Condensation Problem in a 22 Cruiser.

A

AKMel

New member
Summers we boat in Southeast Alaska, surrounded by water in a temperate rain forest. Water temp typically 50˚or less. A problem we experienced each trip was lots of condensation in the cabin. Windows especially sweat.

-- Up front we have a 6” fan on each side facing the forward windows. When underway and on “high” they barely keep the front windows condensation-free on cool days.
-- The boat is garaged with windows open when not in use. The problem exists most after the first night aboard.
-- I installed an Espar heater, which works well, and set it up so the combustion air comes from inside the cabin. This should draw in fresh, less-humid outside air and dispel moisture laden air out the exhaust. I couldn’t tell much difference in the cabin condensation.

Saw this product on-line: “Eva-dry EDV2200.” The EDV2200 is a mid-sized capacity, electric dehumidifier. The unit works in areas of the home that are up to 2,200 cubic feet and helps dry the home via thermal electric Peltier technology. It's effectiveness is measured in gathering approximately 20.5 oz. of water per day at 86° F and 80% R.H. Additional specifications of the EDV2200 include: a power adapter of 12V DC 6AMP, power consumption of 72W, 2 Liter capacity removable water tank and an automatic water level detector switch to indicate tank is full. The unit measures 8 ½"W x 14"H x 6 ¾"D."

Cost $85 on Amazon. Anyone tried this?

I’m thinking the power adapter can be bypassed to run directly off 12v. The power adapter is 6amp, so I suspect it draws a little less??? I’m guessing overnight use should consume 40-50amps 12v. The downside seems to be that the unit will freeze up at 55-60˚. But with a cabin heater that should not be a problem for us.

Your thoughts appreciated. Mel
 
I have not used the EDV2200, but based on experience with Peltier Effect refrigeration, I don't think it will compare favorably with a compressor driven dehumidifier. I have used the MightyDry for about 15 years. It is no longer made--similar to other compressor/refrigeration/heater units, which condense the water on the coils, then blow warm air across and the water falls into the tray and out the drain. Same principle as the Peltier, but much more power. Others who compare agree. The Mighty Dry are SS and bronze/brass, they are marine grade in a SS cabinet--about 12" x 12" x 15" and weight about 28#. The label says 1/12 HP and 5 watts at 110 volts. But with 1 hp being 746 watts, 1/12 hp would be about 62 watts..plus fan motor? (which may be the 5 watts, so I would guess about 70 watts. That would be more current that I think you would want to use from an inverter. I can put it on the Kill O watt meter and find out what the real draw is.

We had that problem on our Cal 46. We insulated the entire hull, and ceilings, using mostly 5/8" fish blanket--a foam we found in hardware stores in AK. We were running a 45,000 Btu hydroponics diesel heater. We could not directly insulate the windows (double pane or triple pane not practical in custom windows that size)--but used mylar bubble wrap inside the windows, which helped.

In the C Dory 25, we just kept the forward deck hatch open at night. Some have used an insulating paint over the entire surface of the boat interior. Some feel that the boats with liners (vinyl and foam) have less condensation.
 
We have used that model for many years and run it 24 7 when stored. We have friends with a 40ft sailboat the they said it made a big difference for them as well. We ran the smaller model on or 25 and it was great as well.

They work great down to about 38 degrees then you need a little heat in the space to keep them from icing up rendering them ineffective.

Greg
 
I installed an Espar heater, which works well, and set it up so the combustion air comes from inside the cabin. This should draw in fresh, less-humid outside air and dispel moisture laden air out the exhaust. I couldn’t tell much difference in the cabin condensation.
Click to expand...

I think condensation is a widespread problem for many of us. I also plumbed my Webasto heater the same way initially using cabin air for combustion. However, I finally decided to draw that combustion air from outside. While the theory of drawing fresh less humid outside air into the cabin might work great for areas where they have very low humidity, that just isn't the case where many of us boat. Especially when we are right in the middle of a very moist lake! :mrgreen: The condensation in my cabin is usually the lowest when I can also keep a few windows open an inch or so, especially the V-berth hatch where we are expelling warm moist air while we sleep. I also run a fan or two. Colby
 
Thanks for the input: Aurelia: I appreciated the input that a Peltier worked well for you in a northwest climate.

