Dehumidifier or Oil Radiator for 25ft boat?

[Pleinmont]

Noticed the boat seems a bit more dank this year so looking at buying a dehumidifier for my 760 to keep the damp out over the winter - wondered if anyone has any recommendations?

Ideally I'd like one that can be left draining into the sink as not sure how long the tanked ones take to fill up.

Or would it be better to have a small oil filled radiator on board left on low with a timer as a background heater?
It would be easier to put one of those down at the front of the boat so it warms the lowest part of the cabin and bedding.
Not sure if a dehumidifier up in the main cabin would affect the air down in the forepeak.

Suggestions welcome - do I heat the boat or dehumidify it...

 

[ChromeDome]

When you bring up the temperature the air will hold more water. If you do not ventilate, that humidity will stay inside. If you ventilate the heat will disappear.

I'd suggest a dehumidifier.
The working principle of the dehumidifier is either condensation or absorption:

Condensation: The humid air is drawn into the machine by the fan and passed through the heat exchanger. At this time, the moisture in the air condenses into water droplets and becomes dry air to be discharged outside the machine.
The heat exchanger will give you a slight increase in the temperature.

Absorption: Often referred to as desiccant dehumidification, an adsorption drying unit brings the air to be dehumidified (process air) through a slowly rotating silica gel rotor. The desiccant material attracts moisture to its surface, removing it from the air stream (dry air).

Devices are sold in many variants, with timers and many settings. Some will survive power outages and just restart on previous settings, others won't.

I've had three different makes. Two condensations and one absorption from which you understand I prefer condensation.
Had one of the popular Meaco absorption models but wasn't impressed. The latest is a condensation type

EEESE ADAM DEHUMIDIFIER 20 LITER

which meets all my expectations.

 

[Mexican]

Does this one reset after power outages and just restart on previous settings?

 

[Pleinmont]

Many thanks for the quick reply ChromeDome.
Understand - all makes sense.
What size boat were you using it on?

I had a quick look for that model but can't find it to buy in UK anymore... Will have a better look later

 

[Momac]

 

[capri]

I'd also vouch for a dehumidifier. My adsorption model (trotec ttr56 iirc) does also heat a bit while running.

What I don't like with mine is that I have to manually press a button to set it on. This means that I cannot use a timer. If I would buy again, I'd choose another model which works with a timer (and where a tube can be attached).

 

[Pleinmont]

I'd also vouch for a dehumidifier. My adsorption model (trotec ttr56 iirc) does also heat a bit while running.

What I don't like with mine is that I have to manually press a button to set it on. This means that I cannot use a timer. If I would buy again, I'd choose another model which works with a timer (and where a tube can be attached).

Yes that's what I was thinking - ideally a small one that restarts on a timer and has a hose to drain away.

 

[Momac]

A desiccant dehumidifier cant be used with a separate time controller as it would interrupt the cycle. However the dd8L cuts in and out and can be used on all the time economically. It using just over 40p in electricity per day on my boat now I have sealed the vents.

 

[Pleinmont]

A desiccant dehumidifier cant be used with a separate time controller as it would interrupt the cycle. However the dd8L cuts in and out and can be used on all the time economically. It using just over 40p in electricity per day on my boat now I have sealed the vents.

Thanks
Roughly what size is your boat and how often do you have to empty or recharge the dessicant?
The elec in my marina is a fixed annual charge regardless of use so financially I'm not too concerned how much the dehumidifier costs

 

[Momac]

Thanks
Roughly what size is your boat and how often do you have to empty or recharge the dessicant?
The elec in my marina is a fixed annual charge regardless of use so financially I'm not too concerned how much the dehumidifier costs

Its 33ft
You don't do anything with the desiccant.
The dd8L will deal with a house so more than adequate for a boat.

 

[ChromeDome]

As much as the size of the boat matters, the insulation and "tightness" are to be factored in when trying to guess the need for capacity.

