that comes out of the dehumidifier is not just drier but 10-12°C warmer than the air that came in.
My Dehumidifier Has Stopped Collecting Water
Desiccant dehumidifiers like the Meaco DD8L and the Meaco DD8L Junior have a pre-set humidistat so in Minimum mode they dry down to 60%rh, in Normal they dry down to 50%rh and in Maximum they dry down to 40%rh. Once they reach that level they turn themselves off and then check the relative humidity once every 30 minutes to see if the relative humidity has increased.
I Have Laundry Out And No Water Is Being Collected
If the relative humidity is below 40%rh then the dehumidifier will not collect any water. The moisture from the washing will evaporate into the air and increase the moisture content of the air but this increase might not be enough to increase the relative humidity above 40%. This is a very common issue in winter when there are temperatures below freezing outside and we have our heating on in the house.
I Have Condensation On My Windows And Still No Water Is Being Collected
Condensation forms when a surface is at the appropriate cold temperature, so if you have a room temperature of say 20°C and a relative humidity of 35%rh then there is nothing more for the dehumidifier to do because the air is cold enough.
If the surface temperature of the windows drops to just under 5°C or colder overnight then you will get condensation. The dehumidifier is not to blame; it is all down to the quality of the glazing.
How Can I Be Sure If The Relative Humidity Has Dropped And The Machine Is Not Just Faulty?
After a bath or a shower, leave the window closed in the bathroom and put your desiccant dehumidifier in the bathroom in its Laundry mode. Shut the door the best you can and turn off the extractor fan, come back in two or three hours time. If water is collected then the machine is fine, if no water is collected then let us know as the dehumidifier is faulty and we need to sort it out for you.
A desiccant dehumidifier is a cost-effective way to manage condensation in your home.
How can I prolong the life of my machine and keep running costs down?
Keep the filter clean. The more dirt on the filter, the more strain on the fan and the greater the risk of the fan or the heater failing. This will also prevent the dehumidifier from become nosier than necessary.
Does running a desiccant dehumidifier cost a lot of money?
Desiccant dehumidifiers are very energy efficient – all energy that is consumed returned to the room as heat. This is a good thing as it replaces the heat generated by your central heating. Desiccant dehumidifiers also dry the air very quickly, so they are in dehumidification mode for much less time than compressor based dehumidifiers. Southampton University tests show that this is around 3.5 times faster. This means that they can actually be cheaper to run than compressor dehumidifiers.
Remember that whatever dehumidifier you use, you are reducing your heating bill by making the air dryer. Dry air is much easier to heat than damp air because there are fewer water molecules in the air. The money you save on the heating bill will outweigh the money that you spend on the dehumidifier.
In fact the best way to waste money is to not run the dehumidifier and let the level of moisture build back up in the house!
The air feels cold coming out of the desiccant dehumidifier
It might but it is not! When the desiccant dehumidifier is drying, the air coming out is 10-12C warmer than the air that came in. This is because the energy used in drying is being returned to the room. When the dehumidifier stops drying and goes into fan only mode to sample the air it does nothing to the air, the air just passes through the machine, nothing more. When it comes out it is exactly the same temperature as when it came in, nothing has happened to it. Moving air feels cooler than still air (like a fan in summer), but it is not cooler and the room temperature will not drop.
How does damp air affect my health?
We are keen to steer clear of claims here that we are not qualified to make, so we will keep it simple.
- Dust mites reproduce in damp environments
- People who suffer from asthma, eczema and other allergies find that inhaling dust mite droppings can make their condition worse.
- Mould grows in damp environments.
- Mould gives off mould spores (seeds)
- Inhaling these spores can make conditions worse.
A dehumidifier keeps conditions dry and therefore stops dust mites from reproducing and mould from growing. Therefore a dehumidifier helps people who suffer from allergies, asthma and eczema.
Find out more about dust mites here.
Does the desiccant need to be changed?
