GB2203567A - Controlling a heating installation - Google Patents

Abstract

Apparatus for controlling a heat generator of a heating installation is provided comprising timer means arranged to provide a heat generating signal to generate heat over a first predetermined time period and a heat suspension signal to substantially stop heat generation for a second predetermined time period. The signals may, for example, control the pump of a central heating installation. The apparatus is arranged to provide the signals alternately during a heating period and the frequency of repetition is sufficiently high that, when used to control a central heating installation for a building, a substantially constant temperature of heating is obtained. The lengths of first and/or second time periods may lie within the range 1 to 30 minutes each. In an embodiment of the invention, two frequency selection devices (5, 6) are provided for controlling the frequency of operation of a pulse generator (1). The pulse generator is connected to a pulse counter (2) and means (3) are provided, responsive to the pulse counter, for controlling the frequency selection devices whenever the pulse counter counts a predetermined number of pulses from the pulse generator.

Description

TIMER The present invention relates to a method of controlling a heating installation, especially a domestic central heating installation and apparatus for controlling such an installation.

According to the invention, there is provided an apparatus for controlling a heat generator of a heating installation, comprising timer means arranged to provide a heat-generating signal to generate heat over a first predetermined time period and a heat suspension signal to substantially stop heat generation for a second predetermined time period, the apparatus being arranged to provide the said signals alternately during a heating period and the frequency of repetition being sufficiently high that, when used to control a central heating installation for a building, a substantially constant temperature of heating is obtained Preferably means are provided to adjust infinitely the lengths of the first and/or the second time period. Such means should preferably provide infinite variability of the periods over a range, for example of 1-30 minutes each.

When the apparatus is used in connection with a central heating installation for a building the heat generator will be the central heating boiler and the heat-generating and heat-suspension signals respectively will turn the boiler pump on and off.

According to the invention there is also provided a method of controlling a heating installation to heat a building, comprising generating heat over a first predetermined time period, substantially stopping heat generation over a second predetermined time period, and carrying out the heating-stopping operation repeatedly during a heating period, the frequency of repetition being sufficiently high that a substantially constant temperature of heating of the building is achieved.

In preferred embodiments of the invention the frequency of repetition is typically several times per hour. For example both time periods may lie within the range of 0-30 minutes; it is necessary to keep the frequency of repetition sufficiently high to avoid sensible fluctuations in the temperature of the building.

Using the method according to the invention it is possible to control the temperature of a building by adjusting the predetermined time periods during which heat is respectively generated and stopped. The operator can adjust either or both periods infinitely.

This should be distinguished from the conventional control of two'nl and two"off"periods offered by prior art central heating timers.The method of the invention not applicable to switching a central heating system on and off at predetermined but adjustable times of the day, but rather, within the *on" periods, to providing a repeated succession of on and off cycles of a much shorter duration; by proportioning which both the economy of the system and the temperature of the building may be controlled.

According to the invention there is further provided a timing device comprising: (a) a pulse generator connected to (b) a pulse counter (c) a frequency control means for controlling the frequency of operation of the pulse generator (d) means responsive to the pulse counter for controlling the frequency control means whenever the pulse counter counts a predetermined number of pulses from the pulse generator and (e) Output means for providing an output control signal in response to the counting of the said predetermined number of pulses by the pulse counter.

The frequency control means may, for example, comprise two or more frequency selection devices which are activated in turn. The means responsive to the pulse counter then switches between the frequency selection devices each of which in turn controls the frequency of operation of the pulse generator. Where the device is used to control a domestic central heating system which can only be "on" or "off" two frequency selection devices only are required but the invention can also be applied to multi-state systems using as many frequency selection devices as there are states of the system.

The invention will now be more particularly described with reference to the accompanying drawings, in which: Figure 1 is a schematic block diagram illustrating the invention Figure 2 is a circuit diagram of a device embodying the invention Figure 3 is a circuit diagram of a power supply suitable for use with the device according to the invention Figure 1 illustrates the principle of the invention. A pulse generator or oscillator 1 is connected to feed pulses to a pulse counter 2. The pulse counter is set so that every time a predetermined total of pulses is reached a multi-way switch 3 is activated. The multi-way switch 3 is connected to the system 4 to be controlled and also to at least two frequency selectors, of which two are by way of illustration only shown at 5 and 6 in Figure 1.

