DE202009001405U1 - Exhaust gas heat exchanger - Google Patents

Abstract

Exhaust gas heat exchanger (1) for heat recovery from exhaust gases of a heating furnace or boiler,
wherein the exhaust gas heat exchanger (1) has at least two exhaust gas trains (2, 3) which are each designed to pass an exhaust gas flow emerging from the heating furnace or boiler, wherein
at least one of the exhaust gas trains (2, 3) is designed as an active exhaust gas train (2) with a heat exchanger device (4) which is set up to carry a heat absorption medium for heat exchange through the exhaust gas flow, and
at least one of the exhaust gas trains (2, 3) is designed as a passive exhaust gas train (3), in which no heat exchange device (4) is provided, and
wherein the at least two exhaust trains (2, 3) have substantially the same volume.

Description

The The invention relates to an exhaust gas heat exchanger.

Exhaust gas heat exchanger, which are used to heat recover from exhaust gases from heating systems, are known in the art.

The However, currently known exhaust gas heat exchangers can only together with heaters or boilers which are heated by oil or gas, and are technically elaborate and Expensive in the production, so that their use hardly pays off.

A The object of the present invention is an improved exhaust gas heat exchanger to provide, together with heaters and boilers, with Any fuel can be heated, used and at the same time simple and inexpensive to manufacture.

One exhaust gas heat exchanger according to the invention has at least two flues, each for passing a from the stove or boiler emerging exhaust stream are formed. It is at least one of the flues as an active exhaust train with a heat exchanger device, which is set up, a heat absorption medium for heat exchange through the exhaust gas flow, formed and at least one of the exhaust trains is as a passive flue, in which no heat exchange device provided is, trained. The at least two exhaust trains essentially have the same volume.

Thereby, that the at least two flues an exhaust gas heat exchanger according to the invention have the same volume is a technically complex vote of the exhaust gas heat exchanger the pressure of the boiler or burner used is not required.

Furthermore has an inventive exhaust gas heat exchanger a simple structure without complex mechanical elements such as springs, levers, joints with shafts, toggle or bushes that are easily polluted, very vulnerable and therefore cause high maintenance and repair costs. Also stay in an exhaust gas heat exchanger according to the invention As a result of the design, hardly any ash or other combustion residues are left behind, which means the maintenance costs are further reduced.

The The invention also relates to a heating system with a boiler for Combustion of fuels with at least one exhaust pipe to lead away combustion exhaust gases from the boiler, wherein in the exhaust pipe at least one inventive exhaust gas heat exchanger is provided.

A such heating system allows an effective recovery the heat present in the exhaust gases of the boiler. It allows in particular a perfect combustion of the fuel, in particular also in wood or coal stoves, leaving an excessive deposit from soot or other combustion products in the exhaust pipes is prevented. Thereby can the cleaning intervals extended and the maintenance costs are significantly reduced

In an embodiment the at least two flue trains end the exhaust gas heat exchanger in each case in a common exhaust gas inlet housing and a common exhaust gas outlet housing. Thereby let yourself an inventive exhaust gas heat exchanger simply in an existing exhaust pipe or an existing chimney draft Install. Heating systems can be easily retrofitted with an exhaust gas heat exchanger according to the invention.

In an embodiment is the heat exchanger device a finned tube heat exchange device. A finned tube heat exchanger device is easy to manufacture and has a high efficiency.

In an embodiment is the heat exchanger device from the exhaust gas heat exchanger removable and reusable. This allows the heat exchanger device Simply clean and replace if necessary, without the entire exhaust gas heat exchanger to have to remove from the exhaust pipe. This will make the maintenance and Repair costs further reduced.

In an embodiment is in the exhaust gas heat exchanger at least one flap provided by the at least one of Exhaust flues openable and lockable is. This makes it possible the exhaust gas flow optionally through the active exhaust train in which the heat exchanger device is arranged, or by the passive flue, in which no heat exchange device is arranged to conduct.

