The CCT test method, developed by the SPF in Switzerland [4] is also an indoor test method and is similar to the DC test method, except that the test sequence of the CCT uses a longer test cycle and has a duration of 12 days instead of 8 days plus 18 hours preconditioning phase. The 12 days of the core phase are chosen with respect to annual seasonal average values of solar irradiation and ambient temperature.

Another important difference is that the building is simulated on-line so that the heat supply is controlled via the controller of the solar combisystem and therefore provides the right flow rates and temperatures. This ensures that all system functions may be assessed, which is one major advantage of this kind of test method. In contrast, the disadvantage is that the systems supply the emulated building with varying amounts of energy and there is no uniform or predictable energy use for space heating. This complicates the characterization of the systems energy-related performance. Unlike the DC method, the CCT can be used in principle to characterize solar combisystems where the system intentionally uses the building’s thermal mass to optimize its heat storage strategy.

Nevertheless, the test method allows a direct comparison of system performance.