DE2215427A1 - HEATING SYSTEM WITH A GAS WATER HEATER - Google Patents

Description

Junkers 620

PLI 1-Ki / Vo

■ March 27, 1972

JUNKERS & CO. GMBH, in Wernau / Neckar

Heating system with a gas water heater

The invention relates to a heating system with a gas-heated water heater, a flow temperature controller and a room temperature controller, which is provided with means for thermal feedback and activated by its switching pulses electrical resistance element controls, which acts as a setpoint generator for the flow temperature controller on an actuator influencing the flow temperature according to the output of the respective Heat demand acts.

In the known heating systems of this type, the switching pulses act of the room temperature controller on the heating coil of a Three-way mixing valve with electrothermal drive, which, depending on the heat requirement, one more or less large proportion of the return water via the gas water heater immediate line admixed. This arrangement has the disadvantage that, particularly when the system is started up the thermal drive of the mixing valve works with relatively long delays that means are provided that have a disruptive temperature transfer from the das

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Valve penetrating feed water on the thermal drive prevent and make the valve not insignificantly more expensive, and that the scope of application is also limited to heating systems, whose hot water heater has such a large heat capacity that the principle of pre-flow admixing through a mixing valve makes sense in the first place.

The invention is based on the object, the advantages of constant flow temperature control with guidance by a 2-point room temperature controller with thermal feedback can also be used in heating systems that do not have a mixing valve have in the flow or where the arrangement of a mixing valve because of the insufficient heat capacity of the water heater would not make sense. The flow temperature should only fluctuate slightly and the means for controlling the flow temperature should be as simple and reliable as possible.

To solve this problem it is proposed according to the invention, that the electrical resistance element controlled by the room temperature controller with the actual value of the flow temperature measuring transducer capturing the input voltage for an electrical Forms a signal generator that acts on a valve that monitors the gas supply to the burner via a hydraulic actuator, whose hydraulic drive system is influenced by a control element acted upon by the signal transmitter. As a signal generator can advantageously be provided a pulse generator, the pulses of the control member in the hydraulic system of the Affect the actuator.

This ensures that a mixing valve to influence the flow temperature is not required and that with low electrical control powers relatively large hydraulic actuating forces are generated, which an exact Ensure that the gas valve is set to the value corresponding to the respective heat requirement.

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A simple arrangement results when the work contact of the room temperature controller monitors the circuit of a heating resistor that controls the setpoint generator for the flow temperature controller forming resistance with negative temperature coefficient heated.

It is particularly advantageous if, according to the invention, im Circuit of the heating resistor is a temperature-dependent series resistor with a negative temperature coefficient.

This ensures that with a corresponding choice of the temperature-dependent Series resistor with simple means an almost proportional relationship between the switch-on ratio of the room temperature controller and the flow temperature achieved can be. The resistance can also have a positive temperature coefficient and. be connected in parallel to the heating resistor.

The input voltage for the signal generator, ζ-B. the pulse generator is obtained in a simple way: if the temperature-dependent resistor heated by the room temperature controller is connected to the actual value transmitter the flow temperature forms a voltage divider whose Center tap is connected to the input of the pulse generator. The input signal can expediently by means of a further temperature-dependent ' Resistance ", which compensates for fluctuations in the ambient temperature.

The invention further provides that a flow switch with at least one chamber is provided as the hydraulic actuator which is connected to the flow path of the heating water. The flow switch in the water heater can be useful as a flow switch Usually, already existing water flow monitors (water shortage protection) to serve. This ensures that tried and tested components of the gas valve and the water section of devices of the previous design essentially retained so that the desired! power regulation is proportionate can be realized in a simple manner.

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It is particularly advantageous if, according to the invention, that of the Signal transmitter acted upon control element is a valve in a control line, which is from a point higher static Pressure of the water flow path leads to a point of lower static pressure of the water flow path and to which the chamber of the flow switch is connected.

This ensures that the signal transmitter, e.g. the pulse generator pressurized control valve only needs to monitor small cross-sections and only need to perform small strokes, so that a small and cheap control valve can be used, which is easy to accommodate in the water heater.

The arrangement can be made in such a way that the control valve is designed as a solenoid valve, which in each case Control pulse executes at least approximately its full stroke and thereby the control pulses on the hydraulic. System transmits, which integrates the control impulses. The solenoid valve can, however, also be designed in such a way that it receives the control pulses itself integrated and able to take appropriate intermediate positions.

