Method for freeze protection
AssigneeThermo King Corporation
InventorsUlrich Fink, Alan D. Gustafson
Life of this patent
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Abstract
A method for freeze protection for a temperature control system, and a temperature control system for controlling the temperature of a temperature-controlled space at a set point temperature. The method includes monitoring a discharge air temperature, monitoring a return air temperature, setting a target temperature to equal the set point temperature, controlling the return air temperature at the target temperature, and adjusting the target temperature based on the return air temperature when the discharge air temperature drops to one of at or below freezing.
Claims23
A method for freeze protection for a temperature control system, the temperature control system for controlling the temperature of a temperature-controlled space at a user-selected set point temperature, the method comprising:
- monitoring a discharge air temperature;
- monitoring a return air temperature;
- with a controller, setting a return air target temperature to equal the user-selected set point temperature;
- controlling the return air temperature to be approximately equal to the return air target temperature;
- and
- adjusting the return air target temperature when the discharge air temperature drops to one of at or below freezing, wherein the controller determines an adjusted value for the return air target temperature during the adjusting step that is dependent on a measured value of the return air temperature.
A temperature control system for controlling the temperature of a temperature-controlled space at a user-selected set point temperature, the temperature control system comprising:
- a heat exchange assembly for heating the refrigerated space in a heat mode and cooling the refrigerated space in a cool mode, the heat exchange assembly positioned in communication with air in the refrigerated space by way of a return air flow path and a discharge air flow path;
- a return air temperature sensor positioned in the return air flow path for sensing a return air temperature;
- a discharge air temperature sensor positioned in the discharge air flow path for sensing a discharge air temperature;
- a controller for controlling the return air temperature to be approximately equal to a return air target temperature wherein the return air target temperature is initially set to equal the user-selected set point temperature, the controller being programmed to adjust the return air target temperature when the discharge air temperature drops to one of at or below freezing, wherein the controller is programmed to determine an adjusted value for the return air target temperature that is dependent on a measured value of the return air temperature sensed by the return air temperature sensor.
A method for freeze protection for a temperature control system, the temperature control system for controlling the temperature of a temperature-controlled space at a set point temperature, the method comprising:
- monitoring a discharge air temperature;
- monitoring a return air temperature;
- setting a target temperature to equal the set point temperature;
- controlling the return air temperature at the target temperature, including
- cooling the refrigerated space in a cool mode, and
- heating the refrigerated space in a heat mode;
- and
- adjusting the target temperature based on the return air temperature when the discharge air temperature drops to one of at or below freezing, including
- setting a timer to count the duration of the cool mode and lowering the target temperature when the timer reaches a predetermined time, and
- incrementing a transition counter when the temperature control system switches between the cool mode and the heat mode and lowering the target temperature when the transition counter reaches a predetermined count.
Dependencies are inferred from the claim text.