EP0108032A2 - Control device for a fuel-heated heat source - Google Patents

Abstract

In a control device for a gas-heated flow heater with a heat exchanger and a burner, which is fed by a fuel supply pipe which is provided with a valve and governed by a thermo-electric safety pilot, the valve (5) of the thermo-electric safety pilot (15, 13) connected to a pressure medium servo motor (53) which is connected to a pressure medium source (42) which is preferably designed as a pneumatic diaphragm pump (49).

Description

The present invention relates to a control device for a fuel-heated heat source according to the preamble of the main claim.

It is known to allow the control process for a fuel-heated heat source, for example a water heater, to prepare hot process water to run fully automatically when the nozzle is opened.

For this purpose, a pilot burner assigned to the main burner is first connected to the gas supply and ignited. The pilot burner heats an expansion sensor, which in turn controls the gas supply to another pilot burner or to the main burner with an actuator.

The operational sequence requires that such expansion sensors have to react very quickly as a result of the inevitable Operating fluctuations keep them constantly in motion and represent a very critical component, since the continuous movements can result in leaks.

The present invention has for its object to provide a control device for a fuel-heated heat source that does not require an expansion sensor and with which a fully automatic ignition and start-up of the heat source is possible with no manual application of the thermoelectric ignition fuse.

This problem is solved with the characteristic features of the independent first claim.

Further refinements and particularly advantageous developments of the invention are the subject of the further independent claims and the subclaims or emerge from the following description which explains an exemplary embodiment of the invention with reference to FIGS. 1 to 5 of the drawing.

Figure one shows a schematic diagram of the circuit of a fuel-heated heat source, in its form as a water heater. But it could just as well be a circulating water heater or Kes act sel. For this purpose, the nozzle should be connected to the cold water supply line by switching on a pump in the water circuit, and radiators should also be looped into the circuit.

The fuel-heated heat source 1 has a heat exchanger 2, which is heated by a gas main burner 3, which is fed from a gas feed line with the interposition of two valves 4 and 5. The heat exchanger is connected to a feeding cold water network via a line 8 provided with a Venturi nozzle 7, and a flow line 10 provided with a nozzle 9 goes from the heat exchanger.

The valve 5 is a valve with a thermoelectric ignition fuse, which has an armature 11 and an electromagnet 13 provided with a winding 12. The winding 12 is part of a circuit 14 into which a thermocouple 15 and two working contacts 16 and 17 are looped. The two contacts 16 and 17 are together with the winding in series with the thermocouple. Between the valves 4 and 5, a pilot gas line 18 branches off from the gas feed line 6 and leads to a pilot burner 19, which is assigned to the thermocouple 15 and the main burner 3.

Two lines 19 and 20 lead from the Venturi nozzle 7 a switch chamber 22 provided with a membrane 21, the membrane is assigned a membrane plate and two actuating rods 23 and 24, of which the actuating rod 23 is connected to a valve body 25 of the valve 4, which is pressed against the restoring force of a compression spring 26 against the seat of the valve 4 is. A tension spring 27 acts on the membrane, which acts in the same direction as the compression spring 26. The actuating rod is assigned the normally open contact 17 and a further normally open contact 28, which lies in the course of a power supply line 29, which is preceded by a further normally open contact 30, which is combined with the normally open contact 16 and forms a main switch.

The mains supply line 29 leads to a branch 31, from which a supply line 32 branches off, which leads to a coil 33 of a pull-in delay relay. A line 34 led from the coil to a branching point 35. A normally closed contact 36 of the delay relay 33 is looped into a line 37 which leads to a branching 38. An ignition transformer 40 is connected to the line 38 via a line 39, the secondary lines 41 and 42 of which lead to ignition electrodes 43 which are assigned to the pilot burner 19. A line 44 branches off from the branching point 38, into which a coil 45 of an electromagnetic valve is looped. Lines 44 and 39 ver an agreement is reached at 46, from this branch point the second network feed line 47 branches off.

A feed line 48 leads from the branching point 38 to a drive motor of an air diaphragm pump 49, the return line 50 of which is led to the branching point 35, which is connected to the second power supply line 47 via a line 51.

A pressure port 52 of the diaphragm pump is connected to a pneumatic control box 53 which has a membrane 54 inside, the control rod 55 of which is connected to the one valve body 56 of the valve 5. The actuating rod 55 passes through the valve body 5 and is connected on its end facing away from the membrane to the armature 11 of the thermoelectric ignition fuse and is under the restoring force of a compression spring 57 which tends to close the valve body 56. At the same membrane chambers to which the pressure port 52 is connected, the solenoid valve 45 is also connected, which controls an outlet opening from the control box into the atmosphere with its valve body 58, which in the idle state due to the action of a spring, not shown, away from the valve seat 59 in opening sense of the control box is pressed.

• Es wird von dem in der Figur eins dargestellten Ruhezustand ausgegangen, beide Brenner sind erloschen, die Wärmequelle ist stromlos. Zum Inbetriebsetzen wird zunächst der Hauptschalter, bestehend aus den Arbeitskontakten 16 und 30, geschlossen, was zunächst noch ohne Wirkung bleibt. Wird das Zapfventil 9 aufgedreht, beginnt in der Wasserleitung 8 Wasser zu fließen, an der Venturidüse 7_.entsteht ein Unterdruck, der über die Leitungen 19 und 20 der Schalterkammer 22 mitgeteilt wird. Aufgrund der Druckdifferenz bewegt sich die Membran gegen die Rückstellkraft der Federn 26 und 27 nach oben, wodurch zum ersten der Ventilkörper 25 des Ventils 4 von seinem Sitz abhebt und zweitens die Kontakte 17 und 28 geschlossen werden. Die Vorrichtung kann hierbei so ausgebildet sein, daß die Kontakte 17 und 28 früher schließen, als der Ventilkörper 25 von seinem Sitz abhebt. Das bedeutet, daß der Stromkreis 14 für die thermoelektrische Zündsicherung geschlossen und daß die Netzspannung an Spule 33 des Anzugsverzögerungsrelais ansteht, das seinen Kontakt 36 verzögert öffnet. Damit steht Betriebsspannung sowohl an dem Motor der Membranpumpe 49 an als auch am Zündtransformator wie schließlich auch an der Spule 45 des Magnetventils. Der Zündtransformator erzeugt nunmehr laufend Funken an den Elektroden 43, die zunächst noch ohne Wirkung sind, da das Gasventil 5/56 geschlossen ist. Die unter Strom stehende Spule 45 des Magnetventils verschließt mit ihrem Ventilkörper 58 den Sitz 59, so daß die Stelldose 53 gegenüber der Atmosphäre abgedichtet wird. Die anlaufende Membranpumpe erzeugt einen Druck, der die Membran 54 entgegen der Rückstellwirkung der Feder 57 nach links bewegt, womit der Ventilkörper 56 des Ventils 5 von seinem Sitz abgehoben wird. Da das Ventil bereits geöffnet ist, steht Gas sowohl am Zündbrenner wie auch am Hauptbrenner. Dieses austretende Gas wird von den Zündfunken der Elektrode 43 gezündet, der Brenner brennt und beheizt mit seinen Abgasen den Wärmetauscher 2. Das durchfließende Wasser wird aufgeheizt und steht als warmes Zapfwasser zur Verfügung. Dieses Inbetriebsetzen der Wärmequelle geht relativ schnell, und zwar innerhalb von einigen Sekunden.

