Gas and liquid coolers are available in ten standard sizes through a capacity range of 15 to 1000 tons of ammonia refrigeration. Designed for installation in the booster discharge line, the gas and liquid coolers sub cools liquid ammonia from the receiver for the low stage load while super heating booster discharge gas to the high stage compressor. Superheat of booster discharge gas is necessary to prevent overheating of the high stage compressor. Sub cooling of liquid refrigerant for the low stage load is essential to obtain economical thermodynamic efficiency of the refrigeration cycle. Gas and liquid coolers performs both of these functions efficiently.