Thus, in the heating phase of the heating furnace or boiler, the exhaust gases can be passed through the passive flue gas duct, where they do not give off heat to the heat exchanger device. As a result, a sooting of the fireplace can be reliably prevented. Exceeds the exhaust gas temperature a predetermined limit, the exhaust gases are ge after folding the flap through the active exhaust pass to the heat exchanger device leads, wherein the existing heat in the exhaust gases is discharged to a guided through the heat exchanger device heat absorption medium.

In an embodiment has the exhaust gas heat exchanger a flap that is designed to be the passive exhaust flue closes, if the active flue is opened is, and that it opens the passive exhaust draft when the active exhaust draft closed is. This allows the exhaust flow with a single Effectively by the active exhaust flue or through led the passive exhaust train become. Due to the fact that in such an exhaust gas heat exchanger only a single flap is provided, such an exhaust gas heat exchanger is inexpensive to manufacture and easy to wait.

In an embodiment the flap is manually adjustable. An exhaust gas heat exchanger with a manual Adjustable flap is particularly easy and inexpensive to produce.

In an embodiment a motor is provided and the flap is operated by operating the Motors adjustable. A motor driven flap is especially convenient to use. In addition, a through a motor driven flap over a corresponding engine control are automatically transferred.

In an embodiment is in the heat exchanger device a thermostat for controlling the heat exchange medium intended.

In a further embodiment is at least one exhaust thermometer for measuring the temperature of Provided exhaust stream. Preferably, an exhaust thermometer is in the exhaust outlet housing and / or disposed in the exhaust gas inlet housing.

By measuring the temperature of the heat exchange medium and / or the exhaust gases, the efficiency of the heat exchanger can be easily detected.

In a further embodiment is a control for driving the motor in dependence from that of the exhaust thermometer and / or the heat exchanger thermometer measured temperature provided. With such a control is it is possible the flap automatically by controlling the motor depending on to operate the temperature measured by at least one thermometer. This allows a particularly effective operation of the exhaust gas heat exchanger.

In a further embodiment is the exhaust gas heat exchanger at least partially made of sheet steel and / or stainless steel sheet produced. A made of sheet steel and / or stainless steel sheet Exhaust gas heat exchanger is also for Exhaust gases with high exhaust gas temperatures, especially for exhaust gases Heizkaminen or solid fuel boilers in which z. B. Pellets are burned, with temperatures of up to 500 ° C suitable.

In a further embodiment is the exhaust gas heat exchanger at least partially made of 2 mm thick sheet steel and / or from 1 mm strong heat resistant Stainless steel sheet produced. Allow sheets of this thickness a particularly effective and cost-effective production of the exhaust gas heat exchanger.

In a further embodiment is in at least one wall of the exhaust gas inlet space and / or Exhaust gas outlet a service opening provided by a heat-resistant, easily removable cover is closed. Through such a service opening, the interior of the exhaust gas heat exchanger particularly easy and inexpensive be cleaned and maintained. In one embodiment, the service opening and the Cover designed as an easy-to-use service door.

In an embodiment is the heating system for passing a liquid heat absorption medium through the heat exchanger device educated. This allows the heat exchanger simply in an existing heating system, with a liquid heat medium, such as B. water, works, integrated.

In an embodiment is the heating system for passing a gaseous heat receiving medium, such. B. room air, through the heat exchanger device educated. Thereby, the recovered in the exhaust gas heat exchanger Heating energy without big technical effort to be given in a room to be heated.

In a further embodiment a pumping device is provided to the heat receiving medium through the Heat exchanger device to pump. By such a pumping device, the efficiency of the exhaust gas heat exchanger further increased become. When using a gaseous heat receiving medium is the Pumping device preferably designed as a fan or blower.

