Abstract:
A warewash machine sump collects hot cleaning water that is recirculated in the chamber during cleaning. A drain line is for draining cleaning water from the sump. A fresh water input system includes at least a hot water input and a cold water input. The fresh water input system has a common input line in communication with the hot water input and the cold water input. A cold water input valve and hot water input valve are provided. The drain line and the common input line are arranged in a heat exchange relationship. A temperature sensor arrangement is associated with the drain line for determining temperature of the cleaning water traveling through the drain line. A controller controls the hot water input valve and cold water input valve based upon the temperature sensor arrangement output.

Description:
TECHNICAL FIELD 
     This application relates generally to warewashers and, more particularly, to a warewasher with a water energy recovery system. 
     BACKGROUND 
     In some commercial warewash machines, drain water is at a temperature above that mandated by plumbing codes for draining. This is because cleaning water and rinse water are typically above this temperature during a cleaning operation. In order to cool the drain water, cold water is sometimes flushed down the drain with the drain water to lower water temperature. 
     Energy efficiency continues to be a significant issue in the field of warewash machines, particularly commercial warewash machines that tend to be high volume machines. It is known to provide heat recovery systems for recovering some heat from drain water that is being purged from the machine as exemplified by U.S. Pat. No. 5,660,193. 
     Nonetheless, it would be desirable to provide a warewash machine with a new and advantageous waste water energy recovery system. 
     SUMMARY 
     In an aspect, a warewash machine includes a housing at least in part defining a chamber for cleaning wares. A sump collects hot cleaning water that is recirculated in the chamber during cleaning. A drain line is for draining cleaning water from the sump. A fresh water input system includes at least a hot water input that receives hot water from a hot water source and a cold water input that receives cold water from a cold water source. The fresh water input system has a common input line in communication with the hot water input and the cold water input. A cold water input valve is for controlling input of cold water into the common input line. A hot water input valve is for controlling input of hot water into the common input line. The drain line and the common input line are arranged in a heat exchange relationship to enable heat from cleaning water traveling through the drain line to enable transfer of heat to water traveling through the common input line. A temperature sensor arrangement is associated with the drain line for determining temperature of the cleaning water traveling through the drain line. A controller receives input from the temperature sensor arrangement and is operable to control the cold water input valve and the hot water input valve such that, during a draining operation, if cleaning water traveling through the drain line is above a preselected temperature, the controller opens the cold water input valve to allow water from the cold water source to enter the common input line. 
     In another aspect, a warewash machine includes a housing at least in part defining a chamber for cleaning wares. A sump collects cleaning water that is recirculated in the chamber during cleaning. A drain line is for draining cleaning water from the sump. A fresh water input system includes at least a hot water input that receives hot water from a hot water source and a cold water input that receives cold water from a cold water source. The fresh water input system has a common input line in communication with the hot water input and the cold water input. The drain line and the common input line are arranged in a heat exchange relationship to enable heat from cleaning water traveling through the drain line to transfer heat to water traveling through the common input line. A storage tank receives water from the common input line once heated by cleaning water traveling through the drain line. 
     In another aspect, a method of providing water energy recovery in a warewash system is provided. The method includes initiating a tank filling operation using a fresh water input system to fill a sump with cleaning water. The fresh water input system includes at least a hot water input that receives hot water from a hot water source and a cold water input that receives cold water from a cold water source. The fresh water input system has a common input line in communication with the hot water input and the cold water input. A ware washing operation is initiated where the cleaning water is sprayed into a washing zone for cleaning wares. The sprayed cleaning water is recirculated in the washing zone and collected in the sump. A ware rinsing operation is initiated where hot water from the hot water source is delivered along the common input line and is sprayed into a rinsing zone. At least some of the cleaning water is drained from the sump along a drain line. Temperature of the cleaning water drained along the drain line is detected. If the temperature of the cleaning water is above a preselected temperature, delivery of hot water from the hot water source into the common input line is prevented and delivery of cold water from the cold water source into the common input line is allowed. The cold water from the cold water source is heated using energy from the cleaning water traveling along the drain line. The common input line and the drain line are in a heat exchange relationship to enable heat from cleaning water traveling through the drain line to heat water traveling through the common input line. 
