A "P" trap is installed when an evaporator coil is located on which side of the blower?

A "P" trap is installed on the negative side of the blower when the evaporator coil is located there to manage condensate drainage effectively. The purpose of the "P" trap is to prevent air from passing back through the drain line and into the evaporator coil, which can occur when the evaporator is situated before the blower in the airflow path.

In systems with the evaporator on the negative side, the blower creates negative pressure, which can potentially pull air through the drain. The "P" trap creates a water barrier that helps to seal the drain line, ensuring that air cannot infiltrate from the outdoors or other parts of the system. This is crucial for maintaining the efficiency of the refrigeration cycle and ensuring proper operation of the system.

Other configurations, such as placement on the positive or neutral side, do not necessitate a "P" trap in the same way, as airflow dynamics and pressure considerations differ significantly, minimizing the risk of air being pulled through the drain line.