An inventive exhaust gas heat exchanger and a heating system according to the invention enable effective use of the heat present in the exhaust gases of a boiler and are technically simple and inexpensive to produce. In addition, they can work together with Heizkes used to produce exhaust gases of up to 500 ° C. This makes them particularly suitable for boilers in which renewable and / or solid fuels are burned. With the resulting high exhaust gas temperatures, up to 80% of the heat energy present in the exhaust gases can be recovered. As a result, fuel can be saved, which reduces the pollutant emissions of the boiler and reduces operating costs.

in the The invention will be explained in more detail with reference to the accompanying figures.

there shows:

1 a longitudinal section through a first embodiment of an exhaust gas heat exchanger according to the invention;

2 a longitudinal section through in a second embodiment of an exhaust gas heat exchanger according to the invention;

3 a plan view of an exhaust gas heat exchanger according to the invention;

4 a side view of an exhaust gas heat exchanger according to the invention;

5 a view of an exhaust gas heat exchanger according to the invention from the direction of the exhaust stack leading to the chimney;

6 a cross section through an exhaust gas heat exchanger according to the invention along the line AA in 1 ;

7 a schematic representation of a heating system with a liquid heat exchanger medium, in which an inventive exhaust gas heat exchanger is used; and

8th a schematic representation of a heating system with a gaseous heat exchanger medium, in which an inventive exhaust gas heat exchanger is used.

1 shows a longitudinal section through an exhaust gas heat exchanger according to the invention 1 ,

The exhaust gas heat exchanger 1 has at its lower end a boiler neck 24 on, which is connected in operation with the exhaust pipe, not shown, of a boiler, not shown. Through the boiler neck 24 the exhaust gases coming from the boiler flow into one above the boiler neck 24 arranged exhaust gas inlet space 6 that has a larger cross-section than the boiler neck 24 having. In the in the 1 In the embodiment shown, the cross section of the exhaust gas inlet chamber widens 6 starting from the boiler neck 24 trapezoidal upward.

Above the exhaust inlet chamber 6 the exhaust gas heat exchanger has a middle range 11 with a constant cross section. In the middle area 11 is centrally one parallel to the longitudinal direction of the exhaust gas heat exchanger 1 extending partition 5 arranged, which is the interior of the exhaust gas heat exchanger 1 in the middle area 11 in two mutually parallel exhaust trains 2 . 3 Splits. Because of the dividing wall 5 centered in the exhaust gas heat exchanger 1 is arranged, have the two exhaust trains 2 . 3 the same volume.

In the in the 1 on the right, exhaust flue 2 is a designed as a spiral tube heat exchanger device 4 intended. In the exhaust flue shown on the right 2 it is therefore an active exhaust flue 2 of the heat exchanger 1 in which a heat transfer from the exhaust gases to a heat exchange medium passing through the heat exchanger device 4 flows, takes place.

In the left flue 3 is not a heat exchange device 4 intended. It is therefore a passive exhaust train 3 the exhaust gas heat exchanger 1 in which there is no heat transfer from the exhaust gases to a heat exchange medium.

At the bottom, the exhaust inlet chamber 6 facing the end of the partition 5 There is a perpendicular to the cutting plane arranged wave 13 on the one swiveling flap 10 is appropriate. The hinged flap 10 is between a first position in the 1 is shown as a solid line, and a second, in the 1 pivoted position shown dashed. In the first position the flap closes 10 the access from the exhaust gas inlet space 6 to the active exhaust flue 2 and the access from the exhaust gas inlet space 6 to the passive flue gas train 3 it is open. In the second position the flap closes 10 the passive exhaust train 3 and the active exhaust train 2 it is open. By pivoting the flap between these two positions are from the boiler neck 24 in the exhaust inlet chamber 6 incoming exhaust gases optionally through the active exhaust train 2 or through the passive exhaust train 3 guided.

In the area of the wave 13 is an engine 12 arranged mechanically so with the shaft 13 connected is that flap 10 by actuating the motor about the longitudinal axis of the shaft 13 is pivotable.

The ends of the spiral tube, which is the heat exchanger device 4 are on the in 1 Right side of the exhaust gas heat exchanger shown as a connecting piece 8th . 9 for the connection of supply and discharge lines of a heating system led to the outside. The connecting pieces 8th . 9 can each be provided with an external thread or other fastening device for attaching connecting lines.

Above the heat exchanger device 4 is perpendicular to the partition 5 an end plate 15 arranged at the the dividing wall 5 ends. The end plate 15 runs over the entire cross section of the middle area 1 and defines the upper end of the flues 2 . 3 , In the end plate 15 are two in the 1 not shown openings 17 . 19 formed, each case one of the openings 17 . 19 an exhaust flue 2 . 3 with one above the end plate 15 trained exhaust gas outlet 7 combines.

