Abstract Long-period food storage vertical freezers are small cooling capacity appliances usually working with HC. The particular system architecture and the small thermal load allow the use of natural draft wires and tube heat exchangers with large heat transfer areas. Despite of the good performance achieved, high refrigerant charges with respect to the cooling capacity of the system are required, due to the high volumes of the heat exchangers. In this work an experimental analysis of an apparatus with a typical arrangement of the heat exchangers and capillary tube is presented. The system was first designed according to the current standards to reach high performances. Then the working conditions of the system were completely characterized experimentally in the whole range of refrigerant charges compatible with steady operation. Some general conclusions about the systems with this kind of architecture are furnished about the determination of the thermodynamic optimum operating condition and, hence, the determination of the optimum charge.