Cold Wall Outdoor Ice Merchandisers are a lower cost option than having an Auto-Defrost model. They also offer slightly lower utility costs to operate. In exchange, these unitdo require the operator to manually defrost the unit from time to time. These units work by having the refrigerant pass through a series of copper tubes whichrun through the walls of the unit.
These tubes create an actual cold wall around the inside of the unit which cools the entire freezer from the outside in. The result of this can leave the chamber with non-uniform temperature where the walls of the unit are cooler than the middle. The cold wall also results in condensation that can freeze on the walls of the unit, which must be manually defrosted and drained.