What is one of the safety devices found on a hot water boiler?

The temperature pressure relief valve is a critical safety device found on a hot water boiler. Its primary function is to prevent excessive pressure buildup within the boiler. When the temperature or pressure exceeds a predetermined limit, this valve automatically opens to release water and steam, thereby ensuring that the pressure inside the system remains within safe operational parameters. This mechanism is essential for preventing explosions and other hazardous situations that can arise due to overheating or over-pressurization.

While other devices mentioned play important roles in the overall functionality and monitoring of a boiler system, such as monitoring pressure, temperature, or water levels, it is the temperature pressure relief valve that directly addresses safety through its emergency release capability. This makes it an indispensable component for safe boiler operation and compliance with safety regulations.