COMMERCIAL DISHWASHING MACHINE AND METHOD FOR OPERATING SUCH A

Description

[0001] The present invention relates to a commercial dishwasher and a method for operating such a commercial dishwasher. Such commercial dishwashers comprise a washing chamber into which dishes to be washed can be placed, and a dispensing device for dispensing one or more different treatment liquids.

[0002] Such commercial dishwashers typically operate with very short cycle times, with numerous cycles occurring per day. Each cycle often includes one or more operating cycles, particularly a wash cycle, a rinse cycle, and / or a drying cycle.

[0003] After each cycle, the dishwasher's cabinet is opened, and the washed dishes can be removed. However, opening the commercial dishwasher after the cycle to remove the dishes causes the steam or vapors created during the cycle to escape into the environment, creating a warm and humid environment in the workspace where the dishwasher is located, especially when numerous cycles are performed in a short period of time.

[0004] In order to mitigate this negative effect, EP 1 355 560 B1 proposes a commercial dishwasher with a heat exchanger or dehumidifier, wherein the dishwasher is designed in such a way that it comprises a device for generating an air flow that circulates in a closed air circuit so that the moist air can be led out of the washing chamber and fed back into the washing chamber, wherein the heat exchanger or dehumidifier is provided in the air circuit.

[0005] DE 10 2007 063 618 A1 further discloses a hood-type dishwasher comprising a condensate precipitation device connected to the washing chamber when the hood is closed. The condensate precipitation device comprises a fan for extracting steam and / or air from the closed washing chamber, so that this steam is at least partially condensed in the condensate precipitation device before being released into the working environment. WO 2006 / 063895 A1 discloses a household dishwasher and a method for operating the same.

[0006] Finally, DE 10 2011 083 179 B4 discloses a conveyor dishwasher which comprises a condenser device for removing moisture from the exhaust air by condensation, the performance of the condenser device being adjustable.

[0007] It is an object of the present invention to further improve such a commercial dishwasher.

[0008] This object is achieved by a commercial dishwasher according to claim 1 and a method according to claim 14. Claims 2 to 13 relate to particularly preferred embodiments of the dishwasher according to the invention.

[0009] A commercial dishwasher according to the invention comprises a washing chamber in which at least one dispensing device for dispensing a treatment liquid is arranged. The dishwasher according to the invention further comprises: a vapor circuit designed so that vapors can be led out of the washing chamber and reintroduced into the washing chamber, a boiler for heating treatment liquid, wherein the boiler can be filled with the treatment liquid by means of a supply line and wherein the boiler is connected to a discharge line via which the treatment liquid can be transported to the at least one discharge device in the washing chamber, wherein the supply line is assigned a valve device, in particular a solenoid valve, which in an open position enables the supply of treatment liquid into the boiler or in a closed position prevents the supply of treatment liquid into the boiler, and wherein the discharge line is assigned a conveying device, in particular a pump,which, in a switched-on state, enables a release of treatment liquid from the boiler to the at least one release device in the washing chamber or, in a switched-off state, prevents such a release, a heat exchanger which is coupled to the vapor circuit and the inlet line in such a way that a heat exchange can take place between the vapors conducted through the vapor circuit and the treatment liquid conducted through the inlet line, an extraction device which is designed in such a way that it circulates vapors through the vapor circuit, wherein the extraction device can be switched into an switched-on state or an switched-off state by means of a control device.

[0010] The treatment liquid can be various treatment liquids, for example, a washing or cleaning liquid. In particular, the treatment liquid in a dishwasher according to the present invention can be a rinse liquid, because this rinse liquid is brought to the desired operating temperature in a boiler and is applied to the dishes during a final operating cycle before the vapors are cooled or dehumidified. Therefore, this rinse liquid, which is passed through the heat exchanger or dehumidifier, is particularly suitable, so that this rinse liquid is already preheated in the heat exchanger before being passed on to the boiler.

[0011] The valve device located in the supply line is, in particular, a solenoid valve. However, various other valve devices can also be used, whereby the term valve device is to be understood in a broader sense as a device that enables the supply of treatment fluid when it is in an open position and prevents it when it is not in an open position. The supply of treatment fluid can be achieved simply by opening the valve device, for example because the treatment fluid on the side to be supplied is under pressure. However, it is also possible to additionally use an active device, such as a pump, which supports the supply of treatment fluid. This active device can be part of the valve device or can be connected upstream or downstream of this valve device.

