GB2173920A

GB2173920A - Heating controller

Info

Publication number: GB2173920A
Application number: GB08509835A
Authority: GB
Inventors: John David Statham
Original assignee: Individual
Current assignee: Individual
Priority date: 1985-04-17
Filing date: 1985-04-17
Publication date: 1986-10-22
Also published as: GR860994B; GB2173920B; GB8509835D0

Abstract

A control system for a multi-zone building (ie one in which the use of different parts of the building dictates different heating regimes) has a heating control valve and a temperature sensitive means in each zone and a time clock so that in each zone the valve means is controlled in response to the temperature sensor output during controlled heating periods of a 24 hour cycle specific to that zone. Either a separate time clock is provided for each zone, or a programmable central controller is provided which controls the time period in several such zones. The valve may be powered by the mains or by rechargeable batteries, and the batteries may be recharged by light or by taking energy from the circulating heating fluid of the system.

Description

SPECIFICATION Improvments in and relating to heating systems Field of invention This invention concerns space heating systems and in particular control systems therefor.

Background to the invention It is known to control the operation of a space heating system using a time clock to control the duty cycle of the heating system and a temperature operated switch known as a thermostat for turning the system on and off during the duty cycle so as to maintain a desired temperature within the building heated by the system.

Such control systems are well suited to controlling space heating systems for factories, offices and the like, where the duty cycle (ie the time when heating is required) during each 24 hour period is the same throughout the building. However, such control systems are not ideally suited to domestic dwellings and the like where heating requirements throughout the accommodation are not uniform and vary quite dramatically each day in that different zones in a house need to be heated not only to different temperatures, but also at different times during each 24 hour cycle.

A building such as a domestic dwelling will be described as a multi-zone building as distinct from an office block or factory or the like which can be thought of as a unitary zone building in that heating is required throughout the whole building during approximately the same period of time during each 24 hour cycle. Indeed, in the case of a hospital, the heating may be required during the whole of the 24 hour cycle.

There are a number of different heating systems currently available but in multi-zone buildings such as domestic dwellings, the most common forms of central heating system split into two general types: 1. ducted hot air systems, and 2. piped hot water systems.

In the former case, air is heated by means of a heat exchanger located at a convenient place within the dwelling and by means of a fan and ducting, the heated air is conveyed to outlets located at a low level in each of the zones in the building which are to be heated.

The outlets normally include adjustable louvres or the like to allow the outlets to be shut off or opened up at will and a return vent communicating with ducting feeding the inlet to the heat exchanger is also provided in each zone so that when operating according to design, hot air flows into each zone and after cooling in the zone is returned to the heat exchanger via the return ducting. By controlling the amount of heat entering the air stream via the heat exchanger and controlling the relative quantities of heat entering each separate zone, so different temperatures can be maintained in different zones within the building. However it is not possible to provide for a different duty cycle for different zones.

In the second example, a boiler supplies hot water to a pipe which feeds the inlets of a number of heat exchangers in the form of radiators located in the different zones and a return pipe connected to the outlet of each such radiator serves to return the water to the inlet of the boiler for re-heating. Normally a pump is included within the circuit so as to force the water therearound. When the pump is operating, heat is conveyed from the boiler to the panel radiators which are heated and in turn dissipate some of the heat to the surrounding air. The water is cooled after passing through the radiators, but on being returned to the boiler is re-heated for circulation once again.

As with the ducted air system, control of the heat input to each zone is achieved by throttling back the flow through the different radiators so that where a lot of heat is required in order to maintain a higher temperature, a relatively large flow of water is provided for and vice versa.

In both such systems, the duty cycle is determined by making power available to the pump or fan for those hours during the 24 hour cycle when heating is required. Whether or not the pump or fan is then operated is determined by monitoring the temperature within one of the zones (referred to as the key zone) using a temperature sensitive switch or thermostat. By arranging that the latter turns the pump or fan off when the desired temperature is reached, but turns the pump or fan on when the temperature in the key zone drops relative to the desired temperature, so the temperature in the key zone is maintained close to the desired level.The temperature achieved in each of the other zones is determined by the relative heat input to each of the zones in question and if a higher temperature in any one of the other zones is required, it is arranged that the net heat input into any such zone is greater in any period of time than that into the key zone. Where lower temperatures are required, it is arranged that the net heat input to such a zone is less than that into the key zone for the same period of time. This is achieved by throttling the radiators back by a greater or lesser extent as required, or adjusting the louvred vents in the outlets of a ducted air system, again to a greater or lesser extent.

