F9 error and thermostat cannot control wireless relay or receiver; heating does not switch on.

Safety: Isolate mains power before opening the wireless receiver housing. Receivers are usually connected directly to 230V.

• Step 1 – Check receiver power:
  • Verify that the Protherm wireless receiver LED is on.
  • If off, check its mains supply, fuse, and wiring.
• Step 2 – Reduce distance and obstacles:
  • Ensure the thermostat is within the specified range of the receiver.
  • Avoid thick concrete walls, metal cabinets, or large appliances between them.
• Step 3 – Re-pair devices:
  • Press and hold the pairing button on the receiver until the LED flashes (refer to manual).
  • On the thermostat, enter the wireless setup menu and start pairing.
  • Wait until the receiver confirms pairing (steady LED).
• Step 4 – Eliminate interference:
  • Keep Wi‑Fi routers, cordless phones, and other 2.4 GHz devices away from the receiver if possible.
  • Reposition the receiver or thermostat to improve signal.
• Step 5 – Test relay operation:
  • Manually raise the set temperature to call for heat.
  • Confirm that the receiver relay clicks and boiler starts.
  • If F9 persists, the wireless module in the thermostat or receiver may be faulty and require replacement.