If the chiller is to be shutdown over a long period, it is advisable to pump down the system and valve off the bulk of the refrigerant charge in the condenser. This is intended to minimize the quantity of refrigerant that might be lost through minor leakage on the low pressure side.
Valve off the supply of chilled water valves and condenser water valves (Water Cooled Units), such that the vessels remain full of water during off season. A drained vessel is more likely to rust and corrode than one that is full of water. However, if ambient temperature falls below freezing temperature then drain all water and flushed the tubes with compressed air. This practice also applies to air handling units, chilled water circuit, condenser water circuit, cooling towers, pumps and etc.