Abstract:
A cover plate for access to the thermostat of an electric water heater associated with a resistive heating element to control the operation thereof is described. The cover plate has mounted on a rear face thereof a remotely controllable switching circuit to control the power being fed to the thermostat and thereby remotely controlling the load. The cover plate with the remotely controllable switching circuit is also provided as a retrofit to convert existing electric water heaters to intelligent remotely controllable water heaters. The remote controller may be a utility, a utility provider or a remote control device. The remote controlled switching circuit is mounted concealed in the access cavity behind the cover plate.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a cover plate for access to the thermostat of an electric water heater and more particularly to a cover plate equipped with a remotely controllable switching circuit to control the operation of the electric resistive heating element associated with the thermostat. The cover plate with the switching circuit is further utilized as a retrofit to convert an existing water heater to an intelligent water heater. 
       BACKGROUND OF THE INVENTION 
       [0002]    Electrical water heaters of the domestic type comprise a tank in which is mounted two or sometimes three resistive heating elements disposed at different levels to heat water. The resistive heating elements are controlled by respective thermostats which have set point temperature values whereby to control the temperature of the water inside the tank at different levels. The thermostats have a control portion and a switching portion to switch the resistive heating elements on and off by allowing and cutting the power supply thereto depending on the temperature of the water in relation to the set point temperature of the thermostats. The power supply wiring is usually through a control box mounted on top of the water heater or through a port in the outer wall of the casing with the wiring extending along the tank wall to the thermostats. The wiring is usually held in place by the foam insulation which is injected between the tank and the outer casing mounted spaced about the tank. Foam dams prevent the injected insulating foam material from propagating into the space surrounding the thermostats and the resistive heating elements whereby to form an access space for servicing and adjustment of the set point temperature of the thermostat. The thermostat is provided with several terminals and the power supply wires are connected to specific ones of these. An access door is removably secured to the outer casing for access to each thermostat and resistive heating element. 
         [0003]    With the advent of more intelligent water heaters it is necessary to mount electronic devices on such water heaters during fabrication and install associated wiring to control the operation of the electric water heater. Although these electronic devices are mounted in housings it is necessary to provide access thereto for trouble shooting and repair. Accordingly, because these housings are exteriorly mounted they are exposed to environmental conditions, such as dust, humidity, water infiltration and are succeptable to physical damage during installation of the water heater. They are also unsightly and occupy space. 
         [0004]    Because intelligent water heaters are progressing quickly, new control devices are continuously being developed by various manufacturers, suppliers and utility providers and the benefit of such more intelligent water heaters can more easily be obtained by the purchasing of a new water heater. Accordingly, existing water heaters cannot benefit from this new technology unless these are modified on site to adapt new control devices thereto. Such modifications are very costly to the consumer or the utility and most will not bear such cost although there is a saving to them by consuming less electricity. Also, depending on the physical location of the water heater the adaption of new control hardware and wiring is often left to the installer to decide how it will be mounted and sometimes resulting in wiring exposed outside the water heating unit and controls being mounted on the outer casing at various locations and sometimes on an adjacent wall of the building structure. 
       SUMMARY OF THE INVENTION 
       [0005]    It is desirable to overcome the above mentioned disadvantages of the prior art electric water heaters. 
         [0006]    It is therefore a feature of the present invention to provide a novel way of mounting a switching circuit and control which is remotely controlled to switch the resistive heating elements on and off. 
         [0007]    It is further feature of the present invention to provide a cover plate for access to the thermostat and resistive heating element and wherein the cover plate is equipped with a remotely controllable switching circuit to control the operation of the electric resistive heating element. 
         [0008]    It is a further feature of the present invention to provide a cover plate for access to the thermostat associated with a resistive heating element and wherein the cover plate has mounted, on an inner face thereof, a remotely controllable switching circuit provided with connection means for easy installation to the power supply wiring of the thermostat. 
         [0009]    A further feature of the present invention is to provide a thermostat cover plate equipped with a remotely controllable switching circuit and which once installed is not visible to the eye as it is integrally mounted inside the access space to the thermostat and associated resistive heating element. 
         [0010]    A still further feature of the present invention is to provide a thermostat cover plate provided with a remotely controllable switching circuit to retrofit an existing electric water heater to convert same to an intelligent water heater by being remotely controlled to regulate the consumption of electrical power. 
         [0011]    Another feature of the present invention is to provide an inexpensive means for a utility or utility providers to convert existing electric water heaters to remotely controllable water heaters and wherein certification is not affected while providing them with a means to regulate power consumption and particularly in power failure situations or peak load sheading. 
         [0012]    Another feature of the present invention is to provide the consumer of an inexpensive way to convert its existing electric water heater to an intelligent water heater to manage the operation of the water heater to thereby consume less electricity during a given time periods and wherein the installation thereof is foolproof and easy. 