The exhaust outlet space 7 is in the in the 1 embodiment shown in mirror symmetry to the exhaust gas inlet space 6 educated. The exhaust outlet space 7 tapers off from the middle area 11 with the exhaust trains 2 . 3 trapezoidal upward. At the upper end of the Abgasauslassraums 7 is a chimney neck 22 formed, which is connected in operation with a leading to a chimney, not shown exhaust pipe.

In the exhaust outlet space 7 are centrally an exhaust thermometer 14 and a controller (thermostat) 16 provided to the temperature of the exhaust trains 2 . 3 to measure outgoing exhaust gases and the engine 12 via control lines, not shown, between the controller 16 and the engine 12 run, depending on the measured exhaust gas temperature to control.

On the in the 1 left side of the exhaust inlet chamber 6 and the exhaust outlet space 7 is each a service door 18 . 20 formed, which can be opened to the interior of the exhaust gas heat exchanger 1 and especially the flap 10 or the heat exchanger device 4 to inspect, clean and / or maintain.

For a boiler with a line of up to 30 kW, the flues have 2 . 3 preferably a diameter of 160 mm. The boiler neck 24 and the chimney neck 22 preferably have a diameter of 150 mm. The exhaust gas heat exchanger 1 preferably has a diameter of 355 mm. For exhaust gas heat exchangers 1 , which are designed for boilers with higher performance, the dimensions are correspondingly larger.

2 shows an alternative embodiment of an exhaust gas heat exchanger according to the invention 1 , The construction of in 2 shown exhaust gas heat exchanger 1 largely corresponds to the one in 1 and the same reference numerals are used for the same elements. In the in 2 shown exhaust gas heat exchanger 1 is the heat exchanger device 4 not formed as a coiled steel tube, but as the largest possible steel tube, the meandering within the active exhaust flue 2 is arranged. The steel tube is z. B. a steel pipe with a diameter of 1.5 inches and the connecting pieces 8th . 9 are each provided with an external thread for screwing in connection lines.

That in the 1 and 2 The embodiment shown is merely exemplary and it will be apparent to those skilled in the art that other equivalent arrangements are possible. So z. B. the service doors 18 . 20 on the same side as the heat exchanger device 4 be formed or it may be additional service doors in the middle area 11 be educated. Also, the heat exchanger device 4 Any known in the art heat exchanger device 4 be.

3 shows a side view of the exhaust gas heat exchanger 1 , From 1 known elements are provided with the same reference numerals and will not be discussed again. On the side of the Abgasauslassraums facing the viewer 7 are the exhaust thermometer 14 and the controller 16 to recognize. In the area above the exhaust inlet chamber 6 is the engine 12 for controlling the in the 3 invisible flap 10 recognizable. The control 16 is not shown electrical lines with the exhaust thermometer 14 and with the engine 12 connected, so the engine 12 depending on the exhaust thermometer 14 measured exhaust gas temperature is controllable.

4 shows a side view of the in the 1 and 3 shown exhaust gas heat exchanger 1 , The from the 1 and 3 known features are provided with the same reference numerals and will not be discussed again.

On the in the 4 right side of the heat exchanger 1 is the end of the wave 13 to recognize that in the 4 invisible flap 10 inside the exhaust gas heat exchanger 1 connected is. The shaft is via externally accessible bearings in the walls of the exhaust gas heat exchanger 1 rotatably mounted, leaving the flap 10 in the interior of the exhaust gas heat exchanger 1 about the longitudinal axis of the shaft 13 is pivotable.

At the wave 13 can one in the 4 not shown counterweight or a locking device may be provided to the flap 10 to hold in a designated position. At one end of the wave 13 a handle or lever may be provided so that the flap is manually pivotable. In this case, on the engine 12 and on the controller 16 be waived to the production cost of the exhaust gas heat exchanger 1 to lower.

