Commercial refrigerators have metal cabinets, often in wet areas, and are touched by staff all day. If a live wire chafes against the frame, the cabinet becomes live. With good earthing, that fault current flows through the earth wire and trips the protective device. Without it, the next person to touch the handle while standing on a wet floor may receive a shock.
Earthing must be continuous: from the earth pin on the plug, through the socket and wiring, to an earth electrode in good condition. Earth pits dry out, connections corrode in humid conditions, and extension boards often have weak or missing earth contacts. Never cut off the earth pin or use a two-pin adaptor on refrigeration equipment.
An electrician can measure earth resistance and check that the earth and neutral are not mixed up. Poor earthing also undermines surge protectors and RCCBs, and can cause controllers to behave erratically or show false readings.