The main conclusions of the studies are the following ones:
- The Chinese independent laboratories which have participated in the round robin testing show a good level of quality for the measurement of the energy efficiencies of air/air air conditioners and heat pumps. Some improvements may be considered for both testing methods. Some of them have been scheduled like in the case of Laboratory 1.
- The differences between the results obtained by the different laboratories are compatible with the maximum uncertainty of measurement for these tests, although the maximum difference of 7% obtained for the energy efficiency seems high for a MEPS system. The higher the maximum difference in the test result, the higher the possibility that the same model tested in different laboratories have different results relative to the MEPS low limits. Actions designed to reduce this difference by improving the quality of the tests should be taken. Periodic round robin tests performed on a regular basis would be the best way to check the effectiveness of the improvements and to verify that the quality of the test remains constant. Furthermore, these periodical round robin tests are mentioned in clause 5.9.1.b) of ISO/IEC 17025:2005 and are considered as a requirement by most of the accreditation bodies.
- A maximum difference of 25.0 % has been observed for the airflow rate measured by different laboratories for the same indoor unit. This difference is very high and should be carefully assessed and sorted out. A specific round robin test designed for this purpose would probably be necessary to achieve this goal.
- No significant difference has been observed between the average capacities and efficiencies measured by the calorimeter method and the air enthalpy method. This result is unexpected considering the differences in the airflow rate measurement and the fact that uncertainty calculations and experience in other parts of the world indicate that the calorimeter room method is more accurate than the air enthalpy method.
- Some improvements concerning the installation and the settings of the samples should be studied. These possible improvements are described in II.3.3.
- Additional round robin tests would be necessary to compare the results of theChinese laboratories with those of the JRAIA laboratory.
In our opinion, it is possible to enhance the quality of the testing without excessive efforts,provided that some periodic verification is performed within the independent laboratories. We would also like to point out that the air enthalpy method is not the best test method in a MEPS environment, as this method has a greater uncertainty of measurement than the calorimeter room method, and above all because there is no verification of the result with a simultaneous measurement outdoor side.