No the machine automatically regenerates the desiccant internally and you will never have to replace it.
Are there are replaceable parts?
No
What about the filter?
Just maintain the filter as per the manual and it will be good for the life of the machine.
My desiccant dehumidifier smells
When you first use the dehumidifier and periodically afterwards you might notice a smell coming from the dehumidifier. This is caused by the Zeolite desiccant material and is not a sign that the dehumidifier is faulty, nor is it harmful to humans or pets. The smell occurs because the Zeolite absorbs odours from items like cigarettes, cosmetics, hair sprays, building materials and new furniture and then when the desiccant is heated the smell is discharged into the room. This smell has been described as being like a burning smell or a sour smell. It is normal, will not last long and is not a sign of a fault. If you prefer you can put the dehumidifier in the garage and run it on Laundry mode there to get rid of the smell outside of the house.
The fan light is flashing
If one of the following events happens then the control panel will lock up and the fan light will flash.
- Temperature below freezing
- Temperature above 40°C
- Relative humidity below 40%rh
- Machine has been working hard and needs to cool down internally
If you find that this happens and you none of the buttons on the control respond then do not worry, this is normal and the dehumidifier will start to work again when the conditions allow.
What can I do about the check light on the DD8L?
The alarm light on the dehumidifier could mean that it is being used at too low a temperature (below freezing), too high a temperature (above 40°C) or that the air flow is being blocked. If the temperature is ok then make sure that the filter is clean and that it is far enough away from the wall to allow the air to flow through (at least 30/40cm).
If it becomes a regular issue then call the office on 01483 234900 for further help.
75 responses
Hi. It’s very kind of you to offer this service. Our Ddl8 has been running very well for 2 years but the red warning light now shows and the machine turns itself off when it is on any more than the single fan setting (this can still be paired with the thumbs up sign). This has occurred after I carefully took it part briefly to remove a blockage into the tank.
It will either be a blockage that is causing the overheating or a reduction in airflow through the unit.
Hello, I’m hoping you can help me to get a better understanding of the real-world performance of compressor and desiccant dehumidifiers, given particular conditions.
I’ve been looking at extraction data and it looks as though the Meaco 12L ABC should extract around 3.3 l/day at around (15C,60%), which is comparable to a desiccant at ‘normal’ speed. On the face of it, it seems the compressor does the same job using 50-66% less energy.
Presumably there’s more to it than that though? Would this be achieved by both in real-world conditions? My experience suggests that compressors struggle below ~(18C,60%) and also require defrost cycles. I imagine that their collection profile is somewhat uneven and slower than desiccant.
If this is true and desiccant initially performs better, why is unable to maintain the advantage? Is it more suited to bursts of an hour or two?
Over 24 hours, does the desiccant gain an energy usage advantage by reaching the target more quickly while the compressor is still running? Overall, how close does the desiccant get to the running costs of the compressor?
Is the desiccant running at ‘normal’ sufficient to reduce humidity to around 50%? If full speed is required, suddenly the desiccant is using perhaps 5x the energy, which could become a significant cost when running for long periods.
To compare the 12L and 20L compressor units, it looks to me as though the 20L is approximately 50% more effective but less efficient like-for-like. Does this seem about right? Is the 20L more prone to entering a defrost cycle?
This post is already too long but I’d welcome the opportunity to discuss options in more depth by email if possible.
Jay,
Thank you for your message. In real life set ups you will get very similar results to the lab conditions and the two types of dehumidifiers will extract similar amounts of water over a period of 24 hours. It is not that either type work in bursts, they will remove that amount of water consistency across the time period. Defrost cycles are all part of the process on a compressor machine and are essential to the process of removing water from the air. The physics of it is one of the reasons why a compressor dehumidifiers delivers less water as the temperature and relative reduces.
The 20L Low Energy and the 25L Ultra Low Energy will by their very nature as larger machines remove more water at these conditions and will offer a better return when you look at the amount of water collected verses the amount of money spent to remove that water.
