Thermostat emits a burning smell or becomes unusually hot to touch

Safety: Immediately switch off power at the fused spur or consumer unit. Do not continue using a thermostat or receiver that smells of burning or is excessively hot.

Steps:

• Allow the device to cool completely before touching.
• Remove the thermostat from its backplate and visually inspect for scorch marks or melted plastic.
• At the receiver or wiring center (with power isolated), check for signs of overheating around the relay and terminals.
• Verify that the connected load (boiler, valves) does not exceed the rated current of the thermostat/receiver contacts.

Remedy:

• Do not attempt to repair a burnt thermostat or receiver. Replace the complete unit with the correct Glow‑worm part.
• Correct any wiring errors and ensure loads are within specification before restoring power.
• If in doubt, have a qualified electrician or heating engineer inspect the installation.