DE3005209C2 - Heating system - Google Patents

Description

a)

b)

The heating medium temperature measuring device (13,! 4) forms the mean value (T _n ) from the flow temperature (Thv) and the return temperature (Y

the control amplifier (9) directly controls the servomotor (8) of the mixing valve (4); c) the circulation pump (5) can be controlled by a control device (16, 17, 18, 19) which in turn responds to at least one of the following parameters. Outside temperature (T _A \ flow temperature (Thv), mean temperature (T _n ,), temperature difference from flow and return temperature, pump delivery head (h) or time (t).

2. Heating system according to claim 1, characterized in that the circulating pump (5) has a digital speed changeover control.

3. Heating system according to claim 2, characterized in that the circulating pump (5) is multi-stage and can be switched over by switches (18, 19) of the control device.

4. Heating system according to claim 3, characterized in that the switches (18,19) of the pump head (h) and the time ^ are controllable.

5. Heating system according to claim 3, characterized in that the switches (18,19) of the pump head (h) and the outside temperature (Ta) are controllable.

The invention relates to a heating system of the type mentioned in the preamble of claim 1 Genus. Such heating systems are installed, for example, in apartment buildings, office buildings, manufacturing plants and the like.

A heating system of a similar type is already known (DE-OS 19 28 575), in which, in contrast to other known heating systems (DE-OS 11 153), the control device does not directly control the servomotor of a mixing valve, but rather the circulation pump. The pressure difference generated during operation of the circulating pump is used as a control variable for the servomotor, ie for the extent to which return water is supplied to the mixing valve via a bypass line. This should result in two mutually supporting actuating effects on the controlled system. It was found that the efficiency is unsatisfactory if the circulation pump is not controlled directly as a function of the Re-Kelßerät, unless the circulation pump with an approximately constant speed is followed by a throttle directly controlled by the control device.However, this additional effort is often undesirable

To improve the efficiency, it is also known (DE-OS 28 i 1 153 and 27 20 526). at constant speed of the circulation pump from temperatures below the flow and return temperature, the heat losses to the outside air and other factors

ίο to create an instantaneous heat balance in order to control the heating system's burner depending on the calculated size of the mixing valve or the burner. Such attempts at a solution are problematic because of the large amount of computing required.

Furthermore, it is also known (DE-OS 24 52 515), with a controller not only the mixing valve but also to control the burner and the circulation pump by only switching on the circulation pump when there is a heat demand and -dinn runs at a constant speed.

An optimization of the efficiency is hereby not easily possible.

After all, it is also known (Recknagei / Sprenger »Pocket book for heating and air conditioning«, 1979. Pages 592-595), in the case of large heating systems several circuits, each with a mixing valve and to use one circulation pump each, which increases the effort and, accordingly, also the susceptibility to failure

The invention is based on the object of

heating system, especially for heating capacities of at least 20 kW of the type mentioned at the beginning improve that they have a good scheme at low levels

Effort and with little energy loss allowed. The invention is characterized in claim 1

net and in subclaims further developments of the same are claimed.

The interaction of the features of claim 1, some of which are already known, leads to the solution of the present problem. Although parallel heating systems with parallel circuits and associated units are avoided and only a single controller with a single heating curve adjuster with only one heating curve for all speeds of the circulation pump is used in their place, an even more favorable degree of efficiency can be achieved, such as this is also explained in more detail with reference to the following description of the figures.

In the drawing, the schematic diagram of a heating system according to the invention is Darge , in which the switching of the two-stage circulating pump in this example is controlled depending on the outside temperature of the building, while the control of the servomotor of the mixing valve is carried out by the controller, its control amplifier makes a comparison of the mean value of the flow temperature and the return temperature applied to its actual value input with the setpoint value applied to its setpoint input, which can be set depending on the outside temperature for one and the same heating curve of a heating curve adjuster.

The heating system of a building 1, only indicated in dash-dotted lines, consists of a boiler 2, a flow water line 3 with a mixing valve 4 and a circulation pump 5, η radiators Wi to H _n and a return water line 6, the mixing valve 4 also having a Bypass 7 is connected directly to the return water line 6. The mixing valve 4 has a servomotor 8, which

is fed by a control amplifier 9, which in turn has a setpoint and an actual value input

A temperature reading from an outside temperature sensor IO installed outside of building 1 is reached via a first temperature / voltage converter 11 e-: a heating curve adjuster 12, the output of which is in turn connected to the setpoint input of the level amplifier 9 A flow temperature sensor 13 and a return temperature sensor 14 are both electrically connected Connected in series and preferably consist of FTC resistors (Positive temperature coefficient). A total measured value of the two temperature sensors t3 and 14 reaches the actual value input of the control amplifier 9 via a second temperature / voltage converter 15.

As already mentioned, the circulation pump 5 is two-stage in the example, and the speed change-over control signal the circulation pump 5 is from the building outside temperature The output signal of the first temperature / voltage converter 11 then also controls the input of a first switching amplifier 16 and a second switching amplifier 17, the two Switching amplifiers 16 and 17 have different input threshold values. The output of the first Switching amplifier 16 reaches a first electrical input of the circulation pump via a first auxiliary contactor 18 5 (speed / i |) and the output signal of the second switching amplifier 17 is reached via a second auxiliary contactor 19 a second electrical input of the circulation pump 5 (speed / 12).

