Thermostat backlight or display flickers when boiler or other loads switch on

Safety: This involves mains wiring. Isolate power at the fused spur and verify dead before opening any wiring center or boiler.

Steps:

• Inspect the wiring center for loose neutrals or shared neutrals between high‑load devices and the thermostat supply.
• Ensure the thermostat or receiver is supplied from a stable circuit, ideally separated from heavy inductive loads where possible.
• Check that pumps and motorised valves have proper suppression (factory‑fitted snubbers or capacitors) and that earth connections are secure.
• Tighten all terminal screws and look for signs of overheating or arcing.

Remedy:

• Correct wiring faults and, if necessary, have an electrician install additional suppression devices on problematic loads.
• If flicker persists and only affects the thermostat, its internal power supply may be sensitive or damaged; replace the thermostat head or receiver.