The test code applies to the determination of the performances of heating boilers and combi boilers fired by liquid fuels. The requirements for the heating performances are laid down in prEN 303-1:2016 and prEN 303-2:2016. This code includes the requirements and recommendations for carrying out and evaluating the procedure for testing boilers and also the details of the technical conditions under which the tests shall be carried out. The requirements and the performance of testing for the sanitary hot water production of combi boilers are laid down in EN 303-6.