5 shows the in the 1 to 4 shown exhaust gas heat exchanger 1 from above, ie, from the perspective of the chimney neck 22 , Through the opening of the chimney neck 22 is the end plate 15 with the openings formed therein 17 and 19 to recognize. Through the opening shown on the right 17 of the active exhaust flue 2 is the spiral tube in the active exhaust flue 2 arranged heat exchanger device 4 recognizable.

Above and below the exhaust gas heat exchanger 1 is the wave 13 to recognize which through the exhaust gas heat exchanger 1 runs and with the hinged flap not visible in this representation 10 connected is.

6 shows a section along the line AA in 1 from the direction of the chimney neck 22 in the direction of the boiler neck 24 considered. The flap 10 is in this representation in a middle position, in which they are parallel to the partition wall 5 is aligned so that both the active exhaust draft 2 with the heat exchanger device 4 on the right side of the flap 10 as well as the passive flue gas train 3 without heat exchanger device on the left side of the flap 10 are visible. In this illustration, the spirally formed heat exchanger device 4 particularly easy to recognize.

7 shows a schematic representation of a heating system with an exhaust gas heat exchanger according to the invention 1 and with a boiler 26 in the heating water through the heat exchanger device 4 the exhaust gas heat exchanger 1 to be led.

In the boiler 26 A gaseous, liquid or solid fuel is burned to generate heat. The exhaust gases of this combustion are caused by a in the 7 not shown exhaust pipe to the boiler neck 24 the exhaust gas heat exchanger 1 guided. The exhaust gases flow from the boiler neck 24 through the exhaust gas inlet space 6 , depending on the position of the flap 10 through the active exhaust train 2 along the heat exchanger device 4 or through the passive exhaust train 3 in the exhaust gas outlet space 7 and through the chimney neck 22 in one in the 7 not shown fireplace.

A return line 30 , the cool heating water from the heating circuit to the boiler 26 leads, is via a three-way switching valve 28 with the inlet nozzle 8th the heat exchanger device 4 connected. The drain neck 9 the heat exchanger device 4 is via a drain line 34 , a security module 36 and a drain valve 38 downstream of the three-way switching valve 28 with the return line 30 connected. Both in the return line 30 as well as in the drainage line 34 is each a temperature sensor 40 . 41 provided, each with a scheme 42 connected is. The regulation 42 is set up, the three-way switching valve 28 depending on the temperature sensors 40 . 41 Switched measured temperatures, so through the return line 30 to the boiler 26 Returning heating water optionally through the heat exchanger device 4 is guided or not. In the drain line 34 is also a thermometer 65 arranged to the temperature of the heat exchanger device 4 flowing heating water to measure and display.

Exceeds that of the exhaust thermometer 14 in the exhaust outlet space 7 measured exhaust gas temperature a predetermined first limit of, for example, 100 ° C, so controls the controller 16 the servomotor 12 so on, that he shut up 10 in the in 7 Dashed position pivots shown in the passive exhaust gas train 3 closed and the active exhaust flue 2 is open, leaving the fumes from the boiler 26 through the active exhaust train 2 along the surface of the heat exchanger device 4 stream.

At the same time controls the scheme 42 the three-way switching valve 28 so on, that buying back heating water from the return line 30 through the heat exchanger device 4 flows while heat from the at the heat exchanger device 4 passing through the active exhaust train 2 receiving flowing exhaust gas. The heated heating water flows through the return line 34 in the boiler 26 , Characterized in that the buying back heating water after passing through the heat exchanger device 4 Having a higher temperature than before, less energy is needed to heat the heating water in the boiler 26 to heat to the desired target temperature. The boiler 26 can therefore be operated at a lower power, so that fuel can be saved. This reduces the pollutant emissions of the boiler and reduces operating costs.

If the exhaust gas temperature falls below a predetermined second limit value, then the controller controls 16 the servomotor 12 so on, that he shut up 10 in the in 7 pivoted with a solid line position shown in the passive exhaust gas train 3 opened and the active exhaust flue 2 closed is. The exhaust gases from the boiler 26 flow through the passive flue gas train 3 without heat to the heat exchanger device 4 leave. Thereby, a further reduction in the temperature of the exhaust gases and a mocking of the chimney is reliably prevented. The second limit can be equal to or different from the first limit.

