Systems, methods, and apparatus for preventing condensation in refrigerated display cases

Abstract

Systems, methods, and apparatuses are provided for preventing condensation in refrigerated display cases. A display case can be provided with one or more heater circuits and one or more sensors communicably coupled thereto. The sensor can sense ambient humidity levels, ambient temperature levels, and surface temperature levels. In certain embodiments, dewpoint temperatures may be calculated based on the ambient humidity and temperature levels provided by the sensor. The sensed ambient humidity level, temperature level, surface temperature, or calculated dewpoint can be compared to preset trigger levels and at least one of the heater circuits can be activated if the preset trigger level is violated. Activation of the heater circuit can be for a predetermined amount or percentage of time or at a predetermined voltage level based on the sensed or calculated level or the amount the sensed or calculated level is over the preset trigger level.

What is claimed is: 
     
         1 . A method for controlling a heating system in a refrigerated display case comprising the steps of:
 providing a refrigerated display case comprising a secondary heater circuit and a sensor communicably coupled to the secondary heater circuit;   receiving an ambient humidity level from the sensor;   determining if the ambient humidity level is greater than a preset humidity level; and   activating the secondary heater circuit based on the determination that the ambient humidity level is greater than the preset humidity level.   
     
     
         2 . The method of  claim 1 , further comprising the steps of:
 providing a primary heater circuit for the refrigerated display case; and   operating the primary heater circuit at a constant power level.   
     
     
         3 . The method of  claim 2 , wherein the refrigerated display case comprises:
 a plurality of walls defining at least one cavity;   an aperture disposed though a first of the plurality of the walls to provide access to the cavity; and   a door comprising a door frame along the first wall and disposed about at least a portion of the aperture,   wherein at least a portion of the primary heater circuit and the secondary heater circuit are disposed within the door frame.   
     
     
         4 . The method of  claim 2 , wherein the refrigerated display case comprises:
 a plurality of side walls, and a floor coupled to one or more of the side walls;   said side walls and floor defining a cavity within the display case, wherein at least one of the side walls include a portion that is at least partially transparent and wherein at least one other of the side walls includes a top portion comprising a metallic panel;   said side walls defining an opening along a top of the side walls to access the cavity from an area above the side walls;   wherein the at least one of the side walls comprises a metallic panel and wherein the primary heater circuit and the secondary heater circuit are in thermal communication with at least a portion of the metallic panel, said primary heater circuit being electrically isolated from said secondary heater circuit.   
     
     
         5 . The method of  claim 1 , wherein activating the secondary heater circuit comprises activating the secondary heater circuit for a predetermined amount of time, wherein the predetermined amount of time the secondary heater circuit is activated is based on the ambient humidity level. 
     
     
         6 . The method of  claim 5 , wherein the predetermined amount of time the secondary heater circuit is activated increases as the ambient humidity level from the sensor increases. 
     
     
         7 . The method of  claim 1 , further comprises the steps of:
 determining, based on the received ambient humidity level, a first voltage level setting for the secondary heater circuit, wherein the first voltage level setting is less than a full voltage level; and   wherein activating the secondary heater circuit comprises activating the secondary heater circuit at the first voltage level based on the determination that the ambient humidity level is greater than the preset humidity level.   
     
     
         8 . The method of  claim 7 , wherein the full voltage level is selected from the group consisting of 120 volts, 230 volts, 240 volts, and 400 volts. 
     
     
         9 . A method for controlling a heating system in a refrigerated display case comprising the steps of:
 providing a refrigerated display case comprising:
 a primary heater circuit; 
 a secondary heater circuit; and 
 a sensor communicably coupled to the secondary heater circuit; 
   operating the primary heater circuit at a constant power level;   receiving an ambient temperature level from the sensor;   determining if the ambient temperature level is greater than a preset temperature level; and   activating the secondary heater circuit based on the determination that the ambient temperature level is greater than the preset temperature level.   
     
     
         10 . The method of  claim 9 , wherein activating the secondary heater circuit comprises activating the secondary heater circuit for a predetermined amount of time, wherein the predetermined amount of time the secondary heater circuit is activated is based on the ambient temperature level. 
     
     
         11 . The method of  claim 10 , wherein the predetermined amount of time the secondary heater circuit is activated increases as the ambient humidity level from the sensor increases. 
     