     The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic, side section view of an embodiment of a warewash system; 
         FIG. 2  is a diagrammatic, side view of an embodiment of a heat exchanger for use with the warewash system of  FIG. 1 ; 
         FIG. 3  is a perspective view of an embodiment of a filter system for use with the warewash system of  FIG. 1 ; and 
         FIG. 4  is another embodiment of a warewasher system. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , an exemplary conveyor-type warewash system, generally designated  10 , is shown. Warewash system  10  can receive racks  12  of soiled wares  14  from an input side  16  which are moved through a tunnel-like chamber from the input side toward an output side  18  at an opposite end of the warewash system by a suitable conveyor mechanism  20 . Either continuously or intermittently moving conveyor mechanisms or combinations thereof may be used, depending, for example, on the style, model and size of the warewash system  10 . The racks  12  of soiled wares  14  enter the warewash system  10  through a flexible curtain  22  into a wash chamber or zone  24  where sprays of liquid from upper and lower wash manifolds  26  and  28  above and below the racks, respectively, function to flush heavier soil from the wares. The liquid for this purpose comes from a tank  30  via a pump  32  and supply conduit  34 . A heater  36 , such as an electrical immersion heater provided with suitable thermostatic controls (not shown), maintains the temperature of the cleansing liquid in the tank  30  at a suitable level (e.g., 160 degrees F. or more). A drain system  38  provides a location where liquid is drained from the tank  30 , as will be described in greater detail below. Not shown, but which may be included, is a device for adding a cleansing detergent to the liquid in tank  30 . During normal operation, pump  32  is continuously driven once the warewash system  10  is started for a period of time. 
     The warewash system  10  may optionally include a pre-wash and/or power rinse chamber or zone (not shown) that is substantially identical to the wash zone  24 . In such instances, racks of wares proceed into a pre-wash chamber and/or from the wash zone into the power rinse chamber, within which heated rinse water is sprayed onto the wares from upper and lower manifolds. Separate tanks may also be provided for the pre-wash and/or power rinse chambers. 
     The racks  12  of wares  14  exit the wash zone  24 , e.g., through a curtain (not shown) into a final rinse zone  42 . The final rinse zone  42  is provided with upper and lower spray heads  44 ,  46  that are supplied with a flow of fresh hot water via pipe  48 . A rack detector (not shown) may be actuated when rack  12  of wares  14  is positioned in the final rinse zone  42  and through suitable electrical controls, the detector causes actuation of a solenoid valve (not shown) to open and admit the hot rinse water to the spray heads  44 ,  46 . The water then drains from the wares into tank  30 . The rinsed rack  12  of wares  14  then exits the final rinse zone  42  through curtain  50  and, in some embodiments, moves into a dryer unit (not shown). 
     The warewash system  10  includes a drain water heat recovery system  52  that utilizes cleaning water to heat incoming cold water from a cold water source (represented by arrow  54 ) thereby reducing temperature of the cleaning water. A common input line  56  is connected to both a hot water input  58  that receives hot water (e.g., at about 110 degrees F.) from a hot water source (represented by arrow  60 ) and a cold water input  62  that receives cold water (e.g., at about 55 degrees F.) from the cold water source  54 . A cold water input valve  64  is used to control inlet of cold water from the cold water source  54  to the common input line  56 . Likewise, a hot water input valve  66  is used to control inlet of hot water from the hot water source  60  to the common input line. 
     The common input line  56  directs the incoming fresh water to a reverse flow heat exchanger  68  having a fresh water input end  70  and a fresh water output end  72 . Any suitable heat exchanger configuration can be used such as a ten pass, reverse flow heat exchanger formed of, for example, stainless steel, copper, etc. that can handle the detergent and food particles in the cleaning water. A plated metal may also be used. 
     The fresh water output end  72  of the heat exchanger  68  is connected to a storage tank  74  capable of holding an amount of fresh water therein by a line  76 . In some embodiments, the storage tank  74  is at least about 5 gallons. In some embodiments, the storage tank  74  is at least about 15 percent of the size of the tank  30 , such as between about 20 percent and about 30 percent the size of the tank  30 . In some embodiments, the storage tank  74  is sized to accommodate a multi-tank warewash system. 
