When does the combination pressure and temperature relief valve typically open?

The combination pressure and temperature relief valve typically opens at 99°C (210°F) because this temperature is set to prevent overheating and excessive pressure buildup in a system. It's designed to activate before reaching the boiling point of water under normal atmospheric conditions, which is 100°C (212°F).

By opening at 99°C, the valve helps to ensure that the system operates within safe thermal limits, preventing potential damage or hazardous situations that could arise from excessive pressure and temperature. This threshold allows for a margin of safety, taking into account that temperature can fluctuate slightly within operational systems.

Choosing a value slightly below the boiling point is crucial in maintaining the safety and integrity of the system.