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Old 10-11-2014, 16:25   #1
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Dehumidifier efficiency in keeping the boat reasonably dry

On my 37 ft power boat I keep in Point Robert, Washington (Pacific North West) I have two of those low power 'dehumidifiers' that have low heat and a fan running. I am not entirely sure how effective they actually are as with them running my two Drizair canisters are collecting a lot of water, even more than without them.

I am wondering if buying a proper power dehumidifier set at say 50% humidity that collects the water would be better option and have better result than these low heat fans.

What are others using on their boats here in PNW? it takes a lot to get used on the musty boat once the trend sets in...

Ideas and opinions are welcome
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Old 10-11-2014, 16:53   #2
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Re: Dehumidifier efficiency in keeping the boat reasonably dry

A real dehumidifier is of course better, You live aboard?
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Old 10-11-2014, 19:35   #3
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Re: Dehumidifier efficiency in keeping the boat reasonably dry

No i do not but i am on my boat every weekend throughout the year. I do not go out with it from late October to late March and am trying not to remove all of the soft clothy stuff of the blat in the fall and winter but at same time do not want it to get that musty smell to permeate once i start using it in spring and summer.
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Old 10-11-2014, 20:50   #4
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Re: Dehumidifier efficiency in keeping the boat reasonably dry

I am struggling to understand how a de humidifier can work if it doesn't have a refrigeration compressor. I doubt just a fan and heater would do anything, if that's what you have.

A de humidifier should work well as long as it has enough capacity for the volume of air and the geographical location.

Ensure the boat is air tight so it can work.

When I get my boat it will have air con. I will install a humidity stat to control the Air con when it is stored at the dock in tropics.
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Old 10-11-2014, 22:56   #5
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Re: Dehumidifier efficiency in keeping the boat reasonably dry

Boat based in Vancouver BC and I run a small home electric dehumidifier that fits in the sink. I let it drain straight out that. Works far better than any of the granular based systems in our climate.
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Old 10-11-2014, 23:21   #6
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Re: Dehumidifier efficiency in keeping the boat reasonably dry

We are in the SF Bay but have similar mildew problems in the winter. I keep two de-humidifiers on my boat. They are small- about 30 pints per day each. I put them in the showers in the fall and run them all winter. The water just runs down the drain and the boat stays pretty dry. I also use a heater in the evenings when it's cold.

I clean the entire inside of the boat in the spring and fall with a good anti-mildew spray. One year I used Tea Tree Oil. Another time I used a commercial anti -mildew spay . Both seemed to work pretty well. This system works well and I don't get any mildew on the boat or on the fabrics
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Old 11-11-2014, 00:16   #7
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Re: Dehumidifier efficiency in keeping the boat reasonably dry

De-humidifiers are great, just make sure it doesn't present a fire hazard.

And others have offered good advice.

Is there a 12 volt option?
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Old 11-11-2014, 10:01   #8
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Re: Dehumidifier efficiency in keeping the boat reasonably dry

Bought a good dehumidifier at Lowes...drained it into my sink. The boat was locked up and on the hard for 6 months in S. Georgia....where you can grow Chia pets overnight. It worked great....when the boat was unlocked in October there were no smells and only a few dots of mold on the ceiling by handrails.

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Old 11-11-2014, 10:22   #9
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Re: Dehumidifier efficiency in keeping the boat reasonably dry

Quote:
Originally Posted by Petar View Post
On my 37 ft power boat I keep in Point Robert, Washington (Pacific North West) I have two of those low power 'dehumidifiers' that have low heat and a fan running. I am not entirely sure how effective they actually are as with them running my two Drizair canisters are collecting a lot of water, even more than without them.

I am wondering if buying a proper power dehumidifier set at say 50% humidity that collects the water would be better option and have better result than these low heat fans.

What are others using on their boats here in PNW? it takes a lot to get used on the musty boat once the trend sets in...

Ideas and opinions are welcome
You're fighting contradictory solutions. One camp is ventilate the boat well. Fans moving air will assist in that. Drizair is removing moisture. If you are ventilating the boat, you are bringing in air with moisture.
I had a van that I used summers for windsurfing. In the off season I put a Drizair in it and it would last pretty much the winter. Once a door or window was ajar and it lasted a couple of weeks.

I have no power at my dock, I use 3 Drizairs on my boat, works pretty well. I need to add one back in the quarterberth / lazarette area as there doesn't seem to be much exchange of air to that area and it gets wet. The guy at our dock that went with the good ventilation plan has a wetter boat than mine. You need a lot of ventilation apparently for that to work.


