I need the low down on dehumidifiers

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Freebee

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Do they work? things on the boat decidely damp, Ive noticied B & Q and argos do £80 electic dehumidiifiers do they work its a 30 foot mobo will one of these small units make a difference?

I am thinking of wall mounting in the heads with a constant water drain to the hand basin and leaving all the doors open open to the cabins is this Ok?

do I need the unit runing 24/7 or can I run it on a timer for less hours?
 
They are worth every penny.

Recommend buying a compressor type as they are energy efficient and can be left on all the time.

Set the humidstat to 'normal' and it will switch on and off as necessary.

Woudn't rekon putting it in the heads or wall mounting is a good idea - the air flows gently through the unit. Would recommend putting in the main cabin area, but I guess how you attach a permanent drain will determine final location.
 
yes they work very well and you can put them on a timer or just run constantly. In winter you may need to add some heating e.g. an electric greenhouse heater, cos some of em freeze up in really cold weather.
 
Use an external mechanical timer in case you get any power cuts that would reset any electronic timer built into the unit.

Run them during the day when it's warmer and they're most effective.
 
Went to the boat at the weekend after leaving it 3 weeks with the same kind of dehumidifier as you describe, and no damp at all. It was from Homebase and has a mechanical (well, not electronic) switch, so will restart after any power cuts, per advice from ChasB. Agree with fluffc, ours is in the saloon, draining into the sink.
 
Works for me.

We don't use it mid-season, but we don't have 8 sweaty race-crew sleeping aboard.

When we're on the hard for the winter, I go for:
(1) constant-drain dehumidifer perched on galley sink with hose draining into sink (sea cock open)
(2) 100w greenhouse tube heater on saloon floor.

All on a 3hr on/3 hr off timeswitch.

This year, we've brought all the cushions home for a dry/shampoo/hoover, so whilst the boat may be fresh, the house currently "smells of boat(tm)" ;-(

I do stick some silica sachets around the chart table, toolbox & electrics, but I don't think the little 12v dehumidifiers have enough oomph.

HTH,
 
The B&Q one works fine for me. I leave it on all winter with a drain into the sink. Makes such a difference - worth every penny.
 
B & Q dehumidifier; 100w heater in forecabin; fan in each cabin all 24/7, boat shut up tight (vents & windows closed); works for me!
 
A dehumidifier relies on there being a (significant) temperature difference between the air and the cooling plate. Hence, they won't work if the temperature drops too low.

I believe that they work best at temperatures above 10oC.
 
"A dehumidifier relies on there being a (significant) temperature difference between the air and the cooling plate"

Which is why I said to run it during the day. By my saying you don't need a heater i mean you don't need a heater per se. Anyhting electrical that puts out a significant amount of heat will do, like a fridge. However heat rises, so the heat source should be below the dehumidifier.
 
yep, they work.

The damper air tends to lurk around the lower areas of the boat, so put it as low down as possible.

Yes, a timer is a good idea too. But of course the boat needs to be sealed.

The dehum extracts water from the body of air in the boat, and this dry air in turn inhibits mildew rust etc associatd with dampness on surfaces (metal) or in fabrics.

Best i have found is to run the dehum full time for a few days during last few days on board (keeping hatches etc shut as much as poss) which means the general fabric is surrounded by dry air. Once you have left the boat then an hour or so a day maintains the dryness.

Other positive moves in this regard is to go through the whole boat with WD40 and kitchen towel tissue bit of spray onto everything metal and wipe off. Hinges, taps everything. This inhibits oxidising (rusting) of often non-marine items.

Other possible is to lift/air anything that could harbour dampness, such as mattress etc. If you can get things out of the boat then so much the better.

You can test and taste dryness: your mouth will feel instantly dryer in a dry boat. And a freshly laundered sheet "feels nice" because it's dry, not especially because there is a touch less grime in it.

Finally, things like curtains on boats can go manky and mildewy as they are near windows which get v cold and hence get any condensation/water. So a good idea with these is to shut out light using cardboard, and keep curtains away or unhook whilst boat not in use.

hope this helps.
 
A bit of cling-film over the hatches, but not directly on the glass, will create a psudo double glazing and help to keep the heat in. Easy to remove in the spring.
 
why put the dehumidifier on a timer? It should cut out when the humidity drops low enough. I would think having the timer switch it off means 1) the humidty creeps back up again (bad thing) and 2) the dehumidifier has to work hard when switched back on. So I would think the power saving small compared with leaving it 'on' the whole time.
 
Because it will last longer if it's only run for 2 hours a day rather than 24.

It never has to work 'hard'. Mine works on a condensation principle - no 'work' involved at all.

During a cold January night mine does nothing at all, even if I left a small heater on. So it's pointless. I'd have to leave a big heater on to make the boat warm enough for it to be effective.
 
It doesnt work 24 hrs anyway. just when the humidity is high. By work hard mean that the fan/compressor would be running continuously for several hours after the timer switched it back on, as the humidity would have risen.

At night, the air is cold, which means it cannot hold much water vapour, hence the humidity is low anyway. So the dehumidifier will have switched itself off.
 
That's what we do, the dehumidifer is on a switch, and goes on and off with the level of water vapour. Don't know how I would know if it was running too "aggressively", i.e. running more than it needs to, but in current temperatures it seems to be working.

Would prefer for it to be lower in the boat, but a downside of a cat is that then I would need two, one in each hull!
 
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