DE2301832B2 - 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 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 to a flow heat exchanger for domestic water, the burner by a Flow thermostat, the sensor of which is in the flow line, and the three-way valve through a Domestic water thermostats, the sensors of which are assigned to the flow heat exchanger, are controlled and in the flow line i.ahe the heat exchanger for the heating medium another temperature sensor of a Temperature limit switch is arranged for putting the boiler out of operation.

A central heating system of this type is from the

DE-OS 16 79 365 known The domestic water thermostat of such a system works in such a way that it is at If the temperature falls below a switch-on temperature, the three-way valve allows the heating medium to flow through the Continuous heat exchanger reverses to heat the domestic water, and when one is exceeded Switch-off temperature, the three-way valve reverses again to allow the heating medium to flow through the To terminate the water heater. This should keep the temperature of the tap water as possible be kept constant. In the known central heating system, however, considerable fluctuations in the domestic 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 heating medium is arranged behind the flow heat exchanger, he speaks very slowly on temperature differences of 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 temperatures mentioned corresponding or even a higher temperature

. accepted. In this case it must be a large amount of domestic water, the temperature of which is constantly decreasing, run through the once-through heat exchanger, before the domestic hot water thermostat switches on again, to cause a renewed supply of heating medium to the once-through heat exchanger. As a result, the temperature of this domestic water fluctuates considerably, especially if a differential pressure valve is not provided or if the water with a moderate

Speed is tapped at which the differential pressure valve is not yet actuated.

The temperature fluctuations are even more pronounced during winter operation when both the central heating and the once-through heat exchanger are used because in this case the three-way valve in the after switching off the domestic hot water thermostat the position supplying space heating is opened and the pump remains in operation, with the result, that relatively hot water from the heat generator to the

so space heaters flows while the heat generator (which can be switched off at this point as the space heaters do not require any heat, whereby the The heat generator can be switched off by an indoor or outdoor thermostat) cold

Receives return water from the space 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

so relatively cold water will initially cool the once-through heat exchanger 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 Flow branch pipe leading to space radiators is in order, the boiler thermostat is out of order, when the three-way valve is switched by the domestic water thermostat into the position supplying the flow heat exchanger, because it is then no longer

is washed around by directly heated heating medium. As a result is the maximum temperature of the heating medium no longer limited by the flow thermostat The heating medium can therefore be used in the Heat exchangers belonging to the boiler, and thus also in the once-through heat exchanger, have a considerably high level Reach temperature. Another disadvantage is that the heat exchanger for the heating medium is constant is subjected to high thermal loads.

This disadvantage of the considerable temperature fluctuations the domestic hot water can be partially eliminated if the domestic hot water thermostat has an extremely sensitive response differential; d. 1). that even the smallest temperature fluctuations Activate or deactivate the thermostat. However, such thermostats are extraordinary expensive and sensitive to interference. The temperature fluctuations can also be reduced somewhat by the fact that a differential pressure valve is provided which at dispensing speeds substantially equal to the normal or nominal tapping speed, the three-way valve in the to the flow heat exchanger sets the leading position before this setting is made by the sluggishly reacting domestic water thermostat takes place At moderate dispensing speeds, however, such a differential pressure valve does not work 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, as in this case the once-through heat exchanger is not kept at temperature, but can cool down and must therefore be warmed up when you tap again. Another The disadvantage is that in this case the hot water thermostat Must be bipolar or as a unipolar thermostat with other devices (e.g. diodes) must be combined, which entails high costs and does not promote the reliability of the operation is.

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.

This object is achieved in that the sensor of the domestic water thermostat in the section of the domestic water pipe lying within the once-through heat exchanger at a distance is arranged both from the inlet end and from the outlet end and that the sensor of the Flow thermostat is arranged upstream of the three-way valve

This has the advantage, on the one hand, that the sensor of the flow thermostat is also from the Heating medium is flushed and can keep its temperature constant when the heating medium through the Through-flow heat exchanger for domestic water flows and the room radiators are not reached Fluctuations in the heating medium temperature, which lead to corresponding fluctuations in the domestic water temperature can lead, avoided. Furthermore, the sensor of the domestic water thermostat speaks directly on the domestic hot water temperature with an inertia that is determined by the distance between the sensor and the inlet and Given the outlet end of the once-through heat exchanger and can therefore be selected at will, whereby the Temperature fluctuations in the domestic water can be further reduced.

Another advantage of the control device of the invention is the fact that the one switch is no longer needed, which is provided in known plants of this kind the Temperatursteue ^r ung (keeping the heat supply) of the continuous heat exchanger for long periods, for. B. at night to turn off the frequent switching of the three-way valve and the heat generator due to the rapid cooling, for example in less than an hour. 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 ° C) , the burner is switched on much less often, even if no water is 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 chosen that it is higher than a maximum possible leakage speed, which is in the case of defects or at several leaking taps can occur in order to prevent the domestic water thermostat from leaking is held in the switch-on position, whereby the three-way valve is held in the position leading to the once-through heat exchanger and the space heating would be blocked. The dispensing speed can be dripping with a single Tap or a larger tapping point that drips is about 03 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 to be less than the lowest dispensing 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 thermostat, which can now switch the heat generator in all operating states, d. H. in the Summer and winter operation, both when the heating medium circulates through the flow heat exchanger as also through the space heater, and the domestic water thermostat, the three-way valve or if desired the circulating pump or, if desired, the heat generator switches, are preferably set in such a way that 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 of the heat exchanger that have been brought to a high temperature (Lamellar block), after the burner has been switched off, still fed to the continuous flow heat exchanger, so that Heat losses are reduced.

