Automatic power transfer switching for a water heater

Abstract

A water heater includes power distribution circuitry receiving primary power and secondary power. The water heater includes a heat exchange system including at least one component powered via the primary power and configured to transfer heat between a refrigerant and water. The water heater includes at least one heater operably coupled with and configured to heat at least one portion of the heat exchange system. The water heater includes switching circuitry electrically interposing the power distribution circuitry and the at least one heater to selectively power the at least one heater via the primary power in a first condition of the switching circuitry and via the secondary power when the primary power is unavailable in a second condition of the switching circuitry.

What is claimed is: 
     
         1 . A water heater, comprising:
 power distribution circuitry receiving primary power and secondary power;   a heat exchange system including at least one component powered via the primary power and configured to transfer heat between a refrigerant and water;   at least one heater operably coupled with and configured to heat at least one portion of the heat exchange system; and   switching circuitry electrically interposing the power distribution circuitry and the at least one heater to selectively power the at least one heater via the primary power in a first condition of the switching circuitry and via the secondary power when the primary power is unavailable in a second condition of the switching circuitry.   
     
     
         2 . The water heater of  claim 1 , wherein the switching circuitry includes a first switch electrically activated via the primary power to electrically couple the primary power with the at least one heater. 
     
     
         3 . The water heater of  claim 2 , wherein the switching circuitry includes a second switch electrically activated via the secondary power to electrically couple the secondary power with the at least one heater. 
     
     
         4 . The water heater of  claim 3 , wherein the switching circuitry includes a timer electrically interposing the power distribution circuit and the first switch to delay primary power to the first switch following the primary power being available. 
     
     
         5 . The water heater of  claim 4 , wherein the timer includes a timer coil and a timer normally-open circuit closing in response to primary power energizing the timer coil longer than a threshold time. 
     
     
         6 . The water heater of  claim 5 , wherein the first switch includes a first coil and a first normally-closed circuit opening in response to the first coil being energized following the delay, wherein the timer normally-open circuit provides the primary power to the first coil in response to closing of the timer normally-open circuit. 
     
     
         7 . The water heater of  claim 6 , further comprising a first intermediate node electrically interposing the timer normally-open circuit and the first coil. 
     
     
         8 . The water heater of  claim 6 , wherein the second switch includes a second coil and a second normally-closed circuit opening in response to the second coil being energized in the second condition. 
     
     
         9 . The water heater of  claim 8 , further comprising a second intermediate node electrically interposing the first normally-closed circuit and the second coil. 
     
     
         10 . The water heater of  claim 9 , further comprising
 a controller powered by the primary power and configured to communicate a control signal to operate the at least one heater in the first condition.   
     
     
         11 . The water heater of  claim 10 , further comprising:
 a control relay electrically activated in response to the control signal and electrically interposing the switching circuitry and the at least one heater, wherein the control relay includes a relay coil and a relay normally-closed circuit opening in response to the control signal energizing the relay coil.   
     
     
         12 . The water heater of  claim 10 , wherein the relay normally-closed circuit is closed when the primary power is unavailable. 
     
     
         13 . The water of  claim 12 , further comprising:
 a third intermediate node coupled to the first normally-closed circuit, the second normally-closed circuit, and the relay normally-closed circuit.   
     
     
         14 . The water heater of  claim 1 , where the heat exchange system includes at least one of piping and a heat pump, and wherein the at least one heater includes resistive heating tape coupled to the at least one of the piping, and the heat exchange system to warm the heat exchange system when primary power is unavailable. 
     
     
         15 . The water heater of  claim 1 , wherein the secondary power is back-up power and the switching circuitry limits primary power and back-up power from activating the at least one heater simultaneously. 
     
     
         16 . A back-up power circuit for a heat exchange system of a water heater, comprising:
 power distribution circuitry receiving primary power and back-up power and configured to power the heat exchanger via the primary power;   at least one heater operably coupled with and configured to heat at least one portion of the heat exchanger; and   switching circuitry electrically interposing the power distribution circuitry and the at least one heater to selectively power the at least one heater via the primary power in a first condition of the switching circuitry and via the secondary power when the primary power is unavailable in a second condition of the switching circuitry.   
     
     
         17 . The back-up power circuit of  claim 16 , wherein the switching circuitry includes a first switch electrically activated via the primary power to electrically couple the primary power with the at least one heater. 
     
     
         18 . The back-up power circuit of  claim 17 , wherein the switching circuitry includes a second switch electrically activated via the secondary power to electrically couple the secondary power with the at least one heater. 
     
     
         19 . The back-up power circuit of  claim 18 , wherein the switching circuitry incudes a timer electrically interposing the power distribution circuit and the first switch to delay primary power to the first switch following the primary power being available. 
     
     
         20 . A water heater, comprising:
 power distribution circuitry receiving primary power and secondary power;   a heat exchange system powered via the primary power and configured to transfer heat between a refrigerant and water;   at least one heater operably coupled with and configured to heat at least one portion of the heat exchange system; and   switching circuitry electrically interposing the power distribution circuitry and the at least one heater to selectively power the at least one heater via the primary power in a first condition of the switching circuitry and via the secondary power when the primary power is unavailable in a second condition of the switching circuitry, wherein the switching circuitry limits primary power and back-up power from activating the at least one heater simultaneously.