In general, a refrigerator which maintains a low temperature is cheapest to operate. The refrigerator should be kept full of ice exposed so that it comes in contact with the air circulating within the refrigerator. The refrigerator which does not hold a low temperature will not only use more ice, but be less efficient in keeping food.
117. The Construction of Refrigerators. The construction of a refrigerator should be such that it may be kept clean. There should be no cracks and corners to catch dirt and make breeding places for molds and bacteria.
118. Lining Refrigerators. The best linings for refrigerators are porcelain, porcelain enamel, or glass for the more expensive ones, and galvanized iron or zinc for the less expensive ones. The shelves are usually made of heavy wire or of bent metal. The latter should be constructed so that they can be thoroly cleaned.
Fig. 57. Diagram showing circulation
in a refrigerator.
119. Insulation of Refrigerators. The more complete the insulation of a refrigerator, the more efficient it will be. Different kinds of material, as well as dead-air spaces, are used for this purpose. The top, as well as the bottom, must be insulated. Materials which are likely to crack or settle down and leave uninsulated spaces should not be used. Because sawdust settles, it is not satisfactory. There are felts, papers and other materials which are good. If the refrigerator is not water-tight and the insulating material absorbs water, it will lose its efficiency for insulation.
120. Circulation in Refrigerators. The better the circulation in a refrigerator, the more efficient it will be. The air in the refrigerator must be free to circulate over the ice. As it cools, it should drop to the bottom of the ice box. When it warms, it will rise and be displaced by fresh falling cold air. It should be free to rise to the top of the refrigerator and from there pass into the ice chamber and over the ice to be cooled again (Fig. 57). When the ice always melts unevenly and in the same relative place—that is, more on the side or bottom—it indicates poor circulation in the refrigerator.
121. Drip from Melting Ice. There should be a pan under the ice to catch the drip from the melting ice, and a drip pipe to carry it out of the refrigerator (Fig. 57). If the drip pipe passes into a pan set under the refrigerator, the pan should be emptied so that it will not overflow. The water in the pan should not be allowed to become stagnant.
If this pipe passes to a drain, it should not be attached to the drain, but drip into it. The small amount of fresh air passing up the drip pipe from the room is advantageous. Because some air does flow thru here, the drip pipe and the drain pipe must be clean and free from gases and odors.