The heat source or its control device just described has the following function:

• It is assumed that the idle state shown in Figure 1, both burners are extinguished, the heat source is de-energized. For commissioning, the main switch, consisting of the work contacts 16 and 30, is first closed, which initially has no effect. If the nozzle 9 is turned on, water begins to flow in the water line 8, at the Venturi nozzle 7 _. creates a negative pressure, which is communicated to the switch chamber 22 via the lines 19 and 20. Due to the pressure difference, the diaphragm moves upward against the restoring force of the springs 26 and 27, as a result of which the valve body 25 of the valve 4 lifts off its seat and secondly the contacts 17 and 28 are closed. The device can be designed so that the contacts 17 and 28 close earlier than the valve body 25 lifts from its seat. This means that the circuit 14 for the thermoelectric ignition fuse is closed and that the mains voltage is present at coil 33 of the pull-in delay relay, which opens its contact 36 with a delay. Operating voltage is thus present both on the motor of the diaphragm pump 49 and on the ignition transformer and finally also on the coil 45 of the solenoid valve. The ignition transformer now generates continuous sparks on the electrodes 43, which are initially still ineffective since the gas valve 5/56 is closed. The energized coil 45 of the solenoid valve closes the seat 59 with its valve body 58, so that the control box 53 is sealed from the atmosphere. The starting diaphragm pump generates a pressure which moves the diaphragm 54 to the left against the restoring action of the spring 57, whereby the valve body 56 of the valve 5 is lifted from its seat. Since the valve is already open, there is gas on both the pilot burner and the main burner. This escaping gas is ignited by the ignition sparks of the electrode 43, the burner burns and heats the heat exchanger 2 with its exhaust gases. The water flowing through is heated up and is available as warm tap water. This start-up of the heat source is relatively quick, within a few seconds.

The burner heats the thermocouple, a thermal current builds up in the circuit 14, which excites the winding 12 of the electromagnet 13 and holds the armature 11 previously applied to the magnet by the control box 53. The valve 5 is thus kept open by the thermoelectric ignition fuse. During this time, the delay time of the delay relay 33, which is the normally closed contact after the delay time has elapsed, approximately 11 seconds 36 opens. The diaphragm pump, the igniter and the solenoid valve 45 are thus de-energized. Thus, the control box 53 is depressurized, but this has no effect since the thermoelectric ignition fuse keeps the valve 5 open. The further ignition is stopped, the control box 57 is relieved of pressure medium.

If for any reason the pilot burner or the main burner goes out during operation, the thermocouple 15 is no longer heated, as a result the valve 5 closes and the further gas supply to the burners is interrupted.

To stop the heat source, only the nozzle 9 is closed, the water deficiency valve 4 closes. By opening the contacts 28 and 17, the circuit of the thermoelectric ignition fuse is interrupted, on the other hand, the diaphragm pump stops working, and the control box 53 is relieved of pressure medium. As a result of this activity, valve 5 also closes.

The task of creating a fuel-heated heat source with a thermoelectric ignition fuse, in which manual application of the thermoelectric ignition fuse is omitted, is also shown in the second exemplary embodiment according to

Figure two, which shows a schematic diagram of a fuel-heated heat source with a fuse and an electrical circuit.

The fuel-heated heat source 101 essentially has a heat exchanger 103 which is heated by a main burner 102 and to which the water in a circuit is fed from a return line 104 and is discharged via a supply line 105. In the course of the return line 104, a Venturi nozzle 105 is arranged, to which a water switch 106 is connected via two measuring lines 107 to form a low water protection device. A consumer 108, consisting of a plurality of radiators connected in parallel and / or in series or a domestic hot water heater, is connected to the flow, from the consumer 108 a connecting line 109 leads to a circulation pump 10, in the pressure port of which the Venturi nozzle 105 is located. It is irrelevant whether the fuel-heated heat source 101 is a circulating water heater or a boiler. If the fuel-heated heat source is designed as a once-through water heater for preparing sanitary service water, line 105 ends in a tap valve, while the return line is formed by a supplying cold water network.

The main burner 102 is fed from a gas line 111, in which a water shortage safety valve 112 is arranged, which is actuated via an actuating rod 113 which can be actuated by the water switch 106 and which is provided with a normally open contact 114 which is connected to a supply line 115 Power source 152 is located.

The gas line 111 continues downstream of the water shortage safety valve 112 and leads to a branch 115, from which a pilot gas line 117 leading to a pilot burner 116 and a main gas line 118 leading to the main burner 102 branches off. A valve 119 of a thermoelectric ignition fuse 120 is arranged in the main gas line 118 and essentially consists of an electromagnet 121, an armature 122 and the valve 119 already mentioned. The armature 122 is connected to the valve body of the valve 119 via a rod 123 which, on the side of the valve 119 facing away from the armature 122, leads to a normally closed contact 124 which is arranged in the course of an electrical line 125 which is in direct contact with the normally open contact 114 on the side of the contact facing away from line 115.

The thermoelectric fuse is under the action of a spring, not shown, which has the tendency to the thermoelectric fuse in the

Figure to transfer position shown, that is, the armature 122 is withdrawn from the electromagnet 121, the valve 119 and the normally closed contact 124 are closed.

