I made my own Wi-Fi adapter for my heat pump hot water system.

I was inspired by this thread on the home assistant forums which documented the modbus registers.

The new module is based a Waveshare ESP32-S3-RS485-CAN.

Waveshare ESP32-S3-RS485-CAN board

Time for the transplant. Turn off power at the isolator first. Undo two screws on the top and two on each side, lift off the cover, then remove the old Wi-Fi module.

Top screws on the heat pump cover Side screws on the heat pump cover Original proprietary Wi-Fi module

The cable provides:

  • Red: 12V
  • Black: GND
  • White: RS485 A
  • Yellow: RS485 B

I just chopped the cable but you can also open up the old wifi module and disconnect the cable

Chopped heat pump Wi-Fi module cable

I put the new module in and tried to keep it off the bottom of the enclosure, since that area can get wet. After reinstalling the cover and switching the power back on, it came alive.

Waveshare module installed in the heat pump
ESPHome web view for the heat pump adapter

All done!

Home Assistant dashboard entities for the heat pump

I also put the external component on GitHub: sjtrny/esphome-hw211.

Original Mastodon posts: starting the project, removing the old module, cable mapping, new module installed, Home Assistant dashboard, and GitHub component.