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Thread: Power requrements for Rheem hybrid water heater?

  1. #1
    Join Date
    Sep 2006
    Location
    Las Cruces, NM
    Posts
    1,667

    Power requrements for Rheem hybrid water heater?

    Can the present (2019) model of a 50 gal Rheem hybrid water heater be run from a 15 Amp breaker at 120 V?

    A Matt Risinger video (https://www.youtube.com/watch?v=omivdhxdGv0 ) seems to say that it can ( at 3:00).

    The specifications on Home Depot say it needs 30 Amps.

    A comment to the above video says it needs 30 Amps. A reply to that comment by a James Methvin says:


    The resistance element can be turned off. If you are replacing an old water the wiring is already there. If you are building new or setting it up for an off the grid system the lower amperage part can be used. with smaller wiring.

    I don't understand what "the lower amperage part" is.

  2. #2
    The hybrid WH has both a heat pump and a resistance heater. The heat pump takes heat from the surrounding air and transfers it to the water. The resistance heater works like a normal electric water heater.
    When HW demand is fairly low, the heat pump can keep up with the demand. When demand is high, the resistance heater turns on to increase the ability to heat the water faster. The heat pump is more efficient than the resistance heater, and requires less power. If you set the unit so the resistance heater is never used, the power requirements are lower and evidently you can get by with a 15 amp circuit. However, the WH cannot then meet high demand using only the heat pump. The "lower amperage part" is the heat pump.

    Note that the higher efficiency is a little misleading if you live in a colder climate, as the heat pump is taking heat out of air that your furnace has already heated, so some of the cost of heating water is just transferred to your furnace. When it's warm out, however, the heat pump is taking "free" heat out of the air and using it to heat the water.

    The heat pump water heaters also have the advantage of dehumidifying the air used by the heat pump, which can replace (or partially replace) the dehumidifier many use in their basements.

    On the down side, a hybrid or even a standalone heat pump water heater is way more complicated than a simple resistance WH; a lot more to go wrong and they need regular maintenance also.

  3. #3
    If you have gas service, the really efficient water heaters are the tankless. When I replaced our tank heater for a tankless I noticed the drop in our gas bill.

    The problem with tank heaters is that you have to keep a lot of water hot all the time. The tankless only heats what you use, when you use it.

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  4. #4
    Quote Originally Posted by Mike Henderson View Post

    The problem with tank heaters is that you have to keep a lot of water hot all the time. The tankless only heats what you use, when you use it.

    Mike
    We have a 21 year old propane gas water heater. When we go out of town, I turn off water supply and drop thermostat back to pilot. Upon returning, seldom does WH come on when shifting from pilot to hot, which means it doesn't lose as much heat as you would expect.

  5. #5
    Join Date
    Dec 2010
    Location
    South Coastal Massachusetts
    Posts
    5,362
    Lower amperage refers to the amount of current drawn at the service panel. Think of it as the amount of water flowing through a pressure washer.

    To run high current loads (like a clothes dryer) a larger circuit breaker is required to pass sufficient current without overheating.

    FYI - I have two of these hybrid hot water heaters, and they pull double duty - they'rd glorified air conditioners.

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