As for the cooling operation, for the following statistics on hourly values, only hours with a constant operation of the machine were considered in order to be sure to consider steady state conditions only. This covers more than 63% of the hours with operation, as can be deduced from Table 1. Fig. 8 shows the frequency diagrams of the hourly COP and heating powers (Fig. 9). For the whole heating operation period a thermal COP of 1.43 is obtained. The hourly mean heating power was 9.43kW with a standard deviation of 1.59kW.

in the period between 11:30 and 14:30.