SAFE AND EFFICIENT DISH WASHING MACHINE

Abstract

A dish washing machine comprising a fresh water reservoir for receiving fresh water configured to be heated, a first tank for receiving the initially heated fresh water from the fresh water reservoir and including a first heating system for heating the initially heated fresh water to form further heated fresh water, a second tank configured to receive the further heated fresh water and including a second heating system for heating the further heated fresh water to form further heated wash water, and a drain pipe for delivering the further heated wash water from the second tank through the fresh water reservoir and to a liquid outlet, with the drain pipe transferring heat from the further heated wash water to the fresh water in the fresh water reservoir to form the initially heated fresh water. The heating systems can comprise a positive temperature coefficient heating element.

Description

FIELD OF THE INVENTION

This disclosure relates generally to the field of dish washing machines, and in particular to a safe and efficient dish washing machine.

BACKGROUND OF THE INVENTION

Commercial establishments for cooking and/or preparing food typically have a commercial dish washer for washing dirty dishes. The dish washers spray a detergent and water onto the dirty dishes to clean the dishes. The dish washers can also spray a rinse aid and water onto the dishes after the dishes have been washed to rinse the dishes and prevent spots on the dishes.

Currently, there are four main types of commercial dish washers in worldwide markets. The commercial dish washers include an under-counter dish washing machine, a hood or door type dish washing machine, a tunnel type dish washing machine and a flight type dish washing machine. The under-counter dish washing machine has a small size and low profile and is positioned under a separate work bench with a wash basin next to the space occupied by the under-counter dish washing machine. The hood or door type dish washing machine, the tunnel type dish washing machine and the flight type dish washing machine all have a medium to large size and are positioned next to a separate side bench with a wash basin on the bench. The under-counter dish washing machine, the hood or door type dish washing machine and the tunnel type dish washing machine all typically use a rack or container having the dirty dishes that is positioned within the machine. The flight type dish washing machine has dishes that are put directly onto an integral conveyor and washed as the dishes pass therethrough.

A more efficient and environmentally friendly commercial dish washer is desired.

SUMMARY OF THE INVENTION

The present invention, according to one aspect, is directed to a dish washing machine comprising a housing having an interior wash space for washing dishes, a liquid inlet for adding fresh water to the dish washing machine, and a liquid outlet for removing dirty liquid from the dish washing machine. A fresh water reservoir receives the fresh water therein from the liquid inlet, with the fresh water in the fresh water reservoir being configured to be heated to form initially heated fresh water. A first water tank receives the initially heated fresh water from the fresh water reservoir, with the first water tank including a first heating system for heating the initially heated fresh water to form further heated fresh water. First piping delivers the further heated fresh water to at least one spray nozzle for spraying the further heated fresh water onto dishes positioned within the interior wash space. A second water tank is configured to receive the further heated fresh water from the interior wash space, with the second water tank including a second heating system for heating the further heated fresh water to form further heated wash water. Second piping delivers the further heated wash water to the at least one spray nozzle for spraying the further heated wash water into the interior wash space. A drain pipe delivers the further heated wash water from the second water tank through the fresh water reservoir and to the liquid outlet, with the drain pipe transferring heat from the further heated wash water to the fresh water in the fresh water reservoir to form the initially heated fresh water.

Another aspect of the present invention is to provide a dish washing machine comprising a housing having an interior wash space for washing dishes and at least one spray nozzle for spraying liquid onto dishes positioned within the interior wash space and a liquid tank for supplying liquid to the at least one spray nozzle. The liquid tank includes a heating system comprising a stainless steel shell with a positive temperature coefficient heating array located therein, the positive temperature coefficient heating array comprising a plurality of positive temperature coefficient heating elements, with a temperature sensor being connected to a heater cover, the temperature sensor measuring a temperature of the first heating system to maintain the temperature of the first heating system under a predetermined temperature. The temperature sensor of the first heating system is not immersed in the liquid within the liquid tank.