Surfing last night on e-commerce sites I found one made by Ivation, same specs as the Eva-dry, for $35 shipped. The distressed freight store lists it as new "other." At that price I jumped. I also researched smaller Peltier units but found they operate off 7.5v or 9v. I want to plug directly into a 12v utility receptacle on the boat so that eliminated those. This will be a cheap solution if it works. Here's hoping

A problem some owners had after a few years was fan failure. I suspect a drop of oil per year will be needed, assuming I can get at the fan bushings.
 
Colbysmith wrote: I think condensation is a widespread problem for many of us. I also plumbed my Webasto heater the same way initially using cabin air for combustion. However, I finally decided to draw that combustion air from outside. While the theory of drawing fresh less humid outside air into the cabin might work great for areas where they have very low humidity, that just isn't the case where many of us boat. Especially when we are right in the middle of a very moist lake! Mr. Green The condensation in my cabin is usually the lowest when I can also keep a few windows open an inch or so, especially the V-berth hatch where we are expelling warm moist air while we sleep.

Colby two thoughts:

1. You may actually be better off to go back to drawing combustion air from the cabin because "makeup air" is needed to compensate for the air lost from the cabin by drawing it out through the Webasto. It has to come into the cabin ... from outside the cabin. That air will sneak in via minor openings, or through any open vent or window. To prevent the Webasto from producing carbon monoxide, I bet you always open a window or a hatch to allow fresh outside air into the cabin. That air is makeup air.

2. "humidity" is a slippery label. When air carries a lot of water in it, we call it "humid." We notice the air is humid when it feels moist on our skin, and when condensation easily appears on cooler surfaces like a window (when the outside air is cold) or the below-water part of the hull (when the water is colder than the cabin air). Our sensation of "humid" air is really a reaction to air with high "relative humidity" aka RH. RH compares the amount of water vapor in the air to how much it could hold before mist or rain would form. One hundred per cent relative humidity (100 % RH) occurs in cold air with relatively small amounts of water vapor. But cold air, when heated to form hot air, will hold lots more water before it reaches 100% RH at its higher temperature.

Here's where choosing to use cabin air versus outside air comes into play. When cooler air at 100% RH is pulled into the cabin and warms up, it will no longer have 100% RH. It will be "dryer" air. So the upshot is that, depending on how cold it is outside, that cold air, at 100% RH outside, becomes relatively dry air inside, and can have a RH well below 50 % RH.

Sorry to go on so long.
 
Aside from the humidity of the air, there is the insensible loss from breathing and skin. Although condensation can occur in an unoccupied boat, the problem here is an occupied boat--with two people: The "insensible" loss is between 700 to 800 ml a day (slightly over 3 cups of water a day.) That liquid has to be added to the amount of moisture in the air (humidity).

There are 3 variables--the amount of humidity, the amount of water added by insensible loss, and the differential temperature (to cause condensation).

I also feel that using inside combustion air is better. It will be interesting to see how much water the dehumidifier removes (measured), and how well it works when the boat is occupied vs not occupied. I took Greg's comment "We have used that model for many years and run it 24 7 when stored. " literally, and don't know if it had any effect if used when the boat was occupied at night.

Look forward to a report.
 
Now that I have a whole keyboard back in front of me. Let me elaborate a bit.

We used the Evadry 1100 https://www.eva-dry.com/dehumidifiers/e ... umidifier/ on the galley counter of our 25 cruiser while we had the boat and ran it always when plugged into a dock (out cruising and in permanent covered moorage) but also ran it off an inverter occasionally while the boat was running. It made a significant difference in cabin humidity to have it running, but we did not run it when the boat was in use often enough to gather any real number based evidence. We did have a habit of hanging wet jackets and gear in the cabin when we left the boat at the dock and went home, always noting that the cabin and the gear was bone dry when I inevitably checked back on the boat a couple of days later. The little water drawer on the unit would be full, and the unit shuts itself off when that happens to prevent an overflow.

Side note: on the 1100 or 2200 models, you can easily drill a little drain whole in the water drawer, add a small pierce of hose, and run that little drain hose to the sink for constant draining and operation. We did that during the last year with the 25 and it could run for weeks without needing any attention.

We also ran a 2200 model https://www.amazon.com/Eva-Dry-Edv-2200 ... B001QTW6KQ inside the storage cover of our lund while it was parked at the house and it did a remarkable job of keeping moisture levels low and preventing all mildew issues during storage.

My brother in law has done the same for over 5 years with a 18ft Tracker parked and covered outside and reports nothing but good results and says it seems to suck water out of the boat carpets and storage areas really well.

