Error A128 means the control board relay failed and the heater was disabled. The following steps can help you check the issue.
- Disconnect power to the unit.
- Check wiring connection.
- Check ohm reading if wires are properly connected.
- If acceptable ohm reading is present, replace the board. If not, replace relay.
Zwell is dedicated to getting homes closer to net zero through the installation of new energy-efficient hybrid water heaters. We are not currently equipped to do service or repair visits but we want to be as helpful as possible. Feel free to reach out to us here or for more information, you can contact the Rheem Hybrid Technical Services Department at 800-995-0982.