     A pump  78  is used to pump the fresh water from the storage tank  76  to a booster heater  80  and then to the upper and lower spray heads  44  and  46 . The booster heater  80  can be used to heat the fresh water between about 40 and 80 degrees F. A tank fill line  82  includes a control valve  84  for allowing a tank  30  fill operation. 
     The heat exchanger  68  also includes a drain water input end  86  and a drain water output end  88 . The drain water input end  86  receives cleaning water drained from the tank  30 . A filter system  90  is provided between the heat exchanger  68  and a drain  92  to filter larger particles from the cleaning water before it passes into the heat exchanger. A temperature sensor  94  is associated with the filter system  90  and used to determine the temperature of the cleaning water passing through the filter system. The temperature sensor  94  provides the temperature to a controller  96 , which also controls operation of the hot water input valve  66  and cold water input valve  64 . It should be noted that controller  96  may control an number of other components of the warewash system  10 , such as valve  84 , pumps  32  and  78 , heater  36 , etc., despite no connecting lines being drawn to those components for clarity. Additionally, while controller  96  is shown, the valves  64 ,  66 ,  84  and other components may be controlled using software based around the warewash control system. The drain water output end  88  is connected to a building drain (represented by arrow  100 ) through which the cleaning water can be drained. 
       FIG. 2  illustrates, diagrammatically, the reverse flow arrangement of the heat exchanger  68 . During a heat exchange operation, the cold fresh water from the cold water source  54  flows into the fresh water input end  70  of the heat exchanger  68 , travels through a passageway  102  formed between an outer heat exchange conduit  104  and an inner heat exchange conduit  106  and exits through the fresh water output end  72 . The cleaning water from the tank  30  flows into the drain water input end  86 , through a passageway  108  formed by the inner heat exchange conduit  106  and exits through the drain water output end  88  toward the building drain. During the heat exchange operation, the drain water may reduce in temperature between about 20 and about 60 degrees F., while the fresh water may increase in temperature between about 20 and about 60 degrees F. In some embodiments, the cleaning water may decrease in temperature from a temperature of between about 150 and 160 degrees F. at the drain water input end  86  of the heat exchanger  68  to a temperature of less than about 130 degrees F., such as between about 115 and 125 degrees F. at the drain water output end  88 . In some embodiments, the fresh water entering the heat exchanger  68  from the cold water input  62  may increase in temperature from a temperature of about 55 degrees F. at the fresh water input end  70  to a temperature of between about 105 and about 115 degrees F. at the fresh water output end  72 . 
     Referring to  FIG. 3 , the filter system  90  includes an input end  110  in communication with the drain  92  of the tank  30  and an output end  112  in communication with the heat exchanger  68 . A collection basin  114  collects particles filtered using a filter  116  (e.g., a screen, filter material, etc.) through which the cleaning water travels during draining. A removable cap  117  is provided to allow for ease of filter  116  replacement. In some embodiments, the cap  117  and/or housing  119  are formed of a transparent or translucent material that allows for viewing of the filter  116  from outside the filter system  90  to determine visually when the filter should be replaced. In some embodiments, the filter  116  may be attached to the cap  117  such that removal of the cap also removes the filter  116  from the housing  119 . 
     Referring back to  FIG. 1 , during an initial tank fill operation (e.g., when the tank  30  is filled at the start of the day), the controller  96  determines that hot cleaning water is not being drained from the tank  30  through the drain  92  using the temperature sensor  94  and the controller opens the hot water input valve  66  thereby causing hot fresh water (e.g., at 110 degrees F.) to enter the common input line  56 . The hot fresh water travels through the heat exchanger  68  and into the storage tank  76  thereby filling the storage tank with hot water. The pump  78  pumps the hot water from the storage tank  76  and into the booster heater  80  where the hot water is heated to a temperature of at least about 140 degrees F. The controller  96  opens the control valve  84  to allow the fresh hot water to fill the tank  30 . In some embodiments, the tank  30  includes a float system (not shown) to prevent over filling. 
     At the beginning of a washing operation, the warewash system  10  suspends some of the cleaning water (e.g., about four gallons) in the tank  30  to fill the wash lines and spray some cleaning water on the wares thereby reducing the water level in the tank. When the rinse system is activated, initially, there is no cleaning water being drained due to use of an overflow pipe  118  having an opening  120  above the water level. The controller  96  recognizes that no hot cleaning water is being drained and allows fresh hot water to flow into the common input line  56 , which flows into the booster heater  80  to feed the drain system. 