At the end of the day the most important factors in selecting the correct machine is the size of the home, how you dry your laundry the number of people in the house and whether you have extractor fans in the bathroom and kitchen. If you could let me know that then I will be able to help you selecvt the correct machine.
Chris
I’m in exact same position as Jay – trying to find information on which type of dehumidifier to buy to run at 15C conditions.
It’s amazing how none of Jay’s quite well formed questions haven’t been answered!
We want to know extraction rate and power consumption at 15C@60% for both “ABC 10L” and “DD8L”
Or even better kWh per litre while running at 15C@60%
Roland,
I checked and a reply was posted to Jay’s question (everything gets answered). I have copied and pasted the reply below for you.
Chris
Jay,
Thank you for your message. In real life set ups you will get very similar results to the lab conditions and the two types of dehumidifiers will extract similar amounts of water over a period of 24 hours. It is not that either type work in bursts, they will remove that amount of water consistency across the time period. Defrost cycles are all part of the process on a compressor machine and are essential to the process of removing water from the air. The physics of it is one of the reasons why a compressor dehumidifiers delivers less water as the temperature and relative reduces.
The 20L Low Energy and the 25L Ultra Low Energy will by their very nature as larger machines remove more water at these conditions and will offer a better return when you look at the amount of water collected verses the amount of money spent to remove that water.
At the end of the day the most important factors in selecting the correct machine is the size of the home, how you dry your laundry the number of people in the house and whether you have extractor fans in the bathroom and kitchen. If you could let me know that then I will be able to help you selecvt the correct machine.
Chris
I have a Meaco Zambezi dehumidifier which is doing a marvellous job but recently it appears often stuck on 2 fans. Every time we try and change it to 3 or 1 fan it reverts to 2 fans.
At the moment the target humidity is set to 45 and the detected humidity it over 60.
What is causing this? How do we make it responsive to run just on a single fan?
We have tried switching off and on with the proper power down cycle. We also do move the dehumidifier around the house though not always using the power down cycle, just pulling out plug.
Any advice please?
Kathryn,
Thank you for your purchase. Zambezi is meant to do this, so this is normal, when the room humidity is 20%rh above your target it will use two fan speeds to drive the humidity down, below 20% gap it will revert to the fan speed you have set. This is page 13 of the manual.
Hope this helps.
Chris
With regards as to what to use at 15C, I would use a 20L litre compressor like the Arete 20L or the 20L Low Energy as they will extract lots of water without costing much in terms of electricity. I would go for Arete if noise was an issue. If you want extra warmth in that space then choose desiccant.
Chris
Hi , I bought the dd8l junior 5 years ago until now no problems .
The alarm light comes on continuous only in the 2 fan normal mode (thumbs up) so have to switch plug off and back on to restart machine filter has been one per week , dehumidifier is only used in winter , it works perfectly well one fan mode , appreciate your help with this ,
Colin,
This tells us that the machine is starting to have problems with it’s air flow, due to age or blockages. It works on the single fan speed because the heater is working on half capacity and therefore it is easier for the machine to deal with the internal build up of heat.
Chris
Hi. I just bought a Meaco 20l Low energy dehumidifier. This is the second day it’s on and i noticed a droning noise, which yesterday wasn’t.
Daniel,
Thank you for your purchase. A compressor dehumidifier will make a range of noises as the compressor operates in different manners. This is normal and nothing to be concerned about.
Chris
We have a DD8L that is working well but has recently starting making a strange whirring sound, almost as if the moving parts inside need a shot of WD40. Is this a common problem and how can we fix it?
Gary,
Hard to interpret what the whirring noise is to be honest. If it becomes a major issue then please do call us on 01483 234900.
Chris
Hello
I have the meaco dd8l and its brilliant.
