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Anticipating dual set-point bistable thermostat

  • US 4,901,917 A
  • Filed: 03/21/1989
  • Issued: 02/20/1990
  • Est. Priority Date: 03/21/1989
  • Status: Expired due to Fees
First Claim
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1. A method of predicting the time required to change the temperature of a zone from a setback temperature to a normal temperature, in a transition from a standby mode to a normal mode, used in a controller for a space conditioning system to modify the temperature of a zone within a structure wherein the system includes a thermal unit which is a bistable or on-off heat source, means for selectively transferring heat between the thermal unit and said zone with a normal mode and a setback mode, wherein the controller includes a system clock and a temperature sensor which measures the temperature in said zone, means providing system operating parameters comprising a normal temperature setting, a setback temperature setting, a clock normal setting and a clock setback setting, wherein during the normal mode the temperature of the zone is to be maintained in a range around the normal temperature at times beginning with the clock normal setting and ending with the clock setback setting, and wherein during the standby mode the temperature of the zone is to be maintained in a range around the setback temperature at times beginning with the clock setback setting and ending with the clock normal setting, with said ranges established by "temperature on" and "temperature off" set-points which control turning the thermal unit on and off, a clock normal offset being used as a time for changing operation to the normal mode in an attempt for the temperature of said zone to reach the normal temperature at the time designated by the clock normal setting;

  • said method comprising the steps;

    measuring "clock dwell begin" and "clock dwell end" times indicated by the clock when the "temperature on" and "temperature off" setpoints respectively occur as determined by comparison to readings from said temperature sensor during the standby mode;

    calculating a prediction of the amount of time required to adjust the temperature of the zone to the normal temperature using "clock dwell begin" and "clock dwell end" times as determined by said measuring step during the offset mode and using that prediction to set the clock normal offset time for the system to commence operation in the normal mode;

    wherein calculating a prediction during the standby mode comprises, following each occurence of "clock dwell begin" followed by "clock dwell end", calculating clock dwell time by subtracting the "clock dwell end" time from the "clock dwell begin" time and using the resulting value to obtain a clock dwell factor which indicates the time required to heat the zone from the "temperature on" setpoint to the "temperature off" set-point, forming a temperature ratio as the range between the normal and setback temperatures divided by the range between the "temperature on" set-point to the "temperature off" set-point, forming a product of the temperature ratio multiplied by the clock dwell factor, subtracting that product from the clock normal setting, and using the result in the prediction to set the clock normal offset time.

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