fig1 - 4 illustrate various models of refrigerators ( or refrigerated appliances such as a freezer , wine chiller , etc . ( generally referred to herein as a refrigerated appliance )) 100 , and although the various models may have different features , for purposes of the present disclosure , many of these detailed features are not pertinent . thus , these various types of refrigerated appliances all commonly include at least one cooled storage compartment , and when describing a refrigerator , the appliance preferably includes first and second cooled storage compartments generally referred to as a fresh food storage compartment and a freezer compartment . therefore , like reference numerals will be used to identify like components throughout fig1 - 4 for ease of identification . more particularly , the refrigerated appliance or refrigerator 100 has a cabinet 102 that includes an outer case , shell , or housing 104 having a top wall 106 , bottom wall 108 , sidewalls 110 , 112 , and a rear or back wall 114 . typically , the housing 104 is formed of a thin metal material and the walls are thermally insulated . at least one dividing wall 120 separates the refrigerator into a fresh food storage compartment 122 and a freezer compartment 124 . these compartments 122 , 124 can be situated in a bottom mount arrangement where the freezer is on the bottom and the fresh food is on the top ( fig1 ), or a top mount where the freezer is on top and the fresh food compartment is on the bottom ( fig2 ), a side - by - side model as shown in fig3 , or more recent vintage model of a fresh food compartment 122 having dual doors disposed on top of a freezer compartment 124 as shown in fig4 . whereas the embodiments of fig1 - 3 each include a fresh food storage compartment door 132 and a freezer compartment door 134 , the model of fig4 includes a pair of fresh food storage compartment doors 136 , 138 that are hinged adjacent the sidewalls 110 , 112 and the freezer compartment is not a hinged door but a slidable drawer 140 . as is well understood in the art , the fresh food storage compartment 122 and the freezer compartment 124 are separated by the dividing wall 120 and closed off from the ambient environment via the drawer or doors . typically the outer surface of the housing 104 is a planar metal surface 150 that is selectively engaged or sealed by gaskets 152 , 154 that are provided on perimeter regions of the respective doors or drawer . the housing surfaces 150 selectively engaged by the gaskets are thus exposed to the cooler temperatures of the fresh food storage compartment 122 and the freezer compartment 124 along one edge or region and to ambient air along an adjacent edge or region . when the cooled , refrigerated air impinges on any exposed metal within the refrigerated space , conducts through the cross - section of the gasket , or leaks past the gasket / seal area , the thermally conductive metal surface tends to fall below the dew point of the surrounding atmosphere . these regions , therefore , are prone to potential accumulation of fog , moisture , condensation , etc . that can form water droplets . the representative encircled regions in fig1 - 4 are such areas where condensation may accumulate and could lead to water dripping on the floor below the refrigerator . to overcome this problem , anti - sweat heaters are employed in these regions and mounted on an interior surface of the metal housing . these anti - sweat heaters are typically located in the mullion regions , i . e ., incorporated along the edges of the door , case flange , mullions , etc . where the gasket typically bears against the housing . commonly - owned u . s . pat . nos . 4 , 332 , 142 and 4 , 822 , 117 show and describe such anti - sweat or mullion heaters that are employed in prior refrigerators to address the moisture issue . the mullion bars typically have insulation generally uniformly provided along an interior surface of the metal housing , i . e ., behind the metal surface , in order to limit thermal conduction from the cooler fresh food and freezer compartments . as shown in fig5 , a preselected region or location 200 on the housing 104 is preferably defined . in a preferred arrangement , the preselected region 200 is formed as a depressed section , i . e ., a region where the fog or sweat may coalesce , and behind the mullion the preselected region preferably has less insulation than adjacent regions of the insulated mullion . as a result , this preselected region will tend to be cooler than adjacent regions or areas of the mullion bar because of the reduced insulation . moreover , the depressed section acts as a collector for the fog or moisture that may develop in this location so that any moisture that does develop can be reliably considered as the location of incipient formation of moisture or a bead of water on the refrigerated appliance . with continued reference to fig5 , a first temperature sensor 210 may be located along the mullion face that senses the dry bulb temperature or ambient temperature around the refrigerator . the temperature data is provided to controller 220 which may be an on - board controller on the refrigerator or may be the controller associated with the home energy manager or home energy gateway ( hem / heg ). this ambient air dry - bulb temperature information , along with humidity data from humidity sensor 230 , allows the controller 220 to calculate the dew point temperature of the ambient environment in a manner known in the art , i . e ., a transfer function . thus , the sensors 210 , 230 , which may be located in separate locations , or may be part of a single module , provide psychometric data to the controller 220 . in addition , a second temperature sensor 240 is provided in the preselected region 200 and is operative to detect a surface temperature