GB2137770A

GB2137770A - Control of Heating Systems

Info

Publication number: GB2137770A
Application number: GB08309416A
Authority: GB
Inventors: Robert John Cobbold
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-04-07
Filing date: 1983-04-07
Publication date: 1984-10-10
Also published as: GB8309416D0

Abstract

A control arrangement for a heating system for premises, such as a domestic central heating system, has a programmable control unit (9) which incorporates a timer and is connected to an electrical control circuit for a main heat source such as a boiler (1). The control unit is also connected to thermostats (5) and heat control devices such as solenoid-operated valves (6). The thermostats (5) are disposed in different zones of the premises and the control unit operates to control the main heat source and the control devices (6) independently in accordance with time and temperature information and programmed instructions relating to the different zones. The programme instructions can be entered by the user e.g. with the aid of a keyboard (11) and a display device (10) (such as an LCD device) which displays user prompts. <IMAGE>

Description

SPECIFICATION Control of Heating Systems This invention relates to the control of heating systems for premises and is particularly although not exclusively concerned with a control arrangement for a domestic central heating system.

With a domestic central heating system of the kind with which hot water is circulated from a boiler through radiators it is common to provide an automatic control arrangement incorporating an electromechanical time clock, a first thermostat arranged to monitor air temperature within a fixed zone such as a hall or living room, and a second thermostat arranged to monitor the temperature of the hot water.

However, with this known arrangement, the degree of automatic control which can be exercised over the operation of the system is limited, in that, for example, time control may be impossible outside a 24-hour cycle and may be restricted in practice to two switch-on times within such cycle, and it may not be possible to allow for different heating requirements in different zones, whereby comfortable heating with efficient energy utilisation may not be attainable.

An object of the present invention is to provide an improved control arrangement for a heating system having extensive automatic control capabilities.

According to the invention therefore there is provided a control arrangement for a heating system for premises comprising an electronic programmable control unit incorporating a timer and adapted to be connected to an electrical control circuit of a main heat source of the heating system, a plurality of electrical thermostats connected to the control unit and arranged to be disposed respectively in different zones of the premises, and a plurality of electrical control devices connected to the control unit and adapted to control distribution of heat from the said main heat source respectively to the said zones, the control unit being arranged to control operation of the main heat source and the said control devices independently in accordance with information derived by the unit from the timer and the thermostats and in accordance with pre-set control instructions stored therein relating to operational times and temperatures for the different said zones, the control unit being user addressable with said instructions.

With this arrangement it will be appreciated that extensive automatic control is feasible and that therefore a desired pattern of heating can be readily attained with efficient energy utilisation.

With regard to the nature of the control unit, this is preferably a housed unit containing microprocessor-based circuitry. User addressing for instruction purposes may be achieved by suitable manual controls on the unit for example in the form of a rudimentary keyboard having, say, number keys and a small number of function keys.

To facilitate entry of instructions the unit preferably incorporates a display device in the form of a screen on which alphanumeric messages can be shown. Most preferably an interactive display routine is used whereby, for example, the user is prompted with directions confirmatory statements and the like during entry of instructions. Conveniently said display screen may be of LCD format supplemented, if desired, by a backlight.

Advantageously, the control unit can provide auxiliary functions related to or quite separate from the space heating control function. Thus, in the former respect, the control unit may also be utilisable to control heating of a hot water supply within the premises using the same or a different boiler, the unit may incorporate a frost guard facility whereby water heating is initiated in the event that the temperature as monitored in a water circuit and/or at a zone within or outside the premises falls below a predetermined value, and the unit may be used in conjunction with a supplementary heat source (such as a solar water heater) to monitor the relative contributions from the main source and the supplementary source to the heating of the premises.In the aforementioned latter respect the unit may be used as a timer or clock for any suitable purpose, or as a control for a fire alarm or burglar alarm system.