[0012] According to the present invention, the dishwasher comprises a control device which is designed such that it switches the extraction device continuously to its switched-on state during an operating cycle A for a total period (Δt-total) extending from a start time (t S ) to an end time (t E ), and so that it switches the valve device in such a way that it is not continuously in its open position over the entire total period (Δt-total) during the operating cycle A.

[0013] According to the invention, the control device is designed such that it the valve device is controlled in such a way that it is in its open position during at least two periods (Δt1, Δt2) separated from one another by an interruption period (Δty), while it is in its closed position within the interruption period (Δty).

[0014] Optionally, the control device is further designed such that it the valve device is controlled in such a way that it is switched from its closed position to an open position only after a time delay (Δtx) after the start time (tS).

[0015] The inventor has found that such a control system delivers significantly better results, in particular a very effective dehumidification and cooling of the vapors takes place, whereby the given conditions, in particular the size of the boiler and the associated maximum absorption capacity of the treatment liquid, in particular the rinsing liquid, are taken into account or influence the control system and determine the corresponding framework conditions.

[0016] This reduces air pollution in the work area where the dishwasher is located while simultaneously minimizing energy consumption. It also makes it possible to keep operating cycles as short as possible, which increases the overall performance of the dishwasher. Overall, this conserves resources, optimizes work processes, and, if desired, shortens them, while simultaneously improving conditions for the dishwasher operators in the work area.

[0017] Preferably, a time delay Δtx after the time t S at which the extraction device is switched on so that vapor is circulated through the vapor circuit, after which the valve device is switched from its closed position to its open position, lies in a range of 5 seconds to 60 seconds, preferably from 10 seconds to 50 seconds, in particular in a range of 20 to 40 seconds. Depending on the size and maximum volume capacity of the boiler, the valve device is switched back from its open position to its closed position, for example when the boiler is filled to a predetermined and preferably controllable percentage or the maximum boiler capacity is reached.Preferably, the suction device remains switched on for a certain period of time after a (final) closing of the valve device, preferably for a period of time from 5 seconds to 25 seconds, preferably from 5 seconds to 20 seconds, in particular in a range of 10 to 15 seconds.

[0018] According to a particularly preferred embodiment of the commercial dishwasher, the control device is designed to control the valve device such that it is in its open position during at least three separate time periods (Δt1, Δt2, Δt3), preferably during at least four separate time periods (Δt1, Δt2, Δt3, Δt4, ...., Δti), while it is in its closed position between these time periods.

[0019] This synchronized approach, with the valve repeatedly switching from its open to its closed position, has been found to be particularly effective in cooling the vapor and thus dehumidifying it. Three to four separate periods have proven particularly effective and suitable.

[0020] Preferably, even with this multiple or clocked control of the valve device, the valve device is switched on for the first time with a delay, i.e., with a time delay Δtx after the time t S at which the suction device is switched on. The length of the delay is preferably shorter if the valve device is switched on and off several times within an operating cycle A, i.e., is operated in a clocked manner. Preferably, with such a clocked mode of operation, the control device is set such that this time delay Δtx is in a range from 5 seconds to 20 seconds, preferably in a range from 5 seconds to 15 seconds.

[0021] The length of the individual time periods Δt1, Δt2, Δt3, Δt4, ...., Δti is preferably in a range from 5 seconds to 20 seconds, preferably in a range from 10 seconds to 20 seconds, in particular in a range from 10 seconds to 15 seconds.

[0022] Particularly preferably, the control device is set such that at least two of the separate time periods Δt1, Δt2, Δt3, Δt4, ...., Δti, preferably all of the separate time periods Δt1, Δt2, Δt3, Δt4, ...., Δti, are of equal length. Preferably, the interruption time period(s) (Δty) during which the valve device is in its closed position are also all of equal length. This enables a smooth process while simultaneously achieving very good results.

[0023] In a particularly preferred embodiment, the dishwasher according to the invention comprises a first temperature sensor, which is preferably arranged in the vapor circuit, in particular upstream of the heat exchanger in the circulation direction. Furthermore, the dishwasher according to the invention preferably comprises a second temperature sensor, which is preferably also arranged in the vapor circuit, in particular downstream of the heat exchanger in the circulation direction.

