So… after I thought more about my project I wonder if this Sonoff unit is what I need.
I have a Rinnai tankless water heater. If you call for hot water, the water heater fires up and then the hot water makes its way to where ever you are running the tap. There is a hot water return loop that allows hot water to circulate out of the heater, past all of the hot water faucets, and then back into the hot water heater.
What I want to do is to put a momentary push-button on my OH2 UI so I can push it and turn on the recirculation pump. Then I have instant hot water at the shower. Once I finish, I can push the button again to turn the pump off.
One other detail - there is an indicator on the heater control panel that shows it is in recirculation mode. After about two hours, if you don’t turn it off earlier, the heater drops out of recirculation mode.
If I had run low voltage wiring to the pump location, I could use one pair to switch on the pump with a momentary closure, and I could use the other pair to pick up the status of the recirculation mode on the control panel. I could use the GPIO pins on my RaspberryPI and I would be good to go. But… no wires are in the walls.
I need some small device that I can put in the wall behind the water heater control panel. I need to be able to send a momentary switch command to a dry contact closure to put the heater in recirculation mode. I also need some sort of input on the device so that I can get the actual status of the water heater off of the panel into OH.
Clearly I could use a Sonos device to produce a momentary push-on, push-off contact closure to remotely push the recirculation mode button, but I would be running “blind”, having no idea whether the last button-press put it into recirculation mode, or took it out of that mode.
Sorry for the TLDR post, but perhaps I need some sort of different solution. Any ideas?