Insulation is primarily used to prevent heat gain in which of the following lines?

Insulation is essential for preventing heat gain in the suction line. The suction line is the pipe that carries refrigerant from the evaporator back to the compressor. It contains low-pressure refrigerant vapor that can absorb heat from the surrounding environment if not properly insulated. This heat gain can lead to reduced system efficiency, as the compressor must work harder to compress the warmer vapor back into a liquid for recycling through the evaporator.

By insulating the suction line, the temperature of the refrigerant vapor remains low, ensuring optimal system performance and energy efficiency. This insulation minimizes heat transfer between the refrigerant and the ambient air, thereby maintaining a consistent refrigerant temperature as it returns to the compressor.

In contrast, the other lines mentioned—liquid line, discharge line, and condensing line—perform different functions within the HVAC system and typically do not require the same level of insulation to prevent heat gain as the suction line does.