GB2124750A - Heating plant comprising a ring pipe - Google Patents

Abstract

A heating plant comprises a ring pipe through which the heating water led through a boiler K is conveyed in circulatory flow by means of a central circulating pump P. The ring pipe also has heating elements H1 to H6 situated in the rooms which are to be heated connected to it in shunt via an inflow pipe and an outflow pipe, the supply of heating water to the heating elements being controllable as a function of the room temperature. Precise control of the temperatures desirable in the separate rooms is assured in such manner that each heating element has a metering unit D installed in its shunt loop allocated to it, and that the delivery flow and/or the operating period of the metering units is controlled as a function of the prevailing room temperatures via a control system ZS. The central pump P may be controlled according to the difference between the water feed and return temperatures. <IMAGE>

Description

SPECIFICATION Heating plants comprising a ring pipe The present invention relates to a heating plant comprising a ring pipe through which the heating water ducted through the heating boiler is conveyed in circulatory flow by means of a central circulating pump and to which the heating elements situated in the rooms which are to be heated are connected in shunt via a feed pipe and an outflow pipe, the supply of heating water to the corresponding heating elements being controlled as a function of the room temperature.

Such systems, also referred to as one-pipe heating plants, are frequently constructed since they are cheaper in particular than two-pipe heating plants, and primarily because an additional sphere of application has just recently been discovered in the restoration of old buildings, because no more than holes or passages need be formed in the walls and floors for a single ducting pipe.

One-pipe heating plants have particular disadvantages however. The possible heat dissipation of the separate heating elements depends on the heat dissipation of the whole system carrying the heating water, so that precise temperature control in the rooms in question is doubtful. Furthermore, the dimensioning of the ducted pipes and of the heating surfaces or heating elements is more difficult than in the case of two-pipe heating plants, so that the heating element will be selected in an unnecessarily large size, on the score of safety. Finally, it should also bethought of that comparatively high pump pressures are needed, for reasons which will be dealt with later. These shortcomings restrict the sphere of application of the one-pipe heating plants which may in essence be constructed in uncomplicated and material-saving manner.

It is an important object of the invention to provide a one-pipe heating plant which may be dimensioned easily, which in principle has the advantages of the one-pipe and two-pipe heating plants, and which amongst other things, assures precise control over the temperatures required in the separate rooms.

Furthermore, the central circulating pump should be apt to operate at comparatively low pressure so that power may be saved and flow noises may be prevented in the piping system.

In accordance with the invention, this problem is resolved in the case of a heating plant of the aforesaid kind, in such manner that a metering unit conveying heating water and installed in its shunt loop is allocated to each heating element, and that the delivery flow and/or the operating period of the metering units may be controlled as a function of the prevailing room temperatures.

To demonstrate the advantages of this solution, let us repeat in connection with the already known one-pipe heating plants, that either the whole flow of water flowing through the piping system is also led through each separate heating element, or that the plant is constructed in such manner that the heating elements are connected to the ring pipe in shunt and that the proportion of the water penetrating into the heating elements from the ring pipe has to be established by means of a resistance arranged parallel to the shunt pipe and which may for example be formed by a special thermostat. Due to the flow resistances present in series, these two alternatives applied until now, cause high pump pressures however.

The distributor or ring pipe lacks such resistances in the case of the plant in accordance with the invention, these resistances are stated otherwise being needed for distribution of the heating water to the separate heating elements. The central circulating pump now merely has to make up for the pressure losses caused by pipe friction and flow resistances in elbow pipes and the like. It may accordingly operate at lower pressure differential, thereby eliminating the disadvantages referred to earlier in this connection.

Since each heating element - this concept should also be taken to denote several separate heating elements of a room connected in series or parallel has in each case allocated to it a metering unit which is controlled, for example by means of a thermostat, as a function of the heat demand of the room in question, the possibility is now available to supply each heating element separately with heating water, since the metering unit installed in the shunt loop for the heating element draws more or less water from the ring pipe according to heating needs and in the course of time.

Furthermore, the metering units need a hydraulic performance factor of a few watts only. Considered with respect to size and cost, they will consequently be at least as advantageous as the conventionai heating element thermostat valves. Electrically operated hydraulic working machines, for example such as rotary pumps, diaphragm pumps and the like, may be considered as metering units. In any event, a small pump will be appropriate for the purpose specified, which appropriately comprises a d.c. drive operated at low voltage, for example at 12 or 24 volts, the r.p.m. or frequency of which may, as known, be adjusted easily and precisely, the room temperature converted in analog manner into a voltage value being utilised as a datum value.

The low-voltage operation of the metering units also offers the advantage that the metal ring pipe may form one of the electrical conductors for the current supply of the d.c. drives without any danger being incurred by touching the ring pipe.

A central control system may moreover be provided, which overrides the metering unit control systems operating as a function of temperature at particular times, so that the metering units may be kept out of operation during these periods, for example. In this connection, it should be considered primarily that the metering units will probably not operate at night time, or do so occasionally only.

