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Ventilating dehumidifier – program settings?

whiteroses | Posted in Mechanicals on

Now that my new Ultra-Aire is installed, I’m wondering about the program settings.

Starting at 6 am, it will get fresh air for 10 minutes, then wait 20 minutes before doing it again. After 10 pm, it will wait 50 minutes.

These settings are a WAG. There’s no guidance in the owner’s manual and I can’t find anything online, not even from competitors.

Is comfort the only guide? I want to maximize the life of the unit as well. It just seems odd that Therma-Stor would leave its customers to experiment for themselves.

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  1. GBA Editor
    Martin Holladay | | #1

    Here is a link to the installation manual, which includes programming guidance:

    Here is a link to the control manual, which also includes programming guidance:

    If these documents don't answer your questions, your next step would be to call Therma-Stor at 800-533-7533 or 608-222-5301.

    Finally, if the manufacturer can't help you, I would suggest:

    (a) You can purchase a hygrometer so that you know your indoor RH. Then you'll get some feedback concerning the operation of the dehumidifier.

    (b) You can hire a home performance contractor to commission the device. Once someone has measured the airflow through the fresh air duct, you should be able to program the unit's ventilation rate to meet the ASHRAE 62.2 rate (if that is your goal).

  2. whiteroses | | #2

    Yes, well, the programming "guidance" in the 150 manual is:

    Occupants should determine ventilation times and rates. Therma-Stor LLC makes no firm recommendations concerning when to ventilate. Common ventilation schedules include constant ventilation, ventilation based on occupancy times, intermittent operation, and seasonal ventilation.

    There is no statement like this in the 70H manual, nor in the control unit manual (DEH3000).

    I expect better from a manufacturer.

    It may be that the contractor will commission the unit when they do their test out; but for now they left it running constantly, and I didn't want that.

    The indoor RH is displayed on the control unit. I will care about RH more next summer, it's zone 5 winter right now, what I'm looking for is ventilation information.

    There's the formula in Krigger's Residential Energy on figuring fan size in CFM given the desired air exchange (eg .35 ACH) and home volume in cubic feet. But nothing about intermittent operation.

    I do understand that the actual CFM may be less than rated.

    I found this:

    which should be balanced with this:

    which looks at cycle times and formaldyde concentration in indoor air.

  3. GBA Editor
    Martin Holladay | | #3

    If you want guidance on ventilation rates, I suggest that you read this article: How Much Fresh Air Does Your Home Need?

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