Additionally, larger or smaller radiators or vents and/or a larger number of radiators and/or vents may be used for different zones so as to increase or decrease the heat available for inputting to the zones concerned, but it will be seen that in essence the control is limited to achieving the same relative heat distribution throughout the zones during each 24 hour cycle, the precise quantity of heat being dictated by the outside ambient temperature and the setting of the thermostat within the key zone.

Such systems make no attempt to reflect the different occupancy rates of the different zones of the building during each 24 hour cycle, nor are they readily adjustable to provide for a different temperature distribution either at different times of the day, or at different times of the year due to overall change of occupancy of the building.

Thus, by way of example, zones of a house reserved for sleeping require a relatively high level of heat at the beginning and end of each day and sufficient heat during the night to maintain a background level of warmth.

Likewise, other zones which are occupied basically during the evening, require considerable heating shortly before occupancy to warm them through, and then during the evening, but as the sleeping zones come on stream, the heating requirement for the evening occupancy zones disappears.

Hitherto it has only proved possible to provide for the same temperature distribution throughout a multi-zone building during each duty cycle and if different temperatures are required, either the setting of the thermostat must be altered as required, or the various radiators of duct outlets must be adjusted throughout each duty cycle and throughout each day to achieve the desired multi-profile temperature characteristic according to occupacy of the different zones.

It is to be understood that the present invention in its various aspects is equally applicable to a ducted air system of heating as it is to a pumped hot water heating system.

Objects of the invention It is an overriding object of the invention to provide a control system for controlling the heat input to each zone of a multi-zone building according to the local heating requirements of each zone during each 24 hour period.

It is another object of the invention to provide devices which can be fitted to existing heating sytems for achieving this objective.

It a further object of the present invention to provide devices which can be fitted to an existing or new heating system which can be programmed to control the heating input of each of a plurality of zones in a multi-zone building and which require no external supply of electrical energy for their operation.

Summary of the invention According to one aspect of the present invention a device for controlling the flow of heat into one zone of a multizone building comprises valve means by which the flow of heat into the zone can be interrupted, drive means for actuating the value means, a time clock for supplying operating power to the drive means during one of more periods of time during each 24 hour cycle and temperature control switch means sensitive to the temperature within the same zone and adapted to actuate the valve means and interrupt the flow of heat into the zone when a desired temperature within the zone is exceeded and to re-actuate the valve means to again permit heat to enter the zone if the temperature subsequently drops below the desired temperature for that zone during any duty cycle dictated by the time clock.

In a radiator system, the valve means is typically a motorised valve in the pipe conveying hot water to the radiator and the temperature sensitive switch comprises a thermostat located within the zone at a point at which the temperature can be said to be typical of that throughout the zone.

In one embodiment the motorised valve, time clock and power supply for actuating the valve may be located in a single unit adapted to be fitted adjacent the radiator infeed pipe and the thermostat may be located elsewhere in the zone (and connected thereto by means of a cable) or may be mounted in a housing forming part of or secured to the housing containing the valve and time clock etc.

The power supply for actuating the motorised valve may comprise one or more batteries which may be of the rechargable variety.

Alternatively, power from an electricity ring main within the building may be tapped in a conventional manner to supply energy to the time clock and motorised valve as required.

The time clock is adapted to make available the power from the battery or mains supply during the duty cycle and the thermostat is set to supply the power to the motorised valve to open or shut the latter as required by the temperature level within the zone.

Where rechargable cells are used to render the device independent of the electricity supply, power for charging the cells and keeping them topped up may be derived from sunlight using a semiconductor junction array for converting light into electric current, or by means of thermocouples or the like which are located on or in the feed pipe to the radiator and derive energy from the heat in the pipe and convert this into an electric current.

In a further arrangement, a paddle wheel is located within the feed pipe so that when water is flowing into the radiator, the paddle wheel is rotated and if this is magnetised, an electric current can be induced in a surrounding coil which after rectification can be used to charge the cells.

Where the heating system is a ducted hot air system, the motorised valve means comprises motorised louvres or shutters which can be opened or shut to control the flow of hot air into the zone. Since the outlets in a ducted air systems are normally at low level, these can be sited conveniently adjacent the outlets of a ring main where supplementary power is required, or as previously mentioned each unit can be rendered independent by providing suitable batteries and making provision for charging same if they are of the rechargable variety.

Whatever the heating medium, if batteries are provided (particularly of the non-rechargable variety) a low battery condition indicator is preferably incorporated into each device. Preferably such a warning device is of a visual nature.

