How much water from de-humidifer

Halo

Halo

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Dear All
I have bought a MX dehumidiifer and put in on a timer so it operates about 6 hour per day. After a week it has collected about 1 litre of water from the boat. Whilst the boat feels dry I am surprised there is not more water - others experience and thoughts appreciated
Martin
 
more details required please before can make a reasoned comment.

MW model number
Size of boat / approx internal volume
Location, so as to get approx relative humidity and temp


FWIW a Delonghi DEC21 working 8 hrs a day in a 36ftx13ft mobo on the Thames over the winter with 1 liveaboard, used to collect about 3 - 4 litres a week.

1 litre a week sounds as if the boat is small or you have not got lots of natural ventilation (which is almost more important than having a dehumidifier in the first place). DHMs work best on warm wet air, so as it gets colder they collect less water.
 
1 litre not very much. To really dry the boat out internally you need to block out the light, and make the inside of the warm, and get the air moving. I once used an oil filled rad with a big fan blowing through it, and a dehu low down in the boat. Lovely and dry, and no, the furniture doesn't crack up. Best is to empty as much fabric (curtains etc) out of the boat, or at least arrange cushions so air can get around them.
 
Not quite the same but after a water leak at home the insurers dried out the wall using a BIG dehu (so big it could barely be lifted, and was wheeled in). Made a noise like a helicopter on start-up!

Running 24 hours a day next to a very wet brick wall, it collected about 4 litres a day for the first coupla weeks during the warm dry weather in May this year.

So a litre a week on 42 hours running does not sound too bad if your lugger is substantially dry in the first place.

Subsidiary question if I may - if putting a dehu in a boat over winter, how long running, and on at what time of the day or night?
 
A Sarabande says basically

To try to put some numbers on that

At present the temperature in my greenhouse ... the nearest outdoor structure I have to a boat with temperature and humidity sensors ... is 15.4 C and the relative humidity (RH) is 81%

From the information In Kaye and Laby one can deduce that the concentration of water vapour in the air in there is approx 10.5g / cubic metre

Multipy 10.5 by the internal volume of your boat in cubic metres and you will arrive at a estimate of the mass of water in grams ( or volume in cm³) that could be removed from the air inside by a 100% efficient dehumidifier. If there is no ventilation then once that much water is removed that's it.
Introduce ventilation then of course you will introduce more moist air from outside. Ultimately with lots of ventilation your dehumidifier will be working overtime dehumidifying the entire earth's atmosphere.


Suppose the internal volume of your boat is 15 cu metres The mass of water vapour in there would be 15 x 10.5 = only 158g ( or 158cm³)

So if sealed up with no ventilation and no source of water vapour that would be all the water you would be able to extract even with a super efficient dehumidifier.

Your figure of a litre in a week suggests that you have some ventilation, maybe not a lot.
Perhaps you have struck the happy medium. Enough ventilation to keep the boat fresh but not so much that your dehumidifier is trying to dry out the entire planet although some of the water you have collected may be water that was absorbed by the soft furnishings.

Even if the RH were to reach 100% at a temp of around 15 - 16C the amount of water would only be 25% more.

As the temperature falls the amount of water vapour in the air will decrease . At 5C and 100% RH the air only contains 6.8g / m³

Perhaps it would be a good idea to put a hygrometer in the boat just to see what sort of RH values you are achieving. One that records max and min values perhaps.
 
Halo said:
Dear All
I have bought a MX dehumidiifer and put in on a timer so it operates about 6 hour per day. After a week it has collected about 1 litre of water from the boat. Whilst the boat feels dry I am surprised there is not more water - others experience and thoughts appreciated
Martin
Click to expand...

What times does the unit switch on/off? It would be best if it switched on when the air is warmest (mid afternoon). Also leave it on for a longish period (several hours) so that the condenser gets nice and cold (it works like a fridge).

Also, does the unit have an adjustable humidistat? If so is it set to maximum dryness?

At this time of year the boat could be relatively 'dry' (if it's a modern GRP AWB) unless you have been living on it and generating condensation. That said, one litre a week does sound low, unless it is a small dehumidifier or a small boat.
 
I think you will find that if the dehumidifier only takes out 1 litre and the hygrostat makes the unit stop regularly then you have reduced the humidity in the boat to its set point. The amount of water collected by a dehumidifier is related to the relative humidity in the boat. So, if your boat is dry it will not remove much mositure, however if the boat was very damp to start with then it will remove a large amount of water from the air. I would recommend if you are using a dehumidifier all the time then it is better to leave all interior doors and bilges and preferably lockers open. Have the boat closed to the outside completely as your dehumidifier will struggle to remove all the moisture from the air of the world. It would be much better to only try and remove it from the volume of air in your boat(and fittings). If you had your boat closed up the bilges are empty and the boat seems dry I would say your dehumidifier is working perfectly.
 
Playtime said:
What times does the unit switch on/off? It would be best if it switched on when the air is warmest (mid afternoon). Also leave it on for a longish period (several hours) so that the condenser gets nice and cold (it works like a fridge).

Also, does the unit have an adjustable humidistat? If so is it set to maximum dryness?

At this time of year the boat could be relatively 'dry' (if it's a modern GRP AWB) unless you have been living on it and generating condensation. That said, one litre a week does sound low, unless it is a small dehumidifier or a small boat.
Click to expand...

Isn't an MX dehumidifier a dessicant type?
 
Playtime said:
If so, ignore (most of) my post :rolleyes: .
Click to expand...

I'll bet he means XM.

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The MX series are huge industrial jobbies ... Unless he has a cruise liner
 
Last edited:
Cunning Plan

Many thanks for all the comments. I will keep moitoring the water collection (am saving it at the moment so that SWMBO can use it in the steam iron and avoid clogging it up with the fall out from hard water.
The week before I put the dehumidifier on the boat I put a load of damp (ex spin dry) washing in the spare room in the room together with the dehumidifier and a fan to stir the air. It dried the washing really well so I am thinking of buying another one and setting up the spare room as a drying room - this will save a lot of money vs all the winter tumble drying of laundry. has anyone else tried this?
 
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