Abstract:
An electric water heater has upper and lower electric resistance type heating elements respectively controlled by a single pole, double throw upper thermostat and a single pole, single throw lower thermostat. The upper and lower thermostats are operatively interconnected by a wiring harness having outer wire end portions that may be connected in various orientations to the terminal block portion of an external junction box to provide the water heater with a variety of heating element operating modes without having to replace either of the thermostats or vary the wiring harness interconnections therebetween. The water heater may thus be advantageously manufactured in a single variant that may be easily and quickly modified in the field to selectively alter the heating element control mode of the water heater.

Description:
BACKGROUND OF THE INVENTION 
     The present invention generally relates to electric heating apparatus and, in a preferred embodiment thereof, more particularly relates to a specially designed dual element electric water heater which is easily field convertible among various heating element control modes without the previous necessity of changing either of the heating element control thermostats or altering the wiring interconnections therebetween. 
     In a common construction thereof a vertically oriented dual element electric water heater has spaced apart upper and lower resistance type electric heating elements which horizontally extend into the interior of the water storage tank portion of the heater. The operation of these upper and lower heating elements is controlled by upper and lower electric thermostats which are respectively associated with the upper and lower heating elements. 
     Various modes of operating the upper and lower heating elements, with either single or three phase electric power supply to the water heater, are typically available. Representatively, these heating element operational modes include (1) single phase simultaneous element operation, in which the two heating elements are simultaneously cycled by their associated thermostats; (2) single phase simultaneous element operation with 4 wire outlet operation, (3) single phase non-simultaneous element operation, in which the two heating elements are independently cycled by their associated thermostats, (4) single phase non-simultaneous element operation with 4 wire outlet operation; (5) single phase non-simultaneous element operation with 3 wire outlet operation; (6) three phase simultaneous element operation; and (7) three phase non-simultaneous element operation. The two heating element-controlling thermostats are typically disposed in openings formed in the jacket insulation structure of the water heater that surrounds its storage tank portion. The electrical wiring that operatively interconnects the thermostats is, for the most part, disposed between the tank and the insulation structure. 
     In the past, in order to provide these seven representative element control modes seven separate embodiments or “variants” of the water heater needed to be built, with each water heater variant having different thermostat wiring configurations and/or combinations of thermostat types. The need to build separate variants to provide all of the representative types of heating element control listed above carries with it several problems, limitations and disadvantages. 
     For example, the construction of the water heater is made more complex since, in essence, it needs to be constructed in seven different ways—each having a different thermostat type combination and/or thermostat wiring interconnection configuration. Additionally, and quite importantly, once the water heater is constructed to provide a predetermined element: control mode, it is not practical or economical to alter this selected control mode. This is due to the fact that to alter the originally built-in element control mode, changes must be made to the thermostat wiring and/or the types of thermostats used must be altered. Because the thermostat interconnection wiring is disposed between the jacket insulation structure and the water heater storage tank portion such wiring is, as a practical matter, inaccessible for such conversion. 
     Accordingly, if a dual element water heater constructed in this conventional manner does not provide the desired heating element control mode, it has to be replaced with another manufactured variant of the water heater that has the desired heating element control mode incorporated therein during its original manufacture. In view of this it can be readily seen that a need exists for a dual element electric water heater which eliminates or at least substantially reduces the above-mentioned problems, limitations and disadvantages typically associated with conventionally constructed dual element electric water heaters. It is to this need that the present invention is directed. 
     SUMMARY OF THE INVENTION 
     In carrying out principles of the present invention, in accordance with a preferred embodiment thereof, a liquid heating apparatus having first and second spaced apart liquid heating elements is provided. The apparatus is representatively in the form of an electric water heater having vertically spaced apart upper and lower electric resistance type heating elements that horizontally extend into the interior of a water storage tank portion of the water heater. First and second electric thermostats are respectively and controllingly associated with the upper and lower heating elements, and wiring, representatively in the form of a wiring harness, is operatively connected to the first and second thermostats and has lead end portions variably connectable to a source of electrical power. The water heater also preferably includes a junction box having a terminal block portion with line side terminals to which electrical power supply leads may be variably connected, and water heater side terminals to which the aforementioned wiring harness lead end portions may be variably connected. 
     Preferably, the first electric thermostat, which controls the upper heating element, is of a single pole double throw configuration, and the second electric thermostat, which controls the lower heating element, is of a single pole single throw configuration. The wiring harness is connected to the first and second thermostats in a manner such that, without replacing either of the first and second thermostats and/or altering the wiring connections to either thermostat, a plurality of heating element control modes may be provided simply by changing the wiring connections to the terminal block. 
