Suction accumulator
Also known as: liquid separator, suction line accumulator
Short definitionAn upright vessel fitted in the suction line just ahead of the compressor. It holds refrigerant that arrives unevaporated from the evaporator at its bottom and sends only gas on to the compressor.
If liquid enters the compressor, valve plates break, the oil is diluted and bearings seize. This vessel steps in and slows the mixture down: the heavier liquid drops, and vapour is drawn off at the top through the mouth of the internal U-tube. The refrigerant left at the bottom warms from the surroundings and slowly turns to gas. At the bottom of the U-tube there is a 1–2 mm hole; collected oil is metered through it into the suction flow and returns to the compressor.
It belongs in the quote for hot gas defrost plants, blast freezing rooms and split installations with long pipe runs and a large charge. The volume is chosen to hold at least half of the total charge; in an oversized vessel the oil stays behind. It must stand upright, and inlet and outlet must not be swapped. Its cold shell sweats, so it is insulated. The vessel is a precaution, not a repair: if liquid keeps coming, check the expansion valve setting, the superheat, a frosted evaporator or an overcharge.