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How much dehumidifcation can I expect from a heat pump water heater?

Matthew Kelch | Posted in Mechanicals on

Hi all,

I’m considering installing a heat pump water heater in the basement of my home in central PA.

As part of my payback time calculation, I’d like to try to determine just how much dehumidification I can expect it to do in the basement. I currently run a dehumidifier in the basement to maintain the humidity at 55% which costs in the area of $0.70 per day to run this time of year. Additionally, my water heater accounts for about $260 of electricity usage every year.

I’m specifically looking at a 65 gallon Rheem model — does anyone know how I might go about determining just how much humidity it will be removing

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Replies

  1. Cody Hazelwood | | #1

    I'm interested in this, too. I'm considering ducting the same water heater to my crawl space.

  2. Jon R | | #2

    Without modification, very little. I expect that you can reduce the airflow over the coil, which will increase the dehumidification it provides. Perhaps cutting your dehumidifier running costs by up to $.27/day. But this will also reduce the water heater efficiency a little. Maybe a net dehumidification savings of $.22/day (all guesses).

  3. BFW577 | | #3

    I have my 50 gallon geospring condensate pipe draining into a 5 gallon bucket. I usually empty the bucket at least once sometimes twice week. Basement runs around 60 percent humidity this time of year. Probably runs an average of 2-3 hours a day.

  4. Matthew Kelch | | #4

    Based on the research I've done last night, the condensate produced will be highly dependent on the ambient humidity, temperature and water demands which make it hard to come up with a definitive estimate. Given the relatively low usage of DHW in our home (only two people) it's looking like it won't completely eliminate the need for the dehumidifier, but it will make a noticeable dent in the overall runtime.

    If I do follow through with this I'll be sure to post an update that details the reduction in power usage I'm seeing.

  5. GBA Editor
    Peter Yost | | #5

    I think all the comments above hit the uncertainty of how much dehumidification you will actually get from your HPWH. I also think that since your HPWH is not designed for dehumidification--it is an incidental result--that you are unlikely to be able to get significant dehumidification, especially not correlated to when as well as how much.

    I did find this interesting research paper, but it is far from conclusive: "15 Years of Dehumidification Results from Heat Pump Water Heaters" - https://docs.lib.purdue.edu/cgi/viewcontent.cgi?article=2818&context=iracc.

    Peter

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