Peltier based dehumidifiers

[Braxton]

Does anyone have any experience with Peltier based dehumdifiers (such as http://www.todaysconcept.com/windchaser-mdh-p-personal-dehumidifier.html)?   They seem appealing due to their low power draw but there seem to be frequent complaints of durability issues.

Any idea if they are safe to leave unattended on a boat?

[Wayne]

I have one of the West Marine 'flat disc' type dehumidifiers; quite a few people use them.  No problems.  They are left plugged in when away from the boat (that is after all their purpose--keep things fresh while you are away).  A couple of times I have left my boat for a week where I was not plugged in to shore power, and so didn't have mine on.  I noticed a difference, so my opinion is that they help keep the mold away.

[Ken Juul]

I can't comment on the Peltier systems.  However I do not like to keep my boat plugged into shore power when I am away.

We use 3 damp rid buckets spread through out the boat.  The bucket and packages of refills are available at WalMart, Target and most grocery stores.  They are also available at WM if you don't mind paying extra.

The buckets generally fill at least half full during the summer and spring in VA's humid air.  Last about 3 months, developing cracks/leaks from removing the dried silica from the bottoms of the tub each week. 

Another option in the battle against mildew.

[Braxton]

My tentative plan was to get one of the west marine units as well as one of the Peltier dehumidifiers.   The point behind the Peltier unit is to help remove moisture when we're on board and sleeping with the cabin closed up (no matter how hard I try I can't keep my family and guests from exhaling water vapor).

Do the damp rid buckets and/or the west marine unit keep up with the moisture when the boat is filled with sleeping people?

[Jon Schneider]

The Damp-Rid system definitely extracts moisture (the container starts to fill up).  I also have the WM dehumidifier (I have the non-WM version), and it doesn't perceptibly remove moisture.  It works by simply warming the enclosed area, pretty much the same a light bulb would do, but since it's meant to be on the floor and has vented holes, it theoretically warms the denser, colder air at floor level.  I continue to use it, but I really don't understand what the equivalent of burning a 100 watt bulb does, other than provide some small level of circulation.  Can heating air in a closed space make water vapor disappear?  That seems to defy high school physics to me.  Yet, I continue to use the thing.  Go figure....

[Ken Juul]

If I'm on the boat alone or with guests either I have ports/hatches/companionway open or the boat is closed up with the heat/air conditioner on.  I don't worry about the moisture then, it's when the boat is closed up with little to no circulation that I worry about.

[Wayne]

The air circulation devices provide a little air movement which can help condensation problems.  The label says something about the 100 watt warming making the inside air a little less humid than the outside air.  100 watts seems like a pretty minimal difference to me, too.  I suspect that the air movement is the main help.  And like I said, when the fan has been off for a week my boat feels a little musty inside.

[Mike Vaccaro]

Proper air circulation is the key to reducing or eliminating mold and odors.  Proper circulation is facilitated by adequate ventilation.  The prime ventilation system consists of the companionway and opening ports.  On the C34, the secondary system consists of dorades, louvered vents and solar vents. 

It's the secondary system that does the lion's share of the work when the boat is unattended.  On a typical C34, a single Nicro type solar fan in conjunction with the two stock dorades is generally sufficient to eliminate most mold, even in humid tropical environments.  The key to making this work is to circulate sufficient amounts of air through the boat at all times.  The best way to ensure a constant exchange of air is to run a small solar fan, since a dorade is only efficient if properly aligned with the wind (that's why it's a good idea to orient one fore and one aft if the boat spends most of it's time at the dock, unless your dock is aligned into the prevailing wind). 

Water tends to condense in lockers and enclosed areas first--so it's important to ensure adequate ventilation in storage lockers.  Adding louvers is a good idea, as is ensuring that items aren't so tightly packed (or ignored), that sufficient mold can form to damage them or produce odor.  Keeping unnecessary items on-board to a minimum helps.  We've installed a small low-voltage fan (which only runs when we're aboard and the DC system is energized) in the large locker area beneath the dinette and have louvers installed to allow air to flow through this area.

Small heaters (the 100 watt bulb example or the small unit offered by West Marine) work by raising the dew point in the cabin slightly.  The West Marine unit combines a small heat source with a fan to improve circulation.  If your refridgeration system runs when you're not aboard, the heat produced by the compressor unit and its fan can perform the same function.  Depending on where it's mounted, it can also assist in pulling air through storage lockers.

If you do install a dehumidifier, the condensate will likely be pumped into the bilge.  It's important that the bilge pump system is working properly and the boat should be checked on a regular basis to make sure that the dehumidifier and pumps are working properly. 

There is a good discussion of ventilation by Thomas Young in Chapter 10 of "Desirable and Undesirable Characteristics of Offshore Yachts" by the Technical Committee of the Cruising Club of America.

Cheers,

Mike   

[Ron Hill]

I completely agree with Mike !!
The way to keep smells and mildew out of a boat is first thru ventilation. 
I have 6 of the teak fixed vents (7 1/2 x 9 1/2 inch) mounted at floor level in port/starboard settees, aft cabin settee and one above the drawer below the sink (plus two 3" round vents).  It all started with venting the battery compartment.  The one just below the sink allows the heat from the water heater (on a long motor) to vent out before that heat migrates over to the fridge. 
Between the two solar vents, two dorades and a dry bilge we have never had mildue on board.  A few thoughts .

[Jon Schneider]

Ron, a vent above the hot water heater is a brilliant idea... makes perfect sense to let the heat escape rather than let the heat envelope the fridge.  You've given me a new project. Next time, though, just give me another hole in my head; I need that more ;)

[Braxton]

At this point I've bought the West Marine dehumidifier and am leaving the head hatch slightly cracked to supplement the two dorades.  In addition McAfee's "The Warm Dry Boat" is on hold for me at the local library and I plan to give it a thorough reading.

I've pretty much decided against a peltier unit.   I don't want to be the first fool to put one on a boat only to see its delicate electronics corrode in the salt air.