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I am struggling to understand how a de humidifier can work if it doesn't have a refrigeration compressor. I doubt just a fan and heater would do anything, if that's what you have.
My understanding is that the problem is temperature differentials. The hull, ports, etc cool down and the moisture in the air condenses out. Increase the temperature in the boat and the relative humidity drops, reducing condensation.
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Old 11-11-2014, 10:56   #10
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Re: Dehumidifier efficiency in keeping the boat reasonably dry

My company does moisture removal at an industrial level and the gurus said this:
It is a boat in water. Unless it is air tight moisture will come back in. To prevent mold, air movement is a key.

Here is one from my first hand experience. A cat we bought was captained ...by the captain from hell, who took six weeks to go 800 miles and left hatches and windows open the whole time. We had to gut it as all fabrics were moldy. There is a woodworker website that recommended Boric acid in solution as the best safe anti mold, fungal, viral available. Having nothing to lose I followed directions and washed the entire inside down with the mix. Four years later running a couple of cheap fans, there is no smell at all. No mold at all. The cat is in the Gulf of Mexico so dew points, and humidity are an issue. This process has now been done on another boat by me and several others by their owners. It really works.
The dehumidifier had no impact.
My two cents.
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Old 11-11-2014, 11:07   #11
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Re: Dehumidifier efficiency in keeping the boat reasonably dry

Close it up, and the dehumidifier will have an impact, all that water is coming from somewhere. (the air, where else?)
Myself I just use the dehumidify setting on the front AC, another boat I had a dehumidifier, sat it on the counter and drained it into the sink like others.

You can either absorb water chemically like the Drizair things do which absorb a lot less than you think, that liquid is not water really it's a salt solution, pour it on hot pavement and it doesn't evaporate much as there isn't much water there. (I've used it in airplanes until I found out the liquid is VERY corrosive)

Or you can use a "real" dehumidifier, which is nothing at all but an air conditioner, the evaporator condenses the water out, and the condenser heats the air back up so you get no cooling, actually you get some heat.

I know of no way to remove water mechanically except with a vapor cycle system (air conditioner) maybe there is another way?
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Old 11-11-2014, 11:10   #12
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Re: Dehumidifier efficiency in keeping the boat reasonably dry

I asked if you live aboard as I believe a dehumidifier would be less effective then, but as you leave the boat closed up for 5 days at a time, I believe the dehumidifier will be very effective, or at least mine have been
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Old 11-11-2014, 11:15   #13
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Re: Dehumidifier efficiency in keeping the boat reasonably dry

Quote:
Originally Posted by ironhorserider2 View Post
Bought a good dehumidifier at Lowes...drained it into my sink. The boat was locked up and on the hard for 6 months in S. Georgia....where you can grow Chia pets overnight. It worked great....when the boat was unlocked in October there were no smells and only a few dots of mold on the ceiling by handrails.

Sent from my DROID RAZR using Cruisers Sailing Forum mobile app
Same experience as mine. We have really humidity here and I got tired of having to clean the mold and mildew off the walls and ceiling every two weeks. I put in a de-humidfier from Lowes, ran the hose into the bildge, set it on 50 per cent, and never had any more mold or mildew.
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Old 11-11-2014, 11:44   #14
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Re: Dehumidifier efficiency in keeping the boat reasonably dry

12 v option. Evadry makes a 12v version. Only about 4 pints/day, which is plenty if the boat is tight.

Heat vs. compressor. Heat raises the temperature which, at a given water content, lower the relative humidity. So yes, heat can low the humidity, but does not remove water, just as houses seem drier in the winter.

Pure ventilation. I think this is climate dependent. In very wet and foggy climates, this is often wishful thinking. You might control actual condensation, but you won't get a dry boat. Other places and other times of year, yup, it's all that is needed. This is one of those subjects where you need to consider the use patterns and location when reading the comments. Winterization threads are like that too.
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Old 11-11-2014, 12:04   #15
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Re: Dehumidifier efficiency in keeping the boat reasonably dry

Thinwater has a good point about climate type and effectiveness of ventilation verse dehumidifier.

In Sydney Australia we have a fair amount of humidity and I notice most of the race boats have dehumidifiers primarily to dry out wet sails stored on board to protect the investment.

Thanks also Thinwater for answering the 12 volt dehumidifier question... Anyone using one?
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