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Old 01-05-2017, 07:01 AM   #1
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Use dehumidify mode or reverse cycle heat

I have been trying to find the best way to hold the humidity down in our very changing temperatures up in the Florida panhandle. We have multiple cruise air systems with reverse cycle heat. I have the dehumidify mode to run every six hours but I have always wondered when it is cold like today, 42 degrees, if I would be better off running the heat. We do not live aboard so the temperature is not a comfort factor, just humidity. What has your experience been. Thanks
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Old 01-05-2017, 07:11 AM   #2
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When we run the heat overnight without the humidifier, we wake up with dry throats and sinuses. Those units, whether heating or cool, dry the air out pretty well. I would say running the heat will be fine.
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Old 01-05-2017, 07:14 AM   #3
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Roger

I know of several people who place a purpose built dehumidifier or two in or near a sink for drainage. The amount of water they pull out of the air is astounding. In the cooler months where the heat they generate is not an issue it is a plus. Mechanically a lot simpler than running the AC units.
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Old 01-05-2017, 07:38 AM   #4
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Generally the cooler the temperature, the less humidity you have. By heating the space you will drive the moisture out of the environment,and into the air. A portable dehumidifier would work at a set point and work only when needed. Would set a/c heat at 50* and humidity at 65%.
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Old 01-05-2017, 09:46 AM   #5
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Roger



I know of several people who place a purpose built dehumidifier or two in or near a sink for drainage. The amount of water they pull out of the air is astounding. In the cooler months where the heat they generate is not an issue it is a plus. Mechanically a lot simpler than running the AC units.

This is what I do. I have a smallish room dehumidifier that I keep running in my boats full time. It sits on the galley counter and drains into the sink. It runs almost full time as I set the humidity level at 35%. That is very low but since it only sits in the galley the rest of the boat won't hit that same level.

The only downside is that even though it is "portable" it still is a bit of a pain to take off the boat and put in a dock box or stash in an empty cabin when getting under way. The boat stays very dry however.
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Old 01-05-2017, 10:02 AM   #6
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For years my prefered method of controlling humidity was ventilation.
It worked to a point, but pulling in near 100% humidity air to replace the same humidity air doesnt really help much.

The symptoms were what we all have experienced. Boat feels damp, towles dont dry, etc....

Then last fall I bit the bullet and bought a real dehumidifier. What a huge difference!

Mine, like the one Dave describes above has a hose attachment. Right now it sits on the counter when we are not on the boat, draining into the galley sink.

When we are on the boat, my intention is to secure it on the floor, and use the built in water collection "bucket", so the boat will stay dry all the time. You have to empty the bucket daily, or before getting underway for the daybut it's a two minute job.

I cannot believe that I went all those years with a damp boat!
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Old 01-05-2017, 10:16 AM   #7
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For years my prefered method of controlling humidity was ventilation.
It worked to a point, but pulling in near 100% humidity air to replace the same humidity air doesnt really help much.

the symptoms were what we all have experienced. Boat feels damp, towles dont dry, etc....

Then last fall I bit the bullet and bought a real dehumidifier. What a huge difference!

Mine, like the one Dave describes above has a hose attachment. Right now it sits on the counter when we are not on the boat, draining into the galley sink.

When we are on the boat, my intention is to secure it on the floor, and use the built in water collection "bucket", so the boat will stay dry all the time.

This last weekend we had 4 adults on board the boat in very cold weather which meant that the boat was buttoned up tight. Add propane cooking, making hot drinks etc, we were putting out a lot of moisture into the boat. Since it was below freezing outside any moisture in the boat would condense on the windows and hatches. This was the first time we ran the dehumidifier away from the dock. It helped a lot. The only downside is that the fan is pretty noisy. I am considering getting a small Peltier dehumidifier to use out on the boat. Quiet and uses less electricity, just not as effective as the regular one.
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Old 01-05-2017, 10:19 AM   #8
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Kevin

What brand, daily liter/gallons listed output and rated amperage draw is your unit?
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Old 01-05-2017, 10:20 AM   #9
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Second that about a purpose built dehumidifier.

For years I battled high moisture in SE USA conditions. Here we get significant temperature and humidity swings and using the installed reverse cycle units gave poor results.

So I finally bought a dehum. Problems solved. Completely.

Boat stays dry and fresh and smells better. Minimal power use. Only runs when actual dewpoint rises over 45F. Less wear and tear on rev cyc units.
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Old 01-05-2017, 10:33 AM   #10
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This last weekend we had 4 adults on board the boat in very cold weather which meant that the boat was buttoned up tight. Add propane cooking, making hot drinks etc, we were putting out a lot of moisture into the boat. Since it was below freezing outside any moisture in the boat would condense on the windows and hatches. This was the first time we ran the dehumidifier away from the dock. It helped a lot. The only downside is that the fan is pretty noisy. I am considering getting a small Peltier dehumidifier to use out on the boat. Quiet and uses less electricity, just not as effective as the regular one.
What I didn't share in my first post was that the unit I purchased was physically large, and yes noisy. It was what the big box store had left in stock.