Yet another aspect of the present invention is to provide a method of washing dishes comprising providing a housing having an interior wash space for receiving dishes, adding fresh water to the dish washing machine, feeding the fresh water to a fresh water reservoir, heating the fresh water in the fresh water reservoir to form initially heated fresh water, delivering the initially heated fresh water from the fresh water reservoir to a first water tank, heating the initially heated fresh water in the first water tank with a first heating system to form further heated fresh water, supplying the further heated fresh water to at least one spray nozzle, spraying the further heated fresh water onto dishes positioned within the interior wash space, delivering the further heated fresh water from the interior wash space to a second water tank, heating the further heated fresh water in the second water tank with a second heating system to form further heated wash water, delivering the further heated wash water to the at least one spray nozzle, spraying the further heated wash water into the interior wash space, and draining the further heated wash water through a drain pipe that passes through the fresh water reservoir and to a liquid outlet. Heating the fresh water in the fresh water reservoir to form initially heated fresh water comprises transferring heat from the further heated wash water to the fresh water in the fresh water reservoir.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the present invention are illustrated by way of example and should not be construed as being limited to the specific embodiments depicted in the accompanying drawings, in which like reference numerals indicate similar elements.

FIG. 1 is a front partial perspective view of a dish washing machine according to an embodiment with walls and a door removed for reference.

FIG. 2 is a front partial perspective view of the dish washing machine according to an embodiment with walls, the door and other structural elements removed for reference.

FIG. 3 is a front partial view of the dish washing machine according to an embodiment illustrating a lower portion of the dish washing machine with walls removed for reference.

FIG. 4 is a front perspective partial view of the dish washing machine according to an embodiment illustrating the lower portion of the dish washing machine with walls removed for reference.

FIG. 5 is a front perspective partial view of a portion of a system for supplying the water to an interior wash space of the dish washing machine according to an embodiment illustrating the lower portion of the dish washing machine with walls removed for reference.

FIG. 6 is a partial side view of a portion of the system for supplying the water to the interior wash space.

FIG. 7 is a perspective view of a positive temperature coefficient (PTC) heating element according to an embodiment of the invention.

FIG. 8 is a front view of the positive temperature coefficient (PTC) heating element according to an embodiment of the invention.

FIG. 9 is a cross-sectional view of the positive temperature coefficient (PTC) heating element according to an embodiment of the invention taken along line IX-IX of FIG. 8.

FIG. 10 is an exploded view of the positive temperature coefficient (PTC) heating element according to an embodiment of the invention.

Certain terminology will be used in the following description for convenience in reference only and will not be limiting. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.

DETAILED DESCRIPTION

Reference will now be made in detail to implementations and embodiments of various aspects and variations of the invention, examples of which are illustrated in the accompanying drawings. Although at least two variations of the systems, methods and uses are described, other variations of the systems, methods and uses may include aspects of the systems, methods and uses described herein combined in any suitable manner having combinations of all or some of the aspects described.

FIGS. 1-5 illustrate various partial views of an embodiment of a dish washing machine 10. The dish washing machine 10 includes an interior wash space 12 for accepting dishes (e.g., glasses, plates, eating and serving utensils, etc.) for cleaning the dishes. While not shown, the interior wash space 12 can include at least one shelf or ledge as is known to those skilled in the art for directly holding the dishes or holding a tray or rack holding the dishes. In FIGS. 1-5, exterior walls of the dish washing machine 10 are not shown in order to be able to view the interior of the dish washing machine 10. It is contemplated that the dish washing machine 10 can include at least one door for selectively accessing the interior wash space 12 of the dish washing machine 10 and enclosing the interior wash space 12 of the dish washing machine 10 during use. For example, a door can be connected to a wall to selectively open the dish washing machine 10 (e.g., a rotatable door) or wall(s) (not shown) can be slid upward along posts 14 of the dish washing machine 10 to allow access to the interior wash space 12 of the dish washing machine 10 and slid back down into position to enclose the interior wash space 12 of the dish washing machine 10 during use.

