EP0159379B1 - Heat pump heating device with a flue gas or an exhaust gas cooler - Google Patents

Abstract

1. A heat pump heating installation, in which flue gas or exhaust gas (R) from a boiler (1) is passed through a heat exchanger (8), through which a heat transfer medium circuit also passes which is passed through a radiator (87, 87b) which on the other side is an evaporator (7, 7b) of a compressor-heat pump (52), via the condenser (5) of which the return of a heating circuit (2) also passes, and which includes an air heat exchanger (6) which is coupled on the evaporator side to the heat pump (52), characterized in that the evaporator (7, 76) forms with the radiator (87, 87b) a common air heat exchanger (100) through which the circuit of the heat pump (52) and the heat transfer medium circuit pass separated from one another in respect of their flow but thermally coupled.

Description

The invention relates to a heat pump heating device, in which flue gas or exhaust gas from a boiler is passed through a heat exchanger, through which, on the other hand, a heat transfer medium circuit is passed, which is passed through a cooler, which on the other hand is an evaporator of a compressor heat pump, on the other hand, via the condenser of which Return of a heating circuit is performed, and with an air heat exchanger which is coupled to the heat pump on the evaporator side.

It is known from DE-A-2855485 to equip so-called bivalent heating devices, which include a heat pump system and a boiler, with a heat exchanger for cooling the flue gas of the boiler, in order to obtain the heat extracted from the flue gas for heating purposes via the heat pumps, for safety reasons For reasons of the heat exchanger, the flue gas is not fully charged, but a multiple of the supply air is mixed into the flue gas. As a result, the energy in the flue gas is partly dissipated with the increased amount of exhaust air, as a result of which it is lost for the heating purpose, and the entropy in the flue gas is lost as a result of the mixing process, and as a result, the efficiency of the heat pump in the recovery is reduced compared to an energy supply at the flue gas temperature .

From WO 83/03133 a heating device is known in which two evaporators with upstream throttles are arranged in parallel in a heat pump circuit, one of which is an outside air cooler and the other is coupled to an auxiliary heater. The disadvantage here is that the entire heating output is conducted via the heat pump, so that it must be dimensioned for the maximum heating output requirement.

From WO 83/03662 a heating device according to the first part of claim 1 is known, the heat pump with its condenser introduces heat into the flow of a boiler and the evaporator cools a heat transfer medium circuit which is connected in parallel via an outside air heat exchanger and a flue gas heat exchanger which follows the boiler is, is led. This arrangement has the disadvantage that in pure heat pump operation, as it is in the so-called transition period, the efficiency is lower due to the temperature drop due to the intermediate heat transfer circuit than when an evaporator is placed directly as an air heat exchanger.

It is an object of the invention to disclose a simplified device of the type mentioned, which works with increased efficiency.

The solution to the problem is that the evaporator forms a common air heat exchanger with the cooler, through which the circuit of the heat pump and the heat transfer medium circuit are separated from one another in terms of flow, but are thermally coupled.

In order to meet the safety requirements that an evaporative cooler is not fully charged with flue gas, the additional heat transfer medium circuit is routed through the flue gas heat exchanger, and this circuit is also routed through a cooler that is coupled to the evaporator of the heat pump circuit. The heat transfer medium is, for example, a well-known antifreeze and consists, for example, of glycols or brine. It extracts the heat energy from the flue gases, which leave the boiler at a temperature of around 250 ° C and are then cooled below the dew point, for example, at this corresponding temperature, which means that the heat pump dissipates it with extremely high efficiency. Since the cooled flue gas has only a low thermal lift, it is discharged through a chimney pipe with the help of a fan. The cross-section of the chimney pipe can, however, be kept relatively small since no supply air is added.

An advantageous arrangement of the flue gas heat exchanger results in the installation above the chimney, since the flue gas fan is then unnecessary and the chimney cannot be stained by condensation.

Advantageous designs are shown for supplying the thermal energy in the heat transfer medium circuit. The cooler-heat exchanger of the heat transfer medium is directly thermally coupled to the evaporator, and with this coupled device, thermal energy is also extracted from the outside air. This combination leads to a simplification since there is no need for a second evaporator and control elements for this evaporator.

The control of the mode of operation of the combined cooler is advantageously provided such that the heat pump extracts thermal energy from the flue gas to the extent that the corresponding efficiency is more favorable than when heat is obtained from the outside air or from the groundwater or the like. The control takes place via a corresponding temperature comparison.

