Smart thermostat display shows 'No RF' or radio symbol with a cross; heating does not respond to set temperature.

Safety first: For any work at the boiler or receiver, switch off power at the fused spur and verify the boiler is isolated. Do not remove boiler covers that seal the combustion chamber; that is Gas Safe engineer territory.

• Check signal path: Move the thermostat closer to the boiler/receiver temporarily (within 1–2 m, line of sight). If the error clears, RF range or interference is likely the issue.
• Reduce interference: Keep the thermostat and receiver away from Wi‑Fi routers, cordless phone bases, microwave ovens, and large metal objects. Reposition the thermostat on an internal wall about 1.2–1.5 m above floor level.
• Re-pair the RF link: On the Worcester Bosch RF receiver (usually mounted near or on the boiler), press and hold the pairing/learn button until the LED flashes. On the thermostat, enter the installer menu and select the RF pairing option, then confirm. Wait for the receiver LED to go solid, indicating a successful link.
• Check power to receiver: Ensure the boiler fused spur is on and the receiver’s power LED is lit. If not, check the fused spur (3 A fuse) and that the receiver wiring is secure (this should be done by a competent person).
• If still no RF: The RF module in the thermostat or the receiver PCB may be faulty. At this point, contact Worcester Bosch support or a heating engineer to test and replace the RF receiver or thermostat.