In the illustrated example, the interior wash space 12 of the dish washing machine 10 includes a top rotating spray arm 16 located at a top of the interior wash space 12 for positioning above the dishes (and possibly the tray or rack) along with a bottom rotating spray arm 18 located at a bottom of the interior wash space 12 and below the dishes (and possibly the tray or rack) for spraying water, a washing fluid and/or a rinsing fluid onto the dishes to clean and rinse the dishes. Water (fresh, with a wash detergent, or with a rinse aid) is supplied to the top rotating spray arm 16 and the bottom rotating spray arm 18 to wash and rinse the dishes. The interior wash space 12, the top rotating spray arm 16 and the bottom rotating spray arm 18 are all located in an upper portion 20 of the dish washing machine 10. Other configurations for spraying the water onto the dishes are contemplated. For example, the system could use only one of the top rotating spray arm 16 or the bottom rotating spray arm 18, the arms could be stationary and/or could employ other nozzles (e.g., stationary nozzles extending from interior walls) for spraying water onto the dishes for cleaning the dishes.

FIGS. 1-5 illustrate a system 22 for supplying the water to the interior wash space 12 of the dish washing machine 10 via the top rotating spray arm 16 and the bottom rotating spray arm 18. The system 22 for supplying the water to the interior wash space 12 is mostly located in a lower portion 24 of the dish washing machine 10 located under the upper portion 20 of the dish washing machine 10.

In the illustrated embodiment, the system 22 passes water therethrough to wash and rinse the dishes in the interior wash space 12 of the dish washing machine 10. The system includes a fresh water input 26, a fresh water reservoir 28, a rinse water pump 32, a rinse water tank 34, rinse water piping 36, the spray arms 16 and 18, a wash water tank 38, a wash water pump 40, wash water piping 42, a wash water drain pipe 44, a hot waste water drain pipe 46, and a waste water drain 48. The elements of the system 22 are discussed in more detail below along with the flow path of water through the system 22.

Water enters the illustrated dish washing machine 10 through an external fresh water connection tube 50 connected to a fitting 52 located in a rear portion of the lower portion 24 of the dish washing machine 10 (see FIG. 4). It is contemplated that the external fresh water connection tube 50 could include a part of the fitting 52 for connection to the dish washing machine 10. The fitting 52 is connected to an inlet tube 54 that leads to the fresh water reservoir 28. The fitting 52 and the inlet tube 54 comprise the fresh water input 26 into the system 22. The fresh water input 26 supplies fresh water to the fresh water reservoir 28.

The illustrated fresh water reservoir 28 holds fresh water before use in the dish washing machine 10 and includes a first stage for heating the water for use in the system. The fresh water reservoir 28 includes a fresh water housing 56 with an interior fresh water holding space 58. The fresh water from the fresh water input 26 is supplied to the interior fresh water holding space 58 through a fitting 60 connected to the fresh water housing 56 as shown in FIG. 6. It is contemplated that the fitting 60 could include a filter for keeping contaminates from entering the fresh water reservoir 28. As discussed in more detail below, the fresh water reservoir 28 has the hot waste water drain pipe 46 passing therethrough for exchanging heat from the hot waste water drain pipe 46 to the fresh water in the interior fresh water holding space 58. It is noted that the fresh water in the interior fresh water holding space 58 of the fresh water reservoir 28 might not have been heated with the hot waste water drain pipe 46 if the dish washing machine 10 has not been used recently to wash and rinse dishes as the interior of the hot waste water drain pipe 46 would not be hot because of the inactivity. As illustrated in FIGS. 2 and 4, an overflow tube 62 can be connected to a top of the fresh water housing 56. The overflow tube 62 has an inverted U-shaped open end 64 located above a top of the wash water drain pipe 44 for allowing excess water pressure in the fresh water housing 56 to be released if needed.

In the illustrated example, the heated fresh water in the interior fresh water holding space 58 of the fresh water reservoir 28 is pumped therefrom to the rinse water tank 34 by the rinse water pump 32. The rinse water pump 32 pulls the heated fresh water in the interior fresh water holding space 58 of the fresh water reservoir 28 and pushes the heated fresh water through pump piping 66 to the rinse water tank 34. The rinse water tank 34 includes a first positive temperature coefficient (PTC) heating element 68 for further heating the heated fresh water within the rinse water tank 34. The first PTC heating element 68 is discussed in more detail below.

