On which line should a relief valve be installed for fuel-oil-heating appliances?

A relief valve is critical in ensuring the safety and proper function of fuel-oil-heating appliances. When installed on the discharge line, it serves as a protective mechanism by releasing excess pressure that may build up during the operation of the appliance. This is essential in preventing potential hazards such as equipment failure or leaks that could lead to dangerous situations.

The discharge line is where the heated fuel is delivered to the burner or appliance, and therefore, any pressure buildup in this line could indicate a malfunction or impending failure of the system. Having the relief valve installed here allows it to effectively manage and release any excess pressure, safeguarding the entire heating system.

In contrast, while the other lines mentioned may serve specific functions in the overall operation of the heating appliance, they do not play the same critical role in directly managing pressure buildup related to the operation of the appliance. The return line carries fuel back to the tank, the intake line is responsible for directing fuel into the system, and the vent line is meant for exhausting combustion gases or vapors. These functions do not necessitate the immediate pressure relief that is essential on the discharge line. Hence, the installation of the relief valve on the discharge line is aligned with best practices to ensure the safety and efficiency of fuel-oil