which is common for the inlet and outlet gas channels 38 and 39 in the outlet gas channel 39 there is a valve comprising of a movable closing element 44 provided with a magnetic insert 45 and a seat 46 in a fitting 47 a fluid level sensor 4 capable of detecting the full filling of a compressing vessel with working fluid 30 placed at the outer side of the body 42 of the shut off device 3 and the magnetic insert 45 are located at the same level in the lower position of the movable closing element 44 a shut off device 3 fig4 of the gas filling device shown in fig2 is similar to the shutoff device 3 shown in fig3 which does not have the tube 40 and the t shaped channel 41 but is additionally provided with a channel 48 only in the shut off device 3 for the compressing vessel 2 to be connected to the drain tube 32 the gas filling device operates as follows in the initial condition shown in fig1 the compressing vessel 1 apart from a small amount of the working fluid is filled with gas from the residential low pressure gas line 28 by means of the pre compressor 26 the compressing vessel 2 is fully.