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Dehumidifier

This topic contains 4 replies, has 5 voices, and was last updated by Profile photo of Michael Nagy Michael Nagy 2 weeks ago.

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  • #136647
    Profile photo of Ellen Paul
    Ellen Paul
    Participant

    Although we are very reluctant to do so, it appears as though we may have to use some kind of device to reduce the humidity in our vault. Does anyone have any experience in selecting and using a dehumidifier?

  • #136648
    Profile photo of Elizabeth McDermott
    Elizabeth McDermott
    Participant

    Hi Ellen,

    From Tara Kennedy of Yale University:

    A couple of questions for her to ask herself before choosing a dehumidifier:
    • How damp is the space?
    • What is the square footage of the space?
    o These two questions will determine which size capacity (removal of pints of water) she will need for the space.
    o [Attached] is a helpful table from AHAM, although you can get a larger capacity unit if it has the ability to shut off once an optimal relative humidity is reached. You are mostly looking to avoid buying a unit that will underserve the space.

    Some other questions:
    • How will the dehumidifier be emptied?
    o Manually (e.g. a human empties the bucket daily)? Is there a floor drain or sink nearby where the water from the dehumidifier can drain safely? Will gravity suffice or will you need a pump to carry the water from the dehumidifier to the floor drain/sink? I’d recommend getting a dehumidifier with a pump if the water has to travel any distance and/or uphill (e.g. into a sink)
    • What type of controls does the dehumidifier offer?
    o Having the ability to control RH level with auto shutoff is recommended
    • Are you concerned about energy consumption?
    o You might consider a dehumidifier that is more energy-efficient, especially if it will need to run 24/7

    Please let us know if you have any more questions, but this should help you get started!

    Thanks much,

    Liz

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  • #136650
    Profile photo of Rachael Arenstein
    Rachael Arenstein
    Participant

    I was going to respond to this query but Ellen and Tara’s answer really covers it! Good work.

  • #136651
    Profile photo of panderson32
    panderson32
    Moderator

    Just one more thing to add: There is an elevated fire risk associated with use of portable dehumidifiers due to the presence of a heating element. Please make sure there are no recalls on the product you choose to purchase. Here is a list of recalled dehumidifiers most recently updated in November 2016:
    https://learn.compactappliance.com/dehumidifier-recall/.

    I also recommend adding facilities/security patrols during unoccupied hours that a dehumidifier is in operation. In addition to making sure the unit is functioning properly, they could assist with emptying the buckets if you are not able to pump out the water automatically.

    Priscilla Anderson

  • #136657
    Profile photo of Michael Nagy
    Michael Nagy
    Participant

    You also need to be aware of your building pressure as you dry your space and push the temparature down. We had a situation where the more we cooled and dried in the summer it was getting wetter and wetter. Turns out the building was not fully sealed and we were creating a negative stack effect – moist outdoor air was rushing into the top floor of the building at a higher rate the more we tried to lower the temp and RH. And our stacks were on this top level. We had to seal this area completely from the outside – walls to ceiling, walls to floor, etc. Now we are able to control the temp and humidity with less energy since outdoor air cannot inflitrate. Be aware that adding more and more dehumidification may not work if it causes more moist outside air to come in during the summer.

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