InterNACHI HVAC Practice Exam 2026 – Complete Test Prep

Insulation is commonly found on the suction line of both heat pumps and air conditioners but is typically not applied to the liquid line. The suction line carries low-pressure refrigerant vapor back to the compressor, and insulating it helps prevent heat gain from the surrounding environment, which can improve system efficiency and reduce energy costs. Conversely, the liquid line, which carries high-pressure refrigerant to the evaporator coil, usually does not require insulation because it operates under different temperature conditions and is less likely to experience heat loss or gain.

Additionally, using insulation on the liquid line could create issues such as condensation and moisture buildup, potentially leading to corrosion and other problems. Therefore, while insulation is essential for optimizing the performance of the suction line, it is not standard practice to insulate both refrigerant lines.