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OT basement humidier off for two weeks

D107 Member Posts: 1,785
Been using a basement dehumidifier in summer for years; when we go away we kept it on constantly by putting it where it could drain into the slop sink. Based on some guitar hygrometers, the humidity would be around 50+% without the dehumidifier and about 45% with. Any harm in leaving it off for two weeks in terms of mold etc?

Also, I'd like to leave main water valve shut off; would I need to turn gas off for the hot water heater to prevent dry firing in case of a leak?


  • icesailor
    icesailor Member Posts: 7,265
    Being Away:

    It's highly unlikely that the water heater will fail and run out of water. Set the control on "Vacation" or set the control to "Pilot" so you don't need to re-light the pilot.

    Turn the water service if you wish but that's your choice.

    50% humidity without the dehumidifier is a level that a lot would like to have.

    Mold forms from condensation and the dew point. If you are not getting mold at 45%, I doubt that you will get it at 50%. Its the cold spots in the corners by the floor where the problems start. Get an infra-red thermometer heat gun and shoot the corners by the floor to see what your temperatures are.

    You may be over-thinking this.
  • Zman
    Zman Member Posts: 7,141
    Condensate Pump

    Why not put an inexpensive condensate pump on your dehumidifier?You would never have to empty it again.

    I agree with Ice on the water heater.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • D107
    D107 Member Posts: 1,785

    Thanks for the answers. Yes usually who would care about a 5% humidity swing. What I didn't mention was that for years I was using a cheap wall thermometer/hygrometer which was saying 75% humidity, maybe down to 65 with full dehumidification. Certainly feels like more than 45% humidity, which is actually kind of dry.  Not sure if i can trust those 2 guitar hygrometers, though they both read about the same. Perhaps I've been wasting electricity all these years.
  • jumper
    jumper Member Posts: 1,757
    dew point is critical

    You want dew point to be below lowest temperature, so that there's no condensation. Dew point relation to R.H. is read on a psychometric chart. With that, a thermometer and a bolometer you can learn what the R.H. and dew point really is. I think running a small dehumidifier is prudent.
  • icesailor
    icesailor Member Posts: 7,265

    The "Dew-point" is critical but the use of a dehumidifier will raise the temperature in the space and increase the margin between the dew point and the temperature. Raising the temperature far above the dew point. Then, the air can hold far more moisture than cooler air.

    What happens in basement rooms is that there are dead air spots. Look for mold in corners. A dead air spot. If you have fans moving the air around, you can often solve many problems. Those condensate pumps are stupid money and last a long time. Just be sure that you end it somewhere sensible. Not in an open drain pit for a sump pump where it will then evaporate and add back to the humidity in the space.

    Air circulation is a wonderful thing.12
  • D107
    D107 Member Posts: 1,785
    air circulation

    thanks. No time to put a pump in now but will strongly consider it in the future. Unit currently sits centrally, right next to the house trap.....Basement is 500 sq ft with mechanical room, open area and office area (no door, all connected). I currently have two 15-in fans going, making things very comfortable. I may buy a third fan and with dehumid. off I'll monitor the humidity until I leave.

    Very good point on dehumidifier raising temperature above the dew point, but all that heat makes it uncomfortable. Small AC would dehumidify and cool. But I am really enjoying the oscillating fan cooling--using only half an amp each. Somehow I survived the first 30 years of my life without AC.

    Thanks all for the science lesson.
  • icesailor
    icesailor Member Posts: 7,265

    The reason the fans work well is because of evaporative cooling. If you wear absorbent clothing like cotton shirts, the cotton will wick the moisture from your body and will be evaporated into the air if the air can hold more moisture. When you have a fan blowing on you, it helps in the evaporation.

    That's why you feel cooler on a windy day with the same temperature as a windless day.
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