Water heater and control system therefor

Information

  • Patent Grant
  • 6465764
  • Patent Number
    6,465,764
  • Date Filed
    Wednesday, August 30, 2000
    24 years ago
  • Date Issued
    Tuesday, October 15, 2002
    22 years ago
Abstract
A water heater having a water tight tank (10) with a cold water inlet (14) and a hot water outlet (16). First and second heating elements (24, 26) are mounted in the upper and lower portions of the tank (10). A controller is provided for energizing element (24) to heat water in the upper portion of tank (10) until the temperature of the water in the upper portion of tank (10) reaches a preset temperature, at which time, the element (24) will be de-energized. The controller is adapted to energize element (26) when element (24) is de-energized. The controller is further adapted to de-energize element (26) and at the same time energize element (24) when the temperature of the water in the lower portion of the tank reaches a preset temperature.
Description




CROSS-REFERENCE TO RELATED APPLICATIONS




Not applicable.




STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT




Not applicable.




REFERENCE TO MICROFICHE APPENDIX




Not applicable.




BACKGROUND OF THE INVENTION




This invention relates to an electric water heater and more particularly to a control system for an electric water heater having an upper and a lower heating element.




BRIEF SUMMARY OF THE INVENTION




The water heater control system operates to cycle the energization of the upper and lower heating elements. The upper element is initially energized to heat the water in the upper portion of the tank to a predetermined set temperature at which time the upper element will be de-energized and the lower element will be energized. The lower element then heats the water in the lower portion of the tank to a predetermined set temperature, at which time the lower element will be de-energized and the upper element will again be energized. The sequence of heating the water in the upper and lower portions of the tank is then repeated.




Another feature of the control system is the prevention of a “dry fire ” condition, i.e., energization of the heating elements without water in the water heater tank.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a partially schematic/wiring diagram for the programmable control for electric water heater of the present invention.











DETAILED DESCRIPTION OF THE INVENTION




Referring to

FIG. 1

, the electric water heater of the present invention is comprised of a water tank


10


, a tank jacket


12


, a tank jacket base


11


and a jacket top


13


.




The water heater tank


10


has a cold water inlet


14


and a hot water outlet


16


, both mounted in jacket top


13


. A dip tube


18


connected to cold water inlet


14


extends downwardly inside tank


10


to the open outlet end


20


of the dip tube


18


. In use when heated water is drawn out of the top portion of the tank


10


through outlet


16


, cold water will be simultaneously drawn into the tank through inlet


14


and dip tube


18


. Cold water flowing downwardly through dip tube


18


will flow out open outlet end


20


of the dip tube into the lower portion of the water heater tank


10


.




The control circuitry and control components for the water heater are shown in FIG.


1


. The control includes an energy cut-off device of conventional design


22


, an upper heating element


24


and a lower heating element


26


mounted inside tank


10


. Upper and lower heat sensors


28


,


30


are mounted on the outer surface of tank


10


. Relays


32


,


34


are provided for controlling the on-off energization of heating elements


24


,


26


. Relays


32


,


34


are mounted exteriorly of the water heater tank.




A 240 VAC to 24 VAC step-down transformer (not shown) is mounted exteriorly of the water heater tank. In a preferred embodiment, the step-down transformer provides 240 volts AC to heating elements


24


and


25


under the control of relays


32


and


34


.




Relay


32


has a winding


32




a


and a movable switch arm


40


. When winding


32




a


is de-energized, arm


40


will be in contact with contact


39


and when winding


32




a


is energized, arm


40


will be moved out of contact with contact


39


and into contact with contact


41


.




Relay


34


has a winding


34




a


and a movable switch arm


42


. When winding


34




a


is de-energized, arm


42


will be in contact with contact


43


. When winding


34




a


is energized, arm


42


will be moved out of contact with contact


43


.




Conductors


36


,


36


carry 24 volts AC from the step-down transformer to winding


32




a


of relay


32


through control unit A.




Conductors


38


,


38


carry 24 volts AC from the step-down transformer to winding


34




a


of relay


34


through control unit B. Relay


32


has a normally closed movable switch arm


40


and relay


34


has a normal open switch arm


42


.




Energy cut-off device


22


receives 240 volts AC through conductors


44


,


44


. The 240 volts AC fed into energy cut-off unit


22


is fed to heating units


24


,


26


through conductors


46


,


48


.




