When any hydrocarbon burns water is produced, whether alcohol, propane or diesel fuel. This is a major reason why fuel burning heat sources must be vented to outdoors in the winter. They produce a lot of water vapor which will rapidly make the boat interior very wet. I A reverse cycle AC in heating mode does not increase the water in the air, the amount of water stays the same, but it does increase temperature so the relative humidity (the amount of water in the air relative to the maximum water the air can hold) actually goes down and the air feels dryer. Hot air does not contain more moisture unless more water is introduced into that air from some source. The usual complaint is like Ron's, his Cruisair (all brands work the same) dries the air in both heat and cooling mode. As the heat goes up, and the amount of water present stays the same, the Relative Humidity, the "dryness" of the air, will go down and the air will "feel" dryer because, since the warmer air can now hold more water, the evaporation rate increases. Turning on your alcohol oven will increase the amount of water in the air and reduce this dry feeling. I will never forget being on board a boat in Charleston SC in the winter that was using a large non-vented propane heater. It was like a rain forest. 100% humidity, actually foggy inside, with water dripping everywhere. Using the AC as a cooling device will also dry the air as the water in the air condenses on the evaporator (the cold part of the AC "sweats") and drips down into the collection pan and is disposed of overboard. Ours goes into the shower sump and is pumped overboard from there. If that water were to be sprayed or evaporated back into the air then the relative humidity would become higher as the water amount in the air stayed the same and the temperature went down. All of the above assumes no outside air coming in. If there is outside air coming in to the boat all bets are off. Typically in cold weather the outside air is very dry because cold air holds less water. So in the winter, you are heating cold, dry air which makes the relative humidify go down even more, thus the need to add water via the oven to feel comfortable. Personally, I would not use a alcohol oven to add moisture because of the poisonous nature of stove alcohol, I would use an actual humidifier device. Norm S/V Bandersnatch Lying Julington Creek 30 07.695N 081 38.484W ----- Original Message ----- From: Ron Rogers To: [email protected] Sent: 10/27/2008 3:15:58 AM Subject: Re: [Liveaboard] Heating Aboard Errr, when alcohol burns, it produces H20. Not good for dehumidifying. Hot hair contains more moisture. There is probably no difference between the reverse cycle process in a Mermaid and that of a Cruisair. My Cruisair dries the air to much. Perhaps itÂ’s the way a system disposes of its condensate? If it goes into the bilge, it probably increases the humidity. Ron Rogers From: Charmaine With the Mermaid and like reverse cycles... I would caution about the heat... I find it a very moist heat, so much so that I usually have the alcohol oven on to keep things from getting damp.
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