| 摘要 |
A refrigeration system contains a common compressor supplying refrigerant to a plurality of evaporators that are refrigerated and defrosted independently of one another. Individual refrigeration/defrost controls are provided in solid state form for the respective evaporators, and the individual controls are connected with a master control that prevents all of the evaporators from being defrosted at one time. The master control includes a digital time clock providing time signals to each of the individual refrigeration/defrost controls, and each of the individual controls can initiate a defrost operation for its respective evaporator on either a timed or demand basis. The master control includes a scanner that interrogates the individual controls in a special manner to initiate defrosting of the units in order of priority. The master control permits an individual defrost control for a selected evaporator to be tested in a timed mode by substantially increasing the speed of the time clock while operation of the remaining defrost controls is inhibited.
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