US Patent 9291383 Demand response mullion sweat protection

An appliance such as a refrigerator receives a demand response signal indicating a peak demand period and operates the refrigerator in an energy savings mode by disabling an anti-sweat heater. A sensor on an external surface of the refrigerator enables the anti-sweat heater during the peak demand period if moisture is detected by the sensor. A preselected location can be defined where incipient moisture would form such as reducing the amount of insulation in this location. By forming a depression in the location and using an impedance-type sensor, moisture can be easily detected. The sensor signal is sent to the controller which then activates the anti-sweat heater to remove the moisture.