An advantageous increase in the overall efficiency of the device is achieved in that a memory is provided in the heat transfer medium circuit, which makes it possible to temporarily store the thermal energy that is continuously extracted from the flue gas and cannot be continuously removed from the heat pump system, so that it can be stored in the The boiler burner can be removed from the heat pump by the heat pump. The heat transfer medium cooled down during the break advantageously lowers the exhaust gas temperature accordingly. The volume or the heat capacity of the storage device is advantageously adapted to the usual burner switch-on times.

A central control device is advantageously provided for controlling the device the necessary temperature signals are supplied and which controls the fans, drives of the valves, mixers and air dampers as well as the burner and the heat pump system in accordance with the optimization specifications.

• Fig. 1 zeigt eine Blockschaltung einer Vorrichtung mit zwei Verdampfern in Parallelschaltung;
• Fig. 2 zeigt einen Luftwärmetauscher kombiniert mit dem Kühler des zweiten Kühlmittelkreislaufs;
• Fig. 3 zeigt eine Anordnung des Luftwärmetauschers nach Fig. 2 im Gehäuse (geöffnet) von der Seite;
• Fig. 4 zeigt eine Alternative zu Fig. 3 als Schnitt durch Fig. 5;
• Fig. 5 zeigt eine Draufsicht auf ein Gehäuse zum Luftwärmetauscher;
• Fig. 6 zeigt einen Rauchgaskühler auf einem Kamin angeordnet, von der Seite;
• Fig. 7 zeigt einen horizontalen Schnitt durch Fig. 6.
• Fig. 1 zeigt eine schematische Darstellung einer bivalenten Heizvorrichtung, bei der aus Zeichnungsgründen der Luftwärmetauscher getrennt vom Kühler und Verdampfer dargestellt ist. Wie bekannte Anlagen dieser Art besitzt diese eine Wärmepumpenanlage 52,4,6, mit einem Kühlmittelkreislauf mit einem Kompressor 52, einem Verflüssiger 5 eines Verflüssiger-Wärmetauschers 4, über den die Wärme abgeführt wird, und einen Verdampfer 6, der Aussenluft Wärme entzieht, die mit einem Ventilator 61 durch die Rippen des Verdampfers 6 gezogen wird. Aus dem Wärmetauscher 4 wird mit einer Pumpe 42 über ein Rückschlagventil 41 der Heizkreislauf 2 und/oder der Brauchwasser-Wärmetauscher 31 je nach der Stellung des Mischers 43 und ggf. dem Betrieb der Pumpe 32 mit dem erwärmten Wasser im Wasserkreislauf beaufschlagt. Die Steuerung der Pumpe 32 und des Mischers 43 geschieht in bekannter Weise, abhängig von vorgegebenen Temperaturen für das Brauchwasser im Speicher 3 und im Vorlauf des Heizkreises, in denen jeweils Temperaturmelder 3m, 13m angeordnet sind.

The design of the device and the method for control in an advantageous manner is shown in detail with reference to FIGS. 1 to 7:

• Fig. 1 shows a block circuit of a device with two evaporators in parallel;
• 2 shows an air heat exchanger combined with the cooler of the second coolant circuit;
• Fig. 3 shows an arrangement of the air heat exchanger of Figure 2 in the housing (open) from the side.
• FIG. 4 shows an alternative to FIG. 3 as a section through FIG. 5;
• Fig. 5 shows a plan view of a housing for the air heat exchanger;
• Fig. 6 shows a flue gas cooler arranged on a chimney, from the side;
• FIG. 7 shows a horizontal section through FIG. 6.
• Fig. 1 shows a schematic representation of a bivalent heating device, in which, for reasons of the drawing, the air heat exchanger is shown separately from the cooler and evaporator. Like known systems of this type, it has a heat pump system 52, 4, 6, with a coolant circuit with a compressor 52, a condenser 5 of a condenser heat exchanger 4, via which the heat is removed, and an evaporator 6, which extracts heat from the outside air is pulled by a fan 61 through the fins of the evaporator 6. From the heat exchanger 4, the heating circuit 2 and / or the domestic water heat exchanger 31 is acted upon by a pump 42 via a check valve 41, depending on the position of the mixer 43 and possibly the operation of the pump 32, with the heated water in the water circuit. The control of the pump 32 and the mixer 43 takes place in a known manner, depending on predetermined temperatures for the process water in the store 3 and in the flow of the heating circuit, in which temperature detectors 3m, 13m are arranged.

