Vapor compression system

A vapor compression system comprising:

• a compressor, a condenser, an expansion device and an evaporator connected by a refrigerant line;
• the evaporator comprising:
• a shell;
• a first tube bundle;
• a hood;
• a distributor;
• a supply line;
• a pump;
• an expansion device;
• and
• a sensor;
• wherein the first tube bundle comprises a plurality of tubes extending substantially horizontally in the shell;
• wherein the distributor is positioned above the first tube bundle;
• wherein the hood covers the first tube bundle;
• wherein the supply line is connected to the expansion device and the expansion device is connected to a discharge of the pump;
• wherein the sensor is configured and positioned to sense a level of liquid refrigerant in the shell;
• wherein the pump is operated in response to a sensed level of liquid refrigerant decreasing below a predetermined level when the expansion device is in an open position.