Frequency selectors 5 and 6 in turn control the frequency of the pulses emitted by generator 1. Thus during a first cycle generator 1 is controlled by frequency selector 5 and emits pulses at a frequency determined by frequency selector 5 until a predetermined total of pulses, counted by counter 2, is reached. Counter 2 then activates multi-way switch 3 which changes the state of system 4, and a second cycle is started in which the frequency of pulses emitted by generator 1 is determined by frequency selector 6.

This second cycle is terminated when the predetermined total of pulses is again reached, as detected by pulse counter 2, the multi-way switch 3 is activated again, and the state of system 4 changed again. Frequency selector 5 then takes over for a third cycle controlling generator 1 to emit pulses at the original frequency.

Thus in successive cycles the frequency emitted by pulse generator 1 is controlled in turn by frequency selectors 5 and 6 and as the predetermined count total remains the same the length of each successive cycle may be controlled by varying the frequency of the frequency selector which it controls. Thus by selecting the frequencies of frequency selectors 5 and 6 cycles of a first time period alternating with cycles of a second time period may be obtained.

It will readily be seen by those skilled in the art that the invention enables, for example, a central heating pump to be switched on for any pre-set period and then off for a further pre-set period, alternating indefinitely. The timer according to the invention will repeat the pre-set sequence of on and off periods until manually switched off or over-ridden by some other means. The device may therefore be used to control the amount of water running through a central heating system at any given time so as to give maximum heat output at the radiators together with minimum heat requirements at the boiler. Temperature fluctuations in the rooms may therefore be reduced and fuel saved as the boiler never has to heat more water than necessary.

Figure 2 illustrates an embodiment of the invention for use in controlling central heating systems. Integrated circuit A is a pulse generator energised by a power supply which may be of known type, and an example of which is illustrated and described later on with reference to Figure 3. The frequency of pulses emitted by generator A is controlled by an input through line 20 and capacitor C.a; the generation of this input will be described in more detail later on.

Pulses emitted by generator A at a first frequency are fed to integrated circuit B which is a counter, for example, a 12-bit counter of a type known in the art.

The output of counter B is fed through line 22 to the input 11 of integrated circuit C which is a multi-way switch, illustrated as, but not necessarily limited to, an 8-way multiplexer. Line 22 is also connected by a resistor R.c to transistor T which controls a system shown generally at 24. In the embodiment illustrated the system 24 is a control circuit for a central heating system comprising a relay 27 fed via a light emitting diode 28 and resistor R.d.

Other outputs of integrated circuit (C) are connected respectively via lines 25 and 26 to potentiometers V.R.a and V.R.b in series respectively with frequency-limiting resistors R.a and R.b, which in turn are connected via a common junction to line 20 and provide the controlling input of generator A.

Potentiometer V.R.a and resistor R.a, and potentiometer V.R.b and resistor R.b correspond to frequency selectors 5 and 6 respectively shown in Figure 1.

In operation, when the circuit is switched on, counter B resets. Pulse generator A feeds pulses, at a frequency determined by V.R.a and R.a, via line 21 to counter B. Counter B is preset to present a high potential via line 22 to multi-way switch C when a pre-determined total of counts, for example, 1,024, is reached.

When this total is reached, the high potential in line 22 causes multi-way switch C to activate potentiometer V.R.b and resistor R.b in place of potentiometer V.R.a and resistor R.a. Potentiometer V.R.b and resistor R.b are preset to control integrated circuit A to emit pulses of a second frequency. These again when fed to counter B cause the latter to fire when the same predetermined total as before (for example 1024) of counts is reached. A low potential is then presented to line 22 and multi-way switch C resets to potentiometer V.R.a and resistor R.a, at the same time deactivating transistor T to change the state of the controlled system 24. A fresh cycle then commences of the same length of the first cycle.

