hot water boiler system

Abstract

Hot water boiler system (1) with a hot water boiler (18), with a fossil or biogenic heat generation device (14), the flue gases of which are passed through heat exchanger tubes (4) arranged in the hot water boiler (18) to heat the water in the hot water boiler (18), the hot water boiler (18) having an inlet (6) for supplying water to the hot water boiler (18) and an outlet (8) for discharging water from the hot water boiler (18), characterized in that a preheating device (10, 20) is arranged in the inlet (6) to preheat the water supplied to the hot water boiler (18), and that the hot water boiler system (1) has a control device (SR) which is connected to at least one temperature sensor (2) which is arranged in the inlet (6) and / or in the hot water boiler (18), and that the control device (SR) is to is designed and intended to be the preheating device (10,20) to control and / or regulate depending on the temperature signal received via the at least one temperature sensor (2).

Description

[0001] The invention relates to a hot water boiler system according to the preamble of claim 1.

[0002] Hot water boiler systems, particularly for use in district heating networks, industrial plants, or larger building heating systems, are known from the prior art, for example, in the form of hot water boiler systems with a hot water boiler equipped with a fossil fuel or biogenic heat generation unit. The heat generation unit produces flue gases that are passed through heat exchanger tubes arranged in the hot water boiler to heat the water inside, the heat exchanger tubes forming at least one flue gas passage of a heat exchanger.

[0003] The hot water boiler always has a supply line for feeding water into the hot water boiler, especially for feeding comparatively cooler return water, as well as a drain for removing water heated in the hot water boiler.

[0004] The hot water boiler is typically part of a closed heating water circuit connected to an external heating network or heating circuit. Return water from the heating network is supplied to the hot water boiler via the supply line; its temperature can fluctuate considerably depending on the current heat load, the outside temperature, and the design of the heating network. The water heated in the hot water boiler is then returned to the heating network as flow via the outlet.

[0005] In practical operation of such hot water boiler systems, operating conditions occur, particularly during partial load operation, with highly fluctuating operating demands, or in heating networks or circuits designed for low system temperatures, in which the return temperature supplied to the hot water boiler drops significantly. In these operating conditions, the comparatively cool water entering the hot water boiler via the supply line can cause a significant local cooling of the heat exchanger tubes, especially in the flue gas passages where the flue gases from the heat-generating unit first come into contact with the heat-transferring surfaces.

[0006] If the surface temperatures inside the heat exchanger tubes fall below the acid dew points of the acidic components contained in the flue gas, particularly sulfuric acid and hydrochloric acid, these acids condense on the tube walls. The acid dew points, depending primarily on the composition of the flue gases and the type of fossil or biogenic fuel, typically range from approximately 130°C to approximately 160°C.

[0007] The condensation of the acids leads to a significant corrosive attack on the heat exchanger tubes, which can result in progressive damage to the flue gas passages, material loss and a significant reduction in the service life of the hot water boiler.

[0008] To prevent this so-called low-temperature corrosion, various measures are known from the prior art. Typically, attempts are made to keep the temperature of the water supplied to the hot water boiler via the supply line above critical limits through suitable operating strategies. For example, minimum return temperatures are specified in the heating network or heating circuit, or mixing systems are used in which hot water from the drain is mixed with the cooler return water.

[0009] However, these well-known solutions have significant drawbacks. Artificially increasing the return temperature regularly leads to a decrease in the overall efficiency of the hot water boiler system, as usable low-temperature heat in the heating network or heating circuit is not fully utilized. This is particularly problematic for modern heating networks, which are designed for the lowest possible system temperatures, and contradicts energy-efficient operating concepts.

[0010] Based on this, it is an object of the present invention to provide a hot water boiler system that avoids these disadvantages and enables reliable prevention of corrosive operating conditions on the heat exchanger tubes.

[0011] This problem is solved by a hot water boiler system according to the features of independent claim 1. The dependent claims relate to particularly advantageous embodiments of the invention.