In the drawing, an embodiment of the subject matter of the invention is shown. Show it

Pig. 1 a heating system in a simplified representation,

Fig. 2 shows a modified circuit of the system according to Pig. 1, and the

Pig. 3 each a diagram to explain the puncture of a and switching element of the circuit according to Pig. 1 and 2. Pig. 4th

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The heating system according to FIG. 1 has a water heater a burner 10, the flames of which in a "known manner" form a heat exchanger Heat a pipe coil through its lamellar block -11 for the circulation water is meandering through «. The gas supply to the burner 10 takes place from a gas supply line 12 via a gas safety valve 13 with a closing element 14 » which is operated by a hydraulic pressure switch, generally designated by the reference numeral 15. The pressure switch-15 has a low-pressure chamber 16, which via a return pressure channel 17 is connected to the water circulation path at a point 18 on the suction side of a circulation pump 19 ο The water circulation * away leads from the lamellar block 11 of the circulation water heater a flow line 20 to the symbolically shown radiators 21 of the collective heating system and from there via the circulation pump 19 and a return line 22 back into the lamellar block 11. The high pressure chamber 23 of the hydraulic pressure switch 15 is known per se via one with a slow ignition device 24 Design provided high-pressure duct L25 with the return line 22 of the water circulation path s connected at a point 26, which is on the delivery side of the circulation pump 19,

The two chambers 16 and 23 of the pressure switch 15 are connected to one another by a channel 30 which is monitored by a small solenoid valve 31 * A membrane 32 is arranged between the chambers 16 and 23 ^ which via an actuator 33 .aiii? the closing element 14 of the gas valve acts “The closing element Η is under the influence of a spring 34 ₉ which tries to press it onto the valve seat.

The solenoid valve 31 is controlled by an electronic pulse generator 36 with a fast pulse train. The pulse generator 36 is fed from the Hetz via a transformer 37 and a rectifier 38. The input of the pulse generator 36 is connected to a switching point 39, to which two temperature-dependent resistors 40 and 41 are connected with a negative temperature coefficient, which in relation to the direct current flow of the

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Rectifier 38 form a voltage divider. The resistance

40 is in thermally conductive connection with. the supply line and records the actual value of the flow temperature. The resistance

41 is heated by a V / iderstand 42, which has a Switching contact 43 of a 2-point room temperature controller 44 is connected to the network. The output of the pulse generator 36 is with connected to one connection of winding 45 of solenoid valve 31, the other end of which is connected to one output of the rectifier 38.

The room temperature controller 44 is provided with a not shown thermal feedback provided. As a result, the switching contact 43 is switched on and off periodically, with the switch-on ratio is a measure of the heat demand of the controlled system. The V / resistance 42 and with this the temperature-dependent resistance 41 are more or more depending on the duty cycle less heated, so that the resistance value of the resistor 41 also depends on the switch-on ratio of the room temperature controller and is a measure for the heat demand of the room as a controlled system. The resistor 41 is used in the voltage divider circuit as a setpoint generator for regulating the flow temperature, whose actual value is recorded by the temperature-dependent resistor 40 The potential of the switching point 39 and thus the input voltage of the pulse generator 36 therefore depend on how strong the actual value the flow temperature deviates from the setpoint controlled by the room temperature controller 44.

The '36 pulse generator generates pulses of rectangular Voltage curve, the switch-on ratio of which depends on the input voltage, i.e. the setpoint deviation of the flow temperature depends on »These impulses are transmitted to the solenoid valve 31, which is tuned in such a way that it closes the channel with each impulse 30 closes. The control impulses are passed on to the hydraulic system, where they can be found in the following V / eise described in more detail are integrated and move the gas valve 13 into a position corresponding to the heat requirement.

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When the circulating pump 19 is running, a differential pressure is exerted on the membrane 32 of the pressure switch 15 ₉ which pushes the membrane 32 upwards, whereby the closing element 14 is lifted from the valve seat against the force of the spring 34 o The differential pressure reaches a maximum value _? if the solenoid valve 31 remains permanently closed and the two chambers of the pressure switch are constantly separated »In this case, the entire static pressure gradient can build up in the pressure switch _s that prevails between points 26 and 18 in the flowing water» The membrane 32 is then capable of the gas valve 13 can be fully opened. so that the burner can deliver its full capacity «

The pulse generator 36 is designed so that it is at maximum Heat demand emits a continuous pulse (duty ratio approx. 1) and that with decreasing heat demand the The switch-on ratio of the pulses is constantly decreasing * At maximum heat demand, the gas valve 13 is fully open, as has already been explained above «