The electromagnet is provided with a first winding, the so-called holding winding 126, which is connected via lines 127 and 128 to a thermocouple 129 which is associated with the pilot burner 116, which in turn is adjacent to the main burner 102 so that its flame ignites the main burner is able. However, the electromagnet is also provided with a second winding, the so-called pull-in winding 130, which is provided with a branching point 132 via a first feed line 131 and with a branching point 134 via a second feed line 133, and both, except for the feed winding 130 are connected electrically parallel to one another via the primary winding 135 of an ignition transformer 136. A secondary winding 137 of the ignition transformer is grounded, on the one hand, and, on the other hand, is connected via a line 138 to an ignition electrode 139, which is assigned to the pilot burner 116, which is also grounded.

The normally closed contact 124 is connected on the side facing away from line 125 via a further line 140 to a timing element 141, the output of which is connected to a branch point 142. The branch point 142 is connected to point 132 by means of a line 143, into which a resistor 144 is inserted. However, point 142 is connected to a further branching point 147 by a line 145 into which a resistor 146 is looped. A capacitor 148 is connected to branch point 147 and a Z diode 149 is connected to the second. The capacitor 148 is connected on its side facing away from the branch point 147 to another branch point 150, from which a line 151 goes to the other pole of the current source 152.

The Z-diode 149 is connected on the side facing away from the branch point 147 to a control electrode 153 of a thyristor 154, one electrode of which is connected to the branch point 134 and the third electrode of which is connected via a line 155 to a branch point 156 which is connected via a line 157 to communicates with branch point 150. A capacitor 158 is connected to the connection point 156, the other connection of which lies at the branch point 132.

Although the exemplary embodiment describes a gas-fired heat source, it would also be possible to provide an oil-fired heat source instead.

• Es wird ausgegangen vom in der Figur zwei dargestellten Ruhezustand, das heißt, der Wasserschalter 106 ist aufgrund der Wirkung der nicht dargestellten Rückstellfeder in der Stellung, daß das Wassermangel-Sicherungsventil 112 geschlossen und der Arbeitskontakt 114 geöffnet ist. Das thermoelektrische Zündsicherungsventil 119 ist gleichermaßen geschlossen, das gleiche auch der Kontakt 124. Der Stromkreis der Stromquelle 152 ist unterbrochen. Bei dieser Stromquelle kann es sich sowohl um eine Batterie, dann beinhaltet das Zeitglied 141 einen Spannungsvervielfacher, es kann sich auch um eine Netzspannungsquelle mit Gleichrichter handeln, dann besteht das Glied 141 als reines Verzögerungsglied.

The fuel-heated heat source according to FIG. 2 just described has the following function:

• It is assumed that the idle state shown in the figure is two, that is, the water switch 106 is in the position due to the action of the return spring, not shown, that the low water safety valve 112 is closed and the normally open contact 114 is open. The thermoelectric ignition safety valve 119 is closed in the same way, as is the contact 124. The circuit of the current source 152 is interrupted. This current source can be both a battery, then the timing element 141 contains a voltage multiplier, it can also be a mains voltage source with a rectifier, then the element 141 is a pure delay element.

If, in the case of the circulation water heater, the pump 110 is operated by a heat request signal from a room or flow thermostat (not shown), a differential pressure builds up on the Venturi nozzle 105 as a result of the water throughput, which causes the water switch 106 to respond, so that the water shortage safety valve 112 opened and the contact 114 is closed. Now the circuit for the current source 152 is closed, the resistor 146 is the capacitor 148 and charged through resistor 144 of capacitor 158. The timer 141 starts to run for a delay time of approximately 10 seconds. After the 10 seconds have elapsed, the timing element interrupts the further current short in line 140. The voltage across capacitor 148 rises relatively quickly, after reaching the voltage specified by tens diode 149, thyristor 154 is triggered, so that a current flow pulse in contact winding 130 of the electromagnet 121 results. At the same time, the ignition transformer 136 is supplied with voltage. As a result, there are ignition sparks to the housing of the pilot burner 116 via the ignition electrode 139. Since the pilot gas path via the lines 111, 115 and 117 is open, pilot gas flows immediately with the opening of the low water safety valve 112, which is ignited by the spark and the thermocouple 129 begins to heat. Thus, in addition to the electromagnetic flux generated in the contact winding 130, a further additional rectified electromagnetic flux begins to build up, namely via the lines 127 and 128 in the holding winding 126.

When the armature is tightened, the contact 124 is opened so that the current flow from the current source 152 via the timing element 141 is stopped. Has the ignition of the pilot burner during this time until contact 124 opens and the heating of the thermocouple has taken place and if a sufficiently large holding current has been built up via the lines 127, 128 from the thermocouple 120 in the holding winding 126, the thermoelectric ignition fuse will hold due to the thermal current, even if the application pulse is now switched off by the contact winding 130. The ignition is also de-energized.

If ignition and monitoring have not taken place, the armature 122 of the thermoelectric ignition fuse falls off the electromagnet, the contact 24 is closed, and renewed application and ignition consumption can take place. Finally, the heat source 101 will go into operation by closing the holding circuit for the thermocouple in the electromagnet 121 and thus opening the thermoelectric ignition safety valve 119. Gas can now flow in the main gas line 118, which is ignited and burned by the pilot burner 116 on the main burner 102 and heats the heat exchanger 103.

A shutdown of the heat source 101 is brought about by de-energizing the motor of the pump 110, the insufficient water flow causes the low water alarm to respond, the low water safety valve 112 to close and the contact 114 to open. In order to the circuit for the current source 152 is interrupted, but also the gas path. The main and pilot burner extinguish immediately, a cooling phase begins for the thermocouple 120, while the armature 122 of the thermoelectric fuse is still activated, but the contact 124 is open. A restart of the pump 110 would have no effect since the circuit for the current source is impossible through the contact 124 which is still open. Only when the thermoelectric ignition fuse drops does the contact 124 close and makes it possible to restart the heat source 101.

In order to achieve the object of specifying a control system for a fuel-heated heat source which goes into operation when a nozzle is opened and which does not require an expansion sensor, the characterizing features of independent claim 15 are proposed.

Further refinements and particularly advantageous developments of the invention are the subject of subclaims sixteen to twenty-three or emerge from the following description, which explains a further exemplary embodiment of the invention with reference to schematic figure three of the drawing.

A heat source 201 has a heat exchanger 202 that flows from a main burner 203 via a gas line 204 is fed from a gas network 205. A liquid fuel could also be considered as fuel. Water from a water network 206 is supplied to the heat exchanger 202 with the interposition of a Venturi nozzle 207 via a return line 208 and, in the heated state, is taken from a supply line 209 which has a nozzle 210. Instead of the continuous gas water heater shown in the exemplary embodiment for preparing hot service water for sanitary purposes, it could just as well be a circulating water heater or boiler, then the outlet of the nozzle would have to be connected to the water line 206 by switching on a pump and one or more radiators.