It will be noted that where the device is wholly self contained and includes the thermostat and power supply all within the same unit, the device does not need the skils of an electrician for installation but can be installed by a heating engineer or householder.

According to another aspect of the present invention, the time clock may be separated from the motorised valve and local thermostat associated with each zone and replaced by a central control unit incorporating a master time clock and independently programmable controllers for the different motorised valves. In such a system, the separate zone thermostats may be arranged in close association with the motorised valves or remotely within the zones and each thermostat may be arranged to control each motorised valve directly within the zone or to feed an electrical signal dependent on temperature within the zone back to the central control unit.

Where a central control unit is employed, the duty cycle for each zone and the temperature profile required in each zone may be stored in a suitable memory which is addressed during each 24 hour cycle to determine the pre-programmed requirements for each zone so that control signals can be generated by the central control unit for turning on or off the heat supply valves for each zone. Where the temperature of each zone is sensed by a thermostat having a simple on/off characteristic, on when the temperature is below and off when the temperature goes above that set by the thermostat, the central control unit simply provides on/off control signals for the motorised valve controlling the input of heat to the zone.

Where the temperature sensitive device in the zone can provide an analogue or digital signal whose value such as amplitude (in the case of an analogue signal), is proportional to the temperature in the zone, then the central control unit may be programmed to provide for a finer control of the input of heat to the zone so as to reduce the actual quantity of heat per unit time as the temperature of the zone closely approaches the desired temperature until equilibrium is reached in which the heat supplied to the zone is just equal to that lost from the zone at the desired temperature.

To achieve this, the motorised valve means must of course be equally finely adjustable typically in a large number of small steps between a fully open and a fully closed position.

This second aspect of the invention is equally applicable to radiator systems as well as ducted air systems.

Since the central control of the system requires electrical signals to be sent from the central control unit to the various zone input controls and electrical signals to be conveyed from the zone temperature sensing elements to the central control unit, considerable cable runs may be required and according to another aspect of the present invention, remote control of the valves and remote addressing of the temperature sensitive devices by the central control unit may be achieved using low power radio links between a transmitting device in the central control unit and receiver devices located in each zone and adapted to control the valves or louvres. In the same way, local transmitter units within the temperature sensitive devices may be utilised to convey temperature information from each zone back to a reciever located at the central control unit.

In another arrangement, the electricity supply main within the building may be used as a carrier for frequency modulated radio signals using suitable transmitters and receivers. Due to the relatively small bandwidth avaliable, a form of time division multiplexing is preferably employed in such a system so that signals relating to one zone are transmitted during one period of time, and those for another zone during another period of time etc. Alternatively, a form of encoding may be used so as to identify the signals for and from the different zones with suitable decoding circuits located at the zone receivers and at the central control unit receiver.

Where cabling is preferred, this may advantageously be run with the pipes feeding the radiators or through the ducting feeding the various hot air outlets and where pipes of suitable diameter are employed, the cabling may even be threaded through the pipes to exit through suitable seals in the wall of the pipe or through the wall of a pipe fitting at or adjacent the position for the zone control to which they relate.

Where cabling is used, the control voltages and signal voltages are preferably kept at a relatively low level so as to reduce the insulation problems and the risk of overheating and fire in the event of any electrical breakdown.

According to another aspect of the present invention, whether the time clock and control device is associated with each valve or hot air outlet and is independently programmable or whether they are combined into a single central control unit, preferably each zone control unit whether it be a valve or duct outlet is controllable to supply heat to the zone during each of a plurality of programmable periods during each 24 hour cycle.

According to a still further aspect of the invention, the temperature sensing device in each zone of a multi-zone building is preferably in the form of a temperature sensitive element having a parameter which varies with temperature so that an electrical signal can be generated having a parameter whose value varies as the temperature in the zone varies and comparison means is provided for comparing the varying parameter electrical signal with a programmed reference value for the zone concerned during each programmed time period and the device controlling the input of heat to the zone is controlled on or off in dependence on the said comparison.

The term zone is not intended to be limited to different rooms within a building, but is intended to include two or more rooms having the same heat requirements during each 24 hour cycle and also includes the heating of the hot water supply for the building.

Where a centralised control unit is employed, it is also possible to provide for a different heating profile for each zone for different days in the week thereby allowing for different occupancies of the zones for example, on weekdays as compared with weekends.

In any heating system where the temperature of a zone is maintained by turning on/off the supply of heat to the zone, so called thermal-cycling results. This arises from the fact that most commercially available temperature controlled switches possess hysteresis. By this is meant a two or three degree difference between the temperature at which the switch turns off and the temperature at which the switch will once again turn on.

