Galvanized and painted galvanized sheet metal frame, screwed modular type, equipped with height-adjustable cushioned feet and level. No. 2, 3 or 4 semi-hermetic compressors of the same size, equipped with taps on the discharge and suction lines, reinforced type check valves on the discharge. Suction manifold fully lined with insulating material (including individual compressor suction lines), fitting for attaching low pressure probe, discharge manifold, oil manifold with taps on individual compressor lines. The units are supplied in helium pressure, already tested with regard to pressure tightness and electrical safeties, prepared to operate with R452A gas; they are also supplied pre-filled with polyester oil.