Dehumidifier. (1 Viewer)

Jan 15, 2022
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Hi we are brand new to Motor Homes and am looking for tips to avoid the dreaded damp. We will get a habitation certificate / check every year we will be regularly checking all the areas that we may get it and taking appropriate action. But my husband has hit on the idea of also buying a dehumidifier. The idea being to use it when we're out of the van. Can any of you advise me please? Many thanks
 

ManTheVan

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Jan 11, 2020
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For what it’s worth, we have both compressor and a desiccant type dehumidifiers and they each have their pros and cons.

The dessicant type (e.g. Medco DD8L or similar) work better than compressor type ones when the temperature is low, because they generate more heat. If we need rapid dehumidifying anytime, that’s the one we use. Compressor types cost less to run but may freeze up at lower temps.

However, as others have said, you can save your money by ensuring adequate ventilation in your van when in storage. We did this with the yacht and never ever had damp or mould problems whether stored afloat or ashore. Same with the MH.

Family use a Meaco in their static caravan over winter just for peace of mind, with the drain fed into the sink. It costs about £1/day on the auto setting.

As others have said, water vapour will move from high to low humidity by laws of physics, but some choose to dehumidify their vans in storage and opt to pay the cost. We opt not to, with no adverse effects so far, but others may have different experiences, so to each their own!

Whichever way the OP decides, the Meaco is a very good dehumidifier. It costs more to run, but will work at the low temps found in the van.
 
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May 15, 2008
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Can some of you physicist/techies please explain to me, in simple terms please, why a dehumidifier tries to dehumidify the atmosphere when in a confined space whist a heater apparently does not.

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Jan 17, 2018
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I think the OP is confusing damp and condensation. The dreaded damp is caused by a fault in the sealing of the outer skin somewhere allowing water to get into the fabric of the walls veiling or floor. Nearly all motorhomes these days have inner linings to the walls and ceiling made of plastic or grp. Thus once water is trapped inside the skin it cannot get out, except by soaking down to the floor and rotting that. Once water has got into the fabric of the walls or ceiling, a dehumidifier will have absolutely no effect whatsoever other than to waste electricity.

Damp can occur inside if there is a leak in the water or waste system somewhere. This is usually quickly obvious when the van is in use, but if the water pump is switched off while in storage there should not be a problem.

Otherwise condensation can and does occur regularly when the motorhome is in use, and largely its harmless, and again because the walls and ceiling are impervious to water, it doesn't get into the fabric of the structure. Opening a window, roof light or door will usually clear condensation quickly. As has been said there is always a significant air flow through the motorhome, coming in through vents in the floor, and escaping through vents in the roof lights. Even here, using a dehumidifier is largely OTT. Before shutting the motorhome up after a holiday, do air the motorhome to clear any condensation first though, and maybe this is the only time a day's use of a dehumidifier is of value.
We dont have any leaks in our van but I will add that we leave the beds made up all winter for spur of the moment trips, there is nothing worse than a damp bed. So I will continue using a dehumidifier it works for me(y)
 
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Apr 19, 2019
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Can some of you physicist/techies please explain to me, in simple terms please, why a dehumidifier tries to dehumidify the atmosphere when in a confined space whist a heater apparently does not.
A good dehumidifier senses the moisture level around it and stops and starts accordingly.

A motorhome is not sealed (or we would all suffocate). Therefore new air is constantly coming in. Your dehumidifier will pointlessly remove the moisture from the new air. It will continue to do this until you have dried out western Europe and the new air contains no moisture.
 
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Apr 19, 2019
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We dont have any leaks in our van but I will add that we leave the beds made up all winter for spur of the moment trips, there is nothing worse than a damp bed. So I will continue using a dehumidifier it works for me(y)
It's doesn't harm. If you can afford the electricity then it's your choice of course.

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May 15, 2008
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A good dehumidifier senses the moisture level around it and stops and starts accordingly.

A motorhome is not sealed (or we would all suffocate). Therefore new air is constantly coming in. Your dehumidifier will pointlessly remove the moisture from the new air. It will continue to do this until you have dried out western Europe and the new air contains no moisture.
Is new cold air not also constantly coming in this a heater will continue to heat the new air and continue to do this until you have heated Western Europe and the new air is heated to the required temperature.
 