         [0013]    According to the above mentioned features, from a broad aspect, the present invention provides a removable cover plate secured to an outer jacket of an electric water heater for access to a thermostat connected to a resistive heating element of an electric water heater. The cover plated has an outer surface and an inner surface and wherein there is mounted on the inner surface switching circuit means having input electrical connection means for connection to power leads and output electrical connections for providing electrical connection to selected terminals to the thermostat. 
         [0014]    The switching circuit means has a control circuit for operating a switch interconnecting the power leads connected to the input electrical connection means to the output electrical connection means. The control circuit is operatively controlled by a remote controller to remotely control the operation of the switch to connect and disconnect power from the power leads to the selected terminals of the thermostat. 
         [0015]    According to a further broad aspect of the present invention there is provided a retrofit cover plate for the replacement of an existing cover plate of an electric water heater for access to a thermostat connected to a resistive heating element of the electric water heater. The cover plate has an outer surface and an inner surface and wherein there is mounted on the inner surface switching circuit means. The switching circuit means has input electrical connection means for connection to power leads disconnected from selected terminals of the thermostat. Output electrical connections means provide electrical connection to the selected terminals. The switching circuit means has a control circuit for operating a switch interconnecting the power leads connected to the input electrical connection means to the output electrical connection means. The control circuit is operatively controlled by a remote controller to remotely control the operation of the switch to connect and disconnect the power from the power leads to the output connection means and thereby control the operation of the resistive heating element by connecting and disconnecting the power leads from the selected terminals of the thermostat. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0016]    A preferred embodiment of the present invention will now be described with reference to the accompanying drawings in which: 
           [0017]      FIG. 1  is a partly exploded view of a two element electric water heater showing the component parts of the resistive heating elements and associated thermostat and cover plate illustrating the retrofit cover plate of the present invention provided with a remotely controllable switching circuit mounted on the back face of the retrofit cover plate; 
           [0018]      FIG. 2  is a conventional wiring diagram of a thermostat and its associated resistive heating element; 
           [0019]      FIG. 3  is a wiring diagram similar to  FIG. 1 , but illustrating the switching circuit of the cover plate connected to the thermostat of a top element of a two element electric water heater; 
           [0020]      FIG. 4  is a wiring diagram similar to  FIG. 3 , but illustrating the switching circuit of the cover plate connected to the bottom thermostat of a two element electric water heater or the middle element of a three element electric water heater; 
           [0021]      FIG. 5  is a wiring diagram similar to  FIG. 3 , but illustrating the switching circuit of the cover plate connected to the top resistive heating element which is connected in series with the bottom resistive heating element for controlling the power provided to both elements; 
           [0022]      FIG. 6A  is a simplified electrical block diagram of a remotely controllable electronic switch; 
           [0023]      FIG. 6B  is a block diagram of an electro-mechanical remotely controllable switch; 
           [0024]      FIG. 7  is a perspective rear view of the cover plate showing a removably mounted switching circuit, and 
           [0025]      FIG. 8  is a perspective front view of the cover plate showing various modifications thereto. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    Referring now to the drawings and more particularly to  FIG. 1 , there is shown generally at  10  a two element electric water heater which is provided with a inner casing  11 , herein a steel tank, in which there is contained water to be heated by two resistive heating elements herein a top resistive heating element  12  and a bottom resistive heating element  13  having the same power ratings. Each resistive heating element has a mounting plate  14  provided with terminals  15  to which is connected wires from an associated thermostat  16  to receive power when the temperature of the water in the tank in the area of the resistive heating elements falls below a set point temperature as set in the associated thermostat  16 . A power supply entrance hole  21  is provided in the outer casing  19  adjacent one of the openings  17 , or surrounding open area of the thermostat and resistive heating element, and is covered by a cover plate  18  removably attached to the outer casing  19  by suitable fastening means such as a screw  20 . As herein illustrated, the top cover plate  18  is to be replaced by a modified retrofit cover plate  25  of the present invention. 
         [0027]      FIG. 2  illustrates the conventional wiring between the thermostat  15  and the top resistive heating element  12  and the interconnection between both resistive heating elements  12  and  13 . Power leads  26  and  27  are connected to power terminals  28  and  29  of the control portion  30  of the thermostat. The switching portion  31  contains a switch, not shown but obvious to a person skilled in the art, which is operated by the control portion depending on the temperature of the water inside the casing  11 . Of course, the bottom resistive heating element  13  may be wired differently wherein a separate power cable may run from a control box usually mounted on top of the water heater, or from a power block conveniently mounted inside the tank next to the top thermostat. 