[0012] According to a key aspect, the present invention relates to a hot water boiler system comprising a hot water boiler and a fossil or biogenic heat generation device. The flue gases from this device are passed through heat exchanger tubes located within the hot water boiler to heat the water. The fossil or biogenic heat generation device, typically a burner, preferably includes at least one flue gas tube and / or combustion tube running within the hot water boiler for transferring heat from the burner to the hot water boiler, which serves as the receiving chamber. The at least one flue gas tube and / or combustion tube running within the hot water boiler can be part of, or even constitute, a heat exchanger. The flue gas tubes and / or combustion tubes can therefore also be designed as heat exchanger tubes.A hot water boiler system of this kind according to the invention is in particular designed as a large water space boiler or storage heater, and is therefore suitable for boiler systems with a net output of 0.5 to 30 MW, in particular 1.5 to 15 MW.

[0013] Furthermore, the hot water boiler has an inlet for supplying water to the boiler, in particular an inlet for supplying cooler water, and an outlet for removing water from the boiler, in particular for removing heated water. In other words, the hot water boiler has an inlet and an outlet, whereby water at a relatively lower temperature flows through the inlet and water at a relatively higher temperature flows through the outlet, each with reference to the operating state of the hot water boiler.Within the scope of the present invention, "water at a relatively lower temperature" is understood to mean, in particular, water whose temperature is below the current operating temperature of the water in the hot water boiler and which is supplied to the hot water boiler via the supply line without having yet fully reached the operating temperature of the hot water boiler. "Water at a relatively higher temperature" within the scope of the present invention is understood to mean, in particular, water that has been thermally heated in the hot water boiler and whose temperature is higher than that of the water supplied via the supply line, wherein the water may preferably be in a liquid or vaporous phase and is discharged from the hot water boiler via the outlet.

[0014] According to the invention, a preheating device is arranged in the supply line to preheat the water supplied to the hot water boiler. Furthermore, according to the invention, the hot water boiler system has a control device connected to at least one temperature sensor, wherein the temperature sensor is arranged in the supply line and / or in the hot water boiler, and the control device is designed and configured to control and / or regulate the preheating device depending on the temperature signal received via the at least one temperature sensor.In more detail, the control device can be designed and intended to control and / or regulate the preheating device depending on the temperature signal received via the at least one temperature sensor in such a way that the internal surface temperatures of at least one flue gas passage, i.e. the surface temperatures inside the flue gas tubes, are kept above an acid dew point critical temperature range.

[0015] The arrangement of the preheating device in the supply line to the hot water boiler according to the invention, as well as the temperature-dependent control and / or regulation of this preheating device by means of the control unit, ensures that water supplied to the hot water boiler can be selectively raised to a temperature level suitable for the respective operating state of the hot water boiler system before entering the hot water boiler.

[0016] A key technical advantage is that preheating the supplied water prevents or at least significantly reduces localized temperature drops in the heat exchanger tubes, particularly in the flue gas passages. This prevents the internal surface temperatures of the flue gas passages from falling below the acid dew point critical temperature range during operation with low return temperatures.

[0017] The temperature-dependent control of the preheating device according to the invention further ensures that the preheating device is not permanently activated, but only in those operating conditions in which an acid dew point critical condition is to be expected or already exists, based on the temperature signal detected by the temperature sensor. This enables demand-based and targeted heat input without unnecessarily raising the temperature of the hot water boiler or the connected heating system to a higher overall level.

[0018] A further technical advantage lies in the fact that the solution according to the invention allows for an effective reduction of corrosive attacks on the heat exchanger tubes, in particular by preventing the condensation of acidic components from the flue gases. This extends the overall service life of the flue gas passages and the hot water boiler, and reduces maintenance and repair costs.