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Apr 19, 2019
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Is new cold air not also constantly coming in this a heater will continue to heat the new air and continue to do this until you have heated Western Europe and the new air is heated to the required temperature.
Yes it is. But remember you don't just heat the air. You heat up the air and all the fabrics of the van. If you just heated the air, you would have to start again every time you opened the door?

You heat up all the furniture and fabric of the van.

So it's slightly different.
 
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Why does it amaze you? There is a plentiful supply of water in the atmosphere. :LOL:

A bit of science puts it into perspective though. At 10 degrees C, every cubic metre of air will hold just under 10gm of water. Lets assume the inside of the motorhome is 2 metres wide, 2.5 metres high and 6 metres long. That's 30 cubic metres of air, each one holding 10gm of water making 300gm, or 300ml, just over a mug full. Dehumidifiers do not remove all the water vapour, therefore you would be lucky to get 150ml of water in your dehumidifier, or about half a mug full.

If you pull more water than that out, it simply proves you are trying to dry the atmosphere.
Just a question if i may........Whilst I agree with your science bit ... if you were to put one of the Aero 360 jobbies on your doorstep outside your house or even in your own garage at home ...It would barely collect anything to be concerned about. Yet...I have two of these in my motorhome. One in the garage section of the motorhome and the other in the middle of the truck. For whatever reason it may be... I can guarantee a half bowl full of blue water after 3 weeks in storage where as I can see next to nothing from my garage at home where they are stored?
I am but a mere amoeba in this world so i understand nothing unless explained thoroughly....feel free to put that into some sort of clarity for me please? Please Don't fret....you cannot offend me . I am a beginner in this life ...even though i am 62 years old!

I am always 'Still learning' ;) (y)

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Oct 6, 2021
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Just a question if i may........Whilst I agree with your science bit ... if you were to put one of the Aero 360 jobbies on your doorstep outside your house or even in your own garage at home ...It would barely collect anything to be concerned about. Yet...I have two of these in my motorhome. One in the garage section of the motorhome and the other in the middle of the truck. For whatever reason it may be... I can guarantee a half bowl full of blue water after 3 weeks in storage where as I can see next to nothing from my garage at home where they are stored?
I am but a mere amoeba in this world so i understand nothing unless explained thoroughly....feel free to put that into some sort of clarity for me please? Please Don't fret....you cannot offend me . I am a beginner in this life ...even though i am 62 years old!

I am always 'Still learning' ;) (y)

Its all to do with temperature and air currents.

In the motorhome, the air is constantly circulating, being drawn in at the floor, and going out through the roof vents built into the skylights in the ceiling. There are two mechanisms for this. Generally the inside of the motorhome will be somewhat warmer than the outside, even with no heating. Thus the air inside is warmed, and rises, drawing in more cold air from the floor. The second mechanism is the change in temperature during a 24 hour period. Obviously the motorhome will be colder at night, and cold air takes up less space than warm air (which is crudely how hot air balloons work). Thus the inside of the motorhome acts like a giant lung drawing air in at night when it is cooler, and pushing it out during the day when the van gets warmer.

OK so far?

So, in the motorhome there is a constant movement of air over the dehumidifiers which increases their efficiency greatly. Also warm air holds more moisture than cold air and as the air gets warmer during the day, it contains more moisture which can be captured by the dehumidifier.

In contrast, depending on the garage construction, it will stay at a more even temperature day and night, and largely being a sealed box, unlike the motorhome, there will be very little air flowing round the dehumidifier, so it won't be able to absorb much moisture.
 
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Oct 6, 2021
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We dont have any leaks in our van but I will add that we leave the beds made up all winter for spur of the moment trips, there is nothing worse than a damp bed. So I will continue using a dehumidifier it works for me(y)
I keep the bed made up, and simply connect up the EHU 24 hours before setting off and put the heating on low to air the van and also switch the fridge on to give it time to cool down properly.
 
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