AIR CONDITIONING SYSTEM AND AIR CONDITIONING SYSTEM OPERATION METHOD

PROBLEM TO BE SOLVED: To provide an air conditioning system technique suited for a data center or the like for performing a free cooling operation.SOLUTION: A piping system B2 is a system for free cooling and configured by a circulation path including a part of an outward water pipe 5a connecting a heat source machine group 2 to a heat exchanger 5d (downstream side of a three-way valve V1), a part of a return water pipe 5e (between the heat exchanger 5d and a three-way valve 6), a pipe 5f from the three-way valve V6 to a vertical pipe group 7, a pipe 5g from the vertical pipe group 7 to a three-way valve V2, a part of the return pipe 5e (between three-way valves V2 and V3), and a pipe 5h from the three-way valve V3 to the three-way valve V1. The vertical pipe group 7 is installed on an outer wall 7b of a building facade. A plurality of vertical pipes 7a constituting the vertical pipe group 7 are non-temperature insulating pipes and configured to be able to cool return water flowing in the pipes by heat exchange between the return water and outdoor air.