     Representatively, these element control modes include (1) a single phase simultaneous dual element control mode, (2) a single phase simultaneous dual element control mode with four wire outlet operation, (3) a single phase non-simultaneous dual element control mode, (4) a single phase non-simultaneous dual element control mode with four wire outlet operation, (5) a single phase non-simultaneous dual element control mode with three wire outlet operation, (6) a three phase simultaneous dual element control mode, and (7) a three phase non-simultaneous dual element control mode. 
     In an illustrated preferred embodiment of the electric water heater, the first electric thermostat has an ECO portion with first, second, third and fourth power supply terminals, and a switch portion with a switch power terminal and first and second switch contacts. The second electric thermostat has an ECO portion with first, second, third and fourth power supply terminals, a switch power terminal and a switch contact. 
     Additionally, the wiring harness includes (1) a first wire interconnected between the first power supply terminal of said first thermostat ECO portion and the switch power terminal of the first thermostat switch portion, (2) a second wire interconnected between the first switch contact of the first thermostat switch portion and the upper heating element, (3) a third wire interconnected between the fourth power supply terminal of the first thermostat ECO portion and the upper heating element, (4) a fourth wire interconnected between the first power supply terminal of the second thermostat ECO portion and the switch power terminal of the second thermostat, (5) a fifth wire interconnected between the switch contact of the second thermostat switch portion and the lower heating element, (6) a sixth wire interconnected between the fourth power supply terminal of the second thermostat ECO portion and said lower heating element, and (7) a series Of electrical leads each having a first end portion operatively connected to one of the first and second thermostats, and a second end variably connectable to the water heater side of the terminal block. 
     The series of wiring harness leads variably connectable to the water heater side of the terminal block preferably include (1) a first lead connected at one end to the first power supply terminal of the second thermostat ECO portion and variably connectable at the other end to the water heater side of the terminal block, (2) a second lead connected at one end to the first power supply terminal of the first thermostat ECO portion and variably connectable at the other end to the water heater side of the terminal block, (3) a third lead connected at one end to the second power supply terminal of the first thermostat ECO portion and variably connectable at the other end to the water heater side of the terminal block, (4) a fourth lead connected at one end to the second switch contact of the first thermostat switch portion and variably connectable at the other end to the water heater side of the terminal block, and (5) a fifth lead connected at one end to the second power supply terminal of the second thermostat ECO portion and variably connectable at the other end to the water heater side of the terminal block. 
     In a preferred embodiment of the dual element electric water heater the water heater has an external well area in which the terminal block ends of the wiring harness leads may be disposed prior to their operative connection to the terminal block, and the junction box is removably connectable to the water heater and may be shipped loose therewith for subsequent mounting thereon and operative connection to external power supply leads and the terminal block ends of the wiring harness leads. 
     While the liquid heating apparatus of the present invention is representatively an electric water heater, it could alternatively be a variety of other types of liquid heating apparatus. Additionally, while the outer ends of the aforementioned wiring harness leads are representatively connectable in selectively variable manners to a terminal block portion of a junction box, it will be readily appreciated by those of skill in this particular art that they could alternatively be variably connected to an electrical power source in a variety of other manners if desired. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a highly schematic cross-sectional view through a field conversion dual element electric water heater embodying principles of the present invention; 
     FIG. 2 is a schematic wiring diagram of a thermostat/heating element portion of the water heater; and 
     FIG. 3 is a schematic diagram of a junction box/terminal block structure operatively associated with the heating element control thermostats of the water heater. 
    
    
     DETAILED DESCRIPTION 
     Schematically illustrated in FIG. 1 is a dual element electric water heater  10  embodying principles of the present invention. Water heater  10  includes a vertically oriented cylindrical metal water storage tank  12  which has, at its top end, suitable water inlet and outlet piping connections  14  and  16 . Vertically spaced apart elongated upper and lower electric resistance type water heating elements  18  and  20  longitudinally extend horizontally into the interior of the tank  12  from a vertical sidewall portion thereof. The tank  12  is surrounded by an insulation jacket structure  22  including an outer metal skin portion  24  and a foamed-in insulation material  26  interposed between the metal skin portion  24  and the tank  12 . 
     Extending along a vertical side portion  12   a  of the tank through which the upper and lower heating elements  18 , 20  inwardly extend is an insulating bag structure  28  which is filled with the insulating material  26  and has a vertically spaced pair of peripherally sealed access openings  30 , 32  extending therethrough and respectively positioned somewhat above the outer ends of the upper and lower heating elements  18 , 20 . Bag openings  30 , 32  are respectively aligned with sidewall access openings formed in the jacket metal skin portion  24  and covered by removable access plates  34  and  36 . Upper and lower electric thermostats  38 , 40  are respectively received in the bag access openings  30 , 32  and may be accessed by removing the plates  34  and  36 . 