The venturi nozzle 207 is assigned two water switches 211 and 212, of which the water switch 211 works as a low water indicator. Its one membrane chamber 213 is connected via a line 214 to the suction point of the Venturi, the other chamber 215 is connected via lines 216 to the pressure point of the Venturi nozzle. The upper and lower pressure chambers of the two water switches 211 and 212 are connected in parallel to one another. Both water switches move in the same direction. A membrane with an actuating rod 217 is assigned to the water switch 211, which acts as a valve body 218 of a gas valve 219 against the rear actuating force of a compression spring 22U is actuated and connected to a normally open contact 221. The water switch 211 forms, together with the valve 219, the lack of water protection, that is to say the gas valve 219 is only opened when an adequate water throughput through the line 206 is ensured.

The line to the valve seat of the gas valve 219 branches off from the gas supply line 205, which continues parallel to this to a further valve 222, the valve body 223 of which controls a supply line 224 to a gas reservoir 225, which has a fill contact 226, which is open in the idle state and then is closed when a minimum gas storage tank has been filled with fuel. The contact 226 is in series with the contact 221 in a circuit 227 which is fed by a battery 228 and in which an ignition device 229 is looped in series with the two contacts. The filling contact can be actuated, for example, by a membrane that is part of the wall of the fuel storage.

The ignition device 229 feeds an ignition electrode 231 via lines 230, which is assigned to a pilot burner 232 or the main burner 203. The ignition device 229 has yet another function, and that of applying the thermoelectric ignition fuse: An electromagnet 233 is provided with two windings 234 and 235, of which the winding 234 is connected to the ignition device 229 via lines 236. In parallel with the delivery of high-voltage pulses for actuating the ignition electrode 231, current surges are applied to the line 236 of the electromagnet 233. The winding 235 is connected via the line 237 to a thermocouple 238 which is assigned to the pilot burner 232 or the main burner 203. An armature 239 corresponds to the electromagnet 233 and is connected to an actuating rod 240 for a valve body 241 of a gas valve 242, which is biased in the closing direction by a compression spring 243. In its extension, however, the rod still leads to a further valve body 244 of a gas valve 245, which is arranged in the course of an ignition gas line 246 to a further pilot burner 261, the ignition gas line 246 branching off from the gas network line 205, in terms of flow parallel to the valves 219 and 242 lies. The valve body 244 rests under the pretension of a compression spring 247, which pretensions the valve body in the direction of closing.

An ignition gas line 249, which is provided with a check valve 248 and leads to the pilot burner 232, branches off from the gas line 204 behind the valve 242.

The actuating rod 240 is also connected to a normally closed contact 250 which is in the circuit of the lines 227. The windings 234 and 235 and the current strengths passing through them are dimensioned such that the armature 239 is held on the electromagnet 233 by current flow in the line 235, but cannot be attracted. Current flow in winding 234 is required for this.

• Zum Inbetriebsetzen der Wärmequelle wird das Zapfventil 210 geöffnet, wodurch in den Wasserleitungen 206, 208 und 209 Wasserfluß resultiert. Beide Wasserschalter 211 und 212 sprechen an und drücken ihre Stellstangen 217 und 260 entgegen der Rückstellkraft der Federn 220 beziehungsweise 258 nach oben. Der Gasspeicher 225 wird eingangsseitig durch Verschließen der Leitung 224 infolge des Schließens des Ventils 222 vom speisenden Netz getrennt, die Ventile 219 und 253 öffnen. Da die Ventile 242 und 245 geschlossen sind, kann kein Gas zum Hauptbrenner und zum Zündbrenner 261 gelangen. Der Gasspeicher, der während der vorhergehenden Zapfpause über die Gasnetzleitung 205 und die Leitung 224 aufgeladen war, so daß der Füllkontakt 226 angesprochen und geschlossen hat, beginnt sich nunmehr über das in Durchflußrichtung öffnende Rückschlagventil 254 und die Leitungen 255 und 256 zu entladen and den Zündbrenner 232 zu speisen. Die sich bewegende Stellstange 217 öffnet nicht nur das Ventil 219, sondern schließt auch den Arbeitskontakt221. Nunmehr kann die Batterie 228 die kombinierte Zünd- und Anlegevorrichtung 229 speisen. Als Folge davon resultieren Hochspannungsimpulse auf den Leitungen 230, die zu der Zündelektrode 231 gelangen und das am Zündbrenner 232 ausströmende Gas entzünden.

Der Zündbrenner 232 brennt und beginnt das Thermoelement 238 zu beheizen. Parallel hierzu wird ein ca. 1/10 Sekunden dauernder Stromstoß auf die Leitungen 236 und damit auf die. Wicklung 234 gegeben, so daß der Elektromagnet 233 bestrebt ist, den Anker 239 anzuziehen. Als Folge hiervon werden die beiden Ventile 242 und 245 geöffnet, so daß Gas zum Hauptbrenner und zum zweiten Zündbrenner 261 gelangen kann und dort vom ersten Zündbrenner 232 gezündet wird. Die Wärmequelle ist in Betrieb gegangen, der Benutzer bekommt warmes Wasser.The valve body 223 is connected via a rod 251 to a further valve body 252 of a valve 253, which is connected to the outlet of the gas accumulator 225 via a gas line 255 provided with a check valve 254. An ignition gas line 256 is connected downstream of the valve 253, which leads to the pilot burner 232 and is connected to the line 249 downstream of the check valve 248. Valves 222 and 253 have compression springs 257 and 258, which are directed towards each other, the spring constant of spring 258 being stronger than that of spring 257. The valve body 252 can be lifted from its valve, which is closed in the rest position, by means of a handle 259. In the idle state, the valve body 223 is lifted off the associated seat, the valve 222 is accordingly opened. Valves 219, 242, 245 and 253 are closed in the idle state. The valve body 212 is connected to an actuating rod 260 of the water switch 212. The heat source just described or their The controller has the following function:

• To start the heat source, the tap valve 210 is opened, resulting in water flow in the water lines 206, 208 and 209. Both water switches 211 and 212 respond and press their adjusting rods 217 and 260 upward against the restoring force of the springs 220 and 258, respectively. The gas storage 225 is separated on the input side by closing the line 224 as a result of the closing of the valve 222 from the supply network, and the valves 219 and 253 open. Since valves 242 and 245 are closed, no gas can get to the main burner and pilot burner 261. The gas storage device, which was charged via the gas supply line 205 and the line 224 during the previous tap break, so that the filler contact 226 has responded and closed, now begins to discharge via the check valve 254 opening in the flow direction and the lines 255 and 256 and the pilot burner 232 to dine. The moving actuator rod 217 not only opens the valve 219, but also closes the make contact 221. The battery 228 can now feed the combined ignition and application device 229. As a result, high voltage pulses result on lines 230, which reach ignition electrode 231 and ignite the gas flowing out of ignition burner 232.