         [0028]    With reference now to the additional Figures, there is described the present invention of the modified cover plate  25 . As shown in  FIGS. 7 and 8 , the cover plate  25  is fabricated from non-electrically conductive material such as plastic, fibreglass, etc. to permit wireless communication with the control circuit. The cover plate has an outer surface  25 ′ and an inner surface  25 ″. The inner surface  25 ″ is provided witch a switching circuit means mounted in a housing  32  secured thereto. The housing  32  could also be detachably mounted by clamps  33  for ease of replacement. On the outer surface  25 ′ there is herein illustrated an antenna module  34  mounted thereon or moulded therein. In the case where the cover plate is a metal plate, then the antenna would be exteriorly mounted on the cover plate or on top of the water heater with the wiring disposed between the tank  11  and the outer casing  19  in a tube (not shown) disposed in place before injection to the foam insulation. A USB port  35  provides for connection to the circuitry of the switching circuit or other circuitry to extract information or download information in associated circuits. A pilot lamp  36  may also be provided to indicate that the resistive heating element is active or dormant. An LED screen  37  may also be mounted on the front face  25 ′ to provide various information associated with the switching circuit and its controls. As illustrated, the bottom edge of the cover plate  25  is provided with legs  24  which are shaped to be retained captive behind notches  23  cut in the lower edge of the opening  17 . Alternatively, the bottom edge of the cover plate  25  could be fitted with a hinge to hingedly attach the cover plate adjacent the lower edge of the opening  17 . Still further, the cover plate  25  could have a tether lead or wire connected thereto for attachment to the outer casing  19  whereby the retrofit cover plate is attached to the outer casing of the water heater for security purposes. 
         [0029]    With reference to  FIGS. 3 to 5 , there is illustrated various wiring arrangement for controlling the operation of the top or bottom resistive heating element  12  and  13 . In a three element electric water heater the bottom element  13  can be considered as a middle element and the third bottom element could also be fitted with the cover plate of the present invention with its control circuit to also control the operation of the bottom resistive heating element. The switching circuit means is generally indicated by reference numeral  40  and may consist of different types of switching arrangements and associated circuitry, a few of which are generally depicted by  FIGS. 6A and 6B , which illustrates an electronic switch and electro-mechanical switch, respectively. 
         [0030]    As shown in  FIG. 3 , the switching circuit  40  is provided input electrical connection means in the form of terminals  41  for receiving power leads directly from the power cable entering hole  21  in the outer casing of the water heater or power leads disconnected from the power terminals  28  and  29  of the control portion  30  of the thermostat  16 . The switching circuit  40  also has output electrical connection means in the form of terminals  42  for providing electrical connection through wires to selected terminals of a selected one of the thermostat depending if it is controlling to top or bottom resistive heating element or both simultaneously. The selected terminals are from the control portion  30  and the switching portion  31  of the thermostat depending on which of the two resistive heating elements is being controlled. In  FIG. 3  the wiring is for control of the top electrical resistive heating element  12  only, whereas in  FIG. 4  the wiring illustrates the connection for operating the bottom resistive heating element only.  FIG. 5  shows the  220  volts entrance power cable connected directly to the input terminals  41  of the switching circuit  40  and the output terminals  42  are connected to the power terminals  28  and  29  of the thermostat control portion of the top resistive heating element  12 . Of course, instead of screw terminals  41  and  42  these may be constituted by leads to which the connection are made when considering that the switching circuit could be encapsulated in electrically insulating molded material. 
         [0031]      FIG. 6A  is a simplified block diagram of an electronic switch, herein in the form of a triac  45 , operated by a driver circuit  46  which is placed into operation by a control circuit  47 . An AC/DC converter circuit  50  provides the necessary  24  vdc to the circuitry of the control circuit  47  and the driver circuit  46 . The control circuit  47  is remotely controlled, in a wireless manner, by signals received from its antenna  48  from a satellite and emanating from a utility  49  or utility provider. The control circuit  47  may also be controlled by wired connection from an Ethernet network topography or an Internet connectivity or any other communication circuit arrangement obvious to a person skilled in the art. 
         [0032]      FIG. 6B  is a further simplified block diagram of an electro-mechanical switch, herein a relay switch  51  having an energizing circuit  52  controlled by a controller circuit  53 . An AC/DC converter  54  provides the necessary  24  vdc to the circuits. The  220  vac is connected to the terminal  56  of the switch arm  57  which is operated by energizing its coil  58 . The coil  58  is energized by its energizing circuit connection  59  controlled by the control circuit  53  which is itself remotely controlled by the utility or utility provider  49  or other remote controller device. 
         [0033]    It is within the ambit of the present invention to cover any obvious modifications of the embodiments described herein provided such modifications fall within the scope of the appended claims.