When the outdoor unit is installed at a position higher than the indoor unit, install...

This statement is true. In split DX/precision cooling refrigerant systems, the “gas pipe” typically refers to thesuction linereturning refrigerant vapor (and entrained compressor oil) from the indoor evaporator to the outdoor unit/compressor. When theoutdoor unit is higher than the indoor unit, the suction line includes avertical riser. Oil naturally tends to settle and flow downward under gravity, so without proper piping measures, oil may accumulate in low points or fail to be carried upward consistently, leading topoor oil return. Insufficient oil return can cause compressor lubrication issues, abnormal noise, overheating, reduced efficiency, and long-term reliability risks. Installingoil trapsat the bottom of the riser and thenevery 5–6 metersof vertical lift helps collect oil and allows it to be periodically swept upward by refrigerant velocity, maintaining stable oil circulation. This requirement is especially important in data center cooling because continuous operation and high availability demand reliable compressor lubrication and stable refrigerant flow under varying load conditions.