The effect can produce unpleasant temperature cycling and particularly at temperate times of the year, the supply of heat to the zone may be off rather more than on so that there is no local source of warmth within the zone.

This can be disconcerting particularly to the elderly and infirm.

According to a further aspect of the invention, this thermal cycling can be reduced to a minimum in a centrally controlled system by supplying to the central control unit information relating to the outside ambient temperature (that is, external to the building containing the zones which are to be heated).Using this information, the central control unit can determine from a look up table the optimum temperature for the water or air which is to be circulated to the different zones to achieve the local heating therewithin and by providing means for controlling the heat input to the heat exchanger in the boiler or other device for heating the water or air to be circulated around the zones, so more or less heat per unit time will be conveyed to the different zones so that the average time for which the radiators or ducts are on or open will be much the same whether the outside ambient temperature is high or low.

It will be seen that by making simple temperature measurements within each individual zone and if required externally of the building, so a very much higher level of local control of the different zones within a multi-zone building can be achieved.

In a typical case as applied to a domestic dwelling, the control system may be programmed to provide heat to the bedrooms and the kitched and bathroom from a point in time shortly before the normal waking time of the occupants to shortly after the time each day when the occupants leave for business, school or the like, and until the occupants are normally expected to return to the house, the heating system may be left in a quiescent state until a short time prior to the arrival of the first occupant in the late afternoon or evening when again the kitchen and one of the living areas of the house such as the dining room or lounge or both are heated, together with perhaps the bathroom.During the evening, heating to the kitchen may be withdrawn and heat concentrated into the main living room such as the lounge and shortly before the normal time at which the occupants would retire to bed, heating is introduced to the bedroom or bedrooms and shortly after the normal retiring time, heat to the living rooms is removed and perhaps one hour after the occupants would normally retire to bed is then removed from the bedrooms except such as is sufficient to maintain a minimum ambient temperature in the bedrooms. The cycle is then repeated the next morning.

According to a further preferred refinement of the system, a low temperature sensing device may be located within one or more of the zones and a control signal generated therefrom in the event that the temperature within that zone or within any of the zones so monitored drops below a programmed minimum. A control signal so generated may be used to initiate the heating system to warm selected zones at least one of which must contain the minimum temperature sensing device and signals from the latter are used to turn off the heating system once the minimum temperature has again been obtained. In this way one or more zones within the building can be prevented from dropping in temperature below the programmed minimum thereby preventing, for example, freezing up of pipes and the like.

The invention will now be described by way of example, with reference to the accompanying drawings, in which: Figure 1 illustrates one embodiment of the invention which is particularly adapted for retrofitting to existing radiator heating systems, where the thermostatically controlled switch is remote therefrom, Figure 2 is a similar view of a device in which the temperature controlling element is integral therewith, Figure 3 shows a similar arrangement in which the time clock and other controlling circuits are situated remote from the heat input controlling device and electrical signals indicative of the temperature within the zone are transmitted to the central remote control unit, Figure 4 illustrates the constituent parts of a heating system, Figure 5 illustrates diagrammatically the application of the invention to control different parts of such a system on a zonal basis in accordance with the invention, Figure 6 illustrates diagrammatically the essential parts of the central controller for Figure 5, Figure 7, Figure 8 and Figure 9 illustrate different timing pulse generating circuits, Figure 10 illustrates how the control unit can be programmed to provide different feed inputs to different radiators at different times on different days, Figure 11 is a block circuit diagram illustrating the control of one of the valves in the system of Figure 5, and Figure 12 illustrates a modified system in which the signals controlling each zone control are supplied serially along a communication bus such as a ring main.

Detailed description of the drawings In Figure 1 the hot water feed to a radiator ID is denoted by reference numeral 12. The flow of hot water to the radiator is controlled by a valve 14 which can be opened or closed by a solenoid or motor 16.

A programmable timer 18 provides electrical signals for actuating the valve 14 in dependence on the temperature in the zone served by the radiator as dictated by the temperature sensed by the thermostat 20 located at a remote position within the zone connected to the programmable timer via a cable 22.

Power for the programmable timer in the drive unit 16 may be obtained from a power supply 24 which may comprise one or more batteries which may or not be rechargable or may its self derive power from electricity supply mains by means of a connection (not shown) to a convenient socket of a ring main associated therewith.

