A heating, ventilation and air conditioning (HVAC) system includes a condenser (18) flowing a flow of refrigerant therethrough and to an output pipe (56) and a falling film evaporator (12) in flow communication with the condenser and having an evaporator input pipe (58) located vertically higher than the output pipe. A plurality of riser pipes (60) connect the output pipe to the evaporator input pipe. The flow of refrigerant flows through selected riser pipes of the plurality of riser pipes as required by a load on the HVAC system.