In the in the 7 embodiment shown is an exhaust gas heat exchanger 1 easy to integrate into an existing heating system, since it uses the existing heating water circuit and that in the boiler 26 heated back flowing heating water. It can largely be used on the existing heating installation, so that no major modifications to the heating system are required.

The regulation 42 is with two feelers 40 . 41 connected. As soon as the sensor located in the heating return 40 one, z. B. by 5 ° C, lower temperature than the sensor 41 at the exhaust gas heat exchanger 1 , switches the scheme 42 the three-way switching valve 28 and the cooler heating return water flows through the heat exchanger device 4 , The boiler 26 now gets that through the exhaust gas heat exchanger 1 heated return water and needs the heating water needed for heating little or no heat at all.

The heating process is preceded by the deflection of the exhaust gases to the heat exchanger device 4 , The thermostat 16 , the Z. B. is set to 100 ° C, has the door 10 with the help of the engine 12 switched so that the exhaust gases through the active exhaust train 2 over the heat exchanger device 4 flow and the heat exchange medium in the heat exchanger device 4 heat.

8th shows an alternative application of an exhaust gas heat exchanger according to the invention 1 in a heating system in which no liquid heat absorption medium, such. B. heating water, but room air through the heat exchanger device 4 to be led. To the inlet pipe 8th and the outlet 9 the heat exchanger device 4 Each is a flexible ventilation pipe 44 . 50 , z. B. aluminum corrugated pipe, so on the outer wall of the exhaust gas heat exchanger 1 Put on that airtight connection between the ventilation pipe 44 . 50 and the outer wall of the exhaust gas heat exchanger 1 is formed. This can be done on the outside wall of the exhaust gas heat exchanger 1 one at each of the nozzles 8th . 9 a flange may be provided on which the respective ventilation pipe 44 . 50 is attached. In a supply air pipe 44 , around the inlet pipe 8th is attached, a fan is provided, the outside or room air through a ventilation grille 48 , the Z. B. is provided with a fly screen, in the Zuluftrohr 44 sucks, and through the inlet nozzle 8th in the heat exchanger device 4 suppressed. The thus sucked air flows through the heat exchanger device 4 and absorbs heat from the exhaust gases through the active exhaust gas train 2 be guided.

The heated air passes through the outlet pipe 9 from the heat exchanger device 4 in the exhaust duct 50 out. From there, the heated air is distributed via a distributor 52 on different air outlets 54 distributed, for example, are designed as a poppet valve and deliver the heated air in a room to be heated.

In such a heating system can be a scheme 56 be provided with a room thermostat 58 for measuring the room temperature and a speed controller 60 for adjusting the desired air flow of the fan 46 connected is. The regulation 56 and the speed controller 60 control the speed of the fan 46 depending on the thermostat 58 measured room temperature. The ventilator 46 is from the thermostat 58 and the speed controller 60 regulated.

The release of the fan 46 via the thermostat 16 that electrically with the scheme 56 connected is.

Once the thermostat 16 an exhaust gas temperature of z. B. 100 ° C feels, the flap 10 switched and the exhaust gases flow over the heat exchanger device 4 and heat that in the heat exchanger device 4 located heat exchanger medium. Thus, the then heated heat exchange medium of the room air or heating water can be supplied.

This in 8th The heating system shown enables a simple and effective heating of rooms, since the air introduced into the room is heated directly and no additional installation of radiators, heating pipes and the like is required. Also, such a heating system is easy to retrofit, as in addition to attaching the exhaust gas heat exchanger 1 in the exhaust pipe no further intervention in an existing heating system are required.

