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Rheem Hybrid Mode Question

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Hello,

I just recently got a Rheem Hybrid hot water heater installed. I ran it in heat pump mode for a week, but after running out of hot water after a shower, bath, and doing dishes, I changed it to Energy Saving mode to speed up its recovery time. 

The “Hot water availability” returned to a full tank and my wife then took a shower that night and I didn’t check the “Hot water availability” until today after work. It says that half the tank has half of its capacity available. Does it not heat the entire tank in Energy Saving mode when there are long periods of no calls for heat (like when my wife and I are at work)? I thought it would still heat the entire tank, but no?

This is my first hot water tank as we just moved away from a tankless unit. Maybe I don’t understand how hot water tanks work? I just assumed they were always full with 120F water being ready to be used whenever needed. 

Thanks!

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,827
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    Not sure but the term "energy saving mode" to me would indicate less hot water than regular mode
  • Jamie Hall
    Jamie Hall Member Posts: 23,635
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    No, they aren't always full -- and the hybrids even less so than the gas or oil. They heat the contents of the tank up to the set temperature, and then the heater shuts off. Then when you start to draw hot water, the cold water comes in at the bottom of the tank and the thermostat turns on the heat. Now... if the heater can restore the heat as fast as you are draining it off, you won't run out. However, if the heater can't, eventually you will run out of hot water.

    How soon depends on how fast you are drawing hot water -- and the power of the heating elements.

    Hybrids are very slow in heat pump mode, so to speed things up they also have a resistance heating element (which draws a lot of power!) if you are getting ahead of the heat pump. There are various settings and choices on the controls to give you some options as to when that occurs -- check the manual.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Robenco_15
  • Robenco_15
    Robenco_15 Member Posts: 1
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    Thanks Jamie! Makes sense. I switched to Energy Saving Mode because last night we got ahead of the heat pump. Thinking I’ll give Energy Saving mode a try for a week and then explore the scheduling if I’m not happy. 

    6-11pm weekdays is when baths, showers, laundry, dishes occur, so maybe a switch to High Demand mode would be called for. 
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,827
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    A general rule with any water tank is you have 80% of the storage capacity available because of incoming cold water cooling the tank. That's if you start with a hot tank
  • psb75
    psb75 Member Posts: 863
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    On most heat pump water heaters you have 3 modes: 1. heat pump only, 2. hybrid, (I think Rheem calls this "Energy Saving Mode") and 3. electric resistance elements only. Number 1. is the most economical. Number 2. is less economical--uses combination of heat pump and resistance elements, and Number 3. is the least economical--uses only resistance elements.