Which device is used to prevent overheating in a central heating system as required by regulations?

• A. Thermal cut off switch
• B. Flow switch
• C. Pressure relief valve
• D. Carbon monoxide detector

Answer: (A)

When overheating protection is needed in a central heating system, a device that directly monitors temperature and shuts the boiler down if it gets too hot is used. This thermal cut-off switch is wired into the boiler’s control circuit and is designed to interrupt the heat source whenever the temperature reaches a dangerous limit, meeting safety regulations. It acts as a hard safety barrier to prevent fires, damage, or scalding if something goes wrong, like a pump failure or flow issue that could let the system overheat.

Other devices have different roles: a flow switch ensures there is water moving through the system before the boiler fires, preventing damage from no-flow conditions but not specifically controlling temperature. A pressure relief valve releases excess pressure, not heat. A carbon monoxide detector warns of harmful gas but does not prevent overheating.