     The upper and lower thermostats  38  and  40  are respectively and controllingly coupled to the upper and lower heating elements  18 , 20  and are electrically interconnected to one another by a subsequently described wiring harness  42  which is disposed between the insulation bag  28  and a vertical sidewall portion of the tank  12 . During shipment of the water heater  10 , upper end portions of various individual wires which make up the harness  42  are placed in a top end well area  44  in the water heater  10  for subsequent operative connection to a terminal block portion  46  of a junction box  48 . Representatively, the junction box  48  is shipped loose with the water heater and is subsequently attached to a top end portion thereof as schematically depicted in FIG.  1 . 
     Turning now to FIG. 2, in the illustrated preferred embodiment of the dual element electric water heater  10 , the upper thermostat  38  is of a single pole double throw configuration and has an ECO (energy cut-off) high limit control portion  38   a  operatively associated with a switch portion  38   b , and the lower thermostat  40  is of a single pole single throw configuration and has an ECO high limit control portion  40   a  operatively associated with a switch portion  40   b.    
     The upper thermostat ECO portion  38   a  has power supply terminals  50 , 52 , 54 , 56 , and the upper thermostat switch portion  38   b  has a switch power terminal  58  and switch contacts  60  and  62 . The lower thermostat ECO portion  40   a  has power supply terminals  64 , 66 , 68 , 70 , and the lower thermostat switch portion  40   b  has a switch power terminal  72  and a switch contact  74 . 
     Wiring harness  42  includes a wire  76  interconnected between the power supply terminal  54  and the switch power terminal  58 ; a wire  78  interconnected between the switch contact  60  and the upper heating element  18 ; a wire  80  interconnected between the power supply terminal  56  and the upper heating element  18 ; a wire  82  interconnected between the power supply terminal  68  and the switch power terminal  72 ; a wire  84  interconnected between the switch contact  74  and the lower heating element  20 ; and a wire  86  interconnected between the power supply terminal  70  and the lower heating element  20 . 
     The wiring harness  42  also includes five water heater power connection leads WH   1   ,-WH   5   which are connectable in various subsequently described, selectively variable manners to the terminal block portion  46  of the junction box  48  to provide the upper and lower heating elements with a variety of control modes without the necessity of removing and replacing either of the thermostats  38 , 40  and/or altering any of the wiring that interconnects the thermostats  38 , 40 . The power connection leads WH   1   -WH   5   extend upwardly from the thermostats  38 , 40  behind the insulation bag  28  (see FIG.  1 ), with upper end portions of the leads WH   1   -WH   5   being received in the well area  44  prior to connection of such upper lead end portions to the terminal block  46  as subsequently described herein. 
     As schematically depicted in FIG. 2, the lower end of lead WH   1   is connected to the lower thermostat power supply terminal  64 ; the lower end of lead WH   2   is connected to the upper thermostat power supply terminal  50 ; the lower end of lead WH   3   is connected to the upper thermostat power supply terminal  52 ; the lower end of lead WH   4   is connected to the upper thermostat switch contact  62 ; and the lower end of lead WH   2   is connected to the lower thermostat power supply terminal  66 . 
     Turning now to FIG. 3, the terminal block portion  46  of the junction box  48  has a line side  46   a  with terminals L A -L D , and a water heater side  46   b  with terminals H A -H D  electrically coupled to the line side terminals L A -L D as indicated by the dashed lines. With the junction box  48  operatively mounted on the top end of the water heater  10  as schematically shown in FIG. 1, the control mode of the water heater&#39;s upper and lower heating elements  18 , 20  may be selectively varied simply by reconfiguring various wiring connections to the terminal block  46  as will now be described. 
     Representatively, there are seven different dual heating element operational control modes available for the water heater  10  simply by altering the wiring connections to the terminal block  46 , and without changing the wiring interconnection between the thermostats  38 , 40  and/or replacing either thermostat with another type of thermostat. These seven heating element operational control modes, and the terminal block wiring configurations that yield them, are as follows: 
     Single Phase Simultaneous Dual Element Control Mode 
     As schematically depicted in FIG. 3, to provide the water heater  10  with a single phase, simultaneous control of its upper and lower electric resistance type upper and lower heating elements  18  and  20 , single phase power supply lines  88 , 90  are respectively connected to the terminal block line side terminals L A  and L B . On the water heater side  46   b  of the terminal block  46  wiring harness leads WH   1   and WH   2   are connected to the terminal H A , wiring harness leads WH   3   and WH   5   are connected to the terminal H B , and the wiring harness lead WH   4   is connected to the terminal H C . 
     Single Phase Simultaneous Dual Element Control Mode With  4  Wire Outlet Operation 
     To provide this dual element operational control mode, the two single phase power supply leads are connected to terminals L A  and L B  on the line side  46   a  of the terminal block  46 . On the water heater side  46   b  of the terminal block  46 , wiring harness lead WH   2   is connected to terminal H A , wiring harness lead WH   3   is connected to terminal H B , and wiring harness lead WH   4   is connected to terminal H C . Wiring harness leads WH   1   and WH   5   are connected to an off peak meter or timer. 
     Single Phase Non-Simultaneous Dual Element Control Mode 
     To provide this dual element operational control mode, the two single phase power supply leads are connected to terminals L A  and L B  on the line side  46   a  of the terminal block. On the water heater side  46   b  of the terminal block  46  wiring harness leads WH   1   and WH   3   are connected to terminal H B , wiring harness lead WH   2   is connected to terminal H A , and wiring harness leads WH   4   and WH   5   are connected to terminal H C . 
     Single Phase Non-Simultaneous Dual Element Control Mode With  4  Wire Outlet operation 
     To provide this dual element operational control mode, the two single phase power supply leads are connected to terminals L A  and L B  on the line side  46   a  of the terminal block. On the water heater side  46   b  of the terminal block  46  wiring harness leads WH   1   and WH   3   are connected to terminal H B , wiring harness lead WH   2   is connected to terminal H A , and wiring harness leads WH   4   and WH   5   are connected to terminal H C . Additionally, if off peak metering is desired, an off peak meter or timer is connected to terminals L C  and L D  on the line side  46   a  of the terminal block, wiring harness lead WH   4   is connected to terminal H C , and wiring harness lead WH   5   is connected to terminal H D . 
     Single Phase Non-Simultaneous Dual Element Control Mode With  3  Wire Outlet Operation 
     To provide this dual element operational control mode, the two single phase power supply leads are connected to terminals L A  and L B  on the line side  46   a  of the terminal block. On the water heater side  46   b  of the terminal block  46  wiring harness lead WH   2   is connected to terminal H A , wiring harness lead WH   3   is connected to terminal H B , and wiring harness leads WH   4   and WH   5   are connected to terminal H C . If off peak metering is desired, wiring harness lead WH   1   is connected to terminal H D  and an off peak meter is connected to terminal L D . 
     Three Phase Simultaneous Dual Element Control Mode 
     To provide this dual element operational control mode, three phase power supply leads are connected to the terminal block line side terminals L A , L B  and L D . On the water heater side  46   b  of the terminal block  46  wiring harness leads WH   1   and WH   2   are connected to terminal H A , wiring harness lead WH   3   is connected to terminal H B , wiring harness lead WH   4   is connected to terminal H C , and wiring harness lead WH   5   is connected to terminal H D . 
     Three Phase Non-Simultaneous Dual Element Control Mode 
     To provide this dual element operational control mode, three phase power supply leads are connected to the terminal block line side terminals L A , L B  and L C . On the water heater side  46   b  of the terminal block  46  wiring harness lead WH   1   is connected to terminal H A , wiring harness lead WH   2   is connected to terminal H B , wiring harness lead WH   3   is connected to terminal H C , and wiring harness leads WH   4   and WH   5   are connected to terminal H D . 
     As can readily be seen from the foregoing, the water heater  10  may uniquely be field-converted selectively among its seven representative dual heating element operational control modes simply by appropriately altering the electrical connections to the terminal block  46 . In contrast to conventionally constructed dual element electric water heaters, there is simply no need to either (1) replace either of the upper and lower thermostats  38 , 40  with another type of thermostat, and/or (2) change the wiring connections to the two thermostats. This advantageously makes the representatively listed seven dual heating element operational control modes available with the single illustrated variant of the dual element electric water heater  10 . While the present invention has been illustratively incorporated in an electric water heater it will be readily appreciated that principles of the invention could also be incorporated in dual element liquid heating devices of other types if desired. It will additionally be appreciated that while the outer ends of the wiring harness leads WH   1   -WH   5   are representatively connectable in selectively variable manners to a terminal block portion of a junction box, they could alternatively be variably connected to an external electrical power source in a variety of other manners if desired. 
     The foregoing detailed description is to be clearly understood as being given by way of illustration and example, the spirit and scope of the present invention being limited solely by the appended claims.