What I am thinking of doing is replacing the large unit I bought, with two much smaller models, one in the salon and one downstairs where the cabins are. I am hoping for a quieter situation, and also hoping to more evenly dry out the air, since there is no forced air exchange between the two areas.

If noise is still a factor the only other choice will be to turn them off at night. Time will tell how it all works out since we havent been at anchor with one running all the time.
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Old 01-05-2017, 10:36 AM   #11
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Kevin

What brand, daily liter/gallons listed output and rated amperage draw is your unit?
I don't remember, sorry it's on the boat. It was the only size left in stock last fall, and is if memory serves correctly the largest unt they sell.

I'll probably move that one to the house, and buy two smaller ones this spring.
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Old 01-05-2017, 10:44 AM   #12
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This is the one we use. Ecoseb DD122EA-SIMPLE desiccant dehumidifier. It's about $200 from Amazon. We drain it into the galley sink. Sorry, don't have the current draw handy, but I know it's not much.
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Old 01-05-2017, 10:55 AM   #13
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Kevin

What brand, daily liter/gallons listed output and rated amperage draw is your unit?

I have used two dehumidifiers since I have too often had two boats (anyone want to buy a 40' sailboat?). I have used the smaller 30 pint units and they work great for my boats from 36 - 43 feet. I have found that using a couple fans in the boat to help circulate the air between cabins and the saloon helps. The next size larger Re typically rated at 70 pints (i.e. Remove 70 pints per 24 hour period). The two that I have are very old. If I was to buy. New one I would likely get this one.
https://www.amazon.com/30-Pint-Dehum...humidifier#Ask

I believe it uses about 320 watts at under 4 amps.
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Old 01-05-2017, 11:17 AM   #14
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We use two Eva-Dry units, one std size in the v-berth and a petite size in the aft stateroom. Quiet and efficient. We are pleased with their performance.
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Old 01-05-2017, 11:24 AM   #15
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Roger

I know of several people who place a purpose built dehumidifier or two in or near a sink for drainage. The amount of water they pull out of the air is astounding. In the cooler months where the heat they generate is not an issue it is a plus. Mechanically a lot simpler than running the AC units.
+1 to that.
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Old 01-05-2017, 11:44 AM   #16
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We use two Eva-Dry units, one std size in the v-berth and a petite size in the aft stateroom. Quiet and efficient. We are pleased with their performance.
Purchased at Fisheries in Seattle.
Good to know Bill, thanks.
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Old 01-05-2017, 11:48 AM   #17
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I too use dehumiifiers. Two Eve Dry petites. One in the galley sink and one in the head sink. Both modified to use a drain tube to self drain into the sinks.

My boat is much smaller so they are enough to help a lot along with the plethora of fans to force circulation constantly. I no longer winter boat so getting away quickly is not a consideration any longer.

Before I got the fans and the dehumidifiers mildew and high humidity was a problem.
Several winters, although no boat use, we were home and I was frequently aboard and the difference was huge-no odour and no whitish spots.

So so know the boat is fully winterized.
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Old 01-05-2017, 12:02 PM   #18
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I have been trying to find the best way to hold the humidity down in our very changing temperatures up in the Florida panhandle. We have multiple cruise air systems with reverse cycle heat. I have the dehumidify mode to run every six hours but I have always wondered when it is cold like today, 42 degrees, if I would be better off running the heat. We do not live aboard so the temperature is not a comfort factor, just humidity. What has your experience been. Thanks
Between your dehumidify mode and your heat you should be in good shape. Heat simply depends on how many degrees you raise the temperature as to how much it will dry the air. I would get some thermometers with humidity readout and simply check to see how well what I was doing was working.

Normally as long as humidity is below 50% you're ok. However, that doesn't hold true for winter and 42 degrees as typically you'll have to lower the humidity further to avoid condensation on the windows, lowering to below 40% and perhaps as low as 30%.
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Old 01-05-2017, 12:24 PM   #19
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I honestly do not think the dehumidify mode on these reverse cycles work that well. WHen selling my last boat, I had a mildew issue and did not know why. I had the boat 6 years at that point and in 3 different marinas. THis particular year I was fighting it. My boat was a very clean boat...as far as showing it by the broker. So he was always confident when showing my boat. I get a phone call....WHAT THE HELL????.....is going on with your boat. I go down there and it is BLACK on the inside....overcome with mildew....headliner...walls...everywhere!!! Well I get the cleaner lady to clean it all up and then buy a small dehumidifier. Never had the issue again. The boat sold to the people who saw it all mildewed out. It really was a clean boat.

My dehumidifier actually fits INSIDE the sink so I just plug it in and drop it inside the sink. It works WAY better than the mode on your AC. I would highly recommend!
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Old 01-05-2017, 12:26 PM   #20
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Just a thought and a question. The cooling cycle on these reverse cycle systems compresses and condenses and takes the water out of the air. If you reverse that cycle, are you not adding water back into the air??? I am asking based on theory AND reality...the reality being when I run reverse cycle heat the air coming out of the vent is noticeably moist/humid!!!
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