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post #42 of Old 04-26-2013
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Re: Tiny Dehumidifiers

Originally Posted by jimgo View Post
PDQ - I read your blog post and found it very informative. I'd be curious as to which is more effective, using a dehumidifier or using solar fans. I also wonder whether the set-up of the dehumidifier drain makes a difference. In Take5's case, the drain is to the sink, which is VERY important, because I believe that drains directly outside the boat. By contrast, I've read comments from people who drain into the bilge, with the expectation that the bilge pump will carry it out. But, if the dehumidifier drops the RH enough, doesn't the air become "dry" and won't the water in the bilge simply evaporate back into the boat's air? Essentially you're creating a closed loop.
* Huge advantage to dehumidifiers. A small unit can maintain 55% at low temperatures when operated 8 hours per day (for defrosting in winter). This is important for boats that have people breathing into them. When the heat comes on, the RH will be 35%, which though it sounds dry, is where it needs to be to prevent cold surface condensation at sub-freezing outdoor temps. A solar fan can only hope to hold you at ambient, which is no good if the air is much warmer than the water.

* The sink drain on my boat is above the water line and drains outboard. The bilge is dry. However, even if the water drains to the bilge the loop is not closed because the bilge is generally not well-ventilated to the rest of the boat. It is not as though a toilet, for example, prevents a dehumidifier from being effective in a house. It just adds to the challenge. The dehumidifier is removing far more water than is evaporating each day (I assure you that bilge water dries VERY slowly at 35F).

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