Heating and cooling systems from the TR series in the secondary circuit unit range consist of either one or multiple heat exchanger modules. They feature a direct media coupling or electric heater module. The additional letters, such as HKT, indicate the number of heating or cooling modules, as well as temperature control functions. These systems produce a temperature-controlled liquid flow and are designed as a compact, fully insulated, ready-to-connect system with control cabinet, completely pre-tested at the factory.