Claims (19)

Exhaust gas heat exchanger ( 1 ) for heat recovery from exhaust gases of a heating furnace or boiler, wherein the exhaust gas heat exchanger ( 1 ) at least two flues ( 2 . 3 ), each of which is designed to pass an exhaust stream leaving the heating furnace or boiler, at least one of the flues ( 2 . 3 ) as an active exhaust train ( 2 ) with a heat exchanger device ( 4 ) configured to carry a heat absorption medium for heat exchange through the exhaust gas stream, and at least one of the exhaust gas trains ( 2 . 3 ) as a passive flue ( 3 ), in which no heat exchanger device ( 4 ) is provided, is formed, and wherein the at least two exhaust trains ( 2 . 3 ) have substantially the same volume. Exhaust gas heat exchanger ( 1 ) according to claim 1, characterized in that the at least two exhaust gas trains ( 2 . 3 ) in each case in a common exhaust gas inlet space ( 6 ) and a common Abgasauslassraum ( 7 ) end up. Exhaust gas heat exchanger ( 1 ) according to claim 1 or 2, characterized in that the heat exchanger device ( 4 ) is a finned tube heat exchange device. Exhaust gas heat exchanger ( 1 ) according to one of the preceding claims, characterized. characterized in that the heat exchanger device ( 4 ) from the exhaust gas heat exchanger ( 1 ) is removable and reusable. Exhaust gas heat exchanger ( 1 ) according to one of the preceding claims, characterized in that at least one flap ( 10 ) is provided by the at least one of the exhaust trains ( 2 . 3 ) can be opened and closed. Exhaust gas heat exchanger ( 1 ) according to claim 5, characterized in that an active exhaust gas train ( 2 ) through the flap ( 10 ) can be opened and closed. Exhaust gas heat exchanger ( 1 ) according to claim 5 or 6, characterized in that a passive exhaust gas train ( 3 ) through the flap ( 10 ) is obvious and lockable. Exhaust gas heat exchanger ( 1 ) according to claim 7, characterized in that a passive exhaust gas train ( 3 ) and an active exhaust flue ( 2 ) by a common flap ( 10 ), which is pivotable between at least two positions, are openable and closable, wherein the passive exhaust flue ( 3 ) and the active exhaust flue ( 2 ) is open when the flap ( 10 ) is in the first position, and wherein the passive exhaust flue ( 3 ) and the active exhaust flue ( 2 ) is closed when the flap ( 10 ) in the second position. Exhaust gas heat exchanger ( 1 ) according to one of claims 5 to 8, characterized in that the flap ( 10 ) is manually adjustable. Exhaust gas heat exchanger ( 1 ) according to one of claims 5 to 9, characterized in that an engine ( 12 ) and the flap ( 10 ) by operating the engine ( 12 ) is adjustable. Exhaust gas heat exchanger ( 1 ) according to one of claims 2 to 10, characterized in that a heat exchanger thermometer is provided for measuring the temperature of the heat exchanger medium. Exhaust gas heat exchanger ( 1 ) according to one of claims 2 to 11, characterized in that at least one exhaust gas thermometer ( 14 ) is provided for measuring the temperature of the exhaust gas stream. Exhaust gas heat exchanger ( 1 ) according to claim 11 and / or 12 insofar as they relate to claim 10, characterized in that a controller ( 16 ) for driving the engine as a function of the exhaust gas thermometer ( 14 ) measured temperature is provided. Exhaust gas heat exchanger ( 1 ) according to one of the preceding claims, characterized in that the exhaust gas heat exchanger ( 1 ) is at least partially made of sheet steel and / or stainless steel sheet. Exhaust gas heat exchanger ( 1 ) according to one of the preceding claims, characterized in that in at least one of the exhaust gas inlet space ( 6 ) and the exhaust gas outlet space ( 7 ) a lockable service opening ( 18 . 20 ) is provided. Heating system with a boiler for combustion of fuels and with at least one exhaust gas line for discharging exhaust gases produced during combustion from the boiler, characterized in that in the exhaust gas line at least one exhaust gas heat exchanger ( 1 ) is provided according to one of the preceding claims. Heating system according to claim 16, for passing a liquid heat absorption medium through the heat exchanger device ( 4 ) is trained. Heating system according to claim 16, for passing a gaseous heat absorption medium through the heat exchanger device ( 4 ) is trained. Heating system according to one of claims 17 or 18, characterized in that a pumping device is provided, which is designed to transfer the heat absorption medium through the heat exchanger device ( 4 ) to pump.