Test chamber and method for its operation

A method for conditioning air in a temperature-insulated test space of a test chamber, the test space being closable with respect to an environment and serving to receive test material, a temperature ranging from −40° C. to +180° C. being generated within the test space by a temperature control device of the test chamber, a temperature being generated within the test space by a cooling apparatus of the temperature control device having a first cooling cycle and a second cooling cycle, the first cooling cycle having a first refrigerant, a first heat exchanger, a first compressor, a first condenser and a first expansion element, the first refrigerant being a hydrocarbon or a refrigerant mixture made of hydrocarbons,

• wherein the second cooling cycle is made of a heat transfer medium, a second heat exchanger in the test space and a pump, the second cooling cycle being coupled to the first cooling cycle by the first heat exchanger, the heat transfer medium being circulated in the second cooling cycle by the pump;
• wherein the temperature control device comprises a regulator having at least one temperature sensor in the second cooling cycle, at least one valve apparatus being able to be actuated in the second cooling cycle by the regulator as a function of a measured temperature;
• and
• wherein the valve apparatus is formed having a three-way valve, which is disposed downstream of the second heat exchanger and upstream of the pump in the second cooling cycle, a second bypass being connected to the three-way valve.