GB2183068A - Control arrangement for a central heating or cooling system - Google Patents

Abstract

In a control arrangement for a central heating or cooling system, a user-programmable micro-processor is connectable with a data transmission line by means of a simple plug and socket arrangement enabling its use at a position remote from system control devices, for example on the desk of an energy manager.

Description

SPECIFICATION Control arrangement for a central heating or cooling system This invention concerns a control arrangement for a central heating or cooling system of the kind (hereinafter termed of the kind referred to) adapted to service a large building or group of buildings such as offices, factories, schools and hospitals for example.

A typical system of the kind referred to may comprise a number of oil or gas-fired boilers adapted to supply heated water to a plurality of zones for space heating purposes as well as at least one further zone including heat exchange means for maintaining supplies of hot water for washing and similar purposes. The supply of heated water is pumped and its distribution is controlled by motor driven control valves operated by a control arrangement including an enabling time clock and temperature sensing means for each zone.

With the increasing cost of energy, particularly fossil fuels, there is a growing awareness of the need for effective energy management to minimise waste and many organisations now appoint an energy manager whose responsibilities will include the setting of times and temperatures for the control arrangement for the heating system, and ensuring that they remain as set.

The use of micro-processors for the control of central heating systems is becoming increasingly popular, as they readily allow the user to enable each zone for as many chosen periods in the day as he wishes and select different periods for different days of the week. Also the micro-processor may be fed with temperature data from each zone for comparison with user-stored data enabling the user to define the required temperatures in each zone which can be varied from chosen period to chosen period.

Such a micro-processor is normally fixed at a convenient location in or adjacent to the boiler house and as such is relatively inaccesible for setting, monitoring and making of fine adjustments by the energy manager who will invariably have other duties and whose work station may be quite remote from the microprocessor.

Until recently it was necessary to connect the micro-processor with circuitry in the vicinity of the boiler house with a multi-cored cable because of the numerous components to be monitored and controlled.

British Patent Application No. 8619123 describes an arrangement wherein the micro-processor receives data and transmits control instructions in coded form through a single line.

The present invention is based upon an appreciation of the possibility of utilising the teachings of the British Patant Application aforesaid to provide a micro-processor for control of a central heating or cooling system which will be relatively accessible for adjustment at all times.

Thus according to the present invention there is provided a control arrangement for a central heating or cooling system of the kind referred to including a user programmable micro-processor adapted to receive temperature data and transmit control instructions through a data transmission line, said micro-processor being connectable with said line by means of a simple plug and socket arrangement local to the position where the micro-processor is to be used.

The micro-processor may be designed to be free standing, for example on the desk of the person responsible for its operation.

The micro-processor may be transportable between a variety of different operational locations, there being a socket entry to said line at or adjacent each such location.

The invention will be further apparent from the following description with reference to the several figures of the accompanying drawings which show, by way of example only, one form of control arrangement for a central heating system for-in the interests of simplicity-a small factory unit having only three heating zones, for office accommodation, a machine shop and hot water supply respectively, and embodying the invention.

Of the drawings: Figure 1 is a diagrammatic representation of the major components of the central heating system; Figure 2 is a block circuit diagram of the control arrangement; and Figure 3 is a plan view of the control panel to the micro-processor of the control arrangement of Fig. 2.

Figs. 1 and 2 generally show line wiring only and omit earth and return wiring in the interests of clarity.

Referring now to Fig. 1, it wil be seen that the central heating system includes an oil or gas-fired boiler 10 which will fire whenever enabled by application of mains voltage on line 10a as long as water temperature within the boiler 10 is below a predetermined safety level of 82"C say set on a cut-out thermostat (not shown) located on the boiler 10.

The boiler 10 can, under the influence of gravity, supply heated water for circulation through a coil 11 to heat water for supply to kitchen and toiler areas from cylinder 12 provided the zone control valve 13 is held open by application of mains voltage thereto through line 13a.

The boiler 10 can also supply heated water to a heating circuit for the machine shop including space heating radiators 14, or a heating circuit for the office accommodation including space heating radiators 15 when zone control valves 16 and 17 are opened by application of mains voltage to lines 1 6a and 1 7a respectively.

Circulation of heated water through the two heating circuits is assisted by a pump 18 which is operated whenever mains voltage is applied thereto on line 18a.

Turning now to Fig. 2 it will be seen that a control box 20 is provided which includes solid state switch means 21 adapted to apply or remove mains voltage to selected ones of lines 13a, 16a and 17a under the control of decoding circuitry 22 which receives coded pulses from a micro-processor 30 through line 31 including a plug and socket connection 32 adjacent the position where the micro-processor is to be used, fdr example, on the desk of an energy control manager for the factory unit. The micro-processor is arranged to be free-standing for this purpose. The plug of the arrangement is on the end of a lead extending from the micro-processor whilst the socket is secured to the fabric of the building.

Transistorised temperature sensing devices 40 are provided for each zone. Two of the devices sense air temperature in desired positions in the machine shop and office accommodation respectively, whilst the third is secured to the wall of cylinder 12 to sense the temperature of the water therein.

The devices 40 are connected to a demultiplexer circuit 41 adapted to feed an analogue current output representative of sensed temperatures to an analogue switch 42. The devices 40 can be interrogated in turn by the micro-processor 30 using again the line 31 and further decoding circuitry 43.

The microprocessor samples via an analogue to digital converter each requested analogue signal a multiplicity of tiems (say 100) in the duration of a single mains cycle and averages the results to obtain a value substantially free of any error arising from mains interference.

The analogue switch 42 is controlled by a monostable vibrator 44 actuated by decoding circuitry 22 and suitable means 21 to enable passage of the selected analogue signal for a predetermined timed period after receipt of the appropriate command to switch means 21.

The micro-processor 30 will generally be located remote from the boiler house and control box 20 and be connected therewith by a cable containing three cores at most. Two cores are used as power supply for the microprocessor and the third comprises the data transmission line 31 previously referred to. If desired connection sockets may be provided at a plurality of desired locations enabling the micro-processor to be used in one of a number of possible locations.

The microprocessor 30 is provided with both RAM and ROM in known manner and a battery reserve to ensure that memory is not lost through temporary interruption of power supply, as for example when moving the micro-processor from one location to another.

The control panel of the micro-processor 30 is shown in Fig. 3 and includes a numeric keypad 50, five function buttons 51, an LCD display 52 and a number of LED indicators 53.

In use the user first presses the "Set Time" button and keys in the current time. He then presses the "Zone" button and keys in the identifying number of the first zone to be programmed. Next the "Time On" "Time Off" and "Temperature" buttons are pressed in turn and the start time, stop time and required temperature for