DE2301832C3 - Hot water central heating system with flow and domestic water thermostats - Google Patents

Description

The invention relates to a hot water central heating system with a circulation pump, a heating boiler with burner and heat exchanger for the heating medium and a three-way valve in the flow line of the Heating medium for its reversal either to the room radiators or to a flow heat exchanger for domestic water, whereby the burner is controlled by a flow thermostat, the sensor of which is in the flow line and the three-way valve through a domestic water thermostat, the sensor of which is connected to the flow heat exchanger is assigned, controlled and in the flow line near the heat exchanger for the Heating medium another temperature sensor of a temperature limit switch to shut down the Boiler is arranged.

A central heating system of this type is from the

DE-OS 16 79 365 known. The domestic hot water thermostat Such a system works in such a way that it opens the three-way valve when the temperature falls below a Einsehaltiemperatur switches to the flow of the heating medium through the flow heat exchanger to the domestic water to heat, and when a cut-off temperature is exceeded, the three-way valve is again Control; to control the passage of the heating medium through the passage; finish heater. As a result, the The temperature of the tap water should be kept as constant as possible. In the known central heating system however, considerable fluctuations in the hot water temperature can occur due to the fact that the sensor of the domestic water thermostat in the line of the heating medium downstream of the Flow heat exchanger and the sensor of the flow thermostat downstream of the three-way valve nearby the space heater is arranged.

Since the sensor of the domestic hot water thermostat in the

Line for the fluid behind the flow heat exchanger is arranged, it only responds very slowly to temperature differences in the domestic water. First if the heating medium is in the immediate vicinity of this sensor, the switch-off temperature for the thermostat has reached, the three-way valve is switched to the position leading to the space heater. to At this point in time, however, practically the entire volume contained in the once-through heat exchanger has Heating medium one of the shutdown temperature mentioned corresponding or even a higher temperature accepted. In this case, a large amount of hot water, the temperature of which is constantly decreasing, must be run through the once-through heat exchanger before the domestic hot water thermostat switches on again, for a renewed supply of leizmediunizme to the flow heat exchanger to effect. As a result, the temperature of the domestic water fluctuates considerably, especially if a differential pressure valve is not provided or if the water with a moderate

• to speed is tapped, with -! He the differential pressure valve is not yet actuated.

The temperature fluctuations are exacerbated during winter operation, when both the central heating as well as the once-through heat exchanger, as in this case after switching off the Domestic hot water thermostats open the three-way valve in the position supplying the space heating elements and the pump remains in operation, with the result that relatively hot water from the heat generator to the Space radiators flows while the heat generator (which can be switched off at this point because the space radiators do not require any heat, whereby the shutdown of the heat generator is carried out by an indoor or Outside thermostats) receives cold return water from the room heaters. As soon as the domestic hot water thermostat switches on again when the minimum temperature is reached, this will be The three-way valve is opened again in the position supplying the flow heat exchanger, whereupon this

μ relatively cold water first passes through the once-through heat exchanger will continue to cool by a certain amount.

Furthermore, since the sensor of the flow thermostat in the heating medium behind the three-way valve in the to the The flow branch pipe leading to the space radiators is arranged, the boiler thermostat is out of operation, when the three-way valve is fed through the domestic water thermostat into the flow heat exchanger Position is reversed because he is no longer

is wound around by directly heated welding medium. As a result, the maximum temperature of the heating medium is no longer through the flow thermostat limited. The Heizniedium can therefore in the for Heat exchangers belonging to the boiler, and thus also s in the once-through heat exchanger, have a considerably high level Reaching temperature - Another disadvantage is that the heat exchanger for the heating medium runs every hour is subjected to high thermal loads.

This disadvantage of the considerable temperature fluctuations of the domestic water can be partly eliminated if the domestic hot water thermostat has an extremely sensitive response differential, d. H. that even the smallest temperature fluctuations cause the thermostat to switch on or off. However, such thermostats are extremely expensive and sensitive to interference. The temperature fluctuations can also be somewhat reduced in that a differential pressure valve is provided, which at Power take-off speed wedges, which are essentially equal to the normal or Ncnn tapping speed, the three-way valve in the to the through-flow heat exchanger sets the leading position before this setting by the sluggishly reacting domestic water herniostat he follows. However, such a differential pressure valve does not work at moderate dispensing speeds. In addition, such differential pressure valves are also expensive and susceptible to interference.

