Water heaters with multiple heating elements

Abstract

A water heating unit includes at least one electrical heating element, a relay configured to allow electrical current to flow through the at least one electrical heating element when the relay is in a closed state and to prevent electrical current from flowing through the at least one electrical heating element when the relay is in an open state, and a controller in communication with the relay to switch the relay between the closed state and the open state. The controller is configured to perform at least one of: maintaining the relay in the open state upon receiving a signal indicating that another water heating unit of the plurality of water heating units is in a heating mode and, upon placing the relay in the closed state, transmitting a signal in order to prevent another water heating unit from entering into a heating mode.

What is claimed is: 
     
         1 . A water heating unit for a water heating system having a plurality of water heating units connected to a single electrical circuit, comprising:
 at least one electrical heating element;   a relay configured to allow electrical current to flow through the at least one electrical heating element when the relay is in a closed state and to prevent electrical current from flowing through the at least one electrical heating element when the relay is in an open state; and   a controller in communication with the relay to switch the relay between the closed state and the open state, wherein the controller is configured to perform at least one of:
 maintaining the relay in the open state upon receiving a signal indicating that another water heating unit of the plurality of water heating units is in a heating mode; and 
 upon placing the relay in the closed state, transmitting a signal in order to prevent another water heating unit of the plurality of water heating units from entering into a heating mode. 
   
     
     
         2 . The water heating unit of  claim 1 , further comprising a current sensing device, wherein said signal indicating that another water heating unit of the plurality of water heating units is in a heating mode is received by the controller from the current sensing device. 
     
     
         3 . The water heating unit of  claim 2 , further comprising a plurality of wiring terminals, the plurality of wiring terminals comprising:
 a first wiring terminal by which the water heating unit is configured to connect to a first electrical phase of the electrical circuit;   a second wiring terminal by which the water heating unit is configured to connect to a second electrical phase of the electrical circuit; and   a third wiring terminal by which the water heating unit is configured to be electrically connected to the another water heating unit of the plurality of water heating units,   wherein the third wiring terminal and one of the first and second wiring terminals are electrically connected and wherein the current sensing device is arranged to detect a flow of current between the third wiring terminal and the one of the first and second wiring terminals.   
     
     
         4 . The water heating unit of  claim 1 , further comprising a current interrupt device, wherein said signal to prevent another water heating unit of the plurality of water heating from entering into a heating mode is transmitted by the controller to the current interrupt device. 
     
     
         5 . The water heating unit of  claim 4 , further comprising a plurality of wiring terminals, the plurality of wiring terminals comprising:
 a first wiring terminal by which the water heating unit is configured to connect to a first electrical phase of the electrical circuit;   a second wiring terminal by which the water heating unit is configured to connect to a second electrical phase of the electrical circuit; and   a third wiring terminal by which the water heating unit is configured to be electrically connected to the another water heating unit of the plurality of water heating units,   wherein the third wiring terminal and one of the first and second wiring terminals are electrically connected to the current interrupt device such that current is prevented from flowing between the third wiring terminal and the one of the first and second wiring terminals when said signal is transmitted by the controller to the current interrupt device.   
     
     
         6 . The water heating unit of  claim 1 , wherein the controller is in wired or wireless communication with a controller of another water heating unit of the plurality of water heating units in order to receive said signal indicating that another water heating unit of the plurality of water heating units is in a heating mode or to transmit said signal to prevent another water heating unit of the plurality of water heating units from entering into a heating mode. 
     
     
         7 . A water heating unit for a water heating system having a plurality of water heating units connected to a single electrical circuit, comprising:
 at least one electrical heating element;   a relay configured to allow electrical current to flow through the at least one electrical heating element when the relay is in a closed state and to prevent electrical current from flowing through the at least one electrical heating element when the relay is in an open state; and   a plurality of wiring terminals comprising:
 a first wiring terminal by which the water heating unit is configured to connect to a first electrical phase of the electrical circuit; 
 a second wiring terminal by which the water heating unit is configured to connect to a second electrical phase of the electrical circuit; and 
 a third wiring terminal by which the water heating unit is configured to be electrically connected to another water heating unit of the plurality of water heating units. 
   
     
     
         8 . The water heating unit of  claim 7 , wherein current from the electrical circuit is directed to flow between the third wiring terminal and one of the first and the second wiring terminals without flowing through the at least one electrical heating element when said another water heating unit is operating in a heating mode. 
     
     
         9 . The water heating unit of  claim 8 , further comprising a current sensor arranged to detect the flow of current between the third wiring terminal and the one of the first and the second wiring terminals. 
     
     
         10 . The water heating unit of  claim 8 , further comprising a switch arranged between the third wiring terminal and the one of the first and the second wiring terminal such that current is only able to flow between the third wiring terminal and the one of the first and the second wiring terminal when the switch is in a closed state. 
     
     
         11 . The water heating unit of  claim 10 , wherein the switch and the relay are a single component, wherein the switch is in the closed state when the relay is in the open state and wherein the switch is not in the closed state when the relay is in the closed state. 
     
     
         12 . A water heating system comprising:
 a first water heating unit connected to an electrical circuit to receive electrical power therefrom, the first water heating unit comprising at least one electric heating element; and   a second water heating unit connected to the electrical circuit to receive electrical power therefrom, the second water heating unit comprising at least one electric heating element;   wherein a flow of electric current through the at least one electric heating element of the second water heating unit is prevented when the at least one electric heating element of the first water heating unit is in an operational state.   
     
     
         13 . The water heating system of  claim 12 , further comprising wiring extending between the first and second water heating units to provide electrical power from the electrical circuit to one of the first and second water heating units. 
     
     
         14 . The water heating system of  claim 12 , wherein the first and second water heating units are fluidly connected in series such that water is directed from the second water heating unit to the first water heating unit. 
     
     
         15 . The water heating system of  claim 12 , wherein the first water heating unit further comprises a first controller, wherein the second water heating unit further comprises a second controller, and wherein the first controller is in communication with the second controller to prevent the flow of electric current through the at least one electric heating element of the second water heating unit when the at least one electric heating element of the first water heating unit is in an operational state. 
     
     
         16 . The water heating system of  claim 12 , wherein the second water heating unit further comprises a relay connected electrically in series with at least one electric heating element, the relay being configured to allow current flow through the at least one electric heating element when the relay is in a closed state and to prevent current flow through the at least one electric heating element when the relay is in an open state, wherein the relay is able to transition between the open state and the closed state independently from the at least one electric heating element of the first water heating unit being in an operational state.