Dehumidifier draining

[Momac]

Key things are:
1 - If you're using it in winter on an unheated boat use a dessicant type dehumidifier not compressor. Compressor type do not work well at low temps.
2 - Don't put it on a timer because they have a shutdown cycle.
3 - Seal boat as best you can, however it's a myth that unless you hermetically seal the boat 100% you'll be trying to dehumidify the planet...

All correct
I have my dehumidifier set to fill its own tank.
It takes more days to fill the tank when the vents from the living spaces to the exterior are covered with masking tape.

 

[DipperToo]

I seem to think that Meaco have a dehumidifier with an optional pump to empty the tank when is is full?
MeacoDry Arete One Pump
It is said to connect internally to the Arete One dehumidifier
"Only one dehumidifier has the option of a pump and a dedicated power supply. The new Meaco Arete One 20 and 25L dehumidifiers have the option of a pump to help empty the tank automatically up to 2.5m in height."

 

[KompetentKrew]

Unless you are neglecting your boat for months at a time, a 25 litre can should collect all the water?

Key things are:
1 - If you're using it in winter on an unheated boat use a dessicant type dehumidifier not compressor. Compressor type do not work well at low temps.
2 - Don't put it on a timer because they have a shutdown cycle.

I'm convinced that we have Meaco to thank for the British obsession with dessicant dehumidifiers - their DDL8 won awards from Which? and one of the yachting magazines, and they marketed it on this basis.

But @V1701 is right! Your desiccant dehumidifier can be damaged if the boatyard or marina has unreliable power, and it cuts out when the dehumidifier is running. Or if the inverter shuts it down to protect your boat's batteries.

Whereas a compressor dehumidifier can be run on a time switch if you like - you could have it come on between 10am and 5pm each day, when it's warmest.

I have a cheap 12L compressor dehumifider, and it can easily extract 2 litres of water a day in the winter. It'll get most of that running for 10 hours or so overnight, when it's cold. So, @B27, I would worry that a 25 litre bucket might be inadequate. I think running the hose through a through-hull is a good idea.

Mine is Seago's Smart Dry 2 - it's a shame they no longer make it, because I'm very pleased with it. It's a convenient shape, but any 12L compressor dehumidifier will extract at the same rate.

 

[jwilson]

I have had a compressor dehumidifier freeze in cold weather - to the point where the buildup of ice turned into a huge block of ice that stopped the fan turning and burnt out the fan motor. That is why a few compressor dehumidifiers have a "defrost" function built in - though not many do.

 

[Momac]

I have no complaints about the Meaco DD8L which I bought in early 2017 (over 6 years ago) . It has been used on the boat every winter.
I am sure it has seen a few power cuts but that hasn't done it any harm.

 

[KompetentKrew]

I have had a compressor dehumidifier freeze in cold weather - to the point where the buildup of ice turned into a huge block of ice that stopped the fan turning and burnt out the fan motor. That is why a few compressor dehumidifiers have a "defrost" function built in - though not many do.

Perhaps I underestimated how much warmth is introduced to the boat by my own breathing, farting and making tea. Clearly one should check. However even Meaco's cheapest 10L compressor dehumidifier, the £150 ABC 10L, has this defrost function.

 

[KompetentKrew]

I have no complaints about the Meaco DD8L which I bought in early 2017 (over 6 years ago) . It has been used on the boat every winter.
I am sure it has seen a few power cuts but that hasn't done it any harm.

I don't think that the DD8L is bad, nor are desiccant dehumidifiers in general.

It's just that every discussion of dehumidifiers has someone saying "make sure you get a desiccant one", like that type is the only kind that works in UK. I think Meaco now acknowledge that they maybe pushed this a bit hard.

Although it probably doesn't make much difference, a compressor dehumidifier is often cheaper to run than a desiccant one - again, Meaco say this themselves - and you can run it on a timer if you want to.

It's a matter of choice not necessity IMO.

 

[Momac]

Yes its a matter of choice.
The favouritism for desiccant type comes from the pbo comparison report carried out in 2014 is probably because of the understanding that the desiccant type extracts more water at low temperatures compared to a compressor type.
And that's what we want in the UK for winter use on a boat.
But no dehumidifier works at really cold temperatures.
Gear test: dehumidifiers - Practical Boat Owner

 

[Momac]

We are involved with a large industrial project where the dehumidification units are desiccant type. So its a popular solution even on an industrial scale.

 

[B27]

I looked at the dessiccant types for the house. About twice the kWh to do the same job.
600W vs 300W for vaguely similar water extraction.
But of course that heat is also helping keep your boat warm and dry.

Strategic use of a small heater is another option.

I think there can be a big difference between the needs of drying the boat out in Autumn, and keeping it dry through the winter.

Getting on board once a fortnight and firing up the chinaspacher and giving the boat 'an airing' also works.

Once the air is down to below 10degC, where compressor types basically give up, the vapour pressure of water is low AKA the 'air doesn't hold much moisture' and mould doesn't really grow much. In these conditions, the name of the game is really having the boat dry in the first place and keeping the rain out.