The programmable controller includes a four position selector switch 26 by which each 24 hour period can be divided into up to four duty cycles when heat will be supplied to the zone via the radiator 10, the beginning and ending of each duty cycle being settable using touch sensitive switches 28 for loading the start time of each duty cycle 30, for loading the off time for each duty cycle, and switches 32, 34, 36 and 38 for controlling the digits in a four digit display 42, 44, 46 and 48 respectively.

In the example shown, switch 26 allows each 24 hour period to be divided into four six hour periods between midnight and 6 o'clock in the morning, 6 o'clock in the morning to 12 midday, 12 midday to 6 o'clock in the evening, and 6 o'clock in the evening to midnight. If the heating is to come on, for example, at 5 o'clock in the morning, switch 26 is set to position 1 corresponding to the first quarter of the day, and by repetitively touching the various switches 32 to 38, so the display can be made to read 0500 hours.

Switch 28 is then pressed to insert into the memory the fact that a duty cycle is to begin at 5 a.m in the morning.

If heat is to be supplied to the radiator during the whole of the second and third quarters of the day, switch positions 2 and 3 are skipped and with switch 26 set to position 4, the turn off time can be entered in the same way as the turn on time using switches 32 to 38 after which the time which has been entered such as 1030 hours can be entered in the memory by pressing the load switch 30.

If the heating system is to go off and come on again at other times during the day then similar entries are made during the second and/or third quarters with switch 26 at the appropriate positions.

As shown, it is intended that the thermostatic control is a simple on/off device which simply indicates when the desired temperature set by the room thermostat has been attained so as to temporarily turn off the valve 14. A control circuit within device 18 is arranged to sense when the thermostatic switch is actuated once again due to falling temperature within the zone and to once again open the valve 14 and admit heat to the radiator.

By providing a similar device for each of the radiators within a heating system in which the pump and boiler are programmed to turn on at the earliest time in the 24 hour cycle at which heat may be called for and to turn off after the last time in the 24 hour cycle at which may be called for, so independent zonal control of the temperature within each of the zones heated by the different radiators of which 10 is an example, is obtained.

In Figure 2 the remote thermostatic switch 20 is replaced by a themostat 50 mounted above the valve 14. The thermostat 50 may as shown feed an electrical signal to the programmable controller 18 or, although not shown, may mechanically operate on the valve 14 to close the latter when the temperature rises to a set level and to open the valve when the temperature drops below that level.

Such devices are known per se and are commonly referred to as thermostatically controlled radiator valves.

Also shown in Figure 2 is a connection to an electricity supply mains by means of a cable 52 and plug 54 fitted in a switched socket 56.

This power supply connection is shown by way of example only, since the arrangement shown in Figure 2 may just as easily be powered by a battery pack or the like, as is the arrangement in Figure 1.

Figure 3 illustrates a further arrangment in which the programmable controller is removed from the motorised valve to a central location.

The separate programmable controllers are then replaced by a single master programmable controller 58 which serves to supply control signals to the motors or solenoid operating devices 16 of the valves 14 for each radiator of which one is shown at 10 and receives temperature information from remote thermostats such as that shown at 60 in Figure 3 and located in separate zones.

Detail of the central control unit 58 is not given in Figure 3 but may for example, comprise a bank of programmable timers each of which is similar to the item 18 shown in Figures 1 and 2, one for each of the zones supplied by the system and preferably labelled as such.

Figure 4 shows the basic ingredients of a multi-zone heating system based on hot water and radiators.

The heart of the system is a boiler 62 to which fuel such as gas or oil or solid fuel is supplied from a source 64. Electrical power is supplied via line 66.

Heat from the boiler is conveyed to the radiators within the system by means of a pump and pipes (not shown in Figure 4).

The boiler and pump are controlled by electrical signals from a central controlling unit 68 along signal path 70 and the control unit is supplied with information from separate thermostats located in each zone and illustrated diagrammatically at 72 receives signals from a hot water thermostat associated with a domestic hot water tank and supplies signals to a valve controlling the supply of hot water to the tank to prevent overheating as shown by the two signal paths 74 and 76. The hot water thermostat and associated valve means is denoted by reference numeral 78. In addition signals are provided from the controller 68 to turn on and off the zone control valves generally designated 80. One example of such a valve is found in Figure 3.

Figure 5 illustrates a heating control system applied to a domestic dwelling having six separately heated rooms comprising six zones and a domestic hot water cylinder. Within the system is located a boiler 82 and a pump 84 for circulating hot water to a flow line 86.

After passing through one or more of the parallel load circuits to be described, the water returns to the boiler via return feed 88.

