What does the combination of low pressures, high superheat (SH), and low suction (SC) typically indicate?

The combination of low pressures, high superheat, and low suction typically indicates an undercharged system. In an HVAC context, when the refrigerant levels are insufficient, the evaporator coil fails to absorb enough heat from the surrounding air, leading to a low suction pressure. This low suction pressure corresponds with an increase in superheat, as the refrigerant vaporizes more completely and absorbs heat without the adequate liquid refrigerant in the evaporator.

High superheat indicates that the refrigerant is fully vaporized before it reaches the compressor, which can be a sign of insufficient refrigerant in the system. The lack of refrigerant prevents efficient heat transfer and cooling performance, highlighting an undercharged situation. This combination of symptoms ultimately helps technicians diagnose issues related to the refrigerant charge level within the HVAC system.