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Dehumidifiers: Pros/Cons

Discussion in 'Technical Discussion' started by csalkows, Jan 26, 2012.

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  1. csalkows

    csalkows New Member

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    I've been considering putting a dehumidifier on my Carver 4207 but I haven't seen much discussion relevant to marine use. I'd be interested in your thoughts. For context, consider operation along the gulf coast and in the keys, and a unit that draws 4A, costs under $200, and can extract several gallons per day.

    1) Perhaps I'll need to leave the boat vacant at the slip for a week or so (or even just for the day). Sure it will be fine closed up but with the humidity here, "boat smell" blooms quickly. I could run the AC, but all 3 systems draw about 40A combined. Wouldn't use of the dehumidifier be a good compromise?

    2) It's not uncommon to experience evenings with 95% humidity and 95 deg here. I'll turn in using just the aft stateroom AC. I'll crank that sucker down trying to get comfortable but then find myself cold and damp. Maybe I could back off the AC if I turned on the dehumidifer?

    3) At anchor, away from land, it's cooler but still pretty damp. At just 4A, the dehumidifier may help and a lot less drain than the AC.

    4) It's making up to 3 gallons a day! I know I can't drink it, but I can wash clothes in it. Also, the most expensive part of running a Katadyn watermaker is replacing those dang membranes due to foul water. The dehumidifier is basically making distilled water. Running that through the Katadyn should make the membrane last forever.

    So has anyone done this?
  2. K1W1

    K1W1 Senior Member

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    Hi,

    If it makes 3 gallons a day and you want to leave it for a week or longer how will you get rid of the 20 odd gallons it makes a week when unattended?
  3. csalkows

    csalkows New Member

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    Run a line to the bilge - or overboard. Yes, I know, what if the line clogs or the system malfunctions. Well there's ways around that, but bottom line, 21 gallons won't sink my boat.

    Thanks for the input
  4. K1W1

    K1W1 Senior Member

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    Hi,

    I was curious as I have thought about doing the same for a house that I have that is often left empty for months and months on end.

    I have thought about drilling a hole in the floor bigger than the pipe and running a pipe outside for the drain. If the thing overflowed hopefully the excess water would drain through the hole in the floor around the pipe anyway.
  5. dennismc

    dennismc Senior Member

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    I put my Florida boat on the hard for summer, shrink wrap and leave a dehumidifier running 24/7 with drain into the galley sink, keeps the boat fresh along with charcoal and open bleach bottles to kill bugs etc..boat smells just like I left it the day before...
  6. NYCAP123

    NYCAP123 Senior Member

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    In the old day my parents left one on a chair with the hose draining into the toilet when their house was vacant. No sense making a permanent solution for a temporary problem.
    More to the point of this thread though, what year is the boat? Most systems installed during the past 10 plus years have a dehumidifier setting. The newer units make it very clear with a drop indication. On older units press heat, cool and fan together (upside-down triangle).
  7. csalkows

    csalkows New Member

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    Good input Dennis - so while in the slip in FL you don't find it worthwhile to use it? Even if you're away from the boat for a day or two? If not, do you leave your AC running?
  8. csalkows

    csalkows New Member

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    NYCAP - 1987 Carver 4207 - no special dehumidifying capability that I can discern
  9. NYCAP123

    NYCAP123 Senior Member

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    Entirely possible on an '87 although the controls prior to the current generation don't have an indicator for dehumidify cycle. This link shows the control I'm referring to: Cruisair Marine Air Conditioning. On this, when you press the upside-down triangle (Heat, Cool, Fan) "HU" will appear where you normally see the temp. If your control is older than these you might be best off just changing over to a modern control that can be set for dehumidifier. That way your unit turns on when humidity reaches a certain point rather than temp (which will probably have your unit running constantly until it clogs in the Gulf).
    I'd also leave a few Damp Rids strategically place throughout the boat down there.
  10. Capt J

    Capt J Senior Member

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    A dehumidifier has a float switch in the drain pan, so if the line clogs and the drain pan fills up it shuts off.

    A dehumidifier will create a little ambient heat while it is running.

    You could run the air conditioners on dehumidifier mode. Why don't you set the temp in your stateroom to whatever temp you would like it at instead of waking up cold? Why not run all of the air conditioning systems, they will cycle on and off as needed and is probably better than running the master and trying to work against the heat throughout the whole boat. Remember the a/c pump runs whether 1 unit is running or all of them at the same time
  11. dennismc

    dennismc Senior Member

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    No, if in the slip, and away, everything goes off except about 4 fans , works ok for short term..
  12. Capt Ralph

    Capt Ralph Senior Member

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    uh?

    Not sure what's happening here...
    I'm in the process of converting the old 3 knob controls to the newer pass-Port I/O so the A/C systems can use the de-humidify mode in 4 out of 7 stations. The latest digital display systems from the last 12 + years offer this.
    No extra equipment in the galley draining in the sink or some big box draining in the bilge (somehow), it's already built in.
    Remember, the A/C system was built to de-humidity, it became popular because to got cold....

    ,rc
  13. Codger

    Codger YF Wisdom Dept.

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    Leave the dehumidifiers in the bathtubs and if there isn't a separate overflow hose just cut a hole in the pan and aim it towards the tub drain. Left one in each bathroom on a 24 hour timer so that they'd run during low rate power times. Just visited the place for the first time in 8 months and all good.
  14. tirekicker11

    tirekicker11 Senior Member

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    We do the same here. A dehumidifyer is an absolute must have, especially this time of year with 80-98% relative humidity. When I first started using it I got a little carried away and set the machine to dehumidify to a 40% humidity. The plaster came falling of the ceilings after a few days.

    We use one Phillips, 20 Gall per 24/H unit to keep 3 floors dry.
  15. dennismc

    dennismc Senior Member

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    Boats with bathtubs that drain overboard by gravity ?? most are pumped which means pump failure leads to bathtub filling up and possible electrical short ?
  16. K1W1

    K1W1 Senior Member

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    Hi, Houses and apartments are also being discussed in the thread.
  17. Codger

    Codger YF Wisdom Dept.

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    Apologies. I should have been specific. I was responding to K1W1's post regarding a house left empty for extended periods.

    In a boat I'd be inclined to find the highest point possible to mount the dehumidifier and pipe the water outside.
  18. Capt J

    Capt J Senior Member

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    No, if the shower sump pump fails, the sump will usually overflow into the bilge and then be pump out by the bilge pump.
  19. dennismc

    dennismc Senior Member

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    Usually is something I try not to trust too often...but, I see your point. hopefully the boat does also..lol..
  20. wcoaster

    wcoaster New Member

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    Several of the vessels I work on have dehumidifiers (steel hulls+cold weather=condensation). They work great. Depending on conditions, the 1.5 gallon drip pan needs to be emptied every 4 to 12 hours. It would be easy to plumb a drain line to the pan. It's noisy and generates a fair amount of heat, though. Dayton brand. Most of the time they are off. I've also used a low wattage heater for dehumidification in unoccupied boats, and that worked well too (a unit designed specifically for that purpose).