On to boat overnight use... We have friends with a 40ft cruising sailboat and they had condensation issues during their first year of ownership before asking about the little 1100 unit we were running on the 25 at the time. They immediately bought the 2200 unit and started running it when the boat was parked at the dock and not in use. With meters on board, they noted a 20-25 percent humidity reduction in that large boat with two heads and staterooms whenever the unit was in use. They concluded, that running it all the time would be even better so they wired it directly to their boat 12v power and have run it ever since. That was 2010 and when their first 2200 unit fan failed, they didn't think twice about replacing it immediately. On average, it pulls about 2 quarts of water from the air each week and that is without anyone on the boat. They said it makes the most difference when they have guests aboard during crummy weather and all the wet gear and showers add up to more humidity.

We have run the same 2200 unit since 2012 and it runs continuously whenever the boat is at home which is most of the time. My brother in law runs his similarly since 2011, and is still running the original unit.

I always guessed that running the unit on a tilting platform, might wear the fan a little differently and shorten the life to 2-3 years. Still worth it in my book.

Don't overlook the power use of these units as those amps add up, especially during the overnight hours. When on dock power, let it rip!

Also, I start to see ice build up on ours as the temperature drops below 40 degrees and during the colder part of our winter, I run a little 200 watt forced air heater on a timer, facing the Evadry unit, to de-ice it a few times perday. Works really well. These units are less effective as the time decreases but I still find a drawer full of water in mine on weeks when it never got out of the 40s.

I try things that don't work all the time. But, I don't continure doing things that don't work pretty darn well, and these units earn their keep in our climate.

Greg
 
"TEMP decreases" Correction needed on the second to last line of my last post. among others, darn auto correct. Plus I find that working across 4 devices and 2 PCs seems to keep my typing less than perfect. Forgive me for not taking more time. So long as folks get the point, I won't feel too bad.

If you are sleeping overnight on a 22 with all the windows closed, stop doing that before you do anything else. Crack the berth hatch, crack the center window, and if you really want to get serious, install a couple of opening portholes on the sides of the berth and leave those open or cracked overnight as well.

Ever since putting the little portholes in, we close the berth hatch, but still leave the center window cracked open and we have less condensation than ever. An hour of heater time on even the sloppiest morning sets everything right again.

Greg
 
Relative-Humidity-Graph-e1367505504127.jpg


Does this help the argument?
 
1. You may actually be better off to go back to drawing combustion air from the cabin because "makeup air" is needed to compensate for the air lost from the cabin by drawing it out through the Webasto. It has to come into the cabin ... from outside the cabin. That air will sneak in via minor openings, or through any open vent or window. To prevent the Webasto from producing carbon monoxide, I bet you always open a window or a hatch to allow fresh outside air into the cabin. That air is makeup air.
Click to expand...

Dave, what makeup air are you talking about? I'm not sure you are understanding how the Webasto works, or I'm not understanding your comments. There are two types of air the Webasto uses. The air to heat the cabin is recirculated thru the Webasto inside the cabin. The other air is the combustion air. That is the air that is drawn into the Webasto for combustion and is expelled overboard thru the exhaust. During initial installation, I was using inside cabin air for the Webasto's combustion chamber. Theory being as I think you do understand, that air brought in from the cabin and expelled overboard thru the exhaust puts a bit of a vacuum in the cabin, thereby drawing air in from outside thru the various openings in our boats. (Anchor hauser, sink drain, etc.) Unless the Webasto has a leak in it's exhaust, there is no Carbon Monoxide being put off in the cabin. (Again, the combustion air is exhausted outside. In fact, if you are using cabin air as your combustion air, you have a bigger chance of drawing in that exhaust air from outside if there are any cabin openings near the exhaust!

I also understand what Bob is saying, but in my case, the air being brought into the boat from outside was not dry enough to make a difference from the bit of breath moisture. That and the fact many times I'm boating in pretty cool or rainy weather when the heater is in use. In fact, I didn't notice any advantage when I was using the inside cabin air for combustion except when there was very low humidity outside.

Having a hard time explaining it, so I found this definition: When warm, moist air comes into contact with either a surface or air that is colder than it is, the warm air is unable to retain the same amount of moisture as it did and the water is released either into the cold air or onto the colder surface, causing condensation to form. So if I'm boating in 40 degree or less weather with my heater going, our boats are not insulated so while I may have my inside air at 60+ my hull is going to be 20+ colder, and condensation is going to happen! Coming home from the Columbia and Snake River run, I spent one night on the boat where the temp got down to 18 F outside, while my heater maintained 60 inside. I forget what the humidity was, but NO, I was not leaving very many windows open very far! lol. And YES, there was condensation inside the boat. Colby
 
Colby,

Yes, my CO comment covers the small chance of a failure in the WEBASTO manifold systems. No leaks, no CO, except whatever an open window or hatch/vent might pick up, and certainly very little chance of that!

