Which statement best characterizes a hermetic compressor?

• A. It uses magnetic drive to seal refrigerant
• B. It is mounted outside the refrigeration cabinet
• C. It uses a piston-style external motor
• D. It will have both the compressor and motor enclosed in a gas-tight housing

Answer: (D)

A hermetic compressor keeps the motor and the compressor inside a single, gas-tight housing that is sealed at the factory. This design means the refrigerant never leaks to the outside and there are no shaft seals to maintain, since the moving parts are enclosed within a welded or brazed shell. That enclosing, gas-tight housing is the defining feature, so the statement that describes both the compressor and the motor being inside a gas-tight housing best characterizes a hermetic unit.

The other descriptions don’t fit because hermetic refers to the sealed enclosure, not how the drive is implemented or where the unit is mounted. Magnetic drive isn’t what makes a compressor hermetic, and mounting outside the cabinet describes installation rather than sealing. A piston-style external motor describes a design where the motor is outside the sealed housing, which is not hermetic.