As indoor relative humidity increases, how does the evaporator temperature of an air conditioner change?

When indoor relative humidity increases, the evaporator temperature of an air conditioner falls. This occurs because higher humidity means there is more moisture in the air. The air conditioner works to remove this moisture through the cooling process, which involves heat exchange.

As humid air passes over the evaporator coils, the added moisture in the air condenses on these coils. This process of condensation absorbs heat, thereby cooling the refrigerant and, ultimately, the air that is being conditioned. The increase in moisture causes the heat exchange process to become more efficient, leading to a reduction in the evaporator temperature. A lower evaporator temperature is essential for maintaining cooling efficiency and effectively reducing indoor humidity levels.

In contrast, when humidity levels are low, the evaporator can operate at higher temperatures since less moisture is condensing on the coils. Thus, it is clear that as relative humidity increases, the evaporator temperature decreases.