     After some time, the cleaning water begins to drain through the drain  92  due to the addition of the rinse water into the tank  30 . The controller  96  recognizes that hot cleaning water (e.g., at least about 120 degrees or more, such as at least about 140 degrees F.) is being drained through the drain  92  using the temperature sensor  94  and, as a result, closes the hot water input valve  66  and opens the cold water input valve  64  thereby allowing cold water (e.g., at about 55 degrees F.) to enter the common input line  56 . Hot cleaning water flowing from the filter system  90  and fresh cold water flowing from the cold water input  62  enter the heat exchanger  68  thereby reducing the temperature of the cleaning water before it enters the building drain  100  and increasing the temperature of the fresh water before it enters the storage tank  76  and booster heater  80  (where the fresh water is heated to a temperature of at least about 180 degrees F. for rinsing) and is pumped to the rinse system. 
     Once the rinse operation is stopped, cleaning water may continue to drain from the tank  30 . The controller  96  recognizes this continued draining using the temperature sensor  94  and allows the fresh cold water to continue flowing into the common input line  56  to cool the cleaning water. The storage tank  76  is sized to collect the fresh water heated by the cleaning water in the heat exchanger  68 . 
     When the warewash system  10  is stopped, cleaning water is eliminated from suspension (e.g., about four gallons), which is also drained through the drain system. The controller  96  recognizes this continued draining using the temperature sensor  94  and allows the fresh cold water to continue flowing into the common input line  56  to cool the cleaning water. In some embodiments, the controller  96  may pulse the fresh cold water using the cold water input valve  64  at a level to reduce the temperature of the cleaning water flowing through the heat exchanger  68  while reducing the amount of incoming fresh water which will be collected in the storage tank  76 . 
     In some instances, it may be desirable to drain the tank  30  completely (in some embodiments, tank  30  may contain about 23 gallons of the cleaning water). During such a draining or dumping operation, the controller  96  recognizes this draining using the temperature sensor  94  and allows the fresh cold water to continue flowing into the common input line  56  to cool the cleaning water. In some embodiments, the controller  96  may pulse the fresh cold water using the cold water input valve  64  at a level to reduce the temperature of the cleaning water flowing through the heat exchanger  68  while reducing the amount of incoming fresh water which will be collected in the storage tank  76 . The water collected by the storage tank  76  will be the initial water used to fill the tank  30  during the next initial tank fill operation. In any of the above operations, if the cleaning water is below the preselected temperature (e.g., of 140 degrees F.) as measured using the temperature sensor  94 , the controller  96  recognizes this and can close the cold water input valve  64  or can leave the cold water input valve closed rather than admit fresh cold water. 
     Referring to  FIG. 4 , an alternative drain water heat recovery system  122  is similar to the drain heat recovery system  52  described above and includes a hot water blending system  124  that includes a second hot water input  126  connected to the hot water source with hot water input valve  128  controlled by controller  96 . Hot water input  126  can provide fresh hot water to a blending valve  130  connected to the fresh water line at a location downstream of the heat exchanger  68 . A temperature sensor  132  is associated with the blending valve  130  to monitor temperature of the fresh water received from the heat exchanger  68 . If the water temperature is too low (e.g., below 110 degrees F.), then the controller  96  can open the valve  128  to allow hot water to blend with water received from the heat exchanger  68 .  FIG. 4  also illustrates an alternative placement from the blending valve  130  downstream of the pump  78  and storage tank  76 . In this embodiment, a drain pump  134  is also provided, which may also be utilized in the system of  FIG. 1 . 
     The above-described warewasher system with drain water heat recovery system may have a number of advantages including utilizing energy from the heated cleaning water to heat incoming, fresh cold water supplied to the rinse system. Use of the drain water heat recovery system can provide water savings in that water used to cool the cleaning water drained from the tank is supplied to the rinse system rather than dumping the cooling water directly into the drain. 
     It is to be clearly understood that the above description is intended by way of illustration and example only and is not intended to be taken by way of limitation, and that changes and modifications are possible. Accordingly, other embodiments are contemplated and modifications and changes could be made without departing from the scope of this application.