The highest pressure on the pressure gauge of a hot water boiler is set to _____ times the pressure relief valve.

The correct choice indicates that the highest pressure on the pressure gauge of a hot water boiler is set to 3.5 times the pressure relief valve setting.

This practice is grounded in safety and operational standards for hot water boilers. The pressure relief valve is a critical safety component designed to prevent excessive pressure from building up in the system, which can lead to hazardous conditions, including the potential for an explosion. By setting the highest pressure on the gauge to 3.5 times the relief valve's pressure setting, it ensures that the pressure build-up remains within safe limits while providing a buffer. This reduces the risk of the boiler operating outside its design parameters, which can lead to equipment failure or unsafe situations.

Additionally, this ratio is recognized in guidelines and codes governing boiler operations, reinforcing the importance of proper pressure management. A pressure gauge reading set too high relative to the relief valve's setting could mislead operators about the actual conditions inside the boiler, increasing the risk of a dangerous scenario. By adhering to the correct ratio, operators can maintain awareness of the boiler's operational safety margins.