What can be concluded if a heat pump's superheat reading is significantly above normal?

When a heat pump's superheat reading is significantly above normal, it often indicates that the metering device is malfunctioning. The superheat is a measure of the vapor temperature above its saturation point at a given pressure. If the metering device, such as an expansion valve, is not passing refrigerant properly, it can lead to excessive superheat as not enough refrigerant is allowed to flow into the evaporator. This restriction causes the refrigerant to absorb too much heat before it exits the evaporator, resulting in a high superheat reading.

While it might seem plausible that factors like overcharging or undercharging could affect superheat levels, typically, an overcharged system would show a lower superheat reading because enough refrigerant would flow through the system. Similarly, an undercharged system would also tend to show different readings because of insufficient refrigerant in the evaporator. Therefore, the indication that the metering device is malfunctioning is the most accurate conclusion when confronted with an unusually high superheat.