The present invention relates to a method and apparatus for cooling down a cryogenic heat exchanger adapted to liquefy a hydrocarbon stream, such as a natural gas stream. The method comprises: (i) receiving one or more refrigerant temperature indications, providing an indication of the temperature of the refrigerant, (ii) comparing the one or more refrigerant temperature indications with one or more associated predetermined threshold values, and (iii) based on the outcome of the comparison under (ii) selecting one of an automated warm cooling down procedure of the cryogenic heat exchanger and an automated cold cooling down procedure of the cryogenic heat exchanger.