After the heated fresh water is further heated in the rinse water tank 34, the rinse water pump 32 is further activated to push the further heated fresh water through the rinse water piping 36. The rinse water piping 36 includes a first rinse water piping path 70 that leads to the top rotating spray arm 16 and a second rinse water piping path 72 that leads to the bottom rotating spray arm 18. If other means are used to spray the water onto the dishes as discussed above, the further heated fresh water in the rinse water piping 36 will be piped to those other means.

After the further heated fresh water is sprayed through the top rotating spray arm 16 and the bottom rotating spray arm 18 onto the dishes in the interior wash space 12, the further heated fresh water will fall into the wash water tank 38 (which has an open top 76 as shown in FIG. 1) located at the bottom of the interior wash space 12. The further heated fresh water will collect within the wash water tank 38 and will be yet further heated by a second positive temperature coefficient (PTC) heating element 74 for yet further heating the heated water within the wash water tank 38. The second PTC heating element 74 is discussed in more detail below. A wash detergent can be added to the yet further heated water that is pooled in the wash water tank 38. An example of a system for adding a wash detergent to the heated water in the wash water tank 38 is disclosed in U.S. Pat. No. 10,905,306 entitled DISH WASHING MACHINE, the entire contents of which are hereby incorporated herein by reference. It is contemplated that other means of adding wash detergent to the heated water in the wash water tank 38 could be employed.

Once the wash water is heated in the wash water tank 38 as outlined above, the wash cycle can begin. To begin the wash cycle, a drain 84 in the bottom of the wash water tank 38 is opened in a first manner to allow the wash water in the wash water tank 38 to be pumped by the wash water pump 40 through the wash water piping 42. The wash water piping 42 includes a wash pump supply pipe path 82 that supplies the wash water to the wash water pump 40, a first wash water piping path 78 that leads to the top rotating spray arm 16 and a second wash water piping path 80 that leads to the bottom rotating spray arm 18. If other means are used to spray the water onto the dishes as discussed above, the further heated wash water in the wash water piping 42 will be piped to those other means.

After the heated wash water is sprayed through the top rotating spray arm 16 and the bottom rotating spray arm 18 onto the dishes in the interior wash space 12, the heated wash water will once again fall into the wash water tank 38 located at the bottom of the interior wash space 12. The heated wash water will collect within the wash water tank 38 and will continue to be heated by the second PTC heating element 74 before once again being pumped by the wash water pump 40 through the wash water piping 42 to be sprayed once again onto the dishes in the interior wash space 12. This wash cycle will happen many times in order to fully clean the dishes.

After the wash cycle is complete, the drain 84 in the bottom of the wash water tank 38 is opened in a second manner to allow the wash water in the wash water tank 38 to drain into the hot waste water drain pipe 46. It is contemplated that the drain 84 could include the wash water drain pipe 44 located within the drain 84. The wash water drain pipe 44 includes an open top area at about the same level as the open top 76 of the wash water tank 38 to allow the heated wash water that pools above the open top of the wash water drain pipe 44 to drain into the hot waste water drain pipe 46 during the wash cycle.

In the illustrated example, most of the waste water in the hot waste water drain pipe 46 after the wash cycle will pass through the hot waste water drain pipe 46 in the fresh water reservoir 28 and the waste water drain 48 located at the end of the hot waste water drain pipe 46. However, as shown in FIG. 6, the hot waste water drain pipe 46 includes a horizontal portion 86 that holds hot waste water within the fresh water reservoir 28. The hot waste water drain pipe 46 can include an elbow hot water waste retainer 88 just outside of the fresh water reservoir 28 that includes a lower surface 90 that is above the horizontal portion 86. Because the lower surface 90 is above the horizontal portion 86, hot waste water will pool in the horizontal portion 86 in a hot waste water pool 92 as shown in FIG. 6. The hot waste water pool 92 is replaced by further hot waste water that enters the hot waste water drain pipe 46 from the drain 84, but the hot waste water pool 92 maintains the same amount of waste water therein because of the elbow hot water waste retainer 88. The waste water that is pushed out of the horizontal portion 86 and through the elbow hot water waste retainer 88 exits the dish washing machine through the waste water drain 48. The hot waste water in the hot waste water pool 92 exchanges heat with the fresh water within the interior fresh water holding space 58 before the fresh water is pumped to the rinse water tank 34 as outlined above.

