What happens to systems with a TXV when overcharged?

When a system equipped with a thermal expansion valve (TXV) is overcharged, it holds the suction pressure steady while simultaneously increasing the head pressure. The TXV is designed to regulate the flow of refrigerant into the evaporator based on the superheat, allowing it to respond to changes in system conditions effectively.

When there is an excess of refrigerant, the system can't efficiently handle the additional volume. As a result, the TXV restricts the flow of refrigerant to maintain the required superheat, which stabilizes the suction pressure. However, this situation leads to an increase in head pressure because the excess refrigerant accumulates in the system, thus raising the pressure at which the compressor operates.

This outcome is important for understanding system performance and the potential issues that may arise from overcharging, including reduced efficiency and possible damage to components like the compressor. It highlights the critical balance of refrigerant charge in maintaining optimal operation within HVAC systems.