Process for controlling a heater, in particular a defrost heater for refrigerating plants

• US 4,932,217 A
• Filed: 02/10/1989
• Issued: 06/12/1990
• Est. Priority Date: 02/11/1988
• Status: Expired due to Fees

• Current Assignee: Friedhelm Meyer
• Original Assignee: Friedhelm Meyer
• Inventors: Meyer, Friedhelm
• Primary Examiner(s): Tanner, Harry B.
• Application Number:
  US07/309,827
• Time in Patent Office: 487 Days
• Field of Search: 62/156, 62/155, 62/234, 236/46 R, 236/46 F, 165/12, 165/32, 165/39, 219/492, 219/497, 340/588, 340/589
• US Class Current: 62/156
• CPC Class Codes: F25D 21/002 Defroster control
• CPC Class Codes: F25D 21/08 by electric heating
• CPC Class Codes: G05D 23/1909 whose output amplitude can only take two discrete values
• CPC Class Codes: G05D 23/20 with sensing elements having variation of electric or magnetic properties with change of temperature G05D23/13 takes precedence

Abstract

In the case of a process for controlling a heater, in particular a defrost heater for a refrigerating plant which has a temperature sensor, which is connected to a system for cutting in and cutting out the heater, during the operation of the heater, the temperature of the room to be heated is measured at certain intervals of time, a measured temperature value being stored in each case and compared with the following measured value, whereupon the heater is cut out whenever the following measured value indicates a temperature which is higher by a certain amount than the preceding stored measured value, and the heater is cut in or remains cut in whenever the following measured value indicates a temperature which is lower by a certain amount than the preceding stored measured value.

Claims

1. Process for controlling a defrost heater for a refrigerator plant having a room, with a temperature sensor, which is connected to a system for cutting-in and cutting-out the heater, characterized in that, during the operation of the heater, the temperature of the room to be heated is measured at certain intervals of time, a measured temperature value being stored in each case and compared with a subsequently measured value, whereupon the heater is cut out whenever the subsequently measured value indicates a temperature which is higher by a certain amount than the preceding stored measured value, and wherein the heater is cut in or remains cut in if the subsequently measured value indicates a temperature which is lower by a certain amount than the preceding, stored, measured value.

2. Process according to claim 1, characterized in that, after cutting-in of the heater at a certain cut-in temperature, only after a predetermined temperature has been reached is the further temperature profile tested at predetermined intervals of time and the heater cut in or cut out in dependence thereon.

3. Process according to claim 1 or 2, characterized in that, in the case of a refrigerating plant having an evaporator having a suction side temperature is measured by a pressure sensor provided on the suction side of the refrigerating plant in the evaporator, in order to determine the temperature profile in the evaporator and consequently the residual heat of the defrost heater.