Anyone know of a good, reliable dehumidifier?

[CLB]

I've never tried a dehumidifier because I've never had a problem with damp, so I'm speaking from a position of authority. What on earth do you think people did before dehumidifiers were invented? What do all those thousands of people with swinging moorings and no electricity do?

Ventilation is fine if that's all you have. Its better than not ventilating. But think of it logically. If you ventilate well, your boat will be at the same temperature and the same humidity as outside. Now think of all those really damp mornings you typically get in autumn through to spring when the air is heavy with moisture. Your boat will be cold and damp inside. On the same day my boat will not only be bone dry, but warm too.

 

[pvb]

Ventilation is fine if that's all you have. Its better than not ventilating. But think of it logically. If you ventilate well, your boat will be at the same temperature and the same humidity as outside. Now think of all those really damp mornings you typically get in autumn through to spring when the air is heavy with moisture. Your boat will be cold and damp inside. On the same day my boat will not only be bone dry, but warm too.

But what's the downside? If there's no mould or mildew, what's the damage? Do you have a dehumidifier working in your car in the drive in the winter?

 

[Hadenough]

I've never tried a dehumidifier because I've never had a problem with damp, so I'm speaking from a position of authority. What on earth do you think people did before dehumidifiers were invented? What do all those thousands of people with swinging moorings and no electricity do?

Sleep on damp mattresses in their hair shirts.

 

[CLB]

But what's the downside? If there's no mould or mildew, what's the damage?

er, I thought I already answered that. Cold and damp.

 

[CLB]

Do you have a dehumidifier working in your car in the drive in the winter?

No, but my car is used daily with the heating on, is 100% watertight and doesn't live on the water.

 

[pvb]

er, I thought I already answered that. Cold and damp.

My boat isn't damp inside. Maybe you have the wrong sort of boat.

 

[Dawnrazor]

We use ElectriQ CD12P dehumidifiers in all our school boats. They do a great job and pretty much look after themselves. We paid about £130 each for them. Gave up using Meaco juniors after three went pop in one year and didn’t quite as good a job.

 

[CLB]

My boat isn't damp inside. Maybe you have the wrong sort of boat.

I don't have one that defies the laws of physics, if thats what you mean. Yours must be very special to keep dry air inside while outside is near on 100% humidity (fog) and you have all it well ventilated. I'll say no more on the subject, as you clearly know best

 

[doug748]

Air is generally drier in the Winter and can cause a lot of problems, useful on boats though.

Google sorts it out.

 

[KompetentKrew]

Dessicant work well at low ambient temperatures, compressor don't work at all well in low temperatures. Less of an issue if you're aboard and have heating on as well I guess...

I'm convinced that a compressor dehumidifier is fine at low temperatures.

I never had the heating on last winter when running mine.

A desiccant dehumidifier might extract more water per hour at 5ªc, but there are 24 hours in a day and a compressor dehumidifier extracts enough. I can definitely tell you that my compressor dehumidifier got the boat from water dripping down the walls to perfectly dry in 3 or 4 days last October.

 

[johnalison]

I'm convinced that a compressor dehumidifier is fine at low temperatures.

I never had the heating on last winter when running mine.

A desiccant dehumidifier might extract more water per hour at 5ªc, but there are 24 hours in a day and a compressor dehumidifier extracts enough. I can definitely tell you that my compressor dehumidifier got the boat from water dripping down the walls to perfectly dry in 3 or 4 days last October.

I used a compressor dehumidifier on a time switch for many years until it packed up. I had it set to function overnight on the grounds that it gave out some heat and that would be helpful. I replaced it with a Meaco dessiccant model. As said, you don't have the option of putting it on a timer, so I leave it on a moderate setting with its fan low and hope that my electrivcity doesn't run out or power cuts happen. With its power cut it resumes at the previous setting but if switched off properly it has to be reset. So far, the few occasions it has been deprived of power haven't caused it harm. It seems to use a lot of power for the first week as it dries the boat and then becomes very economical.

 

[KompetentKrew]

I used a compressor dehumidifier on a time switch for many years …

The ElectriQ CD12P model of dehumidifier used by @Dawnrazor is also a compressor model, I find.

 

[JumbleDuck]

I have never seen any need for a dehumidifier on my boat, which stays nice and dry and smell free throughout the winter. However, I do have a dehumidifier in the house, because 200 year old stone cottages were designed for more ventilation than is economical with central heating.

