I have a rheem hybrid (heat pump) electric water heater (65 gallon tank). I would love to run it off my dedicated loads panel (my storedge system provides me with 5kw continuous backup power) but the heating elements in it seem to be 4500 or 4800 watts so that is a definite no-go. There is another model by Rheem that seems to only need a 15amp breaker (PROPH80 T2 RH350 D15) which would indicate maybe a 2800 watt element or so. Does anyone know of anyone with any experience with these? I figure my options for running this off my solar include 1 (the nuclear option): an entire second system dedicated solely to my water heater. Ouch expensive. 2) Figure out if I can get my hands on the elements for the other model (or some universal low wattage elements) and see if they even will work with my water heater 3) See if I can fool my water heater into not using the elements at all (ideal since I only want it running the heat pump, not the wasteful resistive heaters). If anyone is curious, I normally run my water heater in heat pump mode only (~750-800 watt surge followed by about 400 watts until it shuts off) which cools my garage and keeps it nice and dry. The two times when the water heater ignores my settings and turns on the elements is when the tank is flushed (or perhaps when the water falls below 90 degrees?) and during startup from a power outage while it cycles everything on/off presumably to test itself.
Not exactly solar heating, but...
- Thread starter Rolee
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gnubie
Solar Wizard
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I can't say for your particular heater but looking at the manuals for Rheem heat pump heaters sold in Australia it looks like the behaviour can be set at the factory. I'm guessing via option switches or soft configuration on the controller board. Contact Rheem in your country and check to see if there is an option for your model to have the heater elements turned off completely.
They may want to send a plumber / technician to do it and not tell you how to do it for safety reasons, such is life. Mains voltages are present on the controller boards for those things so it is a valid concern to not have people poking around in them.
They may want to send a plumber / technician to do it and not tell you how to do it for safety reasons, such is life. Mains voltages are present on the controller boards for those things so it is a valid concern to not have people poking around in them.
I was going to suggest this video... nice.
Thanks so much you guys, this is hilarious. I watched this video and his 1 year review and what he does to trick the water heater is put 2 regular light bulbs in series and run the power wires that would go to the element up to the bulbs instead. So whenever the water heater tries to use the elements it just light up the bulbs and that appears to be enough to make keep the water heater happy and not throw errors. I nearly fell out of my chair laughing when I saw that. But good to know I'm not the only crazy person wanting this and no joke, everything he says about how awesome these water heaters are is totally spot on. Though interestingly, I think my rheem is quieter than the AO smith and it seems to pull slightly more power (~400-450 watts) but I think heats more quickly based on his description of its operation.
You can use regular AC water heater elements with DC current of the correct voltage directly from solar panels and preheat the water that goes into your hybrid etc . I am considering doing this to preheat water going into my tankless gas hot water system with my old water heater, just make sure you have a thermostat functional. If you just want to burn the pv and not store it put the elements in a swimming pool lol.
So I finally got around to calling up Rheem and seeing what other elements might fit my heater. I suspect the answer is more or less"any universal 1 1/2 inch threaded style) but they did give the the specific part number (SP10869HL) for a 2500 watt resistored element. I bought two of them and installed them. Max power draw when using element + heat pump seemed to top out at just shy of 3000 watts (and this only happens when the tank has been drained and refilled which drops the temp below some threshold). When the heat pump is running by itself (normal operation) it seems to stay under 500 watts basically the entire time. Looks like my backup battery should have no trouble running it now! Pics of the new element (it looks so small next to the original 4500 watt one) and of the readings from my sense energy monitor. It thinks my heat pump is a "stove" element.
Water heater "High Demand" mode where it uses resistive heater + heat pump.
Water heater "heat pump only" mode. Once the water heats up past ~110F or so then the water heater will respect the setting that you have (in my case the heat pump mode). Before that it is in "pre warm" mode where it uses the elements. I've confirmed that you can cut power to the heater for hours and when you turn it back on it remembers its last mode and (provided the water is still hot) will just use the heat pump if that is what you ask of it.
Water heater "High Demand" mode where it uses resistive heater + heat pump.
Water heater "heat pump only" mode. Once the water heats up past ~110F or so then the water heater will respect the setting that you have (in my case the heat pump mode). Before that it is in "pre warm" mode where it uses the elements. I've confirmed that you can cut power to the heater for hours and when you turn it back on it remembers its last mode and (provided the water is still hot) will just use the heat pump if that is what you ask of it.
Ampster
Renewable Energy Hobbyist
I have messed around with HPWHs for six years. I have mine in Heat Pump mode only and run it off the critical loads panel. As you mention it only takes 500 Watts in that mode.
Have you compared the efficiency of HP mode versus resistive element? It is so large that I would never run it in resistive mode. I have some work arounds for leveraging capacity so recovery time is not an issue.
Have you compared the efficiency of HP mode versus resistive element? It is so large that I would never run it in resistive mode. I have some work arounds for leveraging capacity so recovery time is not an issue.
I haven't bothered trying to compare efficiency since I never willingly run it in resistive heating mode. With a 65 gallon tank and only 2 people at home we have never run into any issues with recovery time and it appears that the water heater runs ~2x a day for about an hour or so at a time (heat pump only mode). The only reason I went through all the headache of dealing with the elements is that I want to wire it up to the dedicated loads panel and my electrician was concerned that if the elements did turn on it would basically trip some internal circuit breakers in the solaredge inverter which require pulling the inverter cover off to flip again (don't get me started on the design of it). This way there is no (mechanical) way for it to pull that much and I should be fine. If there were a way to safely bypass the elements entirely and the water heater not shut down (or rather refuse to start) I would probably be open to that. Given that even when the tank was completely cold after the refill it only ran the elements for about 75 minutes or so before switching back to heat pump mode on its own (it was over 115F when this switchover happened) I'm happy with it. I figure that is the worst case scenario and I'm never going to drain/refill while in an energy outage situation. Even if I did need to for some reason, however, I can sustain that load from my batteries easily especially if if there is sun out and the garage is warm. What HPWHs do you have experience with?
Ampster
Renewable Energy Hobbyist
I originally installed a GeoSpring and have had to repair it myself because there is no warranty since GE sold that business. The only thing good about it is I can run an IFTTT script to run in during the morning to soak up excess solar and cool down my garage. I may get another few years out of it and then buy a Rheem. By then I hope there is some scripting or IOTs interface so I can control it like I do the GeoSpring. Worse case I can put it on a timer.
I installed a Rheem in a rental property I own and the tenant loves it because it is all electric home and he travels and can use the app to put it in vacation home. I also installed one in my sisters home which is also all electric. She often travels so vacation mode works.
The elements in a tank water heater are of two types.
Either it is a 4 bolt flange element, or it is a 1”PIPE thread... not 1-1/2”
Either it is a 4 bolt flange element, or it is a 1”PIPE thread... not 1-1/2”
Woops, I stand corrected. Was typing too fast and got it confused with something else. I'll try to fix the original post so as not to mislead anyone.
Installed a Rheem 50gal. in our house and we love it. It is one of the only (I believe) HPHW options out there that will ONLY run in Heat pump mode. I believe everyone else will force you to use the lower element which is a huge energy suck. I have it plumbed inline with our existing HW tank (indirect off the boiler) and for 99% of the time the Rheem will keep up with our demand (family of 5).
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