[0019] According to an advantageous embodiment, the at least one temperature sensor arranged in the hot water boiler can be designed as a surface temperature sensor located on one of the heat exchanger tubes. By arranging a surface temperature sensor in this way, particularly on the outside of a heat exchanger tube, a representative calculation of the inner surface temperature of this heat exchanger tube can be performed, incorporating the control device, and in particular, a localized drop below the acid dew point critical temperature range can be detected.The surface temperature measured on the outside of the heat exchanger tube is physically and unambiguously related to the inner surface temperature of the heat exchanger tube, since the tube wall of the heat exchanger tube consists of a known material with a known wall thickness and known thermal conductivity, and a reproducible temperature gradient across the tube wall of the heat exchanger tube is established during steady-state or quasi-steady-state operation. The control device can therefore be designed and configured to deduce the inner surface temperature of the heat exchanger tube from the measured outer surface temperature, taking into account at least one predetermined tube parameter, in particular the wall thickness, the thermal conductivity of the tube material, and / or a calibrated correction value, and in particular to calculate this inner surface temperature.For this purpose, the control unit can, in particular, draw on stored characteristic maps, empirically determined correction factors, or simplified thermal models that simulate the heat transfer through the tube wall of the heat exchanger tube. In this way, an indirect, yet sufficiently accurate determination of the internal surface temperature of the flue gas tubes is possible without having to expose a temperature sensor directly to the flue gas inside the heat exchanger tube. This increases operational reliability and improves the service life of the temperature sensor. Preferably, the at least one surface temperature sensor is arranged at a particularly critical point in the flue gas tube, especially at a point with low flue gas temperature, low water flow velocity, or increased heat dissipation.This allows any localized drop below the acid dew point critical temperature range to be detected early and reliably avoided by appropriately controlling the preheating device.

[0020] According to a further advantageous embodiment, the control device can be designed and configured to compare the temperature measured by the at least one temperature sensor with at least one lower temperature limit as a reference signal, and the control device can be designed and configured to control and / or regulate the preheating device based on the reference signal in order to prevent, and preferably eliminate, the temperature of the heat exchanger tubes from falling below the lower temperature limit, particularly below the acid dew point critical temperature of the heat exchanger tubes. This allows for the targeted prevention of the temperature of the heat exchanger tubes dropping below a critical range.This comparison principle allows for flexible adaptation to different operating conditions of the hot water boiler system, such as start-up phases, load changes or varying return temperatures, thus reliably ensuring protection against acid-induced corrosion even under fluctuating operating conditions.

[0021] According to a further advantageous embodiment, the preheating device can be an electric heating element. Advantageously, this electric heating element can be designed as a flanged heating element or at least have one. In particular, the electric heating element is designed to maintain the temperature of the water supplied to the hot water boiler above the acid dew point critical temperature of the heat exchanger tubes in order to prevent corrosion of the tube surfaces. This prevents local condensation of acidic components from the flue gases on the tube surfaces of the heat exchanger tubes, thus preventing corrosion of the tube surfaces.

[0022] According to a further advantageous embodiment, the electric heating device can be provided with at least one heating chamber, which is connected to the supply line in particular continuously, for preheating the water supplied to the hot water boiler. In other words, the electric heating device can be provided with at least one heating chamber connected to the supply line, so that water from the supply line enters the heating chamber and, after heating, is returned to the hot water boiler. Advantageously, this measure can also ensure that preheating the supplied water prevents the temperature of the heat exchanger tubes from falling below the acid dew point critical point, thereby preventing corrosion of the tube surfaces.

[0023] According to a further advantageous embodiment, the hot water boiler system can be designed as a hybrid boiler system, which, in addition to the fossil or biogenic heat generation unit, includes at least one electric heating device for the water in the hot water boiler, and in which the at least one electric heating device preferably serves as the preheating unit. Preferably, the at least one electric heating device is activated in operating conditions in which an acid dew point critical temperature is detected in the supply line and / or in the hot water boiler by means of at least one temperature sensor. The hot water boiler system can therefore be designed as a hybrid boiler system, with at least one electric heating device that simultaneously serves as the preheating unit.This design enables the hot water boiler system to preheat the water supplied to the boiler, regardless of the output of the fossil fuel or biogenic heat generation system. By using the electric heating element as the preheating device, the system ensures the hybrid functionality of the hot water boiler and that electrical energy is used specifically to maintain the supply temperature above the acid dew point critical temperature of the heat exchanger tubes.

[0024] A technical advantage of this design variant is that even during partial load or start-up phases of primary heat generation, the supply line temperature can be reliably controlled and a drop below the critical temperature prevented. This avoids the formation of corrosive condensates on the heat exchanger tubes, which increases the service life of the tubes and reduces maintenance requirements.

