At what temperature must all valves or cocks on a heating boiler be rated at a minimum?

The correct minimum temperature rating for all valves or cocks on a heating boiler is 250°F. This requirement is put in place to ensure that the components can handle the typical operating conditions found in heating systems without risk of failure.

A temperature rating of 250°F is crucial because heating boilers operate under high temperatures, and valves that are rated lower may not sufficiently endure those conditions, leading to potential leaks or failure. The design and material construction of these valves are such that they need to withstand both pressure and temperature while ensuring safety for the system.

Valves rated below 250°F would not be suitable for reliable operation in a heating boiler context, thus necessitating that all components be rated for at least this temperature to maintain safety and efficiency standards in boiler operations.