[0024] Preferably, the measurement results of the first and / or the second temperature sensor are fed to the control device so that the control device can control the suction device and / or the valve device depending on the measurement results of the first and / or the second temperature sensor.

[0025] This leads to a further possible optimization of the process and in particular of the cooling and dehumidification of the vapors, in an automated form, whereby in particular changes in the ambient conditions, in particular the temperature of the working space or the temperature of the treatment liquid as it is made available to the device, can be automatically taken into account.

[0026] Particularly preferably, the dishwasher according to the invention is designed such that the control device determines a temperature difference between the measured values ​​of the first temperature sensor and the measured values ​​of the second temperature sensor, whereby the valve device is controlled depending on this temperature difference. The temperature difference can be used as an indicator of the current effectiveness of the cooling process or the dehumidification of the vapors, so that the valve device, when in its closed position, can be automatically switched back to its open position if this effectiveness decreases or reaches or falls below a predetermined limit.

[0027] In a particularly preferred embodiment, the control device is designed such that it switches the valve device at least once from its closed position to its open position when the differential temperature (ΔT) falls below a specified limit value (ΔTM1) or falls below a specified limit value (ΔTM2) for a specified period of time (ΔtM2).

[0028] In a preferred embodiment, this specified limit value (ΔTM1) lies in a range from 0° Kelvin to 2° Kelvin, particularly preferably in a range from 0.5° Kelvin to 2° Kelvin, particularly preferably in a range from 0.5° Kelvin to 1° Kelvin. In a preferred embodiment, the specified limit value (ΔTM2) lies in a range from 0.5° Kelvin to 3° Kelvin, particularly preferably in a range from 1° Kelvin to 2° Kelvin, especially preferably in a range from 1° Kelvin to 1.5° Kelvin, wherein the specified time period (ΔtM2) is preferably in a range from 1 second to 5 seconds, particularly preferably in a range from 1 second to 3 seconds.

[0029] In a preferred embodiment, the control device is designed such that it switches the valve device back to the closed position after a specified, preferably adjustable, period of time (ΔtE) from the change in its open position. The differential temperature is further determined so that, preferably according to the above-mentioned principle, the valve device is switched back to its open position when the differential temperature meets the described conditions.

[0030] The fixed, preferably adjustable period (ΔtE) is preferably in a range from 5 seconds to 20 seconds, preferably in a range from 10 seconds to 20 seconds, in particular in a range from 10 seconds to 15 seconds.

[0031] The length of the total operating cycle period can be fixed, and it can be incrementally adjusted within a range of 80 seconds to 150 seconds, preferably within a range of 90 seconds to 120 seconds. However, it is possible to adjust the length of the total operating cycle period depending on the measurement results of the temperature sensors, in particular depending on the measurement result of the first temperature sensor.In particular, it is possible to terminate the operating cycle when the temperature of the first temperature sensor falls below a specified value, for example less than 50 °C, or it can be specified that when such a specified value is undershot, or alternatively after such a specified value has been undershot for a specified period of time, for example a period of 5 seconds to 10 seconds, only one more "cycle" of switching the valve device to its open position and then to its closed position is carried out.

[0032] It is further particularly preferred that the dishwasher is designed such that the control device regulates the length of the time periods (Δt1, Δt2, Δt3, Δt4) and / or the length of the time delay (Δtx) or the length of the interruption period (Δty) depending on the measurement results of the first temperature sensor and / or the second temperature sensor and / or the differential temperature (ΔT). This allows a dishwasher to be adapted particularly effectively to the conditions and specific circumstances, in particular automatically, without the user having to adjust anything.

[0033] Various heat exchangers, particularly direct heat exchangers known in the art, can be used as heat exchangers. Preferred heat exchangers here are direct heat exchangers (in which the material flows are not separated from each other), fin-and-tube heat exchangers, and microchannel heat exchangers or other heat exchangers in which the material flows are separated from each other.

[0034] The invention further relates to a method for operating a dishwasher, in particular a dishwasher as described above. With regard to the advantages of such a method or such a control, reference is made to the above-described embodiments to avoid repetition.