The first heating load comprises a heat exchanger coil 90 located within the domestic hot water cylinder and in series therewith is a motorised valve 92 controlled by a first signal path 94 from the central controller unit 96. A temperature sensitive switch or thermostat 98 associated with the domestic hot water cylinder conveys temperature information via line 100 to controller 96.

Each of the radiators for the six rooms is supplied via its own motorised valve and the radiator and valve for room one are denoted by reference numerals 102 and 104 respectively. Within the room is located a room thermostat 106 and a signal path 108 conveys temperature information signals to the controller 96 whilst signal path 110 conveys control signals from the controller 96 to open and close the valve 104 in dependence on the programmed information within the controller and the temperature within the room sensed by thermostat 106.

Each of the other radiators is served in the same way and the signal paths to the valve 112 associated with radiator 114 in the sixth room associated with the sixth room thermostat 116, are shown at 118 and 120 respectively.

The electrical signal is diagrammatically shown in Figure 6. Within the controller 96 is located a real time clock pulse generator 122 for generating clock pulses for a central processor unit 124 which includes one or more microprocessors and memory devices.

Information can be entered into the memories and the latter can be addressed using key switches on the front of the controller denoted by the keyboard 126 and connected to the common bus 128 which also supplies the signals for the display devices and their associated drivers 130.

Each of the valves 92, 104 etc in Figure 5 is energised via a drive circuit and these are denoted at 132 and are shown as being controlled by signals from the common bus 128.

Likewise, the common bus controls the boiler and pump drivers 134.

Temperature information from the different room temperature sensing devices 98, 106 etc in Figure 5 may be in analogue form and this is converted into digital form by means of a multi-channel analogue to digital converted 136. The output therefrom is supplied via the common bus 128 to the microprocessor in the unit 124.

The real time generator 122 may take the form of a circuit synchronised to the electricity supply mains shown in Figure 7 and comprising a connection to the electricity supply mains at 138, a synchronising pulse generating circuit 140 triggered by leading or trailing edges of the electricity supply mains waveform and the output is shown being supplied to the microprocessor unit 142 forming part of the central processor unit 124.

Alternatively, as shown in Figure 8, a crystal controlled oscillator 144 may supply a high frequency to a frequency divided circuit 146 designed to produce a sub multiple of the high frequency from the crystal oscillator and to produce shaped pulses for application to the microprocessor 142.

Figure 9 shows a further alternative in which an integrated circuit which includes a crystal oscillator and frequency divider network as appropriate together with pulse shaping circuitry is contained within a single chip 148 which itself is connected to the common bus within the system and the clock pulse input for the microprocessor 150 is also connected to the system bus to be receptive of the clock pulses thereon.

Figure 10 shows in more detail the control panel of the controller unit 96 shown in Figure 5.

Here seven touch sensitive switch pads are provided at 152 labelled for each day of the week, and four further similar switch pads at 154 are labelled on-time, off-time, temperature and time.

A digital display at 156 allows the number of the radiator to be indicated (up to 9 radiators capacity) and a three element display 158 allows the time and temperature to be displayed.

Further touch sensitive switch pads at 160 and 162 allow each display digit to be increased or decreased incrementally by one, and shift key pad 164 and 166 allow the different displays to be addressed.

When the desired radiator number has been selected, the on-time button in the column 154 is touched, the touch pad 166 is touched and touch pads 160 and 162 are used to set the first digit of the time. The second and third digits can then be set after touching the touch pad 166 once and twice respectively.

After obtaining the desired read-out, the ontime for the selected radiator is loaded by touching the touch sensitive switch pad 168.

If after touching the on-time switch in column 154 and the time switch, the display in 158 is the desired on-time, then it is only necessary to touch switch 170 to confirm that time.

The off-time for the radiator indicated by the display 156 can then be checked in the same way by pressing the off-time switch pad and the time pad in column 154 and again if this is to be confirmed switch pad 170 is touched.

The temperature for the zone governed by the radiator which is indicated in display 156 can be displayed by touching the temperature switch pad 172 and this temperature can either be varied using the switch pads 160 to 166 and the new entry loaded by touching switch pad 168 or the temperature can be confirmed by simply touching switch pad 70.

In this way each of the radiators can be set to come on and go off at selected times on each of the seven days in the week and a target temperature to be attained by the zone served by the radiator can be entered for each on period for the radiator on each day of the week.

In Figure 11 details is shown of the individual drive for each motorised 90 to 104 etc (see Figure 5), and here the common bus 128 of Figure 6 is shown feeding a bus interface 174 for decoding the information on the common bus 128 and supplying appropriate signals to the drive 176. The bus interface and drivers 174 and 176 make up the unit 132 of Figure 6.