Thus each successive cycle is characterised by the emission by generator A of pulses of a certain frequency and its length determined by that frequency.

It will readily be seen that the invention is not limited to the provision of two frequency selecting devices as illustrated in Figures 1 and 2, but that as many such devices can be provided as there are suitable outputs on multi-way switch C. Each frequency selector will establish a cycle of a characteristic length in the series. In central heating systems, only two frequencies will generally be required as the pump may only be on or off; in more sophisticated systems, and for example, in industrial control systems, more than two states of the controlled system may be required, and these can be catered for by providing a corresponding number of frequency selection devices.

The circuit illustrated in Figure 2 can be energised by a power supply such as that shown in Figure 3, but the invention is not limited to the use of such power supplies which are known in the art. In the power supply shown in Figure 3, the primary of a step-down transformer 31 is connected to the mains and the secondary to one arm of a bridge rectifier 32 with a smoothing capacitor C.c and regulator R.e. The rectified output of 15 volts is suitable for the operation of the timer according to the invention.

In use the operator may infinitely control the length of the successive cycles by adjusting the potentiometers V.R.a and V.R.b. It is found that with cycle lengths of up to 30 minutes available the adjustment may be achieved by setting the "on" cycle at a given length and varying the length of the "off" cycle until a satisfactory temperature is obtained. In fact it is thus possible to control the temperature of a dwelling using the timer according to the invention as opposed to a thermostat; a thermostat may still be incorporated to provide overall control but fine control of temperature and economy can be obtained using the timer according to the invention as described above. Likewise it is possible to provide a conventional central heating timer to give two "on" and two "off" periods per day which during the "off" periods will override the timer according to the invention.

Claims (13)

1) Apparatus for controlling a heat generator of a heating installation, comprising timer means arranged to provide a heat-generating signal to generate heat over a first predetermined time period and a heat suspension signal to substantially stop heat generation for a second predetermined time period, the apparatus being arranged to provide the said signals alternately during a heating period and the frequency of repetition being sufficiently high that, when used to control a central heating installation for a building, a substantially constant temperature of heating is obtained.

2) Apparatus according to Claim 1 comprising adjusting means to adjust infinitely the lengths of the first and/or second time period within predetermined ranges.

3) Apparatus according to Claim 2 wherein the predetermined ranges are 0 to 30 minutes each.

4) Apparatus according to any one of Claims 1 to 3 in combination with a central heating generator when installed in a building, the heat-generating and heat-suspension signals being arranged to respectively turn on and off a pump associated with the central heating generator.

5) Apparatus according to any one of the preceding claims further comprising over-riding control means to define the start and end of a heating period.

6) Apparatus according to Claim 5 wherein the over-riding control means includes a thermostat.

7) Apparatus according to Claim 5 or Claim 6 wherein the over-riding control means includes a timer.

8) A method of controlling a heating installation to heat a building, comprising generating heat over a first predetermined time period, substantially stopping heat generation over a second predetermined time period, and carrying out the heating-stopping operation repeatedly during a heating period, the frequency of repetition being sufficiently high that a substantially constant temperature of heating of the building is achieved.

9) A timing device comprising: (a) a pulse generator connected to (b) a pulse counter; (c) a frequency control means for controlling the frequency of operation of the pulse generator; (d) means responsive to the pulse counter for controlling the frequency control means whenever the pulse counter counts a predetermined number of pulses from the pulse generator and (e) output means for providing an output control signal in response to the counting of the said predetermined number of pulses by the pulse counter.

10) A device according to Claim 9 wherein the frequency control means comprises two or more frequency selection devices and the means responsive to the pulse counter are arranged to activate the frequency selection devices in turn.

11) A device according to Claim 10 wherein the frequency control means comprises first and second pulse length adjusters and. the means responsive to the pulse counter comprises switching means to alternately select the adjusters for pulse length determination.

12) A timing device substantially as hereinbefore described and as shown in the accompanying drawings.

13) Apparatus according to any one of claims 1 to 7, wherein the timing means is a timing device according to any one of claims 9 to 12.