You need to consider three sizes when you select a refrigerant line-set for a ductless mini-split system: the liquid-line diameter, the suction-line diameter, and the length. The necessary diameters of the liquid and suction lines depend on the requirements of the indoor mini-split unit. Liquid lines bring refrigerant back to the outdoor compressor. Suction lines supply refrigerant to the indoor unit, while preventing overheating at the compressor. SupplyHouse.com offers pre-flared, insulated JMF line-sets.
The length of your line-set should be based on the distance between the indoor and outdoor units, but make sure to look at the distance limitations of each mini-split system. All systems have maximum distance and height differences between the units, as well as a maximum refrigerant pre-charge. A typical system comes pre-charged with sufficient R-410A refrigerant for a 25-foot run, and is rated for runs up to 50 feet. Such systems would require additional refrigerant for line-set lengths between 25 and 50 feet.
