Method and cooling / liquefaction at low temperature

A method of cooling / liquefaction at low temperatures of a working gas with low molecular weight, the method using a first refrigerator / condenser (1) comprising a station (2) for compressing the working gas and a cold box (3) for cooling the working gas at the outlet of the station (2) of compression, the method comprising: - a compression step, - a step of cooling the compressed working gas in the compression step, the compression step using both compression machines lubricated screw-type (EC1, EC2) and centrifugal compression machines (EC3, EC4), the method being characterized in that the compression step selectively utilizes at least one machine compression (EC3) belonging to a compression station (12) of a second refrigerator / condenser (11) distinct from said first refrigerator / condenser (1), the second refrigerators / liquefier (11) C ilisant a single working fluid such as the first refrigerator / condenser (1).