Which option correctly identifies the two basic types of relief valves used on refrigeration systems?

• A. Automatic relief valve and one-time relief valve
• B. Manual relief valve and automatic relief valve
• C. Pressure relief valve and vacuum relief valve
• D. Safety valve and vent valve

Answer: (A)

Relief devices in refrigeration are there to protect equipment from overpressure by venting when needed. There are two basic kinds: an automatic relief valve, which opens at a set pressure and automatically reseats once the pressure drops, providing repeated protection; and a one-time relief device (often a rupture disk), which opens to vent at a higher overpressure and cannot reseal, so it must be replaced after activation. This pair covers the ongoing, automatic protection and the single-use, last-resort protection, which is why it’s the best match. Other options mix in manual operation or different categories that aren’t the standard two basic types used for automatic protection in most refrigeration systems.