In an operating, water-cooled, multi-box refrigeration system, both low discharge and high suction pressures are being simultaneously experienced. The probable cause for this condition is which of the following?

Correct Answer: Option D — discharge relief valve leaking back to the suction side

Internal bypass past worn or damaged compressor discharge valves allows high-pressure gas to recirculate directly back to the suction chamber during the compression stroke. This equalizes internal pressures, raising suction reading while dropping the discharge pressure.