[0035] The invention and its advantages become even clearer with the help of the following figures: Fig. 1 shows schematically a functional sketch of an embodiment of a dishwasher according to the invention, Fig. 2 schematically shows a time sequence of a control of a working cycle of a dishwasher according to a first example which is helpful for understanding the invention, Fig. 3 shows a temperature profile and a control within an operating cycle of a dishwasher according to the first example, Fig. 4 schematically shows a time sequence of a control of a working cycle of a dishwasher according to the invention according to an embodiment, Fig. 5 shows a temperature profile and a control within an operating cycle of a dishwasher according to the invention according to a first variant of the embodiment, Fig. 6 shows a temperature profile and a control within an operating cycle of a dishwasher according to the invention according to a second variant of the embodiment, and Fig. 7 shows a temperature curve and a control within an operating cycle of a dishwasher according to the state of the art.

[0036] Fig. 1 shows a schematic functional diagram of an embodiment of a dishwasher 10 according to the invention, which has a washing chamber 100. The dishwasher 10 comprises a plurality of dispensing devices, in this embodiment, washing arms 120, which are rotatably arranged in the washing chamber 100 of the dishwasher 10.

[0037] The dishwasher 10 further comprises a tank 140 with a sieve system 144, wherein a heating device 142 is provided in the tank 140 in order to heat the liquid, in particular cleaning liquid, located in the tank 140.

[0038] The Fig. 1 The embodiment of the dishwasher 10 shown further comprises a boiler 200 for heating a treatment liquid, in particular a final rinse liquid. The boiler 200 can be filled with the treatment liquid via a supply line 220. Furthermore, the boiler 200 is connected to a discharge line 230, via which the treatment liquid, in particular the final rinse liquid, can be transported to a discharge device in the wash cabinet 100, here the rinse arms 120.

[0039] The supply line 220 comprises a valve device 222, in this embodiment a solenoid valve. The valve device 222 allows the supply of treatment liquid to the boiler 200 when it is in an open position, and prevents the supply of treatment liquid to the boiler 200 when it is in a closed position.

[0040] The inlet line 220 also contains a water safety device 224.

[0041] In the discharge line 230, a conveying device, here a rinse pump 260, is provided which, in a switched-on state, enables a discharge or conveyance of treatment liquid from the boiler 200 to the discharge devices, here the rinse arms 120, while in a switched-off state of the rinse pump 260, no rinse liquid is delivered to the rinse arms 120.

[0042] The dishwasher 10 further comprises a vapor circuit 400, wherein vapor is guided out of the washing chamber 100 via a line 400, passed through a heat exchanger 300, and then re-entered into the washing chamber 100. For this purpose, a vapor fan 420 is provided in this embodiment, which, in this embodiment, is arranged upstream of the heat exchanger 300 in the circulation direction. However, the vapor fan 420 can also be arranged downstream of the heat exchanger 300 in the circulation direction.

[0043] In this embodiment, the vapor circuit 400 comprises two temperature sensors 422 and 424, wherein the first temperature sensor 422 is arranged upstream of the heat exchanger 300 in the circuit direction, while the second temperature sensor 424 is arranged downstream of the heat exchanger 300 in the circuit direction. The first temperature sensor 422 is particularly preferably arranged near the washing chamber 100, particularly preferably directly at the point in the vapor circuit 400 that borders the washing chamber 100.

[0044] In this embodiment, the dishwasher 10 further comprises a wash pump 146, which can deliver wash liquid from the tank 140 to the wash arms 120. The wash liquid delivered via the wash arms 120 then collects in the tank 140 after being delivered into the wash cabinet 100, thus creating a wash cycle. Furthermore, the dishwasher 10 comprises a drain pump 148, via which contaminated wash liquid can be discharged and disposed of.

[0045] Fig. 2 shows a schematic diagram of a time sequence for controlling an operating cycle of an embodiment of a dishwasher according to a first example, although not all features of the present invention are shown or implemented. During the washing process of the dishwasher 10, the wash pump 146 runs for a predetermined period of time. After a short pause, during which washing liquid can drip off the dishes, so that this pause is also referred to as the dripping time, the rinse pump 260 is switched on for a predetermined period of time, so that rinse liquid is delivered from the boiler 200 via the line 230 to the rinse arms 120, whereby the boiler 200 is emptied.

[0046] The extraction device, here the vapor fan 420, is continuously switched to its on state during an operating cycle A for a total period Δt-total, which extends from a start time t S to an end time t E.