The unit is preferably arranged to be powered from a.c. mains and incorporates a suitable power supply for production of low voltage d.c. A battery back-up may be provided to allow for mains power failure. Preferably also, some or all of the connections between the unit and input and output devices (such as the said thermostats and control devices) are effected at a low voltage level so that safely and conveniently low voltage wiring can be used. Also to facilitate wiring it is possible to use a common cable to which the input/output devices are connected via individual, addressable junction units whereby when desired data can be collected from or instructions transmitted to each device after first actuating the pertaining junction unit with a transmitted code address.

The said thermostats may be of any suitable form although preferably thermistors are used.

Similarly the said control devices may be of any suitable form depending on the nature of the heat source and thus, where hot water radiators are used said devices may comprise solenoidoperated valves.

The invention will now be described further by way of example only and with reference to the accompanying drawing which is a schematic representation of one form of a control arrangement according to the invention.

The drawing shows an arrangement for use in controlling a domestic central heating system of the kind comprising a main boiler 1 of any suitable kind and a hot water circuit including radiators positioned at different zones in the domestic premises. The boiler 1 has an electrically controlled burner 2 and the water circuit includes an electric pump 3, whereby the heating of the premises can be controlled automatically by switching the burner and the pump on and off in accordance with pre-set time and temperature parameters.

The control arrangement includes a water thermostat 4 in the form of a thermistor arranged to monitor the temperature of the water in the boiler, and also a plurality of air thermostats 5 arranged to monitor the air temperature in different zones of the premises (e.g. in different rooms). Further, each radiator is provided with a respective electrical (e.g. solenoid-actuated) water shut-off valve 6.

As shown in the drawing, the pump 3, the electric burner control 2 and the various thermostats 4, 5 and electrical valves 6 are connected to a common cable 7 via respective electronic junction units 8 (described in more detail hereinafter), which cable 7 is connected to a main control unit 9 disposed at a convenient location in the premises (e.g. near to the boiler).

The control unit 9 comprises a microprocessorbased circuit contained within a housing box. The unit also includes an elongate LCD display device 10 (say having a 20 to 80 character display capability on one or two lines) which is visible through a window in the box, a number of manually operable keys 11 accessible externally of the box, a power supply within the box which produces a low d.c. operating voltage from a.c.

mains, and various input/output connections.

As desired, the control arrangement may also include one or more other features as follows.

Backlight illumination may be provided for the LCD device.

The premises may be provided with a supplementary heat supply in the form of a solar heater (not shown) comprising for example, solar energy-absorbing pipes located on a roof surface or elsewhere as appropriate and through which water can be circulated, such water circulation being associated directly or indirectly with the radiator circuit. In this case, a thermostat and an electrical control valve and/or a pump may be provided respectively to monitor the temperature of the water in the pipes and to switch on and off circulation of such water. Such thermostat/ valve/pump may also be connected to the aforesaid cable 7.

In so far as the microprocessor-based circuitry has spare capacity, provision may be made for connection of the unit to a fire alarm or burglar alarm system.

In the case where there is a domestic hot water supply, this may use a hot water tank heated by a circuit connected to the same boiler 1 as that used for the central heating system and an electrical control valve and/or pump may be provided for switching flow of water on and off through such circuit. If desired a separate thermostat may be provided for monitoring the temperature of the hot water supply. Such control valve/pump/thermostat may also be connected to the aforesaid cable 7.

The control arrangement so far described can be used as follows: After installation of the control arrangement, utilising the convenient cable connection mentioned above (and described more fully hereinafter), the control unit is set for the desired operational periods and temperatures for the central heating system in relation to different zones of the premises.

With regard to the setting of operational periods, the control unit includes a timing circuit which monitors current time and date after initial calibration. The times and dates for operational periods can then be entered via the keys 11. It will be understood that it is possible to provide for entry of a complex operational program over a relatively long period of time allowing for example for different heating requirements due to seasonal differences, holiday absences etc.

With regard to the temperature and zone settings, for each zone a respective required target temperature can be entered via the keys 11. It will also be understood that the temperature and zone settings in that provision can be made for different zones to be switched on and off at different times and for the target temperature in any zone to be changed at different times.