In order to achieve a quick response of the flow thermostat, it is preferably arranged behind and as close as possible to the heat exchanger of the heat generator in the flow line. The flow is then thermostat is preferably set to a switching temperature of about 90 ⁰ C and an on-off switching interval of 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 scheme of the invention Control device.

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 according to FIG. 1, the reference numeral 1 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 can be seen from FIG. 1 recognizes, the sensor of the flow thermostat 5 is in the The flow line for the heating medium is arranged as close as possible to the heat exchanger 2. The function of the Temperature limit switch 3 consists in switching off the entire mechanism when the temperature of the heating medium should rise to such a high value due to a defect that it becomes too serious Could cause damage. This is the reason why the limit switch 3 is arranged closer to the heat exchanger 2 should be than the 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 forms a helically extending pipe coil. In this arrangement di < Coils 12 and 13 separated from one another by a cylindrically shaped sleeve 14 of domestic water takes place at the lower end of the part:

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

The heating medium is fed in at 15 and withdrawn at K. By accommodating the sensor 11 de: Domestic hot water thermostats in the domestic water pipe

ίο the low switch-on temperature of this thermostat (about 55 "C), the inventive arrangement unc mode of operation of the flow thermostat as well as aucl 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 far that dei The heat generator is switched on again and the three-way valve 6 in FIG. 1 switched to the other position will.

Due to the arrangement of the sensor 11 between the coils 12 and 13 in the straight part de: Coiled pipe 12, what a particularly advantageous one! The feature of the invention is to ensure that de; Domestic hot water thermostat 8 switches on at a Zapfgeschwindig speed of 1.25 to 1.5 l / min, which in practice is to be regarded as the minimum dispensing speed.

In Fig. 1 is also indicated that a simple! Control member 9 for the water flow rate, for. B. a regulating screw is arranged The heating medium flows after passing through the heat exchanger 7 and the room heater back to the heat exchanger 2 via the circulation pump 10. Di (gas supply for the heat generator (burner) is at T.

and the gas valve located at 123

In the electrical circuit diagram according to FIG. 3 are di <already in FIG. 1 and 2 shown parts with the same reference numerals. In addition, a relay 17, to which a relay contact 17 ¹ belongs, a summer-winter switch 18, an indoor or outdoor thermostat 19, a transformer 20, a rectifier 21 and some diodes 24 are provided. It should be noted in the circuit diagram that in addition to an arrangement with a normal internal thermostat, the

<s Use of an arrangement with an internal thermo staten is possible with remote control. With such an arrangement, the summer-winter switch is superfluous sig, as this switch is then included in the internal thermostat with remote control.

The device according to the invention works as follows. When the electrical circuit is connected to the electrical « If the supply network is connected, the domestic water thermostat 8 becomes the following in the event of a cold start Switching operations cause: The circulation pump 10 wire through the relay 17 and its relay contact 17 switched on, while the three-way valve 6 is switched to a position in which the heating medium durcl the domestic water heat exchanger flows This results from the fact that the flow heat exchanger füi Domestic hot water always has priority over room heating. Furthermore, the flow thermostat 5 switches the Heat generator 1 by means of gas valve 23.

After a given period of time dei forward thermostat 5 reaches its switching temperature of etwi 9O ⁰ C ₁ wherein the heat generator 1 is turned off but the heat medium is circulated further through the heat exchanger 7. Approximately 30 seconds after dei boiler thermostat 5 its switching temperature of etwi

90 ° C has reached, the hot water in the flow heat exchanger 7 is the shutdown temperature of the Reach domestic hot water thermostats, which is around 65 ° C. The latter is now the three-way valve in the Switch 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 Case will only work in the summer position, if the temperature in the Continuous heat exchanger 7 is to be increased.

In the winter position, the pump 10 works continuously, and the flow thermostat is after a have cooled down a bit after the switching operations mentioned above. When 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 has reached the switch-off temperature of the domestic hot water thermostat.

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

If water for domestic purposes is drawn off at a normal tapping speed, which is about 6 l / min, in a system with an output of about 20,000 kcal / hour. with an increase in temperature of 56 ° C, then the temperature of the domestic water and the temperature of the heating medium in the once-through heat exchanger 7 be balanced after a while. The latter temperature is kept lower than the switch-off temperature (90 ° C) of the boiler thermostat 5. The heat generator 1 remains at this Dispensing speed in operation, whereby the temperature of the heating medium remains 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 t 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.

Furthermore, the boiler water thermostat is an additional one Securing the temperature of the heating medium while it is circulating through the heat exchanger as well as 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 U of the domestic hot 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 to a Durctilaufwärmetauscher for domestic water, whereby 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, are controlled and in the flow line close to the Heat exchanger for the heating medium, another temperature sensor of a temperature limit switch is arranged for putting the boiler out of operation, characterized in that the Sensor (II) of the domestic water thermostat (8) in the one inside the flow heat exchanger (7) lying section of the service water line (12, 13) is arranged at a distance from both its inlet end and its outlet 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 3. Central heating system according to Anspmch 1 or 2, characterized in that the within the Through-flow heat exchanger (7) lying section of the domestic water line from two concentric helical tube coils (12 "13) arranged one inside the other, through which flow occurs one after the other and the sensor (11) of the hot water controller (8) in the transition between the two Coiled tubes (12,13) is arranged 4. Central heating system according to claim 1, characterized in that the switching temperatures of the flow thermostat (5) and the domestic water thermostat (8) are coordinated in such a way are that the flow thermostat (5) switches off the burner before the hot water in the hot water line (12,13) of the flow heat exchanger (7) has reached the switching temperature required to switch over the three-way valve (6) at the location of the sensor (11) of the domestic water thermostat (8)