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Rheem-Ruud Hybrid Heat Pump Water Heater

MwN | Posted in Energy Efficiency and Durability on

There are several long threads in this forum regarding Rheem heat pump water heaters that have been very useful to me while I investigated the performance and features of my unit, which replaced a gas water heater about 6 months ago. Here is more information and details of my experience.

My unit is a fifth generation Ruud 50 gal 15 amp Manufactured 29 April 2022. I think this is the same as the Rheem branded model, but supplied through contractors rather than direct to consumers. I got the 15 amp model because I don’t intend to use the heating elements anyway, and I need to keep amps low in my service panel. The heat pump component is the same as the 30 amp models, but the electrical component has half the output.

My household consists of two persons with low hot water usage. The heat pump alone is sufficient for our needs. It doesn’t have any trouble keeping up with our demand. In heat pump mode I don’t see any evidence of the elements ever being used, which is as I hoped.

First the noise issue. Yes, I wish it were quieter. Using a free app for iPad I measure about 58 dB at 3′. It has that rattle that compressors often seem to have. The rest is fan noise. My exhaust is ducted to the outside, which I think helps a bit. It is in a utility closet (shared with a furnace). The utility closet is inside a laundry room, so I can keep two doors closed between the water heater and my living space. With that setup, the noise level is perfectly fine. I don’t hear the rattle at all, just a soft hum when the compressor is running. It’s similar to my refrigerator and quieter than the furnace. But I probably wouldn’t be happy if it were installed in a closet within my living space.

The app (I use it on iPad and iPhone) shows usage graphs, but they seem untrustworthy. As noted in some of the other posts, the daily view is a bar graph with 24 columns (one per hour), but usually every other column is zero. I don’t know why it doesn’t just show hourly usage in 24 columns.

Most suspicious to me is the data for periods without heating. My compressor doesn’t run that often, so the time doing nothing is an important part of the usage. If I disable the unit so no heating can happen (no heat pump, no elements), the charts show 0.10 kWh used every two hours, totaling 1.2 kWh per day. That suggests the electronics alone use 50 watts continuously, which seems way too high when compared to other devices like wireless routers or TVs. I could not get tech support to tell me how much energy the unit should consume when it is not heating water.

Frustrated, I (temporarily) installed a little power monitoring device at the electrical disconnect next to the unit (see photo). It reports about 360 watts in heat pump mode when the compressor is running. It reports about 2400 watts in electric-only mode when it is heating (remember, this is the 15 amp model). These values are comparable to published values, so I am fairly confident the monitor is working.

When the unit is in heat pump mode and the compressor is not running, the monitor reports less than 2 watts! In a 24 hour period it amounts to about 0.04 kWh, compared to the 1.20 kWh shown in the app. The app is off by a factor of 30 for this special case.

I also used the external monitor to record total energy usage for a six day period of normal use. During that time the monitor reported an average of 1.38 kWh per day, while the app reported 2.43 kWh per day. So the app seems to be off by about 75% for my usage pattern. I expect that the error is mostly due to the bad data when the compressor isn’t running. If so, the more you heat water, the less the error will be.

The app has a number of other problems that are less important. It won’t put my unit into Vacation mode, but I work around that by putting into “off” or “disabled” mode instead.

The app complains that the equipment should be set to “Energy Saver” mode for maximum efficiency, but I just ignore that. I think the official definition of efficiency is based on certain usage and recovery periods that don’t apply to my household.

The app sometimes complains “Econet is disconnected”. If I just ignore the orange notification banner everything works normally, although the banner obscures some of the buttons at the top of the screen.

In spite of all the problems with the app, the unit itself seems to be performing very well, if a bit noisy.

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Replies

  1. Danan_S | | #1

    Great writeup. Thanks for sharing!

    I'll add with my own recent experiences with a Rheem Proterra HPWH. It was installed during the pandemic, and I a few months later, I noticed that it behaved very strangely. It seemed very confused about how much hot water it had and when to run the heat pump - it would start operating at relatively high air intake temperatures of ~45F. Nonetheless, it performed well enough. Then suddenly its performance degraded quickly and I called technical support.

    First, Rheem technical support employees were *amazing*. Every support engineer I spoke with understood the intricacies of how the machines were put together and also understood the principles of the refrigeration cycle.

    It turns out that at the beginning of the pandemic, Rheem had trouble sourcing the best thermistors and substituted a lower quality thermistor in some production runs. Apparently these thermistors started causing issues in the devices.

    They sent me a new set of thermistors, and since replacing them the device has performed much better, with the heat pump functioning at air intake temperatures as low as 39F, and more importantly, it seems far less erratic in its display of available hot water.

    Another great feature is that Rheem's Econet software integrates with a program run by my utility that controls the device's temperature and heating time to avoid the dirtiest electricity, and pays me a small monthly amount (like $5) for that, which pays for about 22kWh of electricity at our rates.

  2. CyrusJuliet | | #2

    Finding the cause of a Rheem water heater's malfunction is the first step in troubleshooting. To pinpoint the probable issue, you might wish to think about the following possibilities. Hopefully, the fix for Rheem water heater systems just entails pressing the reset button.

    - If the water is cold, check to see if the water heater is on or if the electrical panel's circuit breaker is in the off position. Any of these scenarios could be the cause of a Rheem water heater not turning on.
    -Water is excessively hot - The thermostat is on the highest setting; alternatively, the thermostat may be broken.
    -A faulty pressure regulator or a closed main water shutoff valve may be to blame for the low water flow rate.
    Find more infor here: https://www.usawaterquality.org/reset-rheem-water-heater/

    1. Expert Member
      DCcontrarian | | #3

      I wish there was some way to report spam.

  3. Expert Member
    DCcontrarian | | #4

    Just curious, what climate are you in? Almost anywhere you're better off venting to the interior rather than the exterior.

    1. matthew25 | | #5

      Agreed. If you’re going to duct to the outside anyways you may as well have gotten the higher efficiency Sanden split system. It’s more expensive and maybe harder to find installers for though, admittedly.

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