A test according to the DC procedure requires the set-up of the complete system in an indoor test facility and its operation for eight days according to a well defined test sequence [1-3]. It is to be used for small factory made systems as well as for small custom built systems with a collector area smaller than 15-20 m2 and a heat store volume of 1500-2000 litres.

The major performance indicator of the solar combiystem given by the DC test is the final energy used by the auxiliary heater, the same as in the CTSS method. For this case, it is essential that the solar combisystem is always tested in combination with the auxiliary heater. This feature is considered to be favourable, because many problems in system operation appear due to improper control strategy for the coupling of the solar and auxiliary parts of the system. In case of absence it is also possible to use a specific well defined laboratory heater.

The prediction for the annual final energy use is only possible when the test conditions during the sequence correspond more or less to the annual conditions. Hence, this test method is restricted to one specific climate zone in Europe and one specific building type with its characteristic insulation parameters, heat distribution system and domestic hot water profile.