Smart Hot Water Recirculation Solution, Part 2

See part 1 here:

Now I have a Rinnai tankless water heater that is compatible with the Rinnai hot water on demand solution. This requires the following accessories:

With the Rinnai system, hot water can be demanded on a press of their button.
Many such buttons may be distributed about the house.

I improved upon the Rinnai system by enabling SmartThings to “push their button” when conditions are right. For me, conditions considered are the same as those described in part 1

  • Presence at a sink
  • Hot water temperature at the sink

SmartThings is quite capable of evaluating such conditions using many kinds of sensors and logic.
The Rinnai/SmartThings integration is worthless (for this and anything else).

To “push their button”, I required a solution much like many garage door opener solutions discussed by the SmartThings community. I use a Qubino Flush 1D Relay …

… and wire its dry contacts to the pads on the Rinnai button.

A required feature of the Qubino Flush 1D Relay is its ability automatically turn off after being turned on (act as a momentary switch). Without this, I found that I could not reliably turn the button off fast enough in SmartThings and, with the button being “held” down too long, it would reset itself (requiring a manual re-pairing with the Control-R module). My SmartThings system gets confused if the button automatically turns off too soon (e.g. one second). A two second automatic off delay seems to work fine.

Unfortunately, the current SmartThings edge driver for this relay does not support configuring this momentary switch behavior. Instead, I used an ecosystem that does support this (SiliconLabs SimplicityStudio with an Aeotec Z-Stick).

While I was at it, I decided to eliminate the need for batteries in the Rinnai button wired to the relay. I wired in power supply module.

I used a project box to house the relay and power supply module and put connectors on it.

I cut a flat RJ45 cable in half and used one half on the inside of this box and the other on the outside (wired to the Rinnai button). A small notch in the Rinnai button case allows the flat cable to pass through.

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I am doing this with my Navien heater and a Zooz Zen17, it does have momentary relay settings… and has button pass through so you can still manually control if you like.

My button remains intact/operable as well. It just has a flat cable linking it to my SmartThings adapter. However, I never use the button as it is more natural (to me) to trigger the recirculation request based on the conditions I have mentioned. As long as the conditions demand it, the button will continue being pressed.

Yes I never press a button either. I find automating it to be plenty. Mine is motion activated, and then also when the washer is running it runs at a specific time interval. Its nice having any trigger, including an external button, reset the virtual counter, so it doesn’t run when it does not need to.