[0025] According to a further advantageous embodiment, the at least one electric heating device can be arranged outside the hot water boiler, and the hot water boiler system includes a heat transfer device connected to the at least one heating device for transferring heat from the at least one electric heating device to the hot water boiler. Arranging the at least one electric heating device outside the hot water boiler and transferring the generated heat via a separate heat transfer device offers several technical advantages. Firstly, it prevents the electric heating device from colliding with the heat transfer elements of the fossil fuel or biogenic heat generation system, such as fire tubes or flue gas tubes.This means that the placement options for the electric heating element are not limited by the geometry of the hot water boiler, and no increase in the boiler size is required. This reduces the complexity of the equipment, particularly with regard to high steam pressures, and simplifies the design. Furthermore, relocating the electric heating element outside the hot water boiler allows for a smaller boiler to be used for a given rated output, thus requiring less water volume. This allows the heat transfer medium to respond more quickly to load changes, making the hot water boiler more dynamic and efficient in operation. At the same time, material and manufacturing costs are reduced, and the system can be designed more flexibly and economically without compromising heating performance or corrosion prevention.

[0026] According to a further advantageous embodiment, the heat transfer device may have at least one heating chamber, the inlet of which is connected to at least one cold water supply and / or the supply line, and the outlet of which is connected to the hot water boiler, in particular leading into the hot water boiler. The cold water supply may be designed as an external feedwater supply or feedwater source. The heating chamber may, in particular, include a liquid heat exchanger. Furthermore, the electric heating device may be interchangeably located in the heating chamber. Advantageously, the electric heating device may be designed as a flanged heating element or may include at least one flanged heating element.It can also be advantageously provided that the at least one electric heating device comprises electric heating elements arranged in electrically insulated casing tubes, and that the heat transfer device has a heating chamber surrounding the casing tubes, the inlet of which is fluidically connected to a cold water supply and / or the supply line, and the outlet of which is connected to the supply line of the hot water boiler, in particular flowing fluidically into the hot water boiler.

[0027] According to a further advantageous embodiment, the inlet can also be connected to the hot water boiler, thus advantageously allowing water to be directed from the hot water boiler to the boiler room and back again to the hot water boiler, in order to maintain a stable circuit for targeted temperature control. For this purpose, the inlet can have at least one branch that can be switched on and / or off by means of a control valve, in particular continuously. In more detail, the inlet can have a branch with a control valve, which is connected to a feedwater supply and / or the supply line. The respective control valve can preferably be continuously adjustable between a closed and an open position.Therefore, the circuit can also be designed as a double circuit, in which one partial flow is routed through the boiler room for preheating, while another partial flow is returned directly to the hot water boiler or combined with feedwater to maintain the surface temperatures of the heat exchanger tubes above the acid dew point critical range. Meanwhile, the inlet, with at least one branch and at least one control valve, can be designed such that the flow rates in the two circuits can be variably regulated and / or controlled in order to specifically adapt the heat input to the current operating conditions and temperature profiles of the heat exchanger tubes.

[0028] According to a further advantageous embodiment, the hot water boiler system can be provided with at least two electric heating devices, one of which is designed as a preheating device. By designing the hot water boiler system with at least two electric heating devices, one of which is specifically designed as a preheating device, a functional separation of the electrical heat input is enabled. A significant technical advantage is that the electrical heating power can be distributed among different tasks within the hot water boiler system. The electric heating device designed as a preheating device serves specifically to raise the temperature of the water supplied to the hot water boiler, while another electric heating device can be used independently for the direct heating of the water in the hot water boiler.

[0029] This results in increased flexibility in plant operation, as the preheating of the supply water can be controlled independently of the other electrical heat input. Particularly in operating conditions with low return temperatures or during short-term load changes, the preheating device can be activated quickly and precisely without having to switch on the entire electrical heating capacity.

[0030] According to a further advantageous embodiment, the outlet can be configured as the flow line of a heating circuit, and the supply line as the return line. This clear assignment of flow and return ensures that the water heated in the hot water boiler is discharged into the heating circuit in a controlled manner and at a defined temperature, while the cooled water flowing back from the heating circuit is returned to the hot water boiler via the supply line in a controlled manner. This results in stable thermal conditions and facilitates precise temperature control within the system.