As the flow temperature approaches the setpoint value, the solenoid valve 31 is acted upon with an increasingly decreasing switch-on ratio ₉ whereby the solenoid valve opens briefly in each pulse pause and connects the two chambers of the pressure switch 15 to one another. As soon as and as long as the solenoid valve 31 is open, occurs a flow in the chamber 23, which experiences a pressure reduction at the throttle 24, which also acts as a slow ignition device. This pressure reduction is all the greater, the faster the flow is at the throttle. The speed of the flow depends not only on the size of the throttle 24 itself, but also on the resistance the flow has to overcome in the channel 30 depends on the switch-on ratio of the solenoid valve. The switch-on ratio thus has the effect of a more or less strong pressure reduction in the chamber 23, whereas the pressure in

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the chamber 16 remains approximately constant. "With decreasing Power On tverhältnia the _t pressure in the chamber 23 decreases, so that the spring 34 can move the Schiiessglied 14 against the valve seat, until the corresponding to the respective duty ratio equilibrium reached again. In effect, this means that with decreasing heat demand, the passage cross-section of the gas valve 13 narrows and thereby the output of the burner is reduced.

In this way, quick regulation is achieved without great effort, in which the fluctuations in the flow temperature kept small and the advantages of a constant flow temperature controller can also be used to the full when a 2-point room temperature controller is connected. Despite great valve forces it is possible to get by with small powers for the solenoid valve 31 and the control circuit. These powers are e.g. 1.5 watts on a scale that also enables the use of independent power sources, e.g. batteries or fuel cells. As a flow switch, the water shortage safety device, which is already present on the device, is provided so that the power control of the Brenners actually only requires a few additional parts and uses proven parts without significant modifications can be. The solenoid valve could also be installed in the high pressure channel 25 or in the low pressure channel 17. In In both cases, at least one throttle would then have to be provided in the channel 30, at which the flow the required pressure reduction learns.

The system of Fig. 2 agrees with that of Fig. 1 to on a slightly different circuit arrangement of the temperature control device. The difference is that in series with the temperature-dependent resistor 41 with a negative temperature coefficient, a temperature-dependent resistor 50 is switched with a positive temperature coefficient, which compensates for fluctuations in the ambient temperature and the signal voltage potential

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tial at switching point 39 regardless of the influences of the ambient temperature power.

The second difference compared to the Pig plant. 1 is that in series with the resistor 42 one. temperature dependent Series resistor 51 is connected with a negative temperature coefficient. The purpose of this arrangement is below "with reference to FIG Diagrams described in FIGS. 3 and 4.

"In both diagrams, the temperature f% ° of the resistor 42 is plotted over the heating or cooling time t, FIG. 3 being based on the circuit according to FIG. 1 and FIG. 4 the circuit according to FIG." 2 . 3 will first be explained below ⁴ . With uninterrupted heating of the resistor 42, that is to say with a switch-on ratio of 1, the heating curve a results, after which the resistor reaches the temperature <hJ *. If the resistor 42 is heated with a small switch-on ratio, that is to say intermittently by individual current impulses, a sawtooth-shaped heating curve results which is flatter than curve a and reaches a lower end value of the temperature / ^ than this. In Fig. ' 3 shows two such heating curves b and c, curve b corresponding to a switch-on ratio of 0.75, for example, and curve c to a switch-on ratio of 0.5, for example. If the pulse frequency is sufficiently high, the sawtooth-shaped irregularity can be neglected. From the position of these curves b and c it can be seen that there is no linear relationship between / the switch-on ratios and the final value, \ fc undrir.

el D C -.

With the erfingungsgemässen proposal, the resistor 42 has a temperature-dependent V / esistance connected upstream 51 with a negative temperature coefficient, can ', as shown in Fig. 4, an almost linear relationship over a wide range of duty ratios between the power on "ratio and the final temperature rö * of the heated. Resistance

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achieve. With the upstream connection of the NTC resistor 51, the heating curve a ^{1 is} approximated over a wide range of a straight line which, in the upper temperature range, merges fairly sharply into a branch approaching the end temperature asymtotically. By appropriately coordinating the resistors 51 and 42, the heating curve a 'can also be made correspondingly steep, so that the linear dependence of the final temperature reached of the resistor 42 on the duty ratio, which can be clearly seen in FIG.

