What happens to the pressure in the system when refrigerant is undercharged?

When a refrigerant is undercharged in a cooling system, the amount of refrigerant present is insufficient to absorb and transfer the heat effectively. This lack of refrigerant leads to a decrease in the refrigerating effect, which impacts the pressure within the system.

In an undercharged condition, the evaporator may not be able to extract enough heat from the surroundings, resulting in lower evaporator pressures. The reduction in refrigerant leads to decreased vaporization, which directly causes the refrigerant pressure to drop in the evaporator. Additionally, lower pressure also can contribute to lower temperatures, which may lead to issues such as reduced cooling efficiency and the risk of system freeze-up.

Though there may be some temporary fluctuations in pressure at various system points, overall, the primary effect of undercharging is a decrease in pressure throughout the system, particularly in the evaporator. This is essential for maintaining a balanced thermodynamic cycle in refrigerant systems.