The known system is also inefficient in the summer, when the space heating is not required, because After switching off the pump, there is still a given amount of heating medium with a high temperature in the heat exchanger, the pipes and the three-way valve, whose heat is transmitted through the Air flowing past these parts is lost The parts of the boiler heated to a high temperature also give off a certain amount of heat to the heating medium resting in the heat exchanger. this has with the result that the heat exchanger is subjected to a high thermal load, this being the case Amount of heat is also lost. These heat losses can be limited by the installation an electrically operated switch that the user can use if there is no hot water for a long period of time is required, can switch off the domestic hot water thermostat so that it can only be operated by means of the differential pressure valve can be switched on. Apart from the cost of such an electrically operated switch Such an arrangement is also disadvantageous because it does not allow hot water to be used immediately to be drawn off, since in this case the continuous air heat exchanger is not kept at temperature, but cool kawn and must therefore be warmed up when you tap again. Another The disadvantage is that in this case the domestic hot water thermostat has to be bipolar or unipolar Thermostat must be combined with other devices (e.g. diodes), which entails high costs and is not conducive to operational reliability.

The invention is based on the object using simple and cost-saving means To keep temperature fluctuations of the domestic water as low as possible.

According to the invention, this object is achieved by 6> that the sensor of the domestic water thermostat is in the one located inside the continuous flow heat exchanger Section of the Brauchwaisjrleit'jng at a distance is arranged both from the inlet end and from the outlet end, and that the feeler of the Flow thermostat is arranged upstream of the three-way valve.

This has the advantage that the one hand The sensor of the flow thermostat is then also surrounded by the heating medium and its temperature can keep constant when the heating medium flows through the once-through heat exchanger for domestic water and the space heater is not reached This causes fluctuations in the heating medium temperature, which lead to corresponding fluctuations in the domestic water temperature are avoided. Continues to speak the sensor of the domestic hot water thermostat directly on the domestic hot water temperature with an inertia that given by the distance between the sensor and the inlet and outlet end of the flow heat exchanger and can therefore be selected at will, which further reduces the temperature fluctuations of the domestic water be reduced.

Another advantage of the control device according to the invention is the fact that the switch that is provided in known systems of this type is no longer required to control the temperature (maintaining the heat supply) of the continuous flow heat exchanger for longer periods of time, e.g. B. at night to turn off the frequent switching of the three-way valve and the heat generator due to the rapid cooling, z. B. in less than an hour to avoid. In the control device according to the invention, the switch-on temperature of the domestic water thermostat (about 55 "C) is set to a lower value than in the known devices, and since the burner is switched off by the flow thermostat, which is set to a high value (about 90 ⁰ C) , the burner is switched on much less frequently, even if no water is being drawn off.

The minimum dispensing speed at which the thermostat should switch is, if available several taps generally about 1.25 to 1.5 l / min. This minimum dispensing speed is like this chooses that it is higher than a maximum possible Leakage rate that occurs in the event of defects or several dripping taps kasin to prevent the domestic water thermostat from leakage of this kind is held in the Einaltstel'iung, whereby the three-way valve in the to Continuous heat exchanger leading position would be held and the room heating would be blocked. The dispensing speed can be for a single dripping tap or a dripping larger tap for example 0.3 l / min. On the other hand, the minimum dispensing speed, in which the domestic water thermostat the three-way valve in the to the flow heat exchanger leading position switches, be less than the lowest tap speed normally required by the user. The domestic water thermostat preferably has a large switching differential, i.e. H. he should preferably on at around 55 ° C and off at around 65 ° C.

The flow thernostat, which is now the heat generator can switch in all operating states, d. H. in summer and winter operation, both when the Heating medium through the flow heat exchanger as well as through the space heater and the domestic water thermostat, the three-way valve or, if desired, the circulation pump or, if desired, the Heat generator switches, are preferably set so that the boiler thermostat when heating the

The flow heat exchanger switches off before the domestic hot water thermostat closes the three-way valve the position leading to the space heater switches. In addition, the device is designed so that during summer operation the circulation pump for the heating medium for a certain time after Shutdown of the heat generator by the flow thermostat remains in operation, d. H. until they become one is switched off later by the domestic hot water thermostat. Both measures are special beneficial for the system's performance and to avoid overheating of the normally considered To prevent lamellar block formed heat exchanger. Because of these measures, the heated heating medium, which is still in the pipes, the heat exchanger and the circulation pump and also the heat content of the parts brought to a high temperature; of the heat exchanger (Lamellar block), after the burner has been switched off, a pipe coil forms. In this arrangement di < Coils 12 and 13 through a cylindriscl molded sleeve 14 separated from each other. The supply of service water takes place at the lower end: of the parts:

12, while hot water at the lower end of the part: 13 is deducted.