After the wash cycle is complete, the rinse cycle begins. The rinse cycle is identical to the wash cycle, except that a wash detergent is not added to the heated water. Therefore, the heated fresh water in the rinse water tank 34 is heated by the exchange of heat in the fresh water reservoir 28 and the first PTC heating element 68 as outlined above. The heated fresh water in the rinse water tank 34 is then pumped through the rinse water piping 36 by the rinse water pump 32 to the top rotating spray arm 16 and the bottom rotating spray arm 18 (or other spraying means). After passing through the interior wash space 12, the heated water will pool in the wash water tank 38 to be further heated by the second PTC heating element 74 as outlined above. A rinse aid can be added to the heated water in either the rinse water tank 34 or in the wash water tank 38. An example of a system for adding a rinse to the heated water in the rinse water tank 34 or the wash water tank 38 is disclosed in U.S. Pat. No. 10,905,306 entitled DISH WASHING MACHINE, the entire contents of which are hereby incorporated herein by reference. It is contemplated that other means of adding rinse aid to the heated water in the rinse water tank 34 or the wash water tank 38 could be employed.

During the rinse cycle, the heated water is continuously pumped from the wash water tank 38 through the wash water piping 42 as outlined above to be sprayed through the top rotating spray arm 16 and the bottom rotating spray arm 18 (or other spraying means). After the rinse cycle is complete, the waste water drains from the wash water tank 38 in a manner identical to the waste water exiting the wash water tank 38 through the drain 84 and into the hot waste water drain pipe 46 as outlined above to exit the dish washing machine 10 and form the hot waste water pool 92 to exchange heat within the fresh water reservoir 28 as outlined above.

In the wash cycle and the rinse cycle as outlined above, the fresh water entering the dish washing machine 10 is heated in three different areas: through the exchange of heat with waste water in the fresh water reservoir 28, by the first PTC heating element 68 in the rinse water tank 34, and by the second PTC heating element 74 in the wash water tank 38. However, it is contemplated that any one or only two of these three methods of heating the water could be employed.

FIGS. 7-10 illustrate the PTC heating elements 68, 74 according to an embodiment of the invention. The first PTC heating element 68 and the second PTC heating element 74 are identical such that only the first PTC heating element 68 will be discussed herein, with the understanding that the second PTC heating element 74 functions identically and includes the same features as the first PTC heating element 68.

The PTC heating element 68 is configured to safely heat the water within the rinse water tank 34 and the wash water tank 38. The PTC heating element 68 includes a stainless steel cylindrical shell 100 having a stainless steel terminal plate cover 102 at one end thereof. An extruded aluminum PTC array holder 104 having a plurality of slots 106 forming a substantially hexagonal ring is located within the stainless steel cylindrical shell 100. A positive temperature coefficient heating array 108 comprising a plurality of positive temperature coefficient heating elements 110 is located within the slots 106 of the extruded aluminum PTC array holder 104. A fiber tubing 112 is located within a center of the extruded aluminum PTC array holder 104. A heater cover 114 having a plurality of mounting flanges 116 encloses the extruded aluminum PTC array holder 104 within the stainless steel cylindrical shell 100. The heated mounting flanges 116 are configured to accept fasteners therethrough for connecting the PTC heating elements 68, 74 to their respective tanks 34, 38. Lead wires 118 connected to the positive temperature coefficient heating elements 110 extend through rubber bushings 117 located in openings in the heater cover 114. The lead wires 118 are connected to further power supply wires 120 by metal connectors 122 surrounded by shrink rubber tubes 124. A temperate sensor 126 is housed in a temperature sensor holder 128 connected to the heater cover 114 by a screw 130 and nut 132 connection.

Currently dish washing machines use resistance heating wire type heaters in the wash water tank and the rinse water tank. The heating wire is a resistance wire with current passing therethrough to generate heat. As the heating wire is used for a longer time, current continues to pass through the heating wire, thereby continuously heating the heating wire. The prior art heating wire can sometimes reach up to or over 1000° C. if there is no outside control to turn on and off the current supply to the heating wire. Furthermore, if the water supplied or reserved in these prior art tanks are interrupted by manual mistake or outside control failure, the heating wire type heater will also overheat. In the overheating situation, a fire could break out resulting in great damages.