The pilot burner 232 burns and begins to heat the thermocouple 238. In parallel with this, a current surge lasting approximately 1/10 seconds is applied to the lines 236 and thus to the. Given winding 234, so that the electromagnet 233 strives to attract the armature 239. As a result, the two valves 242 and 245 are opened so that gas can reach the main burner and the second pilot burner 261 and is ignited there by the first pilot burner 232. The heat source has started up and the user is getting warm water.

If the ignition is not successful, the gas storage can be switched off after max. Empty for 10 seconds so that contact 226 opens. As a result, the ignition and application device 229 can no longer operate, in particular cannot open the valves 242 and 245. When the gas storage tank is emptied, the pilot burner goes out and the heat source comes to rest, even though cold water is flowing. The user can only initiate a new ignition process by closing the dispensing valve, since the gas storage 225 must first be recharged when the water switch is reset.

To switch off the heat source that is in proper operation, only the tap valve has to be closed, whereupon the valve 219 via the water switch 211 closes and the gas supply to the main burner 203 is cut off. The main burner goes out, the pilot burner 232 also goes out. The pilot burner 261 is still burning, but can no longer heat the thermocouple 238. As soon as the main burner 203 is extinguished, the armature 239 is torn from the electromagnet 233 _' by the springs 243 and 247 after the thermoelectric ignition fuse has cooled down, so that the valves 242 and 245 close. This also interrupts the gas supply to the second pilot burner 261. A renewed tapping process during the fall of the thermoelectric ignition fuse means that the gas flowing out of the main burner as a result of opening the valve 219 is immediately ignited by the second pilot burner 261, since the valves 242 and 245 result from holding the thermoelectric ignition fuse during cooling of the thermocouple are still open.

A further exemplary embodiment of the invention is shown in FIG. Four in the form of a schematic diagram of the circuit of a fuel-heated heat source, specifically as a water heater. But it could just as well be a circulating water heater or boiler. For this purpose, the nozzle should be connected to the cold water supply line by switching on a pump in the water circuit, and radiators would also be connected to the circuit loop in.

The fuel-heated heat source 301 has a heat exchanger 302 which is heated by a main gas burner 303, which is fed from a gas feed line 306 with the interposition of two valves 304 and 305. The heat exchanger is connected to a supplying cold water network via a line 308 provided with a Venturi nozzle 307, and a flow line 310 provided with a nozzle valve 309 extends from the heat exchanger.

The valve 305 is a valve with a thermoelectric ignition fuse, which has an armature 311 and an electromagnet 313 provided with a winding 312. The winding 312 is part of a circuit 314 into which a thermocouple 315 and a normally open contact 316 are looped. Contact 316, along with the winding, is in series with the thermocouple. Between the valves 304 and 305, an ignition gas line 365 branches off from the gas feed line 306 and leads to an ignition burner 366, which is assigned to the main burner 303.

From the Venturi nozzle 307, two lines 319 and 320 lead to a water switch 322 provided with a membrane 321, the membrane is assigned a membrane plate and two actuating rods 323 and 324, of which the actuating rod 323 is connected to a valve body 325 of the valve 304, which is pressed against the restoring force of a compression spring 326 against the seat of the valve 304. A pressure spring 327 acts on the membrane, which acts in the same direction as the pressure spring 326. The actuating rod is assigned a normally open contact 317, which lies in the course of a power supply line 329, which is preceded by a further normally open contact 338, which is combined with the normally open contact 316 and forms a main switch.

The power line 329 leads to a branch 331, from which a feed line 332 branches off, which leads to a coil 333 of a pull-in delay relay. A line 334 leads from the coil to a branch point 335. A normally closed contact 336 of the delay relay 333 is looped into a line 337, which leads to a branch 338. An ignition transformer 340 is connected to the line 338 via a line 339, the secondary lines 341 and 342 of which lead to the ignition electrodes 343, which are assigned to a pilot burner 369. A line 344 branches off from the branching point 338, into which a coil 345 of an electromagnetic valve is looped. The lines 344 and 339 merge at 346, the second network feed line 347 goes from this branch point.

A feed line 348 leads from the branch point 338 to a drive motor of an air diaphragm pump 349, the return line 350 of which leads to the branch point 335, which is connected to the second power supply line 347 via a line 351.

A pressure port 352 of the diaphragm pump is connected to a pneumatic control box 353, which has a membrane 354 inside, the control rod 355 of which is connected to the one valve body 356 of a valve 328. The actuating rod 355 passes through the valve body 356 and, on its end facing away from the membrane, is placed against a further actuating rod 360, which is connected to the armature 311 of the thermoelectric ignition fuse, and is under the restoring force of a compression spring which tends to actuate the valve body 305 and 356 close and put the poles together. To the same membrane chambers to which the pressure port 352 is connected, the solenoid valve 345 is also connected, which controls an outlet opening 359 from the control box into the atmosphere with its valve body 358, which in the idle state due to the action of a spring, not shown, from the valve seat 359 in opening sense of the control box is pressed.

Both the valve body 361 of the valve 305 and the valve body 356 of the valve 328 are both under the action of a return spring 362 and 363, which both strive to the associated valve body to press into the seats. Through the interruption point 364 between the rod 355 and the rod 360, which then carries the valve body 361 and is part of the armature 311, it is possible to lift both valve bodies 356 and 361 from the associated seats from the control box 353 via the rod 360 at the same time to apply the armature 311 to the electromagnet 313, but the electromagnet 313 is only able to keep the valve body 361 open against the restoring force of the spring 362 after delivery of thermal current. When the diaphragm pump 349 is stopped and the solenoid valve 345 is excited and the opening 359 is accordingly closed, the valve body 356 moves back into its closed position under the restoring force of the spring 363 and the gap 364 is enlarged.

