Abstract: An ice making refrigeration system embodying an accumulator tank above and externally of a refrigerant chamber and communicating therewith by valved means for gravity flow of liquid refrigerant to the refrigerant chamber during a freezing phase. The upper portion of the accumulator tank communicates with the intake of a compressor to deliver vaporized refrigerant thereto. The upper portion of the refrigerant chamber communicates with the accumulator tank by a vapor-liquid return conduit. The discharge side of the compressor communicates with a condenser and the liquid side of the condenser communicates with the vapor-liquid return conduit downstream of the refrigerant chamber and delivers makeup liquid thereto in the general direction of flow of refrigerant therethrough. Valved means delivers hot gaseous refrigerant under pressure from the compressor to the refrigerant chamber during a harvesting phase.