[0047] How good in Fig. 2 However, as can be seen, the valve device 222 is switched in such a way that it is not continuously in its open position over the entire period Δt-total during the operating cycle A, but rather the valve device 222 is only switched from its closed position to an open position after a time delay Δtx after the start time t S.

[0048] The valve device 222 is then switched back to its closed position after a certain period of time, preferably when the boiler 200 is completely filled again.

[0049] Fig. 3 shows the control system as shown in Fig. 2 shown, the profile of the wash cabinet temperature. The temperature for this measurement was measured using a sensor arranged in the wash cabinet 100, but this also essentially corresponds to the temperature measured by the temperature sensor 422, which is located in the vapor circuit upstream of the heat exchanger 300 in the direction of circulation.

[0050] Fig. 3 further shows the course of the water temperature (T_Wasser_aus) within the inlet line 220 in a position directly after the heat exchanger 300.

[0051] How good in Fig. 3 As can be seen, an increase in the wash cabinet temperature is first measured somewhat before the time t S , which is based on the fact that the wash cabinet temperature first increases during the rinsing process (typical temperatures for the rinsing liquid are in a range of about 65 °C for a glasswashing program, for dishes this temperature is about 85 °C in the commercial sector).

[0052] At time t S , the vapor fan 420 is switched on, and the vapor present in the wash cabinet 100 is guided through the vapor circuit and thus through the heat exchanger 300. The wash cabinet temperature initially drops significantly due to the effect of the heat exchanger 300. However, since the liquid contained in the heat exchanger 300 is initially not exchanged because the valve device 222 is closed, the effect of the heat exchanger 300 decreases, so that the measured temperature decreases only slightly and the temperature reduction levels off.

[0053] However, after a period Δtx, in this embodiment after a delay of approximately 50-55 seconds, the valve device 222 is opened, allowing new treatment liquid to be supplied via line 220, so that cooler treatment liquid is supplied to the heat exchanger 300, while the already warmed treatment liquid is conveyed to the boiler 200. The effect of the heat exchanger 300 therefore increases again during this period, so that a significant drop in the measured wash chamber temperature can be observed.

[0054] The valve device 222 is closed again when the boiler 200 is filled again.

[0055] How to Fig. 3 As can be clearly seen, the measured dishwashing cabinet temperature at the end time t E of the entire period is at a temperature of noticeably below 50 °C, whereby this temperature of 50 °C was empirically determined as the so-called "temperature limit", in particular because this temperature was determined as a value that had an acceptable influence on the room climate even with regular use of the dishwasher.

[0056] For comparison with a control system according to the state of the art, the Fig. 7 Contrary to the control in a dishwasher according to the present invention, in the prior art, the valve device 422 is opened at the same time as the extraction device, ie, the vapor fan 420, is switched on. In this case, too, the valve device 422 is closed again when the boiler 200 is filled.

[0057] As in Fig. 7 However, this obviously leads to a temperature several degrees Celsius higher at the end time t E , which worsens the indoor climate, although any slight temperature reduction leads to a significantly improved indoor climate due to the reduction in the absolute moisture content of the vapor.

[0058] Fig. 4 schematically shows a time sequence of a control of a working cycle of a dishwasher according to the invention according to one embodiment. In this embodiment, the valve device 222 is opened only after a delay Δtx, but then closed again after a period of Δt1, opened again after a further period of Δty1, and closed again after a further period of Δt2, whereby the valve device 222 is in its open position a total of four times, i.e., operated in a cyclical manner.

[0059] Fig. 5 shows a control system and a temperature profile for a dishwasher according to the invention according to a first variant of this embodiment. In this variant, the valve device 222 is opened only after a delay Δtx, in this embodiment after a delay of 20 seconds, but then closed again after a period of 12 seconds, opened again after a further 15 seconds, and closed again after a further 12 seconds. The valve device 222 is in its open position a total of four times, i.e., operated in a cyclical manner.

[0060] As can be seen very clearly in Fig. 5 This leads to an even further reduced wash cabinet temperature at the end time t E . The very advantageous effects described above are therefore even more evident with this clocked control.

[0061] Fig. 6 shows a control and a temperature profile in a dishwasher according to the invention according to a second variant of this embodiment, which is very comparable to the one in Fig. 5 shown variant of the embodiment, in which the valve device 222 is also operated in a clocked manner.