The valve 328/356 lies in the pilot gas line 318 to the pilot burner 369 and is arranged behind the valve 305/361 in terms of flow. From the part of the gas line 318 downstream of the valve 305/361, but upstream of the valve 328/356, another pilot gas line 365 branches off to a further pilot burner 366, this pilot burner is only assigned to the main burner 303, but not to the electrodes 343 or the thermocouple 315 .

Another branches off downstream of the valves 304/325 and 305/361 from the main gas line to the main burner 303 Ignition gas line 367, which is provided with a check valve 368, which opens into the ignition gas line 318 downstream of the valve 328/356.

The control device according to FIG. 4 just described has the following function:

It is assumed that the idle state shown in the figure four, all burners have gone out, the heat source is de-energized. For commissioning, the main switch, consisting of the work contacts 316 and 330, is first closed, which initially has no effect. If the nozzle valve 309 is turned on, water begins to flow in the water line 308, a negative pressure develops at the Venturi nozzle 307, which is communicated to the switching chamber 322 via the lines 319 and 320. Due to the pressure difference, the membrane moves upward against the restoring force of the spring 326, as a result of which the valve body 325 of the valve 304 lifts off its seat and secondly the contact 317 is closed. The device can be designed in such a way that the contact 317 closes earlier than the valve body 325 lifts off its seat. This means that the mains voltage is present at the coil 333 of the pull-in delay relay, which opens its contact 336 with a delay. This means that there is operating voltage both on the motor of the membrane pump 349 as well as on the ignition transformer 340 and finally also on the coil 345 of the solenoid valve. The ignition transformer now continuously generates sparks at the electrodes 343, which are initially ineffective since the gas valves 305 and 356 are closed. The energized coil 345 of the solenoid valve closes the seat 359 with its valve body 358, so that the control box 353 is sealed from the atmosphere. The starting diaphragm pump generates a pressure which moves the diaphragm 354 to the left against the restoring action of the spring 363, whereby the valve body 356 of the valve 328 is lifted from its seat. At the same time, the valve body 361 lifts off its seat, so that gas is present both on the pilot burners and in the main burner. This escaping gas is ignited by the ignition sparks of the electrode 343, the burner burns and heats the heat exchanger 302 with its exhaust gases. The water flowing through is heated up and is available as warm tap water. This start-up of the heat source is relatively quick, within a few seconds.

The burner heats the thermocouple, a thermal current builds up in the circuit 314, which excites the winding 312 of the electromagnet 313 and holds the armature 311 previously applied to the magnet by the control box 353. Thereby the valve 305 from the thermoelectric see ignition fuse kept open. During this time, the delay time of the delay relay 333 runs, which opens the normally closed contact 336 after the delay time, approximately 11 seconds. The diaphragm pump, the igniter and the solenoid valve 345 are thus de-energized. Thus, the control box 253 is depressurized, which results in the valve body 356 closing, since the thermoelectric ignition fuse keeps the valve 305 open. The further ignition is stopped, the control box 353 is relieved of pressure medium. The pilot burner 369 does not go out, it is fed via the check valve 368.

If for some reason the pilot burner 369 or the main burner 303 goes out during operation, the thermocouple 315 is no longer heated, as a result the valve 305/561 closes and the further gas supply to the burners is interrupted.

If the nozzle valve 309 is closed at this moment, the valve 304/325 closes as a result of the decrease in the water pressure difference present at the switching chamber. The pilot burner 366 remains burning, however, because the valve 305/361 remains open during the fall of the thermoelectric ignition fuse. If the nozzle 309 is turned back on during the cooling time of the thermoelectric ignition fuse, the one still burning ignites Pilot burner 366 turns main burner 303 on again. The pilot burner 369 is again supplied with pilot gas via the check valve 368. The diaphragm pump, the ignition transformer and the delay relay are energized again, but switch off again after the delay time of the delay relay has passed without affecting the heat source that has already started to operate. To stop the heat source, only the nozzle is turned off. The low water safety valve 304/325 closes, the main burner 303 and the pilot burner 369 go out. For the thermoelectric ignition protection, the cooling time begins, after which the return spring 362. tears off the armature 311 from the electromagnet 313.

The valve 305/361 closes and the heat source is finally out of operation. The heat source can also be switched off by actuating the main switch 316/330, in this case the circuit of the thermoelectric ignition fuse is disconnected, the valve 305/361 closes suddenly and causes all three burners to go out.

The fuel-heated heat sources described in the preceding examples, provided with a thermoelectric ignition fuse, work with a fixed one Pilot burner setting, that is, the thermocouple of the thermoelectric ignition fuse is subjected to a certain heat output. This heat output must be so large that the solenoid valve of the thermoelectric ignition fuse receives sufficient voltage to hold the open valve body, on the other hand the thermoelectric ignition fuse should not exceed a certain size, so that the fall times after the pilot burner goes out until the solenoid valve closes don't get too big.

Since these two demands are contradictory, there are certain difficulties in meeting the two demands equally.

For this reason, the present invention is based on the object of regulating a thermoelectric ignition fuse. create with which a high thermal voltage is quickly built up to hold the valve body of the solenoid valve of the thermoelectric ignition fuse and, on the other hand, the thermal voltage is kept at the lowest possible value during operation in order to ensure a short fall time.

The solution to this problem lies in the characterizing features of the independent claims twenty-nine and thirty-four.

Further refinements and particularly advantageous developments of the invention are the subject of the further subclaims or emerge from the following description which explains an exemplary embodiment of the invention with reference to FIG. 5 of the drawing.

A basic illustration of a fuel-heated heat source is shown in FIG.

The fuel-heated heat source 401 essentially consists of a heat exchanger 404 heated by a main burner 403, which is connected to a cold water supply line 405 and in the course of which there is a Venturi nozzle 406, from which measuring lines 407 and 408 lead to a differential pressure water switch 409.

It is irrelevant whether the fuel-heated heat source is a tap water heater for sanitary service water or a circulation water heater or boiler. While in the first case the tap line 405 passing through the heat exchanger 404 is led to a tap valve, in the second case the flow line of the heat exchanger 404 is led back to the cold water line 405 via a plurality of heat exchangers in parallel and / or in series and a circulation pump, the water circulating there due to the drive effect the pump circulates.