The 240 volts AC fed to heating unit


24


is fed back to energy cut-off unit


22


through conductor


50


, relay switch arm


40


and conductor


52


. The 240 volts AC fed to heating unit


26


is fed back to energy cut-off unit


22


through conductor


54


, relay switch arm


42


, conductor


56


, relay arm


40


and conductor


52


.




OPERATION




A typical sequence of operation upon a call for heat in the water heater is as follows.




At the start of the sequence, relay switch arms


40


,


42


will be in the positions shown in solid lines in FIG.


1


.




With relay switch arm


40


in the

FIG. 1

position, upper heating element


24


will be energized. When the water in the upper portion of tank


10


heats to 120° F. (or some other temperature setting), sensor


28


will actuate control unit A, which, in turn, will energize winding


32




a


of relay


32


. The energization of winding


32




a


will move relay switch arm


40


from contact with contact


39


(solid line) into contact with control


41


(dotted line) to thereby de-energize element


24


. The movement of switch arm


40


into contact with contact


41


will electrically connect conductors


52


and


56


to each other, thus causing heating element


26


in the lower portion of the tank to be energized.




Lower sensor


30


will then take over control of the water heater as lower element


26


heats the water in the lower portion of tank


10


.




When the water temperature in the lower portion of tank


10


reaches 120° F., sensor


30


will signal control unit A to energize winding


34




a


of relay


34


to thereby move switch arm


42


to its open position (shown in dotted lines). Heating element


26


will thereby be de-energized. Also, when winding


34




a


of relay


32


is energized, control unit A will operate to de-energize winding


32




a


of relay


32


. This will allow switch arm


40


of relay


32


to move back into contact with contact


39


to thereby energize heating element


24


.




When the water temperature in the lower portion of the tank falls below 120° F., control unit A will de-energize winding


34




a


of relay


34


to thereby allow switch arm


42


of relay


34


to be returned to the

FIG. 1

solid line position. The heating sequence described above will then be repeated.




Another feature of the subject control system described above is the prevention of a “dry fire ” condition, Le., energization of the heating elements


24


,


26


without water in tank


10


. This is a condition that may occur upon original installation of the water heater wherein the installer inadvertently fails to fill tank


10


with water before connecting the water heater to a source of electrical energy.




If, for example, upon the initiation of the heating cycle described above, the temperature sensed by sensors


28


,


30


increases at a rate greater than 3° F. per minute, control units A and B will operate to open relays


32


,


34


to thereby shut off current to elements


24


,


26


.




While the invention herein has been shown and described in what is presently conceived to be the most practical preferred embodiment, it will be obvious to one of ordinary skill in the art that many modifications may be made thereof within the scope of the invention, which scope is not to be limited except by the appended claims.