[0062] In this embodiment, the valve device 222 is switched to its open position for the first time after a delay Δtx of 10 seconds after the start time t S , and is then also operated in a cyclic manner. In this embodiment, the valve device 222 is switched to its on position for 12 seconds each time, then switched to its off position for 7 seconds each time, whereby the valve device is in its open position a total of four times, thus also being operated in a cyclic manner.

[0063] As can also be seen very clearly in Fig. 6This also leads to a very significantly reduced wash cabinet temperature at the end time t E .

[0064] A comparison of the various embodiments and variants shows that, in particular, the embodiments of the dishwasher according to the invention which are operated in a timed manner lead to a particularly effective temperature reduction, so that these timed implementations are particularly preferred.

[0065] It should be noted that while both embodiments each implement four activation cycles, a particularly significant temperature reduction within the wash cabinet is also achieved with other embodiments, for example, with two or three activation cycles, or alternatively with more than four activation cycles. It should also be noted that the cycles do not necessarily have to have the same length or the same interruption periods, although this is preferred.

[0066] The features presented in the description and in the figures may be essential for the realization of the invention both individually and in any combination.

Claims

1. Commercial dishwasher (10) having a washing chamber (100) in which at least one dispensing device for dispensing a treatment liquid is arranged, wherein the dishwasher (10) further comprises: - a waste steam circuit (400) that is designed such that the waste steam can be guided out of the washing chamber (100) and introduced back into the washing chamber (100), - a boiler (200) for heating treatment liquid, wherein the boiler (200) can be filled with the treatment liquid by means of a supply line (220), and wherein the boiler (200) is connected to a dispensing line (230), via which the treatment liquid can be transported to the at least one dispensing device in the washing chamber (100), - wherein a valve arrangement (222), in particular a magnetic valve, is assigned to the supply line (220), and, in the open position of the valve arrangement, facilitates a supply of the treatment liquid into the boiler (200), or, in a closed position, prevents a supply of treatement fluid into the boiler (200), and wherein a transportation device, in particular a pump, is assigned to the dispensing line (230) and, in a switched on state of the pump, facilitates a dispensing of treatment liquid out of the boiler (200) to the at least one dispensing device in the washing chamber (100) or, in a switched off state, prevents such a dispensing, - a heat exchanger (300) which is coupled to the waste steam circuit (400) and to the supply line (220) such that a heat exchange can take place between the waste steam guided through the waste steam circuit (400) and the treatment liquid guided through the supply line (220), - a suction device, which is designed such that it circulates the waste steam through the waste steam circuit (400), wherein the suction device can be switched into a switched on state or into a switched off state by means of a regulating device, characterized in that the dishwasher (10) comprises a control device, which is designed such that - it switches the suction device continuously into its switched on state during an operating cycle A for a total time period (Δt-total), which extends from a starting time (tS) to an end time (tE), and such that - it switches the valve device (222) such that it is not continuously located in its open position during the operating cycle A for the total time period (At-total) - wherein the valve device (222) is controlled such that it is located in its open position during at least two time periods (Δt1, Δt2), which are separated from one another by an interruption time period (Δty), while it is located in its closed position within the interruption time period (Δty).

2. Dishwasher (10) according to claim 1, characterized in that the control device is designed such that it controls the valve device (222) such that it is located in its open position during at least three time periods (Δt1, Δt2, Δt3), which are separated from one another, preferably during at least four time periods (Δt1, Δt2, Δt3, Δt4 ..., Δti), which are separated from one another, while it is located in its closed position between these time periods.

3. Dishwasher (10) according to claim 1 or 2, characterized in that at least two of the time periods (Δt1, Δt2, Δt3, Δt4 ..., Δti), which are separated from one another, preferably all of the time periods (Δt1, Δt2, Δt3, Δt4 ..., Δti), which are separated from one another, are of equal length.

4. Dishwasher (10) according to one of claims 2 or 3, characterized in that the interruption period(s) (Δty), within which the valve device (222) is located in its closed position, are all of equal length.

5. Dishwasher (10) according to one of the preceding claims, characterized in that the waste steam circuit (400) has a first temperature sensor (422) which is arranged upstream of the heat exchanger (300) in the direction of the circuit.