The main burner is led via a main fuel line 410, in which a valve 411 assigned to the water switch 409 is provided, to a branch point 412, from which a pilot fuel line 413 branches off, via a control valve 414, which has a control range from a minimum to a maximum position has, is led to a pilot burner 415 assigned to the main burner 403, to which a thermocouple 416 of a thermoelectric ignition fuse 402 is assigned. The thermocouple is connected to two lines 417 and 418, which lead to an electromagnet 419, to which an armature 420 is assigned, which is connected via an actuating rod 421 to an actuating valve 422, which has a handle 423 for opening against the restoring force of a return spring 424 is provided. The control valve 422 is arranged in the fuel line 425 upstream of the branch point 412.

The valve 411 also has a return spring 426 which ensures that the valve is closed in the rest position. An equivalent return spring 427 also has the control valve 414, which has a minimum passage position and a maximum passage position and a continuous intermediate position between the two is able to take.

Lines 428 and 429 lead from lines 417 and 418 to two inputs of an operational amplifier 430, which is connected in an inverting manner. This means that a small input voltage is associated with a large input voltage on lines 417 and 418 and vice versa.

An output line 431 of the operational amplifier 430 leads to a solenoid 432 of the control valve 4I4, the other side of which is connected to a line 433 which leads to a pole of a voltage source 434. The other pole 435 of the operating voltage source is connected via a line 436 to an operating voltage connection of the operational amplifier, likewise the pole 434 of the voltage source is connected via a line 437 to the other supply voltage connection of the operational amplifier.

The fuel-heated heat source 401 according to FIG. 5 has the following function:

In the idle state, that is to say when the water in the cold water tap line 405 is at a standstill, both the valve 411 and the control valve 422 of the thermoelectric ignition fuse 402 are closed, but the control valve 414 is closed opened in a maximum position.

In order to transfer the fuel-heated heat source from the rest position into the ready position, the handle 423 is pressed in against the restoring force of the spring 424. The control valve 422, which can only assume a closed and an open position, is thus opened, and the armature 420 is also applied to the electromagnet 419 of the thermoelectric ignition fuse 402 by means of the control rod 421. The pilot fuel path is now clear since the control valve 414 has reached its maximum open position. This is due to the fact that when the thermocouple 416 is cold, it emits a voltage signal of zero magnitude, that is to say the minimum voltage signal, so that a maximum voltage signal is present at the output 431 of the operational amplifier 430. This maximum voltage signal is applied to the coil 432, which brings the control valve 414 into its maximum open position against the restoring force of the spring 427. The pilot fuel delivered via lines 425 and 413 emerges from pilot burner 415 and is ignited there by means not shown. The pilot burner burns and heats the thermocouple 416. A thermal voltage builds up, which is applied via lines 417 and 418 both to the coil of the electromagnet 419 and to the input of the operational amplifier. An increasing tension in the The input of the operational amplifier causes a decreasing current on the output line 431 and thus a slow throttling of the control valve 414. When the thermal voltage reaches the holding value for the electromagnet 419, the armature 420 remains attracted, although the handle 423 can be released, up to this However, the time must be pressed.

If the thermal voltage continues to increase, the control valve 414 is throttled further in its open position until it is possibly in its minimum position. Thus, a control circuit is formed for the thermoelectric ignition fuse, which consists of the measuring element 416 and the actuator 432 with the aid of the control amplifier 430, on which a setpoint can also be set by means not shown. If the thermal voltage decreases, starting from a stationary idle state, the heating output is increased via the pilot burner. If the thermal voltage increases, the heating output is reduced. It is irrelevant that an oscillation can occur due to the proportional action of the controller.

It is essential, however, that this regulation can keep the thermovoltage at a low value, which on the one hand protects the thermocouple against excessive heating and thus against rapid destruction, and on the other hand guarantees a fast fall-off time.

From the ready position to the operating position, the fuel-heated heat source 401 passes through the venturi 406 in the event of water pressure, since the valve 411 then opens and the main burner 403 receives fuel and heats the heat exchanger 404. Closing the dispensing valve in the course of the cold water dispensing line 405 or de-energizing the circulation pump causes the decreasing pressure difference at the water switch 409 to close the valve 411 and thus the transition to the ready position.

If the pilot burner 415 goes out for any reason (gust of wind or the like), the thermal voltage decreases continuously. This does indeed require an increase in the manipulated variable of the control circuit, namely an opening of the control valve 414, but this has no effect since the pilot burner 415 has gone out. If the holding limit voltage for the electromagnet 419 is undershot, the return spring 424 tears off the armature 420 from the electromagnet, so that the control valve 422 is closed. This closes the entire fuel path.

It is clear that the higher the thermocouple 416 was heated, the longer this process takes. For protection against unburned fuel flowing out of the main and pilot burner, it is essential that this time is kept to a minimum. This can be achieved with the regulation of the thermal voltage according to the invention.

Claims (35)

