Chest-type freezers have an important advantage. Since cold air is heavier than warm air, it has more of a tendency to stay in the bottom of the freezer and not “spill out” each time the door (lid) is opened. Consequently, a lot of moisture does not accumulate in the cabinet. (See fig. 10)
Due to this fact, chest-type units are manually defrosted as defrosting is usually not needed more than once or twice a year. To defrost the freezer, remove the food from the freezer and wrap it in newspaper to keep it from thawing. Unplug the unit or engage the defrost switch (usually located in the lid or rim of the cabinet). The water from defrosting runs out through a drain in the bottom of the cabinet. (With a garden hose attached, water could drain directly to the outside of the house.)
Figures 14 and 15 show different types of evaporators used in frost-free, cycle-defrost, or manual-defrost refrigerators. Usually, frost-free refrigerators and residential freezers have fan-forced evaporators and condensers while manual-defrost and cycle-defrost units use static-type (non-fan-forced) evaporators and condensers.