You might have noticed in that previous project log that one of the DIP switches enables/disables the energy saver function. I now know that it's enabled by default, but I also know how to disable it. The principal function of the energy saver feature is to limit the runtime of the recirculation pump to 5 minutes. My installer told me that's really for the benefit of California residents due to some kind of energy compliance regulation. I'm not sure how long it took my old recirculation pump to get all the way to the bypass valve, but I think it was more than 5 minutes. I spent some time thinking about how I might get Home Assistant to push the button multiple times, but that was before I found out that I could easily disable it and get as many minutes as I might need.

Not to worry. I have since timed it. From completely cold to shutting off the bypass valve, it takes just over 2 minutes (somewhere between 2:05 and 2:10). When standing by the sink that has the bypass valve under it, I can hear the water rushing through it until it closes off. That, and the short period of time, tells me that the recirculation pump in the Navien NPE-A2 is pushing a significantly higher flow rate than my old recirculation pump.

There is one other interesting detail in the recirculation configuration. It's kind of well-known even though it's not that obvious. There is a setting for the distance (in pipe feet) from the heater to the far fixture. The default is 30 feet. Regardless of the time setting, the Navien will stop pumping when it thinks it has pumped that many pipe feet of water. Everybody who looks into this and wants to use a time limit sets that distance value to something really high, like a few hundred feet. There must be some scenario where using that distance setting makes sense, but I don't know what it is. If you are using a bypass valve, then you want to pump until the bypass valve closes. If you are using a closed loop system, where the hot water comes back to the heater, there are temperature sensors and configurations to control that. Maybe the distance thing is intentionally redundant, just like using a timer along with a bypass valve.

Since it only takes 2 minutes to get hot water at the far fixture, and since I have the M5 Atom Lite call button devices in the two upstairs bathrooms, I'm going to skip setting up some kind of scheduled recirculation, at least for the time being.