1. Control device for a fuel-heated. Heat source with a heat exchanger and a burner, which is fed by a fuel supply line provided with a valve and controlled by a thermoelectric ignition fuse, characterized in that the valve (5) of the thermoelectric ignition fuse (15, 13) is connected to a pressure medium actuator (53) which is connected to a pressure medium source (42). 2. Control device according to claim one, characterized in that the pressure medium source is designed as a pneumatic diaphragm pump (49). 3. Control device according to claim one or two, characterized in that the pressure medium motor ausgebil as a pneumatic membrane setting box (53) det. 4. Control device according to one of claims one to three, characterized in that the pressure medium motor can be reset by a solenoid valve (58/59) and a return spring (57). 5. Control device according to one of claims one to four, characterized in that a coil (45) of the solenoid valve (58/59) is arranged in a circuit controlled by a pull-in delay relay (33/36). 6. Control device according to claim one or five, characterized in that the coil (45) of the solenoid valve (58/59) of an ignition device (40) and a motor of the diaphragm pump (49) are electrically connected in parallel. 7. Control device according to one of claims one, five or six, characterized in that a contact (28) of a low water protection device (22) is provided in the circuit for the pull-in delay relay (33/36). 8. Control device according to one of claims one to seven, characterized in that the con. Clock (28) of water shortage protection as a double Working contact is formed and that the second contact (17) is looped into a circuit (14) of the thermoelectric ignition fuse (15/13). 9. Fuel-heated heat source with a heat exchanger heated by a main burner and with a pilot burner monitored by a thermoelectric ignition fuse, characterized by an electromagnetic application device (121, 130, 154, 141) for the armature (122) of the thermoelectric ignition fuse (120). 10. A fuel-heated heat source according to claim nine, characterized in that the electromagnet (121) of the thermoelectric ignition fuse (120) in addition to the holding winding (126) fed by the thermocouple (119) has a pull-in winding (130) fed by a current source (152). 11. A fuel-heated heat source according to claim nine or ten, characterized in that an electrical circuit is provided which has an electronic switch (154) which has an application current pulse and an ignition voltage impulse controls. 12. A fuel-heated heat source according to any one of claims nine to eleven, characterized in that a timer (141) for the electronic switch (154) is provided for the time limitation of the current pulses. 13. A fuel-heated heat source according to one of claims nine or twelve, characterized in that in the circuit of the timing element a water shortage safety contact designed as a work contact and a contact of the thermoelectric ignition protection designed as a break contact are provided. 14. A fuel-heated heat source according to one of claims nine to twelve, characterized in that a parallel circuit of RC elements (146/148 and 144/158) is connected to the output of the timing element (141), of which the connection point of the capacitor with the resistor in one case via a Zener diode to the control electrode of the electronic switch (154) and in the other case the connection point to the primary coil of an ignition transformer (136). 15. Control for a fuel-heated heat source with a heat exchanger heated by a main burner, which, together with a pilot burner, is fed from a fuel supply line provided with a valve controlled by a thermoelectric ignition fuse, characterized in that a fuel accumulator (225) is provided which is the pilot burner (232) feeds during the response time of the thermoelectric ignition fuse (238/233). 16. Control according to claim five, characterized in that the fuel accumulator (225) is assigned a valve combination (222/253) which separates it from the fuel source (205) when the fuel accumulator is started up and an ignition fuel line (255/256) to the pilot burner ( 232) opens. 17. Control according to claim five or sixteen, characterized in that a second pilot burner (261) is provided, which is fed directly from the fuel source (205) with the interposition of a thermoelectric fuse (238/233) controlled valve (245). 18. Control according to one of claims five to seventeen, characterized in that the fuel storage is provided with a fill contact (226). 19. Control according to claim five or eighteen, characterized in that the filling contact (226) with a contact (221) of a low water protection device (211/219) is in series with an ignition device (229) and a voltage source. 20. Control according to one of claims five to nineteen, characterized in that the second pilot burner (261) with its pilot fuel line (246) upstream of the lack of water safety valve (211/219) is connected to the fuel supply line (205). 21. Control according to one of claims fifteen to twenty, characterized in that the lack of water safety valve (219), the inlet valve (222) of the fuel accumulator (225) and the pilot gas valve (245) controlling the second pilot burner (261) are arranged in parallel . 22. Control according to one of claims five to one and twenty, characterized in that a pilot fuel line (249) with a check valve (248) branches off from the fuel supply line (204) to the main burner (203) and leads to the first pilot burner (232) bypassing the fuel accumulator (225) and its valve combination. 23. Fuel-heated heat source with a heat exchanger controlled by a valve, a thermoelectric ignition fuse with a valve in a supply line for fluid fuel to the burner, a pilot burner and a low water indicator, characterized in that a further pilot burner (366) is provided, the Pilot fuel line (365) is controlled exclusively by the valves (305, 361) of the thermoelectric fuse. 24. A fuel-heated heat source according to claim twenty-two, characterized in that in the pilot fuel line (318) to the first pilot burner (369) an additional valve (356, 328) of the thermoelectric ignition fuse is inserted, which during application and operation is open. 25. Fuel-heated heat source according to claim twenty-two or two, characterized in that a further pilot fuel line (367) is connected in parallel to the pilot fuel line (318) to the first pilot burner (369), which is controlled by a valve (304/325) of the low water indicator. 26. A fuel-heated heat source according to claim twenty-four, characterized in that a check valve (.368) is switched on in the further pilot fuel line (367). 27. A fuel-heated heat source according to one of claims twenty-two to twenty-five, characterized in that the thermoelectric ignition fuse has two valves (356/328 and 361/305), which are arranged by two adjacent rods (360, 355) against the restoring force of a spring (362 / 363) and are actuated by an energy source (353/349), whereby only one of these valves (305/361) can be kept open by the thermocouple magnet (313) of the thermoelectric ignition fuse. 28. Fuel-heated heat source according to claim twenty-six, characterized in that this energy source (349/353) is actuated only at water flow and presses both valves (356/328 and 361/305), whereupon the upstream valve from the thermocouple magnet (313), the downstream is controlled only by a return spring (363). 29. Fuel-heated heat source according to one of claims twenty-two to twenty-seven, characterized in that the pilot fuel line to the first pilot burner (369) behind the thermoelectric safety valve and to the main burner (303) behind the low water safety valve (304/325) via a towards pilot burner (369) Passing check valve (368) is connected. 30. A fuel-heated heat source with a heat exchanger which is heated by a main burner and which carries a fluid to be heated, and with a pilot burner, both of which are fed via a fuel supply line provided with a valve, and with a thermoelectric fuse for the pilot burner, characterized in that the voltage of the thermocouple (416) is connected to the input of an amplifier (430), in the output (431) of which a control valve (432/414) is connected. 31, fuel-heated heat source according to claim twenty-nine, characterized in that the control valve (414) has a large and small position as end positions and that it is provided with a reset (427) to the large position. 32. Fuel-heated heat source according to claim twenty-nine or thirty, characterized in that the input of the amplifier (430) is electrically connected in parallel to the electromagnet (419) of the thermoelectric ignition fuse (402) to the output of the thermocouple (416). 33. Fuel-heated heat source according to one of claims twenty-nine to thirty-one, characterized in that the amplifier (430) is switched inverting. 34. A fuel-heated heat source according to any one of claims twenty-nine to thirty-two since characterized in that the control valve (414) in the pilot fuel line (413), the control valve (422) of the thermoelectric fuse (402), on the other hand, upstream of the branching of the fuel supply line (425) into the fuel line (410) to the main burner (403) and in the pilot fuel line (413) to the pilot burner (415) is arranged. 35. Thermoelectric ignition fuse for a fuel-heated heat source with a thermocouple and with a solenoid valve fed by the thermocouple in the fuel feed line and with a further valve in the pilot fuel feed line to the pilot burner, characterized in that a controller (430) is provided, at the input of which the thermocouple is provided and at the output of which the control valve (414) provided in the pilot fuel line (413) is connected, the controller assigning a reduced opening signal for the control valve to a growing thermocouple voltage.

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