Time/date calibration and setting of operational temperatures, periods and zones (and also the obtaining of information pertaining to the existing operational parameters of the system) is effected on an interactive basis, that is, instructions are entered by the user in response to directions displayed on the device 10.

This may be effected in accordance with a number of sequential routines initiated by pressing an appropriate function key 11. For example, there may be six such function keys 11 labelled respectively "set day/time", "program", "display program", "override program", "suspend program", "display temp", and the respective routines may operate on the following lines: 1. Set day/time: after pressing this kay, directions such as "enter current day", "enter current hour" etc. are displayed in sequence, each such display being held until the requisite data is entered via appropriate keys 11 (e.g. numerical keys). Each entry is checked for validity before it is recorded and the next direction is displayed. If invalid, an error message is displayed and there is then an opportunity to enter correct data. After setting of the date and time these are displayed and continually updated. The display automatically reverts to time and date a short period of time (say 30 seconds) after the last step of each of the following routines.

2. Program: after pressing this key, directions such as "enter zone No. requiring new cycle", "enter day for start of cycle", "enter minute at end of cycle", "enter target temperature" etc. are displayed sequentially subject to the entry of valid data as appropriate. Valid entered data is recorded for control purposes.

3. Display Program: after pressing this key directions such as "enter zone No. required", "enter time cycle required" etc. are displayed sequentially subject to the entry of valid data as appropriate. After entry of the last data the LCD device displays the requested information: i.e. the recorded control program relating to the identified zone and cycle is shown.

4. Override Program: after pressing this key directions such as "entre zone No. requiring override", "enter target temperature required" etc. are displayed sequentially subject to the entry of valid data as appropriate. After entry of the last data this supplants the pre-existing data relating to the zone in question for a predetermined period of time (say one hour) after which the program reverts to the pre-existing data.

5. Suspend Program: after pressing this key directions such as "enter No. of days program to be suspended" "enter day of start of suspension" etc. are displayed sequentially subject to the entry of valid data as appropriate. After entry of the last data this is recorded and modifies the pre-existing program. Subsequent reversions to the preexisting program can be effected via the override program key.

6. Display Temp: after pressing this key the direction "enter zone No. required" is displayed and after entry of valid data, the temperature monitored by the pertaining thermostat is displayed.

The above routines represent a brief outline by way of example only. In practice the range and context of directions will vary as required. Thus, the listed routines and/or other routines may encompass the water temperature as well as the zone air temperatures, the control parameters of the hot water supply system, the control parameters of any auxiliary system such as a solar heater system and the like.

For protection purposes, keyboard isolation may be provided to prevent unauthorised tampering with the control unit. This may involve a key switch or a detachable plug or a code routine which has to be entered via the keys 11 before the control unit can be addressed or otherwise.

As indicated in the drawing, the control unit is connected to the various thermostats and other devices via a common cable 7 which may be fourcore having the following leads: a main power supply lead 12, an address lead 13, a data lead 14, a ground lead 1 5. The cable carries low power d.c. voltage say no greater than 24V 100 ma.

Each device 2 to 6 is connected in parallel with the cable 7 via its respective junction unit 8 which comprises an addressable transducer. The transducer is powered by the supply and ground leads 12, 1 5 and acts to control connection of the pertaining device 2 to 6 in accordance with signals received from the address lead 1 3. That is, in the case of a thermostat 5, whenever data is required from any one thermostat, the control unit 9 transmits an appropriate serially encoded address signal unique to the junction unit 8 associated with the particular thermostat 5 and this causes the thermostat to be connected to the data and ground leads 14, 15. Digitally encoded temperature data can then be obtained from the thermostat.In the case of a valve 6 or the pump 3, or the burner control 2, connection of each of these to operating power supply can be controlled by a local switch 1 6 operated by the pertaining junction unit 8 (e.g. an optically isolated triac switch) in correspondence with address signals fed thereto. The operating power supply may be derived locally e.g. by connection to a.c. mains, although in the case of the control valves 6, where these have a low voltage low power consumption rating it may be possible to derive power from the leads 12, 1 5.

