I wish I could put this in “Device Detection” to show you the clean signature, but after two months the water heater has not been detected. The house is not occupied yet so we are in shakedown cruise mode. I was very interested to see the electricity use with and without the recirculator pump going.
With the pump running constantly, the water heater turns on 5 minutes out of every 15. It has a 3800 watt element so this dumb human can easily recognize the signature (ahem). Once I turned the pump off the heater came on for 5 minutes every half hour. Still a lot for a zero water demand situation, IMHO. At $0.10/kwh, it works out to $555/year with NO use…
Rheem advertises in their product brochure that the temperature drops only 5 deg. F in 24 hours when in “standby.” I cut the power and the temperature dropped from 133 to 104 in 24 hours, nearly 30 deg. Hmmmm.
At a minimum I will put some smarts on the recirculator, which my plumber did not feel the need to do.
It’s possible your recirculation loop is moving water even with the pump turned off due to convective circulation. Those pumps use a centrifugal design, so water can flow through them easily even if the motor is off. This flow could be causing the standby losses.
Interesting idea. Seem non-intuitive. If I just pulled the pump out of the line the water would behave the same, right? There’s quite a few feet of pipe to push water through.
I put my circulating pump on a “smart plug”. I use the command “OK Google, turn on the hot water for 1.5 minutes”. This way I don’t forget to turn off the pump. I also have a second smart plug with a large night light that is paired with the circulating pump. I can tell at a glance from the kitchen when the pump is turned on.
I used a motion sensor in their master to turn on the recirculating pump for my parents. It shuts off again after a few mins. They have a real loop, I have a retrofit loop with crossover valves, the valves shut off automatically at 90 deg, I think.
I’m testing a home loop system with a combo tankless, and hybrid Raheem. I wanted to see the the total cost of heating my water, and how much hot water I really use.
I installed a StreamLabs flow meter on my outgoing hot water line. The crossover valves definitely close as expected and flow stops until someone open the tap.
You could add the same flow meter to troubleshoot the issue which requires no plumbing and seems to work well.
You should consider a tankless hot water heater. I have a tankless and I also designed my own Solar/Thermal storage system. I preheat the water in the cooler months, summer time is free hot water on most days.
So I had a near identical situation with my hot water heater. The recirculation system was using ~$550 of energy a year. I’m on track to cut that down to ~$150/year, but it’s been a 6 month saga getting to where I am now.
Most importantly, you NEED to make sure your water is only recirculating when you want it to.
First off, check if your water is hot at the tap even when the recirculator has been off for a while. If so, you have a thermosiphon going on, which you need to fix before you do anything else.
If you don’t have a thermosiphon issue, you’ll want to convert your recirculator to be an “on-demand” system. There are many ways to do this, but I solved it with some Flic smart buttons combined with Alexa routines.
If you have a thermosiphon going on, here’s what to check:
Make sure the system has a functioning check-valve in it. This prevents the water from naturally flowing backwards through the recirculation system (this only applies if your system is an open-loop system; I’m not familiar with whether the taco is open or closed loop). Spring check valves typically have a 5-10 year lifespan. A failure in this $15 part was costing me about $250/yr alone.
Make sure you have either dielectric thermal nipples installed on your water heater outlets, or you have a heat trap plumbed into your recirculation line. Here’s discussion on the topic that helped me.
One needs either an electric valve to stop the thermal siphon circuit from running while the pump is off, or a check valve with a high enough opening resistance to not allow convection. Also, without these, when you turn on the hot water for a shower etc, you could pull from the recirculator side instead of the hot water supply, and not get such hot water!