Function description

The heat demand of building 1 and thus the output of its heating system is for a defined, lowest outside temperature determined. This low outside temperature only occurs on a few days in the year and thus the heating system only works during a small percentage of the heating season to provide full performance. In Central Europe one can expect that the heating system will be on average only operated during around 8% of the heating period with an output greater than 50% of full output must become. the delivery rate of the circulation pump on average during around 92% of the heating period could be below 50% of the maximum value. Since every machine, including a circulation pump, has a specific one Has the efficiency profile over the power range and always has the efficiency in the partial load area The circulation pump 5 should be lower than in the design point to maintain a good degree of efficiency and thus reducing your energy consumption during approximately 92% of the heating period at a lower speed operate. Continuous adjustment of the circulation pump speed to the outside temperature would be ideal. This requires either the use of a circulating pump 5 whose speed is continuous or variable in stages, or the use of several hydraulically parallel or series-connected Circulation pumps with constant but different speeds or delivery rates. First of all, the use a multistage circulating pump 5 is of great technical interest, since this on the one hand has the advantage a digital speed changeover control and, on the other hand, the advantage of inexpensive storage by reducing the variety of pumps.

The pump speed or delivery rate is switched depending on one of the following Parameter:

a) a time f (e.g. day / night switchover using Clock),

b) a pump head A,

c) a building outside temperature T _A (e.g. summer / winter changeover),

d) a heating flow temperature Thy.

e) the difference between a heating flow temperature and return temperature (Thv - Tm) and

f) a heating circuit mean temperature T _m or the arithmetic mean (T _H v + T _H r) I2 of the heating flow temperature and return temperature.

The greatest energy saving with constant comfort brings the consideration of b) possibly for low temperature in connection with a) and for summer / winter changeover in connection with c).
Unfortunately, the strongly changing heating flow makes it impossible to use a simple weather-compensated (target value = T ^) flow temperature control and when using two or multi-stage circulating pumps, two or more controllers with different heating curve settings had to be used up to now. Depending on the pump in a circulating pump group or depending on the pump stage, the appropriate controller must then be selected and put into operation. Such systems are therefore very complex and require an undesirably large amount of components.

However, if you do not regulate the heating flow temperature as usual, but the mean radiator temperature, the variety of rules can be avoided and a single controller is sufficient to operate the heating system correctly despite the changing flow rate of the circulation pump. Since the mean radiator temperature is difficult to measure and the heating circuit mean temperature T _m approximately corresponds to this radiator temperature, it is sufficient to use the arithmetic mean of the heating flow temperature and return temperature (Thv + Thr) / 2 as the actual value for the controller instead of this mean radiator temperature . The flow temperature sensor 13 measures the flow temperature Thv and the return temperature sensor 14 measures the return temperature Thr. Both temperature sensors 13 and 14 each contain two identical PTC resistors connected in parallel. Instead of PTC resistors, other temperature-dependent components can of course also be used, including NTC resistors (negative temperature coefficient) or thermocouples. Due to this and due to the fact that both temperature sensors 13 and 14 are electrically connected in series, the measured value T _m = (T _H v + T _tl n) l2 appears at the output of the series circuit. which is converted by the second temperature / voltage converter 15 into a voltage / W proportional to the measured value, which is used by the control amplifier 9 as an actual value. The arithmetic mean (Tuν + Tuk) I2 can of course also be formed by any other network of temperature-dependent components, such as B. by connecting the two temperature sensors in parallel. The building's outside temperature measured by means of the outside temperature sensor 10 is processed in the usual and known manner by the first temperature / voltage converter 11 (generation of a voltage proportional to the outside temperature) and by the heating curve adjuster 12 (taking into account the control characteristic) and then as

Setpoint value SW supplied to the control amplifier 9. The control amplifier 9 compares whether the heating circuit mean temperature T _n , = (T _H v + Thr) / 2 measured by the temperature sensors 13 and 14 and the outside building temperature Ta recorded by the outside temperature sensor 10 of the heating curve adjuster 12 correspond to the set heating curve. In the event of a deviation, the control amplifier 9 adjusts the mixing valve 4 with the aid of the servomotor 8 so that sufficient cooler water from the return water line 6 mixes with hot water in the supply water line 3, until one of the building's outside temperature is reached assigned heating circuit mean temperature T _n results.

Assuming the use of a two-stage circulating pump 5 and a pump speed change-over controlled by means of the outside building temperature T _A, one of the switching amplifiers 16 or 17 selects the speed n \ or n _{2 of} the circulating pump 5 and corresponding to the outside temperature range in question in parallel with the control process takes the circulation pump 5 with the most favorable speed into operation with the help of the associated auxiliary contactor 18 or 19.

When using a circulating pump 5 with a continuously variable speed, this speed is continuously regulated as a function of a setpoint value SW derived from the building's outside temperature T *.

1 sheet of drawings

30th

35

40

45

50

55

60

Claims (1)

Patent claims: 1. Heating system with a mixing valve that controls the flow temperature and can be controlled by a servomotor, with a control amplifier and a control device with Heizkurveneins plate, at whose TARGET value input the output variable of an outside temperature sensor and on whose ACTUAL value input can be applied to the output variable of a heating medium temperature measuring device, and with a circulation pump arranged in a feed line, the delivery rate of which is controllable, characterized by the combination of the following features: