Residential HVAC Installation Practice Exam

A trap in the condensate line prevents air from being drawn up into the unit from the end of the drain. Without a trap, negative pressure in the HVAC system could potentially draw air into the unit, causing inefficiencies and potential damage. This is why having a trap in the condensate line is crucial for the proper operation of the HVAC system. Condensation buildup is not the correct answer because a trap does not specifically prevent condensation; its main purpose is to prevent air from entering the unit. Options B and C are not directly related to the function of the trap in the condensate line.