Each drive output supplies current to a relay coil 178 having a change over contact 180 associated therewith. Changeover contact is connected to one side of a source of EMF and the two contacts are connected to the close valve and open valve connections on the valve. Energisation of the relay 178 causes the source of EMF to be connected to contact 182 and on de-energisation, the changeover switch reverts to pole 184 to supply energy to close the valve.

Preferably the motorised valve operates in such a way as to inhibit the flow of current thereto when the valve has been fully opened and again when the valve has been fully closed. In this way the device controlling the valve can be rated intermittently.

Figure 12 illustrates a time division multiplex system in which the central controller 186 is arranged to convey encoded serial information along a common communication bus 188 to each of a number of zone controls 190, 192 194 and 196. These are only shown by way of example and other such devices may be employed.

Each zone controller includes a temperature sensing device such as that shown at 198 in association with zone controller 194 and flow control valve such as 200.

By transmitting coded signals along the common bus 188 so that the zone controls 190 192 etc are addressed in turn, so information from the central control unit 186 can be conveyed on a sequential basis one after another to the separate zone controllers and by providing for each separate zone controller to determine the temperature within the zone so comparison can be made with temperature information supplied by the central control unit 186 to dictate whether or not valve 200 should be opened or closed. During period of time when no heat is required, the appropriate encoded information is supplied to the zero heat zone controls and this may typically be in the form of a low temperature setting so that if the temperature within the zone has dropped to below the low temperature information, the valve such as 200 associated therewith will be turned on to convey heat to the zone even though it is not intended that under normal circumstances heat will be delivered. In this way a minimum temperature can be maintained without additional circuitry or information.

The information to be transmitted can thereby be limited to temperature information for each of the zones concened, and a simple comparison at each zone control unit determines whether or not heat is required for that zone.

Claims

1. A device for controlling the flow of heat into one zone of a multi-zone building comprising valve means by which the flow of heat into the zone can be interrupted, drive means for actuating the valve means, a time clock for supplying operating power to the drive means during one or more periods of time during each 24 hour cycle and temperature control switch means sensitive to the temperature within the same zone and adapted to actuate the valve means and interrupt the flow of heat into the zone when a desired temperature within the zone is exceeded and to re-actuate the valve means to again permit heat to enter the zone if the temperature subsequently drops below the desired temperature for that zone during any duty cycle dictated by the time clock.

2. A device according to claim 1 in which the temperature sensitive switch comprises a thermostat located within the zone at a point at which the temperature can be said to be typical of that throughout the zone.

3. A device according to claim 1 or claim 2 in which the valve means is a motorised valve in a duct conveying hot fluid to a heat outlet means.

4. A device according to claim 3 comprising a power supply for actuating the motorised valve comprising one or more batteries.

5. A device according to claim 4 in which the said batteries are rechargeable cells.

6. A device according to claim 5 in which power for charging the cells and keeping them topped up is derived from light using a semiconductor junction array for converting light into electric current.

7. A device according to claim 5 in which power for charging the cells and keeping them topped up is derived from thermocouples or the like which are located on or in the feed duct for the heat outlet means and derive energy from the heat in the duct and convert this into an electric current.

8. A device according to claim 5 in which a magnetised paddle wheel is located within the feed duct for the heat outlet means so that when fluid is flowing to the heat outlet means, the paddle wheel is rotated and a coil is provided surrounding the paddle wheel so that on rotation of the paddle wheel an electric current is induced in the surrounding coil which is rectified and used to charge the cells.

9. A device according to any one of claims 4 to 8 in which a low battery condition indicator is provided.

10. A device according to claim 3 adapted to receive power from an electricity ring main within the building to supply energy to the time clock and the valve means as required.

11. A device according to any one of claims 3 to 10 in which the time clock is adapted to make power available from a power supply during the duty cycle and the temperature sensitive switch is set to supply power to the valve means to open or shut the latter as required by the temperature level within the zone.

12. A device according to any one of claims 3 to 11 in which the motorised valve, time clock and a power supply for actuating the valve are located in a single unit adapted to be fitted adjacent the heat outlet means infeed duct.

13. A device according to claim 12 in which the temperature sensitive switch comprises a thermostat located in the zone spaced from the said single unit, and is connected thereto by means of a cable.

14. A device according to claim 12 in which the temperature sensitive switch comprises a thermostat mounted in a housing forming part of or secured to a housing containing the said valve and time clock and power supply.