The PTC heating elements 68, 74 according to an embodiment of the invention include the stainless steel cylindrical shell 100 that is immersed in their respective tanks. The temperature sensor 126 measures the temperature and sends the temperature to a control system that self-regulates the maximum temperature of the PTC heating elements 68, 74 (via the positive temperature coefficient heating elements 110) to around 250° C. by self-regulating the heating power according to a contacting surface or surrounding or environment temperature. The higher the surrounding temperature, the less heating power the PTC heating elements 68, 74, thus self-regulating the temperature at about 250° C. At 250° C., the PTC heating elements 68, 74 will not cause fire to break out even if there is no water in their respective tanks 34, 38.

The temperature sensor 126 monitors the temperature at the PTC heating elements 68, 74 and this further reduces false alarm and aging, or damages to the parts of the PTC elements 68, 74 due to prolonged overheating in faulty dish washing machines. The temperature sensor 126 is added on the outside of the heater cover 114 of the PTC heating elements 68, 74 for easy installation/inspection and maintenance. The wattage of PTC heating elements 68, 74 is from 4 KW to 12 KW during use of the dish washing machine 10. The PTC heating elements 68, 74 is configurated and designed in shape and dimensions to be interchangeable with the current, common resistance heating wire type heaters in prior art dish washing machines. The heater cover 114 includes a first opening 136 and the positive temperature coefficient heating array 108 includes a longitudinal second opening 134 aligned with the first opening 136 to allow an inside of the PTC heating elements 68, 74 to be connected to open air and the atmosphere-open air. The first opening 136 and the longitudinal second opening 134 can prevent a dangerous situation and damage to the stainless steel cylindrical shell 100 due to expanding hot air inside the PTC heating elements 68, 74 when the PTC heating elements 68, 74 are operating. It is contemplated that other types of PTC heating elements 68, 74 may be used with or in the dish washing machine 10. For example, the PTC heating elements 68, 74 could have water pass through them.

Although particular preferred embodiments of the invention have been disclosed in detail for illustrative purposes, it will be recognized that variations or modifications of the disclosed apparatus, including the rearrangement of parts, lie within the scope of the present invention. For example, it is contemplated that only a single rotating spray arm (upper or lower) could be used.

Claims

1. A dish washing machine comprising: a housing having an interior wash space for washing dishes;a liquid inlet for adding fresh water to the dish washing machine;a liquid outlet for removing dirty liquid from the dish washing machine;a fresh water reservoir for receiving the fresh water therein from the liquid inlet, the fresh water in the fresh water reservoir being configured to be heated to form initially heated fresh water;a first water tank for receiving the initially heated fresh water from the fresh water reservoir, the first water tank including a first heating system for heating the initially heated fresh water to form further heated fresh water;first piping for delivering the further heated fresh water to at least one spray nozzle for spraying the further heated fresh water onto dishes positioned within the interior wash space;a second water tank configured to receive the further heated fresh water from the interior wash space, the second water tank including a second heating system for heating the further heated fresh water to form further heated wash water;second piping for delivering the further heated wash water to the at least one spray nozzle for spraying the further heated wash water into the interior wash space; anda drain pipe for delivering the further heated wash water from the second water tank through the fresh water reservoir and to the liquid outlet, the drain pipe transferring heat from the further heated wash water to the fresh water in the fresh water reservoir to form the initially heated fresh water.

2. The dish washing machine of claim 1, further including: a pump for pumping the initially heated fresh water from the fresh water reservoir to the first water tank and for pumping the further heated fresh water from the first water tank to the at least one spray nozzle.

3. The dish washing machine of claim 1, wherein: the at least one spray nozzle is a plurality of spray nozzles located on a top rotating arm and a bottom rotating arm.

4. The dish washing machine of claim 1, wherein: the drain pipe includes a horizontal portion within the fresh water reservoir and an elbow hot water waste retainer just outside of the fresh water reservoir, the elbow hot water waste retainer including a lower surface that is above the horizontal portion to allow the further heated wash water to pool in the horizontal portion.