Aweather-controlled control operation on the plant may actually be omitted in the case of the solution according to the invention. If a control system of this kind is specified however, the central circulating pump may complementarily be controlled by the ambient or feed temperature via the central control system.

The possibility exists finally, to control the delivery flow and/or operating period of the central circulating pump as a function of the temperature differential between the feed and return temperatures of the heating water.

In order that the invention may be more clearly understood, one embodiment thereof will now be described with reference to the accompanying drawings which show the embodiment in diagrammatic form and in which: Figure 1 shows a block circuit diagram for a heating plant in accordance with the invention, and Figure 2 shows a room with a control for the metering unit provided for this room.

Referring now to the drawings, the plant illustrated has a ring pipe R wherein is placed a central circulating pump P which conveys the heating water ducted through the heating boiler in circulatory flow through the ring pipe. The six rooms which are to be heated in this example are denoted by dotted boxes.

The heating elements present in these rooms and marked H1 to H6 are in each case connected in shunt to the ring pipe R via inflow and outflow pipes a and b in each case.

A metering unit D is installed in each inflow pipe a of the shunt loops, the delivery flow and/or the operating period of these metering units D1 to D6 being controllable as a function of the temperature in the corresponding room. To this end, conventional thermostats T (Figure 2) are placed in the rooms, which control the electrical drive of the metering units D via a control system S and a control line c, that is for example turn the metering units off upon reaching an upper temperature value preset on the thermostat in question, and place these in operation again as soon as a lower preset temperature value is detected.

This control method may also be replaced by a running period control method, the control system S keeping the metering units D in operation for a fixed period upon detection of a preset lower temperature value. The possibility also exists, to control the delivery volumes of the metering units as a function oftemperature, e.g. varying the r.p.m. of a rotary pump or the frequency of a diaphragm pump acting as a metering unit, in accordance with the heating requirement of the room in question.

The metering units D are appropriately provided with low voltage d.c. drives, so that the metal ring pipe R may also be utilised without danger as one of the electrical conductors for the supply of current to the drives. The voltage drawn from the a.c. grid N also supplies the mains appliance NG, amongst others, the d.c. output voltage of say 24 volts of which is fed to the drives of the metering units via the conductor d.

The grid N also supplies a central control system ZS, whereby the control of the metering units D operating as a function of room temperature may be overriden at particular times, for example during the night, to keep the metering units out of action during these times. This may be arranged by the control system simply interrupting the conductor e leading to the mains appliance NG.

Furthermore, the central circulating pump P may be controlled by the heat demand of the heating plant via the control system ZS, for example by controlling the delivery flow and/or operating period of this pump as a function of the differential between the feed and return temperatures of the heating water. To this end, a temperature gauge TV for detection of the feed temperature, and another temperture gauge TR for detection of the return flow temperature, are installed in or on the ring pipe R before and after the boiler K. The temperature gauges transmit the electrical signals corresponding to the temperature values detected to the control system ZS, which compares the two signals.

If, when doing so, the difference between these signals varies towards zero, consequently in the presence of a diminishing heat demand, the control system ZS sets the pump P to lower r.p.m. values via the conductor h. An opposed control operation occurs for an increasing difference between the feed and return flow temperatures, so that the circuit as a whole will adjust itself automatically in adaptation to the thermal output required.

In view of this control method, there is no absolute need for a feed temperature controlled as a function of the weather, so that the control elements to be installed may be produced in economic manner. If a weather-affected control system is specified however, the ambient temperature or the feed temperature alone may be co-opted to control the r.p.m. of the central circulating pump P.

Claims (7)

1. A heating plant comprising a ring pipe through which the heating water ducted through a heating boiler by means of a central circulating pump is conveyed in circulatory flow and to which heating elements situated in the rooms which are to be heated are connected in shunt via an inflow pipe and an outflow pipe, the supply of heating water to the corresponding heating elements being controlled as a function of the room temperature, wherein a metering unit conveying heating water and installed in its shunt loop is allocated to each heating element and the delivery flow and/or the operating period of the metering units are controllable as a function of the prevailing room temperatures.

2. A heating plant as claimed in claim 1, wherein a central control system is provided which at particular times overrides the temperature-governed control of the metering units to keep the metering units out of operation during such periods.

3. A heating plant according to claim 1 or 2, wherein the metering units are operated by lowtension direct current.

4. A heating plant as claimed in claim 3, wherein the ring pipe forms one of the electrical conductors for the supply of current to the d.c. drives.

5. A heating plant as claimed in claim 2,3 or 4 comprising a feed temperature control system operating as a function of the weather, wherein the central circulating pump is controlled by the ambient or feed temperature via the central control system.

6. A heating plant according to any of the preceding claims, wherein the delivery flow and/or the operating period of the central circulating pump is/are controlled by the temperature differential between the feed and return temperatures of the heating water.

7. A heating plant substantially as hereinbefore described with reference to the accompanying drawings.