In the heating circuit, a further pump 22 with a check valve 21 is provided for an intensive flow, and a check valve 23 leads back to the pump 22 via a return line 24 and a mixer 12. In this way, only a permissible partial flow of the circulating water flows through the heat exchanger 4 via the circulation line 44, so that destruction is prevented.

If the performance of the heat pump system is not sufficient to cover the heat requirement, that is to say if the temperatures in the store 3 and / or flow 13 drop below the lower limit values, the boiler 1 is put into operation by the burner control unit Bs. This is connected with its heating register on the one hand via a check valve 11 to the flow 13 of the heating circuit and on the other hand to the second outlet of the mixer 12 and in parallel to the return of the process water heat exchanger 31. The mixer 12 is actuated by the mixer drive 12a in such a way that a predetermined flow temperature is maintained in each case. If heat is no longer extracted from the boiler, the burner control switches off in a known manner when a predetermined boiler temperature is exceeded.

The temperature of the flue gas R is usual when leaving the boiler 250 ° C. According to the invention, this flue gas is passed over a flue gas heat exchanger 8 and discharged through a chimney with an exhaust gas fan 81 as cooled exhaust gas A.

The flue gas heat exchanger 8 is connected to its own heat transfer medium circuit which, via a line 84, a pump 82, a line 85, a heat exchanger 87, a line 86 with the pressure and / or pressure flow meter 86pv, a memory 83 for heat transfer medium and past a temperature detector 86m back to the flue gas heat exchanger 8. The heat exchanger 87 contains an evaporator 7, which may be parallel to the evaporator 6 in the heat pump circuit.

The distribution of the condensate, which is fed to the coolant circuit of the heat pump system from the condenser 5 via line 55 to the evaporators 6 and 7 in parallel, takes place via controllable condensate valves 56, 57 and condensate lines 62, 64, 65; 72, 74, 75, each consisting of a circulation control valve 62, 72, a bypass 64, 74, a temperature sensor 66t, 76t on the steam outlet lines 66, 76 and a circulation control 65, 75, which are based on the temperature at the temperature sensor and the respective comparison values given to the drive 62a, 72a of the circulation control valve 62, 72 is actuated, so that there is an independent closed control loop in each case.

The comparison values are selected so that the heat pump achieves an optimal efficiency and the temperature sensor 66t is 0 ° C when the supply air temperature is 7 ° C and the temperature sensor 76t +1 ° C when the temperature of the cooled heat transfer medium is in Line 86 is +10 ° C. This setting of the reference of the controller takes place during operation of the circuit components involved, that is to say of the heat pump, boiler, fans 61, 81, pump 82, etc.

• - Kondensatventile KVs-Antriebsmagnete 56a, 57a für Kondensatventile 56, 57
• - Stellantriebe Ss - Antriebsmotore 12a, 43a für steuerbar 3-Wege-Stellventile 12, 43
• - Kompressorantrieb Ks - Antriebsmotor - Kompressor 52
• - Pumpenantriebe Ps - Pumpenmotore - Pumpen 22, 32, 42, 82
• - Ventilatorantriebe Vs - Ventilatoren 61,81
• - Brennersteuerung Bs des Heizkessels 1 Umluftlappenantrieb UKs - Antrieb 91a der Kaltluftklappe 91 (Fig. 3).

The condensate valves 56, 57 are actuated in parallel with the corresponding fan 61 or the pump 82 by the magnets 56a, 57a. To control the heating device, a control device ST is provided, which can be designed as a microprocessor that receives the signals from the temperature detectors Tm for, among other things, supply air 9m, cold air 6m, heat transfer medium 86m, flow 13m, process water 3m and the pressure or flow detector 86pv as well as input data for the limit value comparison or operating states from an input device E, for example, a keyboard or selector switches. It also contains purpose moderate, a timer for controlling the operating conditions depending on the time of day and for monitoring the minimum and maximum times or controlling the switch-on periods of the heat pump and the boiler. Depending on the output values generated, outputs (each designated with index «s») are activated, which individually control the following drives (each designated with index «a»):

• - Condensate valves KVs drive magnets 56a, 57a for condensate valves 56, 57
• - Actuators Ss - drive motors 12a, 43a for controllable 3-way control valves 12, 43
• - Compressor drive Ks - drive motor - compressor 52
• - Pump drives Ps - Pump motors - Pumps 22, 32, 42, 82
• - Vs fan drives - 61.81 fans
• - Burner control Bs of the boiler 1 circulating air flap drive UKs - Drive 91a of the cold air flap 91 (Fig. 3).

