Announcement

Collapse
No announcement yet.

Power for dehumidifier

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Paul Land
    replied
    Originally posted by ZachI View Post
    I am looking to run a small dehumidifier that pulls 3.5-7 amps depending on the overall size while the cabin isn't occupied. What is a budget system that would accomplish running this 24/7?
    I use 4 of these, very low draw wall warts

    humi.jpg

    Leave a comment:


  • Ninety-9 SE-L
    replied
    Originally posted by J.P.M. View Post
    For the same moisture removal, the dehumidifier will probably have a slightly higher per draw than a 5,000 BTU window rattling A/C unit, and the window rattler probably won't need to be drained manually and it may be a bit easier to live with. Dehumidifiers are no more than de facto air conditioners anyway. They'll remove about equal amounts of water vapor from moist air for the same power consumption but the dehumidifier will usually reheat the dehumidified air before exhausting it to the conditioned space. That reheating will cause the dehumidifier to use slightly more energy. The reheating may or may not add to the comfort level of the conditioned space.

    Another thought is to consider ways to eliminate/reduce how the moisture content is produced/introduced. No need to dehumidify air that's not moist in the first place.
    Dehumidifiers don't have an extra heater.

    A traditional AC has a hot coil and cold coil, which generally produce a net-0 energy (in theory). A dehumidifier is an AC unit, but both the cold and hot coil are together. Air is moved through the cold coil to take out the moisture and then through the hot coil to complete the cycle. There is no heater, just a complete loop of cold to hot with a net-0 gain.

    That said, the Net-0 is just in theory. Because the compressor pump and fan motor are doing work on the system, there actually is a slightly positive heat gain being added to the room. The room will continue to heat up over time.

    There's Absolute Humidity and % Relative Humidity, which is based on temperature. Hot air can hold more water. Dehumidifiers pull water out of the air and reduce the absolute humidity, the %RH is just a value that depends on the temperature.

    Basically, you're at an advantage in a warm room because the %RH goes down as temp goes up (assuming the AH never changes). If you make the room cold, the %RH will go up and it will be harder to pull out the last little bit.

    Bottom line, A dehumidifier will run about 600W+, depending on size. If you set it, properly to about 50%RH, it will hopefully cycle and not run 100% of the time, saving you kWh, if you keep the temperature in the room mildly warm, like about 78-82°F the %RH will read lower, and if you seal cracks for humidity to enter, you will help it cycle on less, also saving kWh.

    Just keep in mind, you also have to figure out how to remove that extra Net heat, at least in the summer. Winter, you should be fine.

    Leave a comment:


  • Heatmypannel
    replied
    I'm going with a feeling that you have mold/mildew built up over the long time you didn't have a de-humidifier. And that mold/mildew is what is smelling. Go look for it on your walls, ceiling in the basement. Running the de-humidifier 24/7 won't stop the smell. On the other side, I would advise follow this article and pick what you find more suitable for your interior.

    Leave a comment:


  • J.P.M.
    replied
    Originally posted by mzs112000 View Post
    As others have said, get a window AC unit, or a mini-split. It will use a bit less power for the same effect, and you have the added bonus of being able to control the temperature of the room. I found an LG window AC unit that only uses 480 watts, which at 120v is 4 Amps. It says that it can cool down a 480 square foot room or something along those lines, now of course, it will cool down a larger space, but will not be as effective, either way it should work for your needs.
    To run this 480W aircon for 24 hours will use about 11.5kWh. You could probably reduce that usage by adding extra ventilation. I know of a few roof-top vent fans that only use 30 watts or so, which for 24 hours is only 0.720kWh(that's much better than 11.5kWh).

    There are also some units that run directly off of 48vdc, they might also fit the bill... Just note that these are not very common, and will be much more expensive than a normal one. Also, I have yet to find one from a major manufacturer so your mileage may vary in terms of find a unit, and support for the unit if you ever need it. Also, some of the companies putting out these 48v units have questionable track-records.
    The key to effective environmental control of a conditioned space is to first understand how air and heat pass through the space along with how much internal generation of those two things occurs, and then take effective measures to control the flow of those things into and out of a conditioned space to produce the desired effect.

    The product blurb that says the unit will cool 480 ft.^2, is pretty useless statement for a lot of reasons. If that 480 ft.^2 behaves like a heat and ventilation sieve, the unit will be mostly useless both for moisture and temperature control. If the 480 ft^2 space is very tight and superinsulated, without some way to prevent moisture generation (rather than simply removing it), a dehumidifier that reheats the dehumidified air would be necessary to keep the space from turning into a 480 ft.^ refrigerator, but under those conditions, the unit would only need to run to get rid of internal moisture generation.

    Point is, size the unit for the duty and the load, not simply the size of the space.

    My original post assumed that the likely action will be to reactively and ineffectively throw energy at the problem via some method that cools air without any proactive sealing or insulating measures. Under those assumptions, a small window air conditioner will be a better choice than a dehumidifier, although pest ingress, security and potential theft during periods of absence need consideration when something is hanging in a window and easily accessible form the outside.

    The last sentence of that post pointed to the benefits of air changes and circulation which, for this application, along with first getting rid of the sources of moisture, is probably more effective and a less energy intensive but a more labor and hassle intensive way to achieve the goal.

