Residential HVAC Installation Practice Exam

Sludge is produced in an HVAC system when moisture, acid, and oil are present. Oil plays a crucial role in the formation of sludge because it can break down under certain conditions and create a thick, gummy substance that can clog components and reduce system efficiency. While water and dirt can also be harmful to the system, it is the presence of oil that specifically contributes to the formation of sludge in this scenario.