The signal outputs are designed several times depending on the number of connected drives. The drive of the fan 61b or 61c in FIGS. 3, 4, 5 can be regulated in speed by corresponding control signals from the control device ST, as explained below.

The control works as follows:

As soon as the burner control unit Bs is switched on with a corresponding energy requirement, which cannot be provided by the heat pump system if the supply air ZL is too low, i.e. the flow temperature is too low, the pump 82 and possibly the condensate valve 57 are also activated. The condensate valve 56 may be turned off during this time. The flue gas R is thereby cooled below the condensation point, which means that energy is largely removed. If the performance of the heat pump system is not sufficient to continuously supply the entire energy to the heating circuit, the heat transfer medium heats up, the volume of which is determined by the store 83, which is advantageously designed so large that a temperature increase of a maximum of 20 ° C during the normal duty cycle of the Brenners occurs.

After the burner has been switched off, that is if there has been sufficient post-heating, the pump 82 continues to operate until the temperature of the heat transfer medium at the temperature detector 86m has dropped to the temperature of the supply air at the temperature detector 9m. Then the pump 82 is switched off and the condensate valves 57, 56 are switched over so that normal heat pump operation takes place.

The signal from the pressure or flow meter 86pv is used to monitor the heat exchanger 87, in that if the pressure or flow drops below a predetermined value, which can be an indication of icing or leakage of the circuit, the condensate valve 57 is controlled closed and preferably an operating alarm message is displayed by the control device. In general, icing is not to be expected as long as the freezing point of the coolant is reduced to -20 or -30 ° C, for example, by antifreeze.

The details of the design of the device according to the main claim are shown in FIGS. 2 and 3. Here, the heat transfer medium heat exchanger 87b, which replaces the heat exchanger 87, is thermally coupled directly to the evaporator 7b, which takes over the function of the evaporators 7 and 6 in FIG. 1, and is assembled to form a common air heat exchanger 100. The heat exchanger, which is made up of fins or bulging cooling surfaces, is traversed on the one hand by supply air ZL or circulating air UL and on the other hand is connected to lines 87, 86 of the heat transfer medium circuit and also to the condensate line 55 and steam line 53 of the heat pump coolant circuit, each with a pipe loop or an evaporator chamber connected.

A preferred way of installing this air heat exchanger 100 is shown in FIG. 3, which shows a vertical section so that the functionally essential components can be seen. The air heat exchanger 100 is mounted vertically in a housing 9, filling it in height. The supply air ZL leads into this housing 9 on the inflow side via a supply air pendulum flap 93 and a circulating air line 98 via a recirculating air pendulum flap 92.

On the downstream side, a fan 61 b, which is preferably a radial fan, is arranged behind the exhaust air chamber 99 and, depending on the position of the controllable cold air flap 91, drives the cooled air through the recirculation line 98 or to the cold air outlet. If the cold air flap 91 is closed, the air recirculation pendulum flap 92 opens, which closes the supply air pendulum flap via a flap coupling 94. Of course, it is also possible to control one of the other flaps or all of them instead of using swing flaps. In front of the air heat exchanger 100, an air baffle 95 is expediently arranged, which causes a uniform action on the inflow side. A condensate tray 96 with a condensate drain 97 is attached below the air heat exchanger.

The thermal coupling of the two heat exchanger parts 7b, 87b can thus take place directly via common cooling plates or fins, and it continues to take place via the circulating air UL. The control of the air circulation or cold air flap 91 takes place by the control device ST in such a way that as long as the temperature at the temperature sensor 99m in the exhaust air space 99 is higher than the temperature of the supply air ZL at the temperature sensor 9m, the cold air flap is closed.

Furthermore, the speed or power of the fan 61 b is controlled in such a way that the temperature in the exhaust air space 99 corresponds to a predetermined temperature, for example 40 ° C., in recirculation mode and that the temperature in the exhaust air space 99 in the supply air mode, that is to say when the cold air flap 91 is open to a featured given temperature difference is below the supply air temperature.

