A system comprises the integrated combination of: a condenser having a condenser water path leg extending from a water inlet to a water outlet; a first expansion device; a flash tank economizer; a second expansion device; an evaporator having an evaporator water path leg extending from a water inlet to a water outlet; and a refrigerant flowpath passing sequentially through the condenser, the first expansion device, the economizer, the second expansion device and the evaporator. The flash tank economizer comprises a horizontally elongate body having a first end and a second end. The economizer has an inlet conduit having an outlet. The economizer has a liquid outlet, a vapor outlet, and a medium between the outlet of the inlet conduit and the liquid outlet. A length of the refrigerant flowpath between the first expansion device and the outlet of the inlet conduit is at least 0.5 m.