It's a Mitsubishi MJ-E20BG-E1 20 litres per day compressor one which I originally bought to dry out a wall in another equally old house. It's a bit of a brute and cost £400 but has been running about half the time for almost five years now with no problems.

At the other end of the price scale, I also have a compressor dehumidifier from Aldi which got very good reviews at £120 and was a snip at the £60 I paid for last-one-in-stock. I have only had that one for two years but it, too, seems very good.

In general I don't think there is any point in trying to remove moisture which came in with air. If it came in that way it will go out that way and if you dry it more will come in, unless you have no ventilation in which case a small crystal dehumidifier will do fine. A dehumidifier is potentially useful if something is supplying moisture to the air. In my house that's walls wicking it up from the ground and in a boat it might be people breathing.

 

[MonniotC]

" What do all those thousands of people with swinging moorings and no electricity do? "
After years of everything going mouldy, I fitted an extra mushroom vent in the forehatch, and a vent in the companionway hatch.
Drizabone for 13 years.

 

[Hot Property]

I bought one yesterday Blyss WDH-316DB 16Ltr Dehumidifier -

to dry out my garage conversion with lots of wet timber.

I got bored with emptying the 2.5 litre bucket so attached a hose so it drains continuously.

Very quiet too.

It consumes 300 watts per hour so it heats the space too.

I'm going to use it to dry out some plaster in a 30 M2 room and will report back...

 

[Ian_Edwards]

I use an old B&Q compressor dehumidifier and an 800Watt oil filled electric heater. The dehumidifier is on a timer and runs for 2 hours in the early afternoon, because I think it is less likely to freeze up when the boat is likely to be at its warmest. The dehumidifier is in the galley with a hose into the sink.
The 800watt heater is on a thermostat set at 10 deg C. Typical winter bill is less than £20 per month including £3.75 monthly standing charge.
I seal the boat as best I can.
The dehumidifier constantly remove water from the boat. Logically, that means the boat has to be drier that it would be if it was just ventlated, but I am aware that I'm paying to dehumidify the planet, because the boat isn't completly sealed and moisture will creep back in. But the boat will always be drier than if it was just ventilated.

 

[pvb]

" What do all those thousands of people with swinging moorings and no electricity do? "
After years of everything going mouldy, I fitted an extra mushroom vent in the forehatch, and a vent in the companionway hatch.
Drizabone for 13 years.

According to CLB, you're defying the laws of physics!

 

[CLB]

According to CLB, you're defying the laws of physics!

Yours and MonniotC 'dry' is purely a perception. It is simply not possible for it to be dry inside when open to the outside air which is at anything up to 100% humidity. Dam, you drew me back in. Clearly you won't quit until you have had the last word, so sorry for that. Please feel free to have another go and I promise I won't bring any more facts to this discussion.

 

[johnalison]

We HR owners like to think of ourselves as smart, and in a Facebook discussion a year or two ago we all agreed that the right way to seal up vents was to stuff socks into them. I also seal the ventilated companionway hatchboard by taping plastic from a shopping-bag over it.

 

[JumbleDuck]

Yours and MonniotC 'dry' is purely a perception. It is simply not possible for it to be dry inside when open to the outside air which is at anything up to 100% humidity.

Remember that "100% humidity" means "100% relative humidity". Air at 5C can carry 6.92 g /m^3 and air at 20C can carry 17.3g /m^3, so 50% RH (that's the limit for most dehumidifiers, by the way) on a nice summer day is actually "wetter" than 100% RH on a damp winter's day.

And what does some damp in the air matter, anyway? It doesn't, really, unless it condenses out on anything and it won't unless it comes across a surface colder than it is. My boat is sitting in a yard at the moment with a slightly open forehatch at one end and a companionway vent at the other. Damp air may well be blowing through, but the keyword there is "through". The small quantity of water it brings in at one end will be going straight out the other end. If it's at less than 100% RH when it comes in it may even take some more water out with it. My bilges normally have an inch or two at the end of the season, thanks to a stern gland, and are normally bone dry by spring.

Dehumidifying a vented boat is pointless, because it's basically trying to dehumidify the atmosphere. So if you are going (one is going) to dehumidify, you should seal it as well in which case, as I wrote, a crystal dehumidifier will easily take out all the moisture from the trapped air. Of course that moisture in the air may be getting topped up from damp bedding, damp clothes, damp lockers, damp sails and so on, in which case the dehumidifier will compensate for a problem which could be sorted in another way.

If your boat needs a dehumidifier to stop it going mouldy then of course using one could be a good idea. However, many of us have boats which simply do not go mouldy.