By combining the two heat exchanger parts 7, 87b in the one air heat exchanger 100, the condensate valves 56, 57 (FIG. 1) and a condensate bypass as well as the corresponding control means are unnecessary.

Furthermore, there is the additional great advantage that, in such operating conditions, especially in the so-called transition period, in which temperatures are close to zero degrees and high air humidity and icing occurs on the air heat exchanger, the heat from the flue gas defrosts the ice as soon as the boiler is switched on. An additional defrosting control is not necessary, and the air cooler works with maximum heat transfer since it is hardly iced up and defrosted and dried again and again.

Another arrangement of the air heat exchanger 100 in the housing 9a is shown in FIG. 4, which is a schematic vertical section. Here, the air heat exchanger 100 is mounted approximately diagonally in the housing 9a, so that the supply air space 99z corresponds at the bottom approximately to the width of the housing and the exhaust air space 99 corresponds approximately to the diameter of the inlet opening of the fan 61b. In this way, the cross section of the housing 9a can be kept smaller than that of the housing 9, FIG. 3. The air recirculation line is not shown.

The housing 99a is shown in plan view in FIG. 5. The standard version of the housing has; only half the length up to the line of symmetry H and has a fan 61b. If there is a high power requirement, expansion with two fans 61b, 61c is provided. The second fan is switched on when there is a greater demand for heat. The relatively low overall height achieved as a result enables installation in basements. Since the fans run relatively slowly, except when the supply air temperature is very low, there is only a small amount of noise, which in turn is advantageous when installed in buildings.

A design corresponding to FIG. 4 is also advantageously provided for the housing of the flue gas heat exchanger, so that an arrangement can be made directly behind a boiler. This makes it very easy to retrofit existing heating systems. Since no additional oxygen-containing air acts on the flue gas heat exchanger with the flue gas, the aggressiveness of the condensate which is separated from the flue gas is limited, which extends its durability compared to the known devices.

6 and 7 show a further advantageous embodiment of the flue gas heat exchanger 8a, b, c, d, an exhaust gas fan being dispensed with, since the flue gas heat exchanger is arranged on the chimney 88a and the flue gas rises through the chimney due to its own thermal buoyancy. Here, it cools down due to expansion, but the fan drive energy is saved.

A condensate tray 102 is mounted on the chimney 88a with a chimney sleeve 101, on which the flue gas heat exchanger 8a, b, c, d is arranged in blocks or in a circle around the chimney opening 88, so that the cooled exhaust air A flows out laterally. A cover 104 is attached with supports 103 above the cooler and the chimney opening 88.

It is within the scope of the invention to provide other designs of the heat exchanger and to connect the flue gas heat exchanger to other smoke or flue gas lines instead of behind a boiler. Furthermore, the air heat exchanger 100 (FIG. 3) can also be replaced by a water heat exchanger, that is to say water instead of air flowing through it. Instead of the cold air flap 91, the water removal is then controlled accordingly.

Outside air can also serve as supply air, as can warm or humid air in work rooms. In this case, it is advisable to switch from pure heat pump operation to additional boiler operation if the supply air temperature is below 15 ° C. The air heat exchanger can be installed directly in the work rooms, so that long air inlets and outlets are no longer necessary.

Claims (12)

1. A heat pump heating installation, in which flue gas or exhaust gas (R) from a boiler (1) is passed through a heat exchanger (8), through which a heat transfer medium circuit also passes which is passed through a radiator (87, 87b) which on the other side is an evaporator (7, 7b) of a compressor-heat pump (52), via the condenser (5) of which the return of a heating circuit (2) also passes, and which includes an air heat exchanger (6) which is coupled on the evaporator side to the heat pump (52), characterized in that the evaporator (7,76) forms with the radiator (87, 87b) a common air heat exchanger (100) through which the circuit of the heat pump (52) and the heat transfer medium circuit pass separated from one another in respect of their flow but thermally coupled.

2. An installation according to claim 1, characterized in that the air heat exchanger (100) is provided with a fan (61 b) and at its inlet side the air heat exchanger (100) is connected in a controllable manner with an air circulation duct (98) or an intake opening and at its outlet side it is connected in a controllable manner with the air circulation duct (98) or an intake opening and at its outlet side it is connected in a controllable manner with the air circulation duct (98) and a cold air outlet respectively.