[0031] According to a further advantageous embodiment, a pump can be arranged in the heating circuit, preferably controlled by the control unit based on the temperature signal. A technical advantage lies in the targeted control of the mass flow rate depending on the actual thermal demand. By controlling the pump based on temperature, the circulation volume of water in the heating circuit can be increased or decreased as needed. This makes it possible to quickly compensate for thermal conditions with low return temperatures without unnecessarily overheating the entire hot water boiler. The hot water boiler system thus reacts not only faster but also more reliably to critical temperature conditions. A further technical advantage is the decoupling of the temperature control from purely static flow conditions.While in an unregulated heating circuit the flow rate is essentially determined by pressure losses and geometric boundary conditions, the controlled pump allows for active control of the heat distribution.

[0032] According to a further advantageous embodiment, the hot water boiler's outlet can be located above the heat exchanger tubes, while the boiler's inlet is positioned below them. A technical advantage of this vertical separation of the inlet and outlet is that it optimizes the flow through the heat exchanger tubes. The cooler water enters the hot water boiler via the inlet, positioned below the tubes, rises along the heat exchanger tubes as it heats up, and is then discharged through the outlet located above. This ensures that all heat exchanger tubes are subjected to uniform flow, minimizing temperature gradients and maximizing heat transfer.

[0033] The invention will be explained in more detail below with reference to exemplary embodiments shown in the figures. The figures show: Fig. 1 only sketchily and roughly schematically depicted an advantageous embodiment of the hot water boiler system according to the present invention; Fig. 2. Roughly schematic representation of another design variant of a hot water boiler system in front view, which is designed as a hybrid boiler system, and Fig. 3 a side view of the hot water boiler system Fig. 2.

[0034] For identical or similarly functioning elements of the invention, identical reference numerals are used in the figures, where appropriate. Furthermore, for the sake of clarity, only reference numerals necessary for describing the respective figure are shown in the individual figures. The invention is also presented in the figures only as a schematic view to illustrate its operation. In particular, the representations in the figures serve only to explain the fundamental principle of the invention.

[0035] Fig. Figure 1 shows a hot water boiler system 1 with a hot water boiler 18 and a fossil or biogenic heat generation unit 14, the flue gases of which are passed through heat exchanger tubes 4 arranged in the hot water boiler 18 to heat the water. In more detail, the hot water boiler system 1 has a hot water boiler 18 with a combustion chamber containing a burner for fossil or biogenic fuels, serving as the heat generation unit 14, located on its underside. The combustion chamber 14 is connected to the hot water boiler 18 via a flue gas passage 28, which supplies the heat transfer medium. The flue gas coming from the flue gas passage 28 is traversed by heat exchanger tubes 4. The water serves as the heat transfer medium in the hot water boiler 18.The burner system in the burner chamber 14 heats the water in the hot water boiler 18 and can therefore be used for energy supply via a corresponding supply line 6 and a discharge line 8.

[0036] For this purpose, the hot water boiler 18 has a supply line 6 for feeding cooler water into the hot water boiler 18 and a discharge line 8 for discharging heated water from the hot water boiler 18. The discharge line 8 of the hot water boiler 18 is located above the heat exchanger tubes 4, and the supply line 6 of the hot water boiler 18 is located below the heat exchanger tubes 4. The discharge line 8 forms the flow of a heating circuit 12, and the supply line 6 forms the return of the heating circuit 12.

[0037] In Fig. In the supply line 6, a preheating device 10, designed as an electric heating device 20, is arranged to preheat the water supplied to the hot water boiler 18. The preheating device 10, designed as an electric heating device 20, has a heating chamber 26, which is continuously connected to the supply line 6, for preheating the water supplied to the hot water boiler 18. The more detailed structure of this heating chamber is described below. Fig. 2 and Fig. 3 becomes apparent.

[0038] Furthermore, the hot water boiler system 1 has a control unit SR, which is connected to at least one temperature sensor 2 located in the supply line 6 and / or in the hot water boiler 18. The at least one temperature sensor 2 located in the hot water boiler 18 is positioned on the outer surface of the lowest heat exchanger tube 4. The control unit SR is designed and intended to control and / or regulate the preheating unit 10 based on the temperature signal received from the temperature sensor 2. A pump 11 is also arranged in the heating circuit 12 and is controlled by the control unit SR based on the temperature signal.

[0039] In more detail, the control device SR is designed and configured to compare the temperature measured by the temperature sensor 2 with at least one lower temperature limit as a comparison signal, and to control and / or regulate the preheating device 10 depending on the comparison signal in order to prevent the temperature of the heat exchanger tubes 4 from falling below the lower temperature limit, in particular below the acid dew point critical temperature of an inner surface of the heat exchanger tubes 4.