With the temperature of the resistor 42 is also the temperature of the resistor 41 serving as a setpoint generator is proportional to the switch-on ratio of the room temperature controller 44. In the end this means that the resistance value of the setpoint generator 41 and ultimately also the burner output is proportional to the heat demand of the controlled system, so that an exact Control with only minor fluctuations in the flow temperature.

The present invention can be applied not only to circulation heaters for heating systems, but also for instantaneous water heaters and with combined thermal baths that supply circulating water for heating purposes and domestic water and where the temperature and the amount of water being drawn can be selected independently of one another. The control device can be used in addition to that of the room temperature controller guided setpoint generator also have a manually adjustable setpoint generator for the domestic water temperature. In this case, the arrangement can be made so that when there is a demand for heat from the domestic water boiler, e.g. when tapping of water, the corresponding setpoint transmitter takes precedence over the other and instead of this with the actual value transmitter of the Flow temperature forms the input signal for the pulse generator.

The pulse generator can be designed so that the change

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of the unity ratio takes place with a constant prequing, or that the frequency changes with the incidence ratio. The frequency is so dimensioned to ₉ that the control pulses from the control valve or already integrated into the hydraulic system and are not transmitted to the gas valve.,

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Claims (4)

Junkers 620 - 12 - Expectations lly heating system with a gas-heated V / water heater, a Flow temperature controller and a room temperature controller that is provided with means for thermal feedback and an electrical resistance element through its Sehaltimpulse controls which is used as a setpoint generator for the flow temperature controller on an actuator influencing the flow temperature acts according to the respective heat demand, characterized ", that the dated Room temperature controller (43,44) controlled electrical resistance element (41) with the actual value of the flow temperature detecting transducer (40) forms the input voltage for an electrical signal transmitter (36), which is based on the Gas supply to the burner monitoring valve (13) acts via a hydraulic actuator (15) whose hydraulic The drive system is influenced by a control element (31) acted upon by the signal transmitter. 2. Installation according to claim 1, characterized in that a pulse generator is used as the signal transmitter (36) is provided, the pulses of which influence the control member (31) in the hydraulic system of the actuator (15). 3. System according to claim 1 or 2, "characterized in that the normally open contact (43) of the room temperature controller (43,44) monitors the circuit of a heating resistor (42), which is the setpoint generator for the flow temperature controller forming resistance with negative tempera-,. turbo coefficient (41) heated. . ~ 4. Plant according to claim 3, characterized in that in the circuit of the heating resistor (42) 3 0 9 8 A 1/0 U 1 Junkers β20 - 13 - ■ "221542?" - there is a temperature-dependent series resistor (51) with a negative temperature coefficient. ^ ^- 5. Plant according to claim 3, characterized that a resistor with a positive temperature coefficient is connected in parallel to the hot resistor (42) is. ' 6 ,. Plant according to one of the preceding claims, d a ~ characterized that the resistance element controlled by the room temperature controller (4,3,44) (41) together with the actual value of the flow temperature detecting transducer (40) forms a voltage divider, the center tap (39) of which the input voltage for the signal transmitter (36) yields. 7. Installation according to one of the preceding claims, characterized in that the input voltage of the signal generator (36) is influenced by the fluctuations the ambient temperature compensating temperature-dependent resistor (50) is influenced. 8. Installation according to one of the preceding claims, dadur.ch marked, that as hydraulic Actuator a flow switch (15) with at least one chamber (23) is provided, which is connected to the Strb'raungsweg of the heating water is connected. . 9. Installation according to claim 8, characterized in that the signal transmitter (36). the actuated control element is a valve (31) in a control line (25 ₉ 30, 17) which leads from a point (26) of higher static pressure of the water flow path (15) to a point (18) of lower static pressure of the water flow path, and to 3-09841 / 0141 . Junkers 620 which the chamber (23) of the flow switch (15) is connected is. 10. System according to claim 9, characterized in that in · the control line (25, 30, 17) at least one throttle point (24) is installed. 11. System according to claim 9 or 10, characterized in that the control valve is designed as a solenoid valve (31) which at each control pulse of the signal generator designed as a pulse generator (36) executes at least approximately its full stroke and thereby the control pulses to the hydraulic system transmits, which integrates the control pulses ¹ . 12. Plant according to claim 9 or 10, characterized in that the control valve as a solenoid valve (31) is designed, which integrates the control pulses of the signal generator designed as a pulse generator (36) and able to take appropriate intermediate positions. 13 «Plant according to one of claims 8 to 12, characterized marked that the flow switch (15) used in the device is the water flow monitor (low water protection) serves. IG 30 9 841 /0.14 1 Read 11 e