Abstract: In a compression type refrigeration system having a volatile refrigerant circulating along with lubricating oil, member for causing oil to flow from a first location to a second location, where the member comprises an educator connected to receive the oil from the first location, a high pressure source within the system connected to the educator, and a connection from the eductor to the second location.

Abstract: A refrigeration system having compressors positioned higher than the dispersed evaporators requires multiple suction risers. To better ensure oil return to the compressors, only a single oil return riser is employed. This oil return riser is connected to one end of an oil collection main positioned near the lower portion of the suction risers. The oil collection main is connected by restricted oil drain conduits to the lower portions of the suction risers, thereby collecting the oil which failed to be conveyed to the top of the suction risers by their vapor velocity. The restrictions in the oil drain conduits ensure adequate vapor velocity within the oil collection main even with widely varying loads on the suction risers.

Abstract: In a multi story air conditioning system having elevated compressors and varying loads, a suction line oil return arrangement comprising dual parallel suction risers having a pressure relief valve positioned in one to ensure a minimum pressure drop for oil return in the other.