15. A device according to any one of claims 3 to 11 which controls the heat flow into a plurality of said zones, each having respective said motorised valves and respective thermostats, and in which the time clock is separated from the motorised valve and the temperature sensitive device associated with each zone and provided by a central control unit incorporating a master time clock and independently programmable controllers for the different motorised valves.

16. A device according to claim 15 in which each temperature sensitive device is arranged to control its respective motorised valve directly within the zone.

17. A device according to claim 15 in which each temperature sensitive device is arranged to feed an electrical signal dependent on temperature within the zone back to the central control unit.

18. A device according to any one of claims 15 to 17 in which the duty cycle for each zone and the temperature profile required in each zone are stored in a suitable memory which is addressed during each 24 hour cycle to determine the pre-programmed requirements for each zone so that control signals can be generated by the central control unit for turning on or off the said valves for each zone.

19. A device according to any one of claims 15 to 18 in which the temperature of each zone is sensed by a thermostat having a simple on/off characteristic, on when the temperature is below and off when the temperature goes above that set by the thermostat, and the central control unit provides on/off control signals for the motorised valve controlling the input of heat to the associated zone.

20. A device according to any one of claims 15 to 18 in which the temperature sensitive device in each zone can provide an analogue or digital signal whose value is proportional to the temperature in the zone, the central control unit is programmed to control the input of heat to the zone so as to reduce the actual quantity of heat input per unit time as the temperature of the zone approaches the desired temperature until equilibrium is reached in which the heat supplied to the zone is substantially equal to that lost from the zone at the desired temperature, and the motorised value means is adjustable in steps between a fully open and a fully closed position.

21. A device according to any of claims 15 to 20 in which remote control of the valves and remote addressing of the temperature sensitive devices by the central control unit is achieved using low power radio links between a transmitting device in the central control unit and receiver devices located in each zone.

22. A device according to any of claims 15 to 21 in which low power radio transmitter units within the temperature sensitive devices are used to convey temperature information from each zone back to a receiver located at the central control unit.

23. A device according to any of claims 15 to 20 in which the electricity supply main within the building is used as a carrier for frequency modulation radio signals between the central control unit and devices in each zone.

24. A device according to claim 23 in which time division multiplexing is employed in transmitting the signals so that signals relating to one zone are transmitted during one period of time, and those for another zone during another period of time.

25. A device according to claim 23 in which the signals are encoded so as to identify the signals for and from the different zones and decoding circuits are provided at receivers for each zone and a receiver for the central control unit.

26. A device according to any one of claims 1 5 to 20 in which the central control unit receives and transmits signals from and to each zone over cables which run with the said ducts.

27. A device according to claim 26 in which the cables run within the said ducts.

28. A device according to any of claims 15 to 27 in which a different heating profile can be provided for each zone for different days in the week.

29. A device according to any one of claims 15 to 29 in which information is supplied to the central control unit information relating to the ambient temperature external to the building and the central control unit is provided with a look-up table so as to determine the optimum temperature for the said fluid to be supplied to the different zones to achieve the local heating therewithin, and the device further having means to control the input of heat to the said fluid, whereby more or less heat per unit time is conveyed to the different zones with different said ambient temperatures so that the average time for which the said valves are open remains substantially constant.

30. A device according to any one claims 3 to 29 in which the said fluid is water and the said heating outlet means comprises a radiator.

31. A device according to any one of claims 3 to 29 in which the said fluid is air and the said heating outlet means comprises an air outlet vent.

32. A device according to claim 31 in which the said motorised valve comprises louvres to close the said vent.

33. A device according to any one of the preceding claims in which the said valve means of the or each said zone is controllable to supply heat to the zone during each of a plurality of programmable periods during each 24 hour cycle.

34. A device according to any one of the preceding claims in which the said temperature sensing device in the or each zone is in the form of a temperature sensitive element having a parameter which varies with temperature so that an electrical signal can be generated having a parameter whose value varies as the temperature in the zone varies and comparison means is provided for comparing the varying parameter electrical signal with a programmed reference value for the zone concerned during each said time period and the said valve means is controlled in dependence on the said comparison.

35. A device according to any one of the preceding claims in which a low temperature sensing device is located within the or one or more selected zones and a control signal is generated therefrom in the event that the temperature within that the or any of the selected zones drops below a programmed minimum, to initiate heating of at least the zone providing the control signal until the minimum temperature has again been obtained.

36. A device for controlling the flow of heat substantially as herein described with reference to Figures 1, 2, 3 or 4 to 11 of the accompanying drawings.