I'm not using my dehumidifier at the boat since October 2022 when I installed a bespoke full, breathable Fibertex cover. Now just leave the boat with windows and hatches open - and as always remove cushions and everything else, to keep indoors at home.

The cover is a different solution, just wanted to show you. Here loosely put on, before tightening the straps

 

[Pleinmont]

Thanks for the info - good points re the breathable cover and how airtight the cabin is (another member mentioned that to me - no point trying to dry out a cabin that is constantly replenishing wet air from outside - losing battle)!
Our boat isn't draughty with the doors and windows closed but def not airtight either.
Suspect it is too draughty to bother drying out with a humidifier but not draughty enough to keep fully ventilated in winter when cold and rainy.

Our boat is always in the water and haven't tended to take the cushions home as we use it all year round (Channel Islands) if the weather is calm (sometimes stop overnight in winter too if weather mild).

Will maybe look at improving the ventilation a bit rather than trying to dry out humidity in the boat and also in the air surrounding it! ?
Thanks for the info all.

 

[ChromeDome]

Maybe consider a solar fan with built-in battery backup?

 

[paradave]

My mf805 (similar layout to yours) used to stay lovely and dry with a oil filled rad in the front cabin and then a tube heater down in the engine bay. Cushions all lifted and stood up /\/\ with storage hatches open to allow air flow. I used one with a thermostat and left it on permanently all winter. At the time it was about £5/week from memory. Added benefit of a nice warm boat when you go to use her.

 

[Pleinmont]

Interesting points paradave thanks

In the engine bay did you keep the floors down shut or have them open a crack? Mine has quite large vents in the side of the hull so prob quite a lot of air flows in and out of the pipes. Think the 805 is similar.

Yes I might try a bit of background heat on low for a bit and see how it goes. Looking at rads they are easier to get my head round and a small one is much cheaper for a punt than £150-200 on a dehumidifier.
I have DryMat fitted under the mattress cushions (brilliant stuff for keeping condensation at bay when sleeping over) so that helps the area that would get the worst affected Ship Shape Bedding

To be honest I might be over thinking it. The boat isn't visibly wet inside or showing mildew, just felt a bit cold and dank last few times I've been down and condensation on the windscreen hence the questions
Will try the heater for a few weeks first and see if that sorts it out.
Cheers

 

[paradave]

Hopefully it’ll be like mine, not fall just cold, and a small rad will make the difference.

I had the engine bay open a crack - mainly just so the power cable could go in. I’ve heard of people blocking up the external vents in the winter to help protect the engine from low temps. Probably not as important if your boats always afloat though.

 

[Pleinmont]

Hopefully it’ll be like mine, not fall just cold, and a small rad will make the difference.

I had the engine bay open a crack - mainly just so the power cable could go in. I’ve heard of people blocking up the external vents in the winter to help protect the engine from low temps. Probably not as important if your boats always afloat though.

Yes fingers crossed.
Our water temp is about 8-9deg at worst in the winter here so frost is not really the issue.

I just spotted these Solar Vents too - like deck mushroom vents but apparently do about 20m3 air change an hour!
AAA Solar Deck Vent (217mm OD / Stainless Steel with Solar Panel) | ASAP Supplies

 

[ST840]

Dehumidifier all day every day. They heat and remove moisture. Turn on, set the moisture level required, run the hose into the sink and leave.

 

[capri]

A desiccant dehumidifier cant be used with a separate time controller as it would interrupt the cycle. ...

Most devices can't use a separate time controller (as you said). But there are some that can, e.g. https://www.amazon.de/dp/B07G2MMW5R/&language=en_GB

If I understand the description correctly, I could set a humidity level, say 50 % and use a timer. After a stop, the device would continue where it was before i.e at the 50 % level.

 

[mil1194]

I’ve been using this on my 50ft flybridge and it has been excellent.

Meaco DD8L Zambezi Dehumidifier