[0040] The Fig. 2 and Fig. Figure 3 shows an embodiment of the hot water boiler system 1, which is designed as a hybrid boiler system and, in addition to the fossil or biogenic heat generation unit 14, has two electric heating devices 20 for the water in the hot water boiler 18, one of which forms the preheating unit 10. This embodiment shows a hot water boiler system 1 with heating devices 20 arranged on both sides next to the boiler 15. In other words, the two heating devices 20 are arranged outside the hot water boiler 18. A heat transfer unit 21 is provided for each of the two heating devices 20 to transfer the heat from the electric heating device 20 to the hot water boiler 18. The heat transfer unit 21 includes the boiler chamber 26.

[0041] In more detail, the heating chambers 26 can have a liquid heat exchanger or be designed as a liquid heat exchanger, each of which can be connected to the hot water boiler 18 via inlets 22 and outlets 24. The liquid heat exchanger 26 surrounds the jacket tubes of the electric heating elements 32 of the electric heating device 20 and transfers their heat to the hot water boiler 18 via the outlets 24. The inlet 22 from the hot water boiler 18 to the liquid heat exchanger 26 of the two electric heating devices 20 is located further down on the hot water boiler 18, while the outlets 24 from the liquid heat exchangers open further up into the hot water boiler 18, so that the heat exchange between the hot water boiler 18 and the liquid heat exchanger 26 preferably occurs by natural convection. The two electric heating devices 20 stand on platforms 34, which are arranged on both sides of the boiler 15.The arrangement of the two heating devices 20 on both sides allows, firstly, the volume of the hot water boiler 18 to be kept small for a given nominal output, and secondly, the accessibility of the electric heating devices and their liquid heat exchangers and their supply and return lines is optimized. This makes them very easy to maintain and install.

[0042] In the illustrated version of the Fig. 2 and Fig. In section 3, the right-hand of the two boiler rooms 26 is assigned an inlet 22, which is connected to both a feedwater supply 27 and the supply line 6 of the hot water boiler system 1. This right-hand inlet 22 also flows fluidically into the hot water boiler 18, so that the right-hand inlet 22 can be supplied with water from the hot water boiler 18, as well as from the return of the supply line 6 and with feedwater from the feedwater supply 27. For this purpose, branches 40, in particular pipe branches, which can be switched on and / or off by means of control valves (not shown), are provided in the inlet 22, via which the supply line 6 and the feedwater supply 27 are fluidically connected to the inlet 22. The flow rate of the respective branch 40 of the right-hand inlet 22 can be controlled and / or regulated by means of continuously adjustable control valves, in particular by incorporating the control device SR.However, according to an embodiment not shown, it is also possible that this right inlet 22 is not fluidically connected to the hot water boiler 18, but only to the supply line 6 and / or the feed water supply, so that the colder water arriving via the supply line 6 and / or the feed water supply can be heated by the heating device 20 before being fed into the hot water boiler 18 via the outlet 24.

[0043] Fig. Figure 3 shows the hybrid hot water boiler system 1 from Fig.Figure 2 shows a side view. It is clearly visible how the electric heating devices 20 are designed as flanged heaters, the head 30 of which, from which electric heating elements 32 extend into the liquid heat exchanger 26, is flanged to the front end of the liquid heat exchanger. The flanged heater 20 is thus flanged to the liquid heat exchanger 26 in such a way that its head 30 protrudes, which also facilitates maintenance. The electric heating elements 32, surrounded by jacket tubes, protrude into the liquid heat exchanger 26, so that only the heat is transferred. The jacket tubes, however, ensure electrical insulation of the electric heating elements 32 from the heat transfer medium of the liquid heat exchanger 26 and the hot water boiler 18.