6. Dishwasher (10) according to one of the preceding claims, characterized in that the waste steam circuit (400) has two temperature sensors (422, 424), wherein a first temperature sensor (422) is arranged upstream of the heat exchanger (300) in the direction of the circuit and a second temperature sensor (424) is arranged downstream of the heat exchanger (300) in the direction of the circuit.

7. Dishwasher (10) according to claim 6, characterized in that the measurement results of the first and / or the second temperature sensor(s) (422, 424) are supplied to the control device, and the control device controls the suction device and / or the valve device (222) depending on the measurement results of the first and / or the second temperature sensor(s) (422, 424).

8. Dishwasher (10) according to claim 6 or 7, characterized in that the control device determines a differential temperature (ΔT) of the measurement values (T1) of the first temperature sensor (422) and of the measurement values (T2) of the second temperature sensor (424) and controls the valve device (222) depending on this differential temperature (ΔT, where ΔT = T1 - T2).

9. Dishwasher (10) according to claim 8, characterized in that the control device is designed such that it switches the valve device (222) from its closed position into its open position at least once if the differential temperature (ΔT) underruns a defined threshold (ΔTM1), or underruns a defined threshold (ΔTM2) for a defined time period (ΔtM2).

10. Dishwasher (10) according to claim 9, characterized in that the control device is designed such that, after the switch into the open position, the control device switches the valve device (222) back into the closed position after a defined, preferably adjustable time period (ΔtE).

11. Dishwasher (10) according to one of claims 5 to 10, characterized in that the control device regulates the length of the total time period (Δt-total) of the operating cycle depending on the measurement results of the first temperature sensor (422).

12. Dishwasher (10) according to one of claims 5 to 11, characterized in that the control device regulates the length of the time periods (Δt1, Δt2, Δt3, Δt4) and / or the length of the temporal delay (Δtx) or the length of the interruption time period (Δty) depending on the measurement results of the first temperature sensor and / or of the second temperature sensor (422, 424) and / or the differential temperature (ΔT).

13. Dishwasher (10) according to one of the preceding claims, characterized in that the control device is designed such that it controls the valve device (222) such that it is only switched from its closed position into an open position after a temporal delay (Δtx) after the starting point in time (tS).

14. Method for operating a commercial dishwasher (10) having a washing chamber (100) and a dispensing device for dispensing a treatment liquid, in particular a dishwasher (10) according to one of the preceding claims, wherein the dishwasher (10) further comprises: - a waste steam circuit (400) that is designed such that the waste steam can be guided out of the washing chamber (100) and introduced back into the washing chamber (100), - a boiler (200) for heating treatment liquid, wherein the boiler (200) can be filled with the treatment liquid by means of a supply line (220), and wherein the boiler (200) is connected to a dispensing line (230), via which the treatment liquid can be transported to the at least one dispensing device in the washing chamber (100), - wherein a valve arrangement (222), in particular a magnetic valve, is assigned to the supply line (220), and, in the open position of the valve arrangement, facilitates a supply of the treatment liquid into the boiler (200), or, in a closed position, prevents a supply of treatement fluid into the boiler (200), and wherein a transportation device, in particular a pump, is assigned to the dispensing line (230) and, in a switched on state of the pump, facilitates a dispensing of treatment liquid out of the boiler (200) to the at least one dispensing device in the washing chamber (100) or, in a switched off state, prevents such a dispensing, - a heat exchanger (300) which is coupled to the waste steam circuit (400) and to the supply line (220) such that a heat exchange can take place between the waste steam guided through the waste steam circuit (400) and the treatment liquid guided through the supply line (220), - a suction device, which is designed such that it circulates the waste steam through the waste steam circuit (400), wherein the suction device can be switched into a switched on state or into a switched off state by means of a regulating device, characterized in that the dishwasher (10) comprises a control device, which is designed such that - it switches the suction device continuously into its switched on state during an operating cycle A for a total time period (Δt-total), which extends from a starting time (tS) to an end time (tE), and such that - it switches the valve device (222) such that it is not continuously located in its open position during the operating cycle A for the total time period (At-total) - wherein the valve device (222) is controlled such that it is located in its open position during at least two time periods (Δt1, Δt2), which are separated from one another by an interruption time period (Δty), while it is located in its closed position within the interruption time period (Δty).