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post #11 of 23 Old 09-26-2019
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Re: Dehumidifiers

Check online for a pro breeze. I have seen them for $25+ shipping.
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post #12 of 23 Old 09-28-2019
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Re: Dehumidifiers

Many variables.

* On the Chesapeake, spring/early summer is when dehumidifiers really help. The water can still be cold when the air is warm and humid. Ventilation only makes it worse when the water (hull) temperature is below the dew point (this is before most people put boats in the water, so they don't all know about this). Early winter can also be a problem (humid air because of the water, but cold decks). Snow on the deck is often a problem (deck colder than air during the melt). Other seasons ventilation is generally enough. But a dehumidifier is better. I've done both.
* Peltier effect dehumidifiers freeze, but it is non-damaging. If you put it on a timer, it will run at night (when it is most efficient) and defrost during the day (when the sun its the boat).

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post #13 of 23 Old 10-06-2019
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Re: Dehumidifiers

Quote:
Originally Posted by Minnewaska View Post
I'm not familiar with any that won't freeze in low temperatures. Long before freezing air temps. The good news is that freezing air temps won't hold much moisture in the first place.
The self regenerating desiccant types will work down to about 30F. Compressor and pelletier types stop working below 50F or so due to freezing. I started out with a Mermaid AIr compressor type, but I have now replaced it with the EcoSeb desiccant type. The Mermaid Air is sitting on the shelf in my garage.

The dessicant type has the side benefit of putting out about 100W of heat (required as part of the self-regeneration process), which is good in the winter. I have the same type as Wakefield posted above, and it works well. It weighs about 10 lbs, so it is easy to move around and stow.

I started off just letting it drain into the bilge and the bilge pump handle it, but now I bolted a mini-condensate pump to the side of it, and let it pump overboard directly through a drain.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Unfortunately, EcoSeb has discontinued the model I have, which has simple analog type controls, which will always restart following a power outage. Their "improved" model has electronic controls, and I suspect those won't automatically power back on.

pelletier = 0.5 pints/day (too little)
desiccant = 15 pints/day (just right)
compressor = 50-70 pints/day (more than needed on a mid sized boat)

Last edited by TimMarks; 10-06-2019 at 07:13 PM.
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post #14 of 23 Old 10-19-2019
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Re: Dehumidifiers

[QUOTE=TimMarks;2051629906... pelletier types stop working below 50F or so due to freezing....[/QUOTE]

Yes... and no.

They continue to build ice without damamge. Then, if you allow it to cycle off (timer) during the heat of the day (above freezing in the cabin due to solar heating) they defrost without damamge. I have done this for many years.

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post #15 of 23 Old 10-19-2019
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Re: Dehumidifiers

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Yes... and no. They continue to build ice without damamge.... I have done this for many years.
Yes, I have used those for years as well. Until I found a better way.

With the pelletier and compressor types, the amount of moisture pulled from the air slows to a trickle due to the icing-melting cycle.

But the self-regenerative desiccant types continue to chug along without any reduction in output.

Try them. You will be converted. I know I was.

Anyone want a beautiful stainless mermaid-air marine compressor type dehydrator? It is sitting on a shelf in my garage.
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post #16 of 23 Old 10-19-2019
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Re: Dehumidifiers

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... But the self-regenerative desiccant types continue to chug along without any reduction in output....
Next time I will!

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post #17 of 23 Old 10-21-2019
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Re: Dehumidifiers

Sweating on the inside of a hull is due to temperature diffferences on either side (inside/outside) of the hull, etc. To keep condensation at a bare minimum, simply keep a portlight / hatch etc. OPEN so that the boat will easily equilibrate vs. those temperature differences. If you tightly close a boat those thermial difference will LAG the outside temperatures ... and will enhance condensation (because you cannot seal a boat against humidity)

Mold prevention.
1. WASH the interior of the boat with fresh water before storage - to remove any micro-salt deposition; the salt is delequescent ... meaning it attracts water.
2. Use 3M "mildew Block" on all interior surfaces.
3. If the boat is subject to severe mold infection, spray the interior (all surfaces including 'undersurfaces' with a 'caustic' solution (I use a boat soap - Roll-Off). Spray on, wipe once to spread, let dry. The caustic surface will 'deactivate' any mold spores that attach to the surface. Not to be used on paint nor varnish.
https://www.westmarine.com/search?Ntt=amazing+roll+off

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post #18 of 23 Old 10-21-2019
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Re: Dehumidifiers

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Originally Posted by RichH View Post
Sweating on the inside of a hull is due to temperature diffferences on either side (inside/outside) of the hull, etc. To keep condensation at a bare minimum, simply keep a portlight / hatch etc. OPEN so that the boat will easily equilibrate vs. those temperature differences. If you tightly close a boat those thermial difference will LAG the outside temperatures ... and will enhance condensation (because you cannot seal a boat against humidity)
This can be true, but it's not exactly how it works. If equilibrium were all it takes, we'd never see dew outside. Leave a hatch open and you could still get serious dew inside. Ambient air temps can decline with moist air, causing dew.

Warmer air can hold more moisture before become saturated. The Dew Point is the temperature at which the current moisture level would be at 100% and any further decline will cause condensation to form. This is also why you commonly see fog when the air temp and dew point are nearly the same.

You have to come at this from one of two places, or both. First, lower the moisture in the air, so the dew point gets even lower and cold temps don't condensate. Or keep the surfaces of the boat from going below the dew point.


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post #19 of 23 Old 10-21-2019
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Re: Dehumidifiers

As an example think about a light mass/weight trash can standing outside .... never saw one with condensation. The reason is that such quickly equilibrates the temperature and without that thermal LAG.
regards !!!
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post #20 of 23 Old 10-21-2019
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Re: Dehumidifiers

Quote:
Originally Posted by RichH View Post
As an example think about a light mass/weight trash can standing outside .... never saw one with condensation. The reason is that such quickly equilibrates the temperature and without that thermal LAG.
regards !!!
Then why did I have dew on both sides of the dodger glass yesterday? Yes, Iíve seen it on a trash can too.

Humid warm air during the day, condensates when the temps drop at night.


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