I have seen an increase in the amount of dust that has collected inside the fan area and on the elements behind the filter. Is there someway to clean this ? I suffer terribly from allergy allergies to dust and mould spores and am worried that the machines efficiently is going to be compromised.
Samantha,
Unfortuantely you cannot clean it yourself for safety reasons. But dust in the areas that you have described will not effect the performance of the machine and should not get blown back into the room.
Chris
I have a Meaco DD8L 8 Litre Desiccant Dehumidifier. I have had it running in my attic which never goes below 9degrees for a year now. It has not been running in the summer as the humidity level has laways been belove 50%. It ran all last winter before the summer came, set at 50% humidity, which it managed very well. I switched it on two days ago for the 1st time since spring time. When I went to empty it the water in the tank was pink coloured. I also noticed this the last time I emptied it in spring. But it got darker. I googgled it and got that it might be a dangerous bacteria growth called Serratia marcescens. Have you come across this before and how do I cean the interior of the dehumdifer if if it has this growing inside it, or do I need a new one. The loft is lined and seems very dry inside, I have a humidify monitor up there and its been below 50% all summer and even now is only at 55-60%. Has this Serratia marcescens started to grow in the machine, from what I can see it will only grow on wet surfaces. Any help would be great
Iain,
This is an unusual situation but one that our engineer understands. We can either offer you a full service to help clean the machine completely. Or you can run the machine at a room temperature of above 21°c for 24 hours will kill the bacteria, however spores will still be active and will reform. This type of bacteria is very common in society and can often be found in showers in leisure centres for example.
Feel free to call the office on 01483 234900 if you would like to arange a service.
Chris
I have a DD8L model and the warning light keeps flashing when I turn the machine on and the machine becomes unusable The filter has been cleaned and it has been placed clear of obstruction. I have rang the office this morning to be told you do not repair machines over 4 years and I would have to buy another. So much for helping existing customers!
Antony,
Thank you for your purchase and your message. The internals of the machine have changed a lot since 2015 as improvements have been made. We kept spares for the older models for as long as possible but eventually we ran out and the mould was no longer in a condition to make any more. So we can no longer repair machines made in 2015 or earlier, if a machine is under warranty then we will replace it, if it is outside of warranty then we will offer a discount on a new machine.
We do look after customers and if a machine is outside of warranty but has been well looked after we will repair it free of charge (not many brands do this) where we can. You can see from the reviews on Trust Pilot that we do this on a regular basis.
Drawing a line and having a date whereby you can no longer do repairs is not unique to ourselves, even a massive conpany like Sony do this (Playstation 2).
Why when I set my dehumidifier at 50 it switches off but is reading 77? I thought it wud only switch off once it reached 50? If I turn it off at the mains then put it back on it comes on so why is it switching off at 77? I have bought two of these machines and both do the same…. I’m confused
Deb,
If the high reading is only seen when the fan is turned off then it is reading the dehumidifier’s internal relative humidity and can be ignored. Only worry about readings that are seen when the fan is running, these are room readings.
The dehumidfiier will have turned off when the room relative humidity was below 50%rh and the sensor will then have read it’s internal relative humidity which is always higher and the machine ignores.
regards
Chris
Shouldn’t VOC (volatile organic compounds) being combusted or at least heated up together with the dessicant be cancerogenous?. So running a dehumidifier should really be a Health hazard?
Concerned
Not at all, any VOCs in your home would see a higher temperature when they come intocontact with the surface of a hot radiator in the home. The dehumidifier will not have a negative effect on them.
hi
How long do you have to run the dehumidifier to make the dessicant not throw smell of burned plastic in the air?
Where can I run it?
This can happen when the chemical that creates the smell is in the room, so as long as the chemical that is creating the smell in the first place is in the air then the problem can continue. For example paint smell after decorating, new leather furniture or room air fresheners. We recommend removing the dehumidifier from the space and running it somewhere else for 24 hours to clear the issue from inside the machine.