The heating medium is fed in at 15 and withdrawn at K. By accommodating the sensor 11 de: Domestic hot water thermostats in the brewing water line reduce the switch-on temperature of this thermostat (about 55 ° C), the arrangement according to the invention and the mode of operation of the flow thermostat and also Due to the usual thermal insulation of the once-through heat exchanger, 6 to 8 hours are generally required after switching off the heat generator pass before the water has cooled down so much that the The heat generator is switched on again and the Drciwe fjeventil 6 in [· 'i g. I switch to the other position will.

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Heat losses are reduced.

In order to achieve a quick response of the flow thermostat, it is preferably behind and Arranged as close as possible to the heat exchanger of the heat generator in the flow line. The flow thermostat is then preferably set to a switching temperature of around 90 ° C and an on-off switching interval set at about 5 ° C.

An embodiment of the invention is explained in more detail below with reference to the drawings.

F i g. 1 shows a general diagram of the control device according to the invention.

F i g. 2 shows a section through a once-through heat exchanger of the device according to FIG. 1.

3 shows an electrical circuit diagram for the device according to FIG. 1.

In the schematic representation of FIG. I, the reference symbol I designates the boiler as Heat generator and reference numeral 2 an associated heat exchanger for the heating medium in the form of a Lamellar blocks. The heating medium flows from the heat exchanger 2 via the temperature limit switch 3 and the unipolar flow thermostat 5 to the three-way valve 6. From the three-way valve 6, the heating medium flows depending on its position either to the space heater or to the flow heat exchanger 7 for domestic water. The domestic water thermostat 8 is arranged in this once-through heat exchanger 7. As one can see from FIG. 1 recognizes the sensor of the flow thermostat 5 in the flow line for the heating medium as close as possible arranged on the heat exchanger 2. The function of the temperature limit switch 3 is to control the entire Mechanism shut down when the temperature of the heating medium due to a defect on a so should rise high that this could lead to serious damage. This is why the Limit switch 3 should be arranged closer to heat exchanger 2 than flow thermostat 5.

Fig.2 shows in more detail the arrangement of the Sensor 11 of the domestic water thermostat in the flow heat exchanger. How to get from the drawing recognizes, this sensor 11 is in the line for the domestic water between two concentric, helical formed parts or coiled tubes 12 and 13 of this line are arranged. Part 12 consists of an inner helically extending pipe coil, while the part 13, the part 12 concentrically outside surrounds and also a helically extending the coils 12 and 13 in the straight part dei Coiled tube 12, which is a particularly advantageous feature of the invention, it is ensured that dei Domestic water thermostat 8 switches on at a tapping speed of 1.25 to 1.5 l / min, which in practice is to be regarded as the minimum dispensing speed.

In Fig. I it is also indicated that in the supply line for domestic water a simple; Control gan 9 for the water flow rate, e.g. Legs Regulierschraubc, is arranged. The heating medium flows after passing through the continuous heat dew schers 7 and the space heater back back Heat exchanger 2 via the circulation pump 10. The gas supply for the heat generator (burner) is at 2i and the gas valve located at 23.

In the electrical circuit diagram according to FIG. 3 are the parts already shown in Fig. I and 2 with the the same reference numerals. In addition, a relay 17 is provided, to which a relay contact 171, a summer-winter switch 18, an indoor or outdoor thermostat 19, a transformer 20, a Rectifier 21 and some diodes 24. With respect to da; It should be noted that in addition to an arrangement with a normal internal thermostat also the

* 5 Using an arrangement with an indoor thermostat with remote control is possible. With such an arrangement, the summer-winter switch is superfluous, because this switch is then included in the indoor thermostat with remote control.

The device according to the invention works as follows If the electrical circuit is connected to the electrical supply network, t..iern Cold start of the domestic water thermostat 8 cause the following switching operations: The circulation pump 10 is through the relay 17 and its relay contact 17 'switched on, while the three-way valve 6 in a Is switched to the position in which the heating medium flows through the domestic water heat exchanger. This is the result from the fact that the once-through heat exchanger for hot water always has priority over space heating Furthermore, the flow thermostat 5 switches on the heat generator 1 by means of the gas valve 23.

After a given period of time, the flow thermostat 5 reaches its switching temperature of about 90 ° C, at which the heat generator 1 is switched off. However, the heating medium continues to circulate through the heat exchanger 7. About 30 seconds after the Boiler thermostat 5 its switching temperature of about

^{Has reached 90 0} C, the domestic water in the flow heat exchanger 7 will reach the switch-off temperature of the domestic water thermostat, which is about 65 ° C. The latter will now switch the three-way valve to the position in which the heating medium is supplied to the ■, room heating elements.

Modern central heating systems are often provided with a summer-winter switch 18. In this In the summer position, the circulation pump 10 only work when the temperature in the in-flow heat exchanger? should be increased.