5. The dish washing machine of claim 1, further including: a first pump for pumping the initially heated fresh water from the fresh water reservoir to the first water tank and for pumping the further heated fresh water from the first water tank to the at least one spray nozzle; anda second pump for pumping the further heated wash water from the second water tank to the at least one spray nozzle.

6. The dish washing machine of claim 1, wherein: both the first heating system and the second heating system comprise a stainless steel shell with a positive temperature coefficient heating array located therein, the positive temperature coefficient heating array comprising a plurality of positive temperature coefficient heating elements, with a temperature sensor being connected to a heater cover, the temperature sensor measuring a temperature of the first heating system to maintain the temperature of the first heating system under a predetermined temperature.

7. The dish washing machine of claim 6, wherein: the temperature sensor of the first heating system is not immersed in the initially heated fresh water.

8. The dish washing machine of claim 6, wherein: the temperature sensor of the second heating system is not immersed in the further heated wash water.

9. A dish washing machine comprising: a housing having an interior wash space for washing dishes and at least one spray nozzle for spraying liquid onto dishes positioned within the interior wash space;a liquid tank for supplying liquid to the at least one spray nozzle;the liquid tank including a heating system comprising a stainless steel shell with a positive temperature coefficient heating array located therein, the positive temperature coefficient heating array comprising a plurality of positive temperature coefficient heating elements, with a temperature sensor being connected to a heater cover, the temperature sensor measuring a temperature of the first heating system to maintain the temperature of the first heating system under a predetermined temperature;the temperature sensor of the first heating system not being immersed in the liquid within the liquid tank.

10. A method of washing dishes comprising: providing a housing having an interior wash space for receiving dishes;adding fresh water to a dish washing machine;feeding the fresh water to a fresh water reservoir;heating the fresh water in the fresh water reservoir to form initially heated fresh water;delivering the initially heated fresh water from the fresh water reservoir to a first water tank;heating the initially heated fresh water in the first water tank with a first heating system to form further heated fresh water;supplying the further heated fresh water to at least one spray nozzle;spraying the further heated fresh water onto dishes positioned within the interior wash space;delivering the further heated fresh water from the interior wash space to a second water tank;heating the further heated fresh water in the second water tank with a second heating system to form further heated wash water;delivering the further heated wash water to the at least one spray nozzle;spraying the further heated wash water into the interior wash space; anddraining the further heated wash water through a drain pipe that passes through the fresh water reservoir and to a liquid outlet;wherein heating the fresh water in the fresh water reservoir to form the initially heated fresh water comprises transferring heat from the further heated wash water to the fresh water in the fresh water reservoir.

11. The method of claim 10, further including: pumping the initially heated fresh water from the fresh water reservoir to the first water tank and pumping the further heated fresh water from the first water tank to the at least one spray nozzle with a pump.

12. The method of claim 10, wherein: the at least one spray nozzle is a plurality of spray nozzles located on a top rotating arm and a bottom rotating arm.

13. The method of claim 10, wherein: the drain pipe includes a horizontal portion within the fresh water reservoir and an elbow hot water waste retainer just outside of the fresh water reservoir, the elbow hot water waste retainer including a lower surface that is above the horizontal portion to allow the further heated wash water to pool in the horizontal portion.

14. The method of claim 10, further including: pumping the initially heated fresh water from the fresh water reservoir to the first water tank and pumping the further heated fresh water from the first water tank to the at least one spray nozzle with a first pump; andpumping the further heated wash water from the second water tank to the at least one spray nozzle with a second pump.

15. The method of claim 10, wherein: both the first heating system and the second heating system comprise a stainless steel shell with a positive temperature coefficient heating array located therein, the positive temperature coefficient heating array comprising a plurality of positive temperature coefficient heating elements, with a temperature sensor being connected to a heater cover, the temperature sensor measuring a temperature of the first heating system to maintain the temperature of the first heating system under a predetermined temperature.

16. The method of claim 15, wherein: the temperature sensor of the first heating system is not immersed in the initially heated fresh water.

17. The method of claim 15, wherein: the temperature sensor of the second heating system is not immersed in the further heated wash water.