3. An installation according to claim 2, characterized in that the air heat exchanger (100) is arranged in a housing (9a) at an inclination of about 30° to the vertical, thereby forming, in the lower region, an intake chamber (99z) having approximately the width of the housing (9a) and, in the upper region, an outlet chamber (99) corresponding in diameter to the air inlet opening of the fan (61 b) disposed in the upper region, said fan being a radial blower.

4. An installation according to claim 3, characterized in that the a plurality of fans (61 b, 61 c) are arranged juxtaposed, viewed from the side of the air inlet of the intake air (ZL), and the housing (9a) is approximately twice as wide as it is high on the air inlet side.

5. An installation according to any of the preceding claims, characterized in that a storage means (83) is disposed in the heat transfer medium circuit on the downstream side of the heat exchanger (87, 87b), the thermal capacity of which is so calculated that during the average operating period of the burner for the boiler (1) the heat transfer medium undergoes an increase in temperature of 20 °C at maximum.

6. An installation according to any of the preceding claims, characterized in that the heat transfer medium is an antifreeze agent having a freezing point below -30 °C and preferably consisting of glycols or sols.

7. An installation according to any of claims 2 to 6, characterized in that temperature indication signals (Tm) from an air intake temperature indicator (9m), a heat transfer medium temperature indicator (86m), a cold air temperature indicator (6m), a circulating air temperature indicator (99m) and a preliminary temperature indicator (13m) are fed into a control device (ST) and to the output side of the control device (ST) there are connected a fan drive (Vs) for the fan (61,61 b), an exhaust fan (81), a pump drive (Ps) for a heat transfer medium pump (82), the drive (Ks) for the heat pump (52), a cold air valve drive (91 a) for a cold air valve (91), a burner control (Bs) for the boiler (1), and the control device (ST) energises these outputs as a function of the temperature indication signals and timer signals in accordance with control and comparison variables, wherein as a function of the air intake temperature indicator (9m) and the preliminary temperature indication (13m, 3m) the heat pump (52) and, if necessary, additionally the burner control (Bs) are energised, and with the heat pump (52) the heat transfer medium pump (82) and the air circulating fan (61 b) are energised, and in that each time the burner control (Bs) is switched off the heat transfer medium pump (82) remains energised until the temperature at the heat transfer medium temperature indicator (86m) falls below the temperature of the air intake indicator (9m) or a predetermined limit value and it is then switched off, and in that the heat pump (52) is energised at least until this instant.

8. An installation according to claim 7, characterized in that, in response to the indications from the air intake indicator (9m) and the preliminary temperature indicator (13m, 3m), the control device (ST) energises the heat pump (52) and, if necessary, the burner control, and simultaneously the heat pump (52), the heat transfer medium pump (82) and the air circulating fan (61 b, 61 c) are energised and the cold air valve (91) is closed, thereby opening an air circulation flap valve (92) and closing an air intake flap valve (93), and in that each time the burner control (Bs) is switched off the heat transfer medium pump (82) remains energised and the cold air valve (91) remains closed until the temperature at the circulating air temperature indicator (99m) is less than or equal to the temperature at the air intake indicator (9m), and in that the pump (82) is then switched off and the cold air valve (91) is opened, whereby the air circulation and air intake flap valves (92, 93) respectively occupy the other position.

9. An installation according to claim 8, characterized in that, when the cold air valve (91) is closed, the speed or output of the fan (61 b, 61 c) is so regulated that the temperature at the air intake indicator (9m) [sic] has a predetermined value and, when the cold air valve is open, it is so regulated that a predetermined difference prevails between the temperature indications at the air intake indicator (9m) and the circulating air temperature indicator (99m) [sic].

10. An installation according to any of the preceding claims, characterized in that the flue gas heat exchanger (8) is disposed above a chimney (88a) connected to the boiler (1) and the outgoing exhaust gas (A) is discharged horizontally and the flue gas (R) is fed in centrally.

11. An installation according to claim 10, characterized in that the flue gas heat exchanger (8a, 8b, 8c, 8d) is connected to the chimney (88a) by a chimney sleeve (101), on which is disposed a condensation through (102) on which the flue gas heat exchanger (8a, 8b, 8c, 8d) is mounted about a chimney opening (88), above which a covering hood (104), which also covers the chimney opening (88), is mounted with supports (103) on the condensation through (102).

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