Suction gas temperature minus saturated suction temperature equals

• A. Condensing temperature
• B. Superheat
• C. Evaporator operating temperature
• D. Subcooling

Answer: (B)

The amount of superheat is the difference between the actual suction gas temperature and the saturated suction temperature at the same evaporator pressure. In the evaporator, refrigerant boils and becomes vapor; as it travels through the suction line to the compressor, it picks up more heat, so the actual suction gas temperature ends up higher than the temperature at which that vapor would be saturated. This rise above saturation is called superheat. Measuring it helps ensure the refrigerant entering the compressor is vapor, not liquid, protecting the compressor and indicating proper evaporator operation.

The other terms don’t describe this particular difference. Condensing temperature relates to high-side conditions after the refrigerant has condensed, not suction gas. Evaporator operating temperature isn’t a standard term for this measurement. Subcooling is the cooling of liquid refrigerant below its saturated temperature at condenser pressure, not the rise in suction gas temperature above saturation.