In the winter position, the pump 10 works continuously, and the flow thermostat is switched off by him after a certain period of time according to the above triggered switching processes must have cooled down a little. r> If the internal thermostat 19 requests heating, the heat generator 1 is switched on again.

In the summer position, the circulation pump 10 is switched off when the hot water in the heat exchanger 7 the temperature of the domestic hot water 2 » i'nermostaten has reached.

If no hot water is drawn off, the insulated once-through heat exchanger 7 only be cooled down so far after a very long period of time that the The domestic water thermostat 8 switches on again and the three-way valve 6 again in the other position is switched over, the pump 10 starting again in summer and the heat generator 1 again is switched on.

If water for domestic purposes is drawn off at a normal tap speed, which is about 6 l / miti, in a system with an output of about 20,000 kcal / hour. at a temperature increase of 56 ° C., the domestic water temperature and the temperature of the heating medium in the once-through heat exchanger 7 will be equalized after some time. The latter temperature is kept lower than the cut-off temperature (9O ⁰ C) of the boiler thermostat 5. The heat generator 1 remains remains in this journal speed in operation, whereby the temperature of the heating medium door at a constant value.

If the dispensing speed is reduced, the equilibrium temperature of the heating medium is increased. The value at which this temperature is equal to the switch-off temperature of the boiler thermostat becomes Called the "vibration threshold". When the temperature of the heating medium is just about the switch-off temperature of the flow thermostat exceeds 5, the heat generator 1 is switched on and off periodically, d. H. he begins to vibrate. In this case, the domestic water is less heat in the once-through heat exchanger 7, as the heating medium in the heat exchanger 2 by the heat generator 1 is fed.

If domestic water is drawn off at a very low speed, e.g. B. 1 l / min, then this is small Amount of water already in the pipe section of the flow heat exchanger 7 so far preheated that the The domestic water thermostat does not switch at the beginning and the three-way valve 6 initially remains in the position in which the heating medium is fed to the space heaters. However, if heat from the once-through heat exchanger 7 is withdrawn, it will finally cool down so far that the domestic water thermostat is now back switches on, whereby the three-way valve 6 is switched into the position leading to the continuous heat exchanger 7 is, the pump 10 is switched on or kept in operation and also the heat generator 1 switched on or kept in operation.

The control device according to the invention provides a simple and relatively inexpensive mechanism created without using a relatively expensive differential pressure switch, with relatively simple and cheap means of adjusting the amount of water, e.g. B. a regulating screw, and without using any expensive precision thermostats guarantee a control that only has very small temperature fluctuations of the tap water at any desired tapping speed.

The boiler water thermostat also provides an additional safeguard for the temperature of the heating medium while it is circulating through the heat exchanger and in the event of malfunctions in the three-way valve.

The lines 12, 13 for the service water in the once-through heat exchanger 7 do not need any pipe coils, but can e.g. B. also be bent into an S-shape. It is only important that the pipe length is between the Entry point of the cold domestic water and the sensor 11 of the domestic water thermostat a sufficient Length.

For this purpose 2 sheets of drawings

Claims (4)

Patent claims: 1. Hot water central heating system with a Circulation pump, a boiler with burner and heat exchanger for the heating medium and a Three-way valve in the flow line of the heating medium for its reversal either to the Space heaters or a once-through heat exchanger for domestic water, with the burner through a flow thermostat, the sensor of which is in the flow line, and the three-way valve a domestic water thermostat, the sensor of which is assigned to the flow heat exchanger and another one in the flow line near the heat exchanger for the heating medium Arranged temperature sensor of a temperature limit switch for putting the boiler out of operation is, characterized in that the sensor (H) of the domestic water thermostat (8) in the section of the service water line (12) located within the once-through heat exchanger (7) 13) is arranged at a distance from both its entry end and its exit end, and that the sensor of the flow thermostat (5) is arranged upstream of the three-way valve (6) 2. Central heating system according to claim 1, characterized in that the sensor of the Flow thermostat (5) is arranged in the vicinity of the heat exchanger (2) for the heating medium. J. Central heating system according to claim I or 2, characterized in that the within the Through-flow heat exchanger (7) lying section of the domestic water pipe from two concentric arranged one inside the other helical pipe coil, η (12, U) and the sensor ill) of the domestic water thermostat (8) is arranged in the transition between the two pipe coils (12, 13). 4. Central heating system according to claim I, characterized in that the switching temperatures the flow thermostat (5) and the domestic water thermostat (8) matched to one another in this way are that the flow thermostat (5) switches off the burner before the domestic water in the domestic. water line (12,13) of the flow heat exchanger (7) at the location of the sensor (U) of the domestic water thermostat (8) has reached the switching temperature required to switch over the three-way valve (6).