What happens to suction pressure when there is a low refrigerant charge in an air conditioning system?

When there is a low refrigerant charge in an air conditioning system, the suction pressure decreases significantly. A lower refrigerant charge means there is less refrigerant in the system to absorb heat, leading to inadequate evaporation in the evaporator coil. As a result, the refrigerant does not boil effectively, which results in lower pressure on the suction side of the system.

In a normally operating system, the suction pressure is maintained by the balance of refrigerant flow and heat exchange. When the charge is low, the refrigerant cannot maintain the necessary pressure. The decreased amount of refrigerant reduces the system's ability to maintain the correct pressure levels, directly impacting the suction side readings. Low suction pressure can lead to various operational issues, including inefficient cooling and potential compressor damage if allowed to persist.