Rinnai - Hacking the Wireless Water Controller - MC-503RC


I live in an apartment and our hot water unit is located in a plant room which as a resident we don’t have access to. We are provided with a remote control to turn the unit on/off and adjust temperature (batteries only last about 4 weeks!).

It is using the MC-503RC Rinnai which is a wireless (not wifi) controller. Since I dont have access to the plant room, I am hoping to simulate the remote control I have using an ESP32 or similar device.

Has anyone achieved this?