     
         12 . The method of  claim 9 , further comprises the steps of:
 determining, based on the received ambient temperature level, a first voltage level setting for the secondary heater circuit, wherein the first voltage level setting is less than a full voltage level; and   wherein activating the secondary heater circuit comprises activating the secondary heater circuit at the first voltage level based on the determination that the ambient temperature level is greater than the preset temperature level.   
     
     
         13 . A method for controlling a heating system in a refrigerated display case comprising the steps of:
 providing a refrigerated display case comprising:
 a primary heater circuit; 
 a secondary heater circuit; and 
 a dewpoint sensor communicably coupled to the secondary heater circuit and disposed outside of the display case; 
   operating the primary heater circuit at a constant power level;   receiving an ambient humidity level from the dewpoint sensor;   receiving an ambient temperature from the dewpoint sensor;   calculating a dewpoint temperature;   determining if the calculated dewpoint temperature is greater than a preset dewpoint temperature; and   activating the secondary heater circuit based on the determination that the calculated dewpoint temperature is greater than the preset dewpoint temperature.   
     
     
         14 . The method of  claim 13 , wherein activating the secondary heater circuit comprises activating the secondary heater circuit for a predetermined amount of time, wherein the predetermined amount of time the secondary heater circuit is activated is based on the calculated dewpoint temperature. 
     
     
         15 . The method of  claim 14 , wherein the predetermined amount of time the secondary heater circuit is activated increases as the calculated dewpoint temperature increases. 
     
     
         16 . The method of  claim 13 , further comprises the steps of:
 determining, based on the calculated dewpoint temperature, a first voltage level setting for the secondary heater circuit, wherein the first voltage level setting is less than a full voltage level; and   wherein activating the secondary heater circuit comprises activating the secondary heater circuit at the first voltage level based on the determination that the calculated dewpoint temperature is greater than the preset dewpoint temperature.   
     
     
         17 . A method for controlling a heating system in a refrigerated display case comprising the steps of:
 providing a refrigerated display case comprising:
 a display case comprising a plurality of walls defining at least one cavity; 
 an aperture disposed though a first of the plurality of the walls to provide access to the cavity from an exterior of the display case; 
 a door frame along the first wall and disposed about at least a portion of the aperture; 
 at least one temperature sensor disposed along an outer exposed surface of the door frame; 
 a heater circuit disposed within the door frame; and 
 a dewpoint sensor communicably coupled to the heater circuit; 
   receiving at least one surface temperature reading from the at least one temperature sensor;   sensing an ambient temperature at the dewpoint sensor;   sensing an ambient relative humidity at the dewpoint sensor;   calculating a dewpoint temperature based on the sensed ambient temperature and sensed ambient relative humidity;   determining if the surface temperature reading is less than the calculated dewpoint temperature; and   activating the heater circuit based on the determination that the surface temperature reading is less than the calculated dewpoint temperature.   
     
     
         18 . The method of  claim 17 , wherein the step of receiving at least one surface temperature reading comprises receiving a plurality of surface temperature readings from a plurality of temperature sensors disposed along the outer exposed surface of the door frame, the method further comprising:
 determining a lowest surface temperature reading from the received plurality of surface temperature readings;   determining if the lowest surface temperature reading is less than the calculated dewpoint temperature; and   activating the heater circuit based on the determination that the lowest surface temperature reading is less than the calculated dewpoint temperature.   
     
     
         19 . The method of  claim 17 , wherein the refrigerated display case further comprises a data storage device communicably coupled to a controller and the at least one temperature sensor, the data storage device configured to store control information for the heater circuit, the control information capable of being used to generate a chart of operational parameters for the heater circuit to educate the customer on the effect of humidity on energy consumption by the heater circuit. 
     
     
         20 . The method of  claim 17 , wherein the refrigerated display unit further comprises an alarm communicably coupled to a controller controlling the heater circuit, wherein the controller evaluates the energy consumed by the heater circuit and initiates the alarm if the energy consumed by the heater circuit is greater than a predetermined level. 
     
     
         21 . The method of  claim 17 , wherein the refrigerated display unit further comprises an alarm communicably coupled to a controller controlling the heater circuit, wherein the controller evaluates the received surface temperature reading to determine if the surface temperature remains below the calculated dewpoint temperature for a predetermined amount of time after activating the heater circuit and wherein the controller initiates the alarm based on a positive determination that the surface temperature remains below the calculated dewpoint temperature for a predetermined amount of time after activating the heater circuit.