The transmission of address signals to the various junction units 8 may occur periodically on a regular, predetermined basis and/or may occur as required in accordance with program instructions or otherwise.

The control operation of the unit 9 may be influenced by certain predetermined factors, in addition to the program instructions.

Thus, for example, in the event that data from a thermostat is missing or anomolous, the control unit may switch the associated radiator on and off in correspondence with a switching pattern, based for example on switching of other radiators, rather than wastefully keeping the radiator permanently switched on. Also, the system may include a frost guard whereby the heating is switched on if the temperature monitored by any thermostat falls below say 50C. Where a solar heater system is provided, the control unit may selectively utilise heat from the boiler and from the solar heater in accordance with a pattern directed towards optimising energy utilisation.

With the arrangement described above, by virtue of the extensive control facility, it will be appreciated that it is possible to achieve comfortable and convenient heating without undue wastage of fuel energy. Moreover, having regard to the mode of temperature monitoring (i.e. using thermistors with microprocessor-based circuitry) it is possible to achieve temperature control with low hysterisis, say within 1 OC.

Further, it is possible readily to make provision for extension or adaptation of the control arrangement to suit changing requirements.

It is of course to be understood that the invention is not intended to be restricted to the details of the above embodiment which are described by way of example only.

Claims

1. A control arrangement for a heating system for premises comprising an electronic programmable control unit incorporating a timer and adapted to be connected to an electrical control circuit of a main heat source of the heating system, a plurality of electrical thermostats connected to the control unit and arranged to be disposed respectively in different zones of the premises, and a plurality of electrical control devices connected to the control unit and adapted to control distribution of heat from the said main heat source respectively to the said zones, the control unit being arranged to control operation of the main heat source and the said control devices independently in accordance with information derived by the unit from the timer and the thermostats and in accordance with pre-set control instructions stored therein relating to operational times and temperatures for the different said zones, the control unit being user addressable with said instructions.

2. A control arrangement according to claim 1, wherein the control unit comprises a housed unit containing microprocessor-based circuitry.

3. A control arrangement according to claim 2, having manual controls on the unit for said user addressing thereof.

4. A control arrangement according to claim 3, wherein said manual controls comprise keys.

5. A control arrangement according to claim 3 or 4, wherein said unit incorporates a display device in the form of an alphanumeric screen.

6. A control arrangement according to claim 5, wherein an interactive display routine is used whereby the user is provided with prompts on the screen during entry of instructions.

7. A control arrangement according to claim 5 or 6, wherein the display device is an LCD device.

8. A control arrangement according to any one of claims 1 to 7, wherein the control unit is also arranged to control heating of a hot water supply.

9. A control arrangement according to any one of claims 1 to 8, wherein the control unit also incorporates a frost guard facility whereby water heating is initiated in the event that a monitored temperature falls below a predetermined value.

10. A control arrangement according to any one of claims 1 to 9, wherein the control unit is also arranged to monitor the relative contribution of the main heat source and a supplementary source to the heating of the premises.

11. A control arrangement according to any one of claims 1 to 10, wherein the control unit is also arranged to be used as a clock or timer.

12. A control arrangement according to any one of claims 1 to 1 0, wherein the control unit is also arranged to be used as a control for a fire alarm.

13. A control arrangement according to any one of claims 1 to 10, wherein the control unit is also arranged to be used as a control for a burglar alarm system.

1 4. A control arrangement according to any one of claims 1 to 13, wherein the thermostats and control devices are connected via individual addressable junction units to a common cable connected to the control unit.

1 5. A control arrangement according to any one of claims 1 to 14, wherein the thermostats comprise thermistors.

1 6. A control arrangement according to any one of claims 1 to 15, wherein the control devices comprise solenoid-operated valves.

1 7. A control arrangement substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.