[0044] The invention has been described above using an exemplary embodiment. It is understood that numerous modifications or adaptations are possible without departing from the underlying inventive concept. Reference symbol list 1 hot water boiler system 2 temperature sensors 4 heat exchanger tubes 6 Supply line 8th derivative 10 Preheating device 11 Pump 12 Heating circuit 14 Heat generation unit 15 boilers 18 hot water boilers 20 Heating device 21 Heat transfer device 22 Inflow 24 Procedure 26 Boiler room 27 Feedwater supply 28 Flue gas passage 30 heads 32 Heating element 34 Podium 40 Branch SR control unit

Claims

[1] Hot water boiler system (1) comprising a hot water boiler (18), comprising a fossil or biogenic heat generation device (14), the flue gases of which are passed through heat exchanger tubes (4) arranged in the hot water boiler (18) to heat the water in the hot water boiler (18), the hot water boiler (18) having a supply line (6) for supplying water to the hot water boiler (18) and a discharge line (8) for discharging water from the hot water boiler (18), characterized by, that a preheating device (10, 20) is arranged in the supply line (6) to preheat the water supplied to the hot water boiler (18), and that the hot water boiler system (1) has a control device (SR) which is connected to at least one temperature sensor (2) which is arranged in the supply line (6) and / or in the hot water boiler (18), and that the control device (SR) is designed and provided to control and / or regulate the preheating device (10, 20) depending on the temperature signal received via the at least one temperature sensor (2). [2] Hot water boiler system according to claim 1, characterized by , that the at least one temperature sensor (2) arranged in the hot water boiler (18) is designed as a surface temperature sensor which is arranged on one of the heat exchanger tubes (4). [3] Hot water boiler system according to one of claims 1 to 2, characterized by, that the control device (SR) is designed and configured to compare the temperature measured by the at least one temperature sensor (2) with at least one lower temperature limit as a comparison signal, and that the control device (SR) is designed and configured to control and / or regulate the preheating device (10, 20) depending on the comparison signal in order to avoid falling below the lower temperature limit at the heat exchanger tubes (4), in particular below the acid dew point critical temperature of an inner surface of the heat exchanger tubes (4). [4] Hot water boiler system according to one of the preceding claims 2 or 3, characterized by, that the at least one temperature sensor (2) designed as a surface temperature sensor is arranged on an outside of a heat exchanger tube (4), and that the control device (SR) is designed and configured to calculate an inner surface temperature of the heat exchanger tube (4) from a measured outer surface temperature, taking into account at least one predetermined tube parameter. [5] Hot water boiler system according to one of the preceding claims, characterized by , that the preheating device (10) is formed by an electric heating device (20). [6] Hot water boiler system according to claim 5, characterized by , that the electric heating device (20) has at least one heating chamber (26) which is in particular continuously connected to the supply line (6) for preheating the water supplied to the hot water boiler (18). [7] Hot water boiler system according to one of the preceding claims, characterized by, that the hot water boiler system (1) is designed as a hybrid boiler system which, in addition to the fossil or biogenic heat generation device (14), has at least one electric heating device (20) for the water in the hot water boiler (18), and that at least one electric heating device (20) forms the preheating device (10). [8] Hot water boiler system according to claim 7, characterized by , that the at least one electric heating device (20) is arranged outside the hot water boiler (18), and that the hot water boiler system (1) has a heat transfer device (21) arranged in connection with the at least one heating device (20) for transferring the heat from the at least one electric heating device (20) to the hot water boiler (18). [9] Hot water boiler system according to one of the preceding claims 7 or 8, characterized by, that at least one heat transfer device (21) has a boiler room (26) whose inlet (22) is connected at least to the supply line (6) and / or a feedwater supply (27), and whose outlet (24) is connected to the hot water boiler (18). [10] Hot water boiler system (10) according to claim 7, characterized by , that the inlet (22) is also connected to the hot water boiler (18). [11] Hot water boiler system according to any one of the preceding claims 7 to 10, characterized by , that the hot water boiler system (1) has at least two electric heating devices (20), one of which is designed as a preheating device (10). [12] Hot water boiler system according to one of the preceding claims, characterized by , that the outflow (8) forms the flow of a heating circuit (12), and that the supply line (6) forms the return of a heating circuit (12). [13] Hot water boiler system according to claim 12, characterized by , that a pump (11) is arranged in the heating circuit (12), which is preferably controlled by means of the control device (SR) depending on the temperature signal. [14] Hot water boiler system according to one of the preceding claims, characterized by , that the outlet (8) of the hot water boiler (18) is located above the heat exchanger tubes (4) and the supply line (6) of the hot water boiler (18) is located below the heat exchanger tubes (4).

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