A suction superheat measurement lower than the manufacturer's recommended superheat setting indicates that:

• A. Too little refrigerant is being fed into the evaporator
• B. Too much refrigerant is being fed into the evaporator
• C. System is correctly charged
• D. The superheat setting is not applicable

Answer: (B)

Suction superheat shows how far the evaporated refrigerant has heated above its saturated temperature as it leaves the evaporator. If this value is lower than the manufacturer’s recommended setting, the vapor exiting the evaporator is closer to saturation, meaning not all the liquid has fully vaporized before reaching the compressor. That situation usually means there is too much refrigerant in the evaporator—an overcharge. The excess liquid tends to leave the evaporator with less added heat above the saturation point, so the measured superheat drops below the target. If there were too little refrigerant, the evaporator would be starved and the suction gas would be more superheated, not less. The low reading thus points to an overfed evaporator.