On the other issue, even external air at 100% RH, ducted into the cabin via a window or hatch/vent when it is raining and cold outside can help dry the air in the cabin. Sounds weird, yes? That's because when that external air warms, its RH will drop substantially, thereby lowering the overall RH in the cabin.

On the other hand, If the makeup air for the Webasto comes directly via ducting into the unit from the outside, then there is no drying effect from it.
 
Greg mentioned it. Put some v-berth portholes in, Pt & Stbd, and get some cross flow air in. Bet you see an improvement.

Martin.
 
I appreciate everyone’s contributions. Especially Dave's logic and the chart.

Now I understand why my millwright uncle always heated to keep a humidity gauge at 50% rather than by temp. He needed to keep the wood dry.

What I got out the discussion is warm air can absorb more moisture than cold air. Using the chart to confirm, makeup air at 10˚ C holds about 8 grams of water per Kg of air to have 100% relative humidity. Heat that air to 20˚ C and, going straight across the chart at the 8g level, that same air is only 50% relative humidity. Thus, theoretically, drawing in makeup air and raising it’s temp helps reduce the relative humidity in a space. Even if a Webasto or Espar only intakes 30-40 cu ft per night of makeup air it helps to reducing relative humidity.

We are generally cool and wet all summer in our neck of Alaska. I generally heat for 55˚ at night. Perhaps heating a little more will help? First I’ll try opening the hatch and center window a little more. Presently I get condensation even with some ventilation and makeup air. I’m beginning to understand I need to overcome the human contribution. I now understand my options better. I’m hoping a Peltier system will help and perhaps b e enough. But it may take other factors in combination.
 
On the other issue, even external air at 100% RH, ducted into the cabin via a window or hatch/vent when it is raining and cold outside can help dry the air in the cabin. Sounds weird, yes? That's because when that external air warms, its RH will drop substantially, thereby lowering the overall RH in the cabin.
Click to expand...

You still have the moisture. Warmer air does not make it disappear. Warmer air just holds more moisture. As soon as it hits your colder cabin walls, it will condensate. Ever walk outside on a cool morning and see all the dew on your car? The bottom line is, the only way to help remove the moisture is ventilation. That alone would make it seem like drawing my combustion air from inside would help ventilate the boat. In practice it hasn't. :? Colby
 
I hear you, Colby. I agree the added ventilation from windows or hatches achieved by pulling combustion air into the Webasto from the cabin "should" help reduce condensation. But, it is not. Better air circulation within the cabin from fans is about all I can think of. Or, a dehumidifier. But Aurelia's careful notes of his experiences with the units he has tried suggest they are pretty slow.

Directing warmed air over the cabin walls is another possible help, but cumbersome to achieve, and likely costly in added fuel for whatever method you choose.

It is a puzzlement, for sure.
 
The dehumidifiers are very slow in practice and need to be run for hours just to start making a real difference. I only run our current unit when the boat is back home, but if you ran one overnight, it would make a serious difference, but I would tend to try less ventilation in that scenario. Leaving a bunch of cracked windows, while operating such a small unit, wouldn't get a person very far. But in cold conditions, when folks tend to limit ventilation, it would have a greater effect with less overall air to work with. I think cracked windows, and serious blown BTUs are most effective in the short term. Our little heater is technically too much for our boat in all but the coldest sub freezing weather, and it only has one setting. This encourages us to ventilate, whenever it is running to at least some degree and often to the tune of many cracked windows.

How about a breathing snorkel to send the humid air outside overnight. That would make a good April fools picture on the site.

Greg
 
I’m brainstorming. I wonder if it would be possible to route some plastic pipe or tubing out (and back in) a side window as a night-time condensate trap. A small low volume fan would push cabin air through the tubing and back into the cabin. The cool/cold outside air would then cause humidity to condense inside the tube. (It’s already condensing, especially on interior windows. But on windows it stays in the cabin.) A hole at a low point of the tubing would allow humidity to drain to the outside.

The downside would be the condensate trap would act like a heat exchanger, cooling the return air. I’m reasoning that can’t be much different than leaving a hatch or window open.

Am I barking up the wrong tree? This would be energy efficient, removable, and cheap to build.
 
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