    Leave a comment:


  • Mike90250
    replied
    Where is the humidity coming from? Often, if your crawl space is not covered with a tarp or layer of plastic, moisture from the earth, goes right into the building, where the walls trap it. Some tarps or sheet plastic under the building may help reduce the humidity

    Leave a comment:


  • mzs112000
    replied
    As others have said, get a window AC unit, or a mini-split. It will use a bit less power for the same effect, and you have the added bonus of being able to control the temperature of the room. I found an LG window AC unit that only uses 480 watts, which at 120v is 4 Amps. It says that it can cool down a 480 square foot room or something along those lines, now of course, it will cool down a larger space, but will not be as effective, either way it should work for your needs.
    To run this 480W aircon for 24 hours will use about 11.5kWh. You could probably reduce that usage by adding extra ventilation. I know of a few roof-top vent fans that only use 30 watts or so, which for 24 hours is only 0.720kWh(that's much better than 11.5kWh).

    There are also some units that run directly off of 48vdc, they might also fit the bill... Just note that these are not very common, and will be much more expensive than a normal one. Also, I have yet to find one from a major manufacturer so your mileage may vary in terms of find a unit, and support for the unit if you ever need it. Also, some of the companies putting out these 48v units have questionable track-records.
    Last edited by mzs112000; 09-07-2018, 02:45 AM.

    Leave a comment:


  • J.P.M.
    replied
    Originally posted by ZachI View Post
    Moderate, located on top of mountain with no trees around, raised floor with r15 insulated.floor, one big.room, 770 sf, currently using 24k but new.mini.split, open to.fireplace.but would prefer not.to.
    Get a 5,000 BTU window shaker. If possible, locate it out of the sun and in dominant exterior air flow patterns. Put in a small circulating fan blowing upward from a central ceiling location if possible.. Use natural ventilation as much as possible when in residence via screened windows/doors, etc. Empty/dry out any sinks, toilets, etc. when not in residence. Do the same with any refrigeration, turn off and leave the door(s) open. You have moisture in the dwelling that's not getting out fast enough to avoid problems. Eliminate the sources of moisture first and foremost. Do a thorough job there and the problem will eventually subside. Then work on adequate and hopefully natural air changes through the dwelling both when occupied and when vacant. Use the air conditioner to eradicate the last of the problem.

    Leave a comment:


  • ZachI
    replied
    Moderate, located on top of mountain with no trees around, raised floor with r15 insulated.floor, one big.room, 770 sf, currently using 24k but new.mini.split, open to.fireplace.but would prefer not.to.

    Leave a comment:


  • J.P.M.
    replied
    Originally posted by ZachI View Post
    Thank you for the feedback. The problem is the cabin is only uses once every couple weekends so the humidity builds up and has caused some cracked drywall, etc. Do you have any other reccomendations? Any recommended mini split to run off batteries while not occupied?
    If the question is directed to me, the answer is maybe, but before that, a few pieces of info : Is the cabin located in a warm, moderate or cold(er) climate ? Forrest, desert, windy, not, ? Any solar exposure ? Slab or grade/other ? Raised/crawl space ? # of rooms or one big one ? HVAC methods, if any ? Fireplace venting/draw OK ?

    Leave a comment:


  • ZachI
    replied
    Thank you for the feedback. The problem is the cabin is only uses once every couple weekends so the humidity builds up and has caused some cracked drywall, etc. Do you have any other reccomendations? Any recommended mini split to run off batteries while not occupied?

    Leave a comment:


  • J.P.M.
    replied
    For the same moisture removal, the dehumidifier will probably have a slightly higher per draw than a 5,000 BTU window rattling A/C unit, and the window rattler probably won't need to be drained manually and it may be a bit easier to live with. Dehumidifiers are no more than de facto air conditioners anyway. They'll remove about equal amounts of water vapor from moist air for the same power consumption but the dehumidifier will usually reheat the dehumidified air before exhausting it to the conditioned space. That reheating will cause the dehumidifier to use slightly more energy. The reheating may or may not add to the comfort level of the conditioned space.

    Another thought is to consider ways to eliminate/reduce how the moisture content is produced/introduced. No need to dehumidify air that's not moist in the first place.

    Leave a comment:


  • bcroe
    replied
    Originally posted by ZachI View Post
    I am looking to run a small dehumidifier that pulls 3.5-7 amps depending on the overall
    size while the cabin isn't occupied. What is a budget system that would accomplish running this 24/7?
    What is costly, is the batteries to run 24/7. I suggest you find equipment that will run any time
    the sun is decent, and shut down otherwise.

    That may not exist in a dehumidifier. But there have been great advances in air conditioner
    efficiency with some mini splits being powered directly from solar panels. It will dehumidify
    in normal operation. Bruce Roe

    Leave a comment:


  • ZachI
    replied
    If I could cut it to less than 1 amp/hr what system.would you recommend? Would a DC system be better for continuous use?

    Leave a comment:


  • SunEagle
    replied
    Well the math comes to the following;

    7amps x 120v = 840watts x 24 hours ~ 20kWh. Give or take. Having a Kill A Watt meter to measure what it actually uses in a 3 day time frame will probably be less.

    Based on previous solar/battery systems you can expect to spend about $1500 for each kWh you use a day. So at 20kWh that comes to $30,000. Which might be high because you may actually use less than 20kWh.

    IMO that is still a huge load and will not be cost effective to power from solar charged batteries.

    Leave a comment:


  • ZachI
    started a topic Power for dehumidifier

    Power for dehumidifier

    I am looking to run a small dehumidifier that pulls 3.5-7 amps depending on the overall size while the cabin isn't occupied. What is a budget system that would accomplish running this 24/7?
Working...
X