of the preselected region of the housing . the second temperature sensor 240 likewise conveys temperature data regarding the preselected region or surface of the metal housing to the controller 220 . in addition to calculating the dew point temperature of the ambient environment , the controller 220 undertakes a comparison of the preselected region surface temperature data received from the second temperature sensor 240 with the dew point temperature calculated from the psychometric data received from the first temperature sensor 210 and the humidity sensor 230 to determine whether to activate the anti - sweat heaters . typically , a safety factor is incorporated into the comparison . for example , if the dew point temperature is calculated to be 74 ° f ., it is understood that if the surface temperature of the preselected region reaches this temperature , then sweat or condensate will develop . thus , a safety factor of a predetermined amount greater than the calculated dew point temperature , one degree ( 1 °), for example , could be used so that if the controller receives data from the second temperature sensor 240 that the surface temperature in the preselected region is 75 ° or less , then the anti - sweat heater ( s ) is enabled to raise the temperature of the metal housing further away from the dew point temperature . likewise , once the temperature of the preselected region 200 is increased a predetermined amount above the calculated dew point temperature , e . g ., two degrees ( 2 ° f . ), the anti - sweat heater may then be disabled via a signal received from the controller 220 to the appliance . of course , one skilled in the art will recognize that these values are exemplary only and should not be deemed to limit the present disclosure . the temperature sensor 210 and humidity sensor 230 may be part of a module or a combination temperature / humidistat as is commercially available in the industry . these transducers provide the desired electrical data to the controller 220 . similarly , the second temperature sensor 240 may be an electronic transducer such as a thermistor , thermocouple , resistance temperature device , or any other temperature measuring device that supplies the temperature data to the controller . the second temperature sensor 240 is placed in the door area between the fresh food and freezer compartments in a region 200 where moisture is most likely to accumulate due to condensation . to assure that this is the incipient moisture forming region , the insulation may be reduced in the preselected region 200 . thus , the anti - sweat heater is already located in this condensate - prone area and specifying a location by reducing insulation in this region allows the condensate issue to be addressed before the moisture coalesces and becomes a potential problem . thus , moisture at this specific location disappears due to a rise in temperature when the anti - sweat heater is activated . the sensors 210 , 230 or single module that monitor the ambient air dry - bulb temperature and humidity may be located at an alternative location as long as the temperature and humidity conditions in the room are effectively determined . for example , the sensors may be located at an inlet to the condenser where return air is coming from the room to the refrigerated appliance . alternatively , the module may be located along the front grill . although these are preferred locations , one skilled in the art will appreciate that still other locations that effectively monitor the ambient conditions may be used without departing from the scope and intent of the present disclosure . the software and the microprocessor controller 220 may use a set point to assure that sweat is not formed . this allows the heater to cycle on and off with a hysteretic control , e . g ., if the dew point 74 ° f ., then the controller may establish a set point of 76 ° f .+/− 1 ° f . as the moisture disappears due to a rise in temperature , the anti - sweat heaters can be again disabled to shed load or energy . this process may be repeated throughout the demand response event . imposing a void in the insulation behind the mullion bar or another specific region of the housing , and likewise strategically locating the temperature sensor on the housing surface at that location , is also desired . as a result , the strategic location on the mullion bar will become the first location where sweat would likely form . likewise , one could experimentally determine a different strategic location on the mullion bar or other external surface where the temperatures will be minimal due to the inherent design and locate the sensors at this location . it will be appreciated that sensing the moisture or sweat early in the process can be helpful in preventing formation of beads of water . thus , positioning the sensor in an area where the anti - sweat heater is located and where those skilled in the art expect sweat to form in the absence of the heater being on would be advantageous . as a result of using the concepts of the present disclosure , one demand supply response to a peak pricing period can now be to turn off the mullion heaters since the inactivated anti - sweat heaters can be selectively turned on once the sweat or moisture is detected . it is also contemplated that if the energy savings period is still active , another response is to reduce the voltage or alter the operation of the anti - sweat heaters , e . g ., the voltage can be pulsed or proportionally controlled , etc . the disclosure has been described with reference to the preferred embodiments . obviously , modifications and alterations will occur to others upon reading and understanding the preceding detailed description . it is intended that the invention be construed as including all such modifications and alterations .