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Community and Q&A

Hybrid Heat Pump / Electric Water Heater

mechnut | Posted in GBA Pro Help on

I own a Rheed Hybrid water heater and live in an area where my water supply is from a well. We like the water as is, untreated. We don’t use a softener.  Yes it is definitely hard water. My question is:
I wish to disconnect the elements from my water heater so it only works from the heat pump system 100% of the time without exceptions. Tghis way I can be sure I will not have to deal with deposits in the tank.
Will the water heater accept to run this way and if yes will there be damage to the heat pump at all?

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  1. charlie_sullivan | | #1

    It's possible you could still get deposits, but it will be less than with the electric elements.

    You should be able to just set it on heat pump mode without disconnecting anything. But iif you do disconnect the elements, it shouldn't hurt anything. Worst case it shows an error message and you have to plug them back in but it should run fine without them connected.

    1. mechnut | | #3

      Thank you very much for the quick reply. I may try it w/o elements then. I know I have four settings. We use the heat pump mode all the time. Just realized recently that it still requires help from the elements. Just was not sure of the basic reason. If it is to accelerate the heating process in particular cases and no other reason I would like to avoid the elements.

      1. severaltypesofnerd | | #18

        I've run those without the elements. But needed to put in a booster

        The Eemax tank booster and the Rheem booster are the same product. They're a good match for a slow water heater. I suspect they're an energy win, as the boost is only used if the tank is below temperature AND there is water demand.

  2. walta100 | | #2

    I not sure a Rheem water heater will work with the heating element disconnected. In an old thread we looked at Rheem’s patent from that it seems the heating element is necessary for operation. On power up the board checks the tanks temp if that temp happens to be below an undefined minimum temp the element is turned on only once the tank is above the undefined temp will the heat pump start. Also if the tank fails to reach the set point after undisclosed amount of time the heat pump will be turned off and the element turned on.

    As I recall you get 4 options in the menu but none will disable the element.


    1. mechnut | | #4

      Thanks so much foryour input.
      I guess if I try and get stone cold water we will know the elements should not be disconnected.

  3. Jon_R | | #5

    If this water heater enforces a minimum temp, disabling it is likely to cause compressor damage.

    Any heating of hard water will cause some deposits. Would be interesting to see more about the effect of calcium deposits on efficiency (probably significant). It might be wise to plumb the system with valves such that an acid cleaning is easy to do.

    1. mechnut | | #9

      Jon R,
      This cleaning system is interesting. Is this a common add-on?
      Unless you are working on a patent on this idea I would like to know how you would make it.
      I know plumbing but I am not a pro. I did install my water heater though.
      Thanks very much.

      1. Jon_R | | #11

        Not common, but would have been convenient when I was cleaning mine out. Say a plumbed drain (vs using buckets), valves to disconnect from the house system and valve/connection to put non-toxic acid (Mag-Erad?) in.

  4. this_page_left_blank | | #6

    A good compromise might be to install a softener that feeds only the water heater. That way water you use for cooking and drinking is still untreated, and water you use for washing and bathing will only be about 1/2 or 2/3 treated.

    1. Expert Member
      AKOS TOTH | | #7

      Be careful with water softeners and water heaters. These typically increase the conductivity of the water chewing through your anode rod. If you do install a water softener, check and replace the anode rod regularly before the tank starts corroding on you.

  5. mechnut | | #8

    Thank you all for the good replies.
    Lots of options and very wise comments.
    The last thing I need is a damaged compressor caused by my own fault.
    I like the idea of adding valves to clean the system per Jon R's message.

    Thank you again.

  6. walta100 | | #10

    I can see cleaning a tankless unit by pumping 2 gallons of vinegar thru it for 30 minutes. Do you real plan on filling a 40-80 gallon tank with vinegar ever year or so?


    1. mechnut | | #12

      I don't think so. Not going to pour 50 gallons of vinegar in the tank!. Would the calcium form mostly at the bottom of the tank?
      I guess it is possible to circulate 2-3 gallons of vinegar in the empty tank with a pump. It qwill not make contact with all inner surfaces but it would cleanup the lower portion I think.

  7. walta100 | | #13

    The most lime will collect at the warmest point of the heat exchanger. It seems unlikely the entire heat exchanger could be submerged in 3 gallons of liquid.

    I am not sure I understand your reluctance to have a water softener.


  8. user-2310254 | | #14


    I have a Rheem 80 gallon HPWH, which I like very much. But I suspect the heat pump will die long before anything else. So I'm not sure extraordinary measures on the tank will do much to improve the overall service life. I'd worry more about keeping the heat pump air intake filter clean.

    In hard water areas, Rheem recommends draining a few quarts of water every month to remove deposits from the tank. That sounds reasonable to me.

  9. krom | | #15

    we have hard water here, and used to have an oil fired water heater.
    I went about 5 years before opening the drain valve on the tank... That turned into a 2 day project, during which I got more than a 5 gal bucket of deposits that looked like rocks and sand out of the tank.
    Realized I was in trouble when I opened the valve, and it didn't even drip, had to remove the valve from the tank, and go at it with a rod trying to keep the hole unplugged while working out as much debris as possible.
    as much as I prefer the taste of our well water without the softener, it treats the water to all but one hose bib on the outside.

  10. kkrugler | | #16

    Was there ever a definitive answer to what would happen if I disconnected the 4.5KW heating element from my Rheem Hybrid (40 gallon) water heater? My reason is a bit different than the original poster - I'm asking because it's on my battery-backed up 50A sub-panel, and I'd like to not need a 30A breaker or ever draw that much power when PG&E shuts off electricity. But some of the comments above make me think that the heat pump might not start (or might "give up"?) without the ability to rapidly heat using the resistive element. Thanks!

    1. bfw577 | | #17

      It's possible the elements need to turn on occasionally to protect them. I have an 8 year old GE Geospring that will run in heat pump only mode and bypass the elements. I found that if don't occasionally run it in electric element only mode they end up acting like a anode rod and will dissolve.

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