Claims
  • 1. A water heater comprising:(1) a water-tight tank (10); (2) said tank (10) having a cold water inlet (14) and a hot water outlet (16); (3) a first electrical heating element (24) mounted in an upper portion of said tank (10); (4) a second electrical heating element (26) mounted in a lower portion of said tank (10); (5) a first temperature sensor element (28) mounted on the outer surface of said tank (10); (6) a second temperature sensor element (30) mounted on the outer surface of said tank (10); (7) a first relay (32) mounted outside of said tank (10) having a first switch arm (40) and a winding (32a), said first switch arm (40) movable between a first position and a second position; (8) a second relay (34) mounted outside said tank (10) having a second switch arm (42) and a winding (34a), said second switch arm (42) movable between a first closed position and a second open position; (9) a source of high AC voltage connected to said first (24) and second (26) heating elements; (10) a source of low AC voltage connected to said windings (32a and 34a) of said first and second relays (32, 34) respectively; and (11) an electrical control unit (A) electrically connected to said first temperature sensor element (28) and said first relay winding (32a), said control unit (A) also connected to said second temperature sensor element (30) and said second relay winding (34a); (12) said first relay (32) adapted to energize said first electrical heating element (24) when said first relay winding (32a) is in a de-energized condition; (13) said first electrical heating element (24) adapted to actuate said control unit (A) to thereby de-energize said first electrical heating element (24) when the water in the upper portion of said tank (10) reaches a preset temperature; (14) said first relay (32) is further adapted to energize said second electrical heating element (26) when said first arm (40) of said relay is actuated to move from its first position to its second position; and (15) said second temperature sensor element (30) adapted to actuate said control unit (A) to energize said second relay winding (34a) of relay (34) to thereby move said second switch arm (42) to its open position to thereby de-energize said second electrical heating element (26) when the temperature in the lower portion of the tank reaches said preset temperature; wherein said control unit (A) is adapted to sense a temperature rise in the tank (10) at an abnormally high rate, at which time the control unit (A) will operate to open said first and second relays (32, 34) to thereby shut off current to said first and second electrical heating elements (24, 26).
  • 2. A water heater according to claim 1 in which said high AC voltage is 240 volts AC and said low AC voltage is 24 volts AC.
  • 3. A water heater according to claim 1 in which said preset temperature is 120° F.
  • 4. A water heater according to claim 1 in which the abnormally high rate is 3° F. or greater per minute.
  • 5. A water heater comprising:(1) a water tight tank (10); (2) said tank (10) having a cold water inlet (14) and a hot water outlet (16); (3) a first electrical heating element (24) mounted in an upper portion of said tank (10); (4) a second electrical heating element (26) mounted in a lower portion of said tank (10); (5) control means adapted for energizing said first electrical heating element (24) to heat water in the upper portion of said tank (10) until the temperature of the water in the upper portion of said tank (10) reaches a preset temperature, at which time said first electrical heating element (24) will be de-energized and said second electrical heating element (26) will be energized, said control means further adapted to de-energize said second electrical heating element (26) and at the same time energize said first electrical heating element (24), when the temperature of the water in the lower portion of the tank (10) reaches said preset temperature; wherein said control means is adapted to sense a temperature rise in the tank (10) at an abnormally high rate, at which time the control means will operate to shut off current to said first and second electrical heating elements (24, 26).
  • 6. A water heater according to claim 5 in which said control means includes a first temperature sensor (28) mounted in the upper portion of said tank (10) and a second temperature sensor (30) mounted in the lower portion of said tank (10).
  • 7. A water heater according to claim 6 in which said control means further includes a control unit (A) controlled alternately by said first temperature sensor (28) and said second temperature sensor (30).
  • 8. A water heater according to claim 7 in which said control means further includes a pair of relays (32, 34) controlled by control unit (A).
  • 9. A water heater according to claim 7 in which said relays (32, 34) control the energization and de-energization of said heating elements (24, 26) respectively.
  • 10. A water heater according to claim 5 in which said preset temperature is 120° F.
  • 11. A water heater according to claim 6 in which said control means includes a step-down transformer operable to supply said heating elements (24, 26) with a source of high AC voltage and further operable to supply said temperature sensors (28, 30) with a source of low AC voltage.
  • 12. A water heater according to claim 11 in which said high AC voltage is 240 volts AC and said low AC voltage is 24 volts AC.
  • 13. A water heater according to claim 9 in which said abnormally high rate is 3° F. or greater per minute.
  • 14. A water heater comprising:(1) a water-tight tank (10); (2) said tank (10) having a cold water inlet (14) and a hot water outlet (16); (3) a first electrical heating element (24) mounted in an upper portion of said tank (10); (4) a second electrical heating element (26) mounted in a lower portion of said tank (10); (5) a first temperature sensor element (28) for sensing the water temperature in the upper portion of said tank (10); (6) a second temperature sensor element (30) for sensing the water temperature in the lower portion of tank (10); (7) a first relay (32) for controlling the energization and de-energization of said first temperature sensor element (28); (8) a second relay (34) for controlling the energization and de-energization of said second temperature sensor element (30); (9) an electrical control unit (A) operable in response to electric signals from said first and second temperature sensor elements (28, 30), said control unit (A) operable to cycle the operation of said first and second relays (32, 34) to thereby cycle the energization and de-energization of first and second temperature sensor elements (28, 30); wherein said control unit (A) is adapted to sense a temperature rise in the tank (10) at an abnormally high rate, at which time the control unit (A) will operate to open said first and second relays (32, 34) to thereby shut off current to said first and second electrical heating elements (24, 26).
US Referenced Citations (5)
Number Name Date Kind
4833398 Buchan May 1989 A
5442157 Jackson Aug 1995 A
5808277 Dosani et al. Sep 1998 A
5968393 Demaline Oct 1999 A
6242720 Wilson et al. Jun 2001 B1