Refrigerant lines consist of two copper pipes of different diameters, one for the liquid refrigerant and one for the gas, and they are routed through the wall hole drilled during installation to connect the indoor evaporator unit to the outdoor condenser. The ends of the copper pipes are cut to the required length, flared using a flaring tool to create a leak-proof connection, and then fitted and tightened to the corresponding ports on both units using flare nuts and a torque wrench. The lines are wrapped in insulation to prevent condensation and energy loss, then bundled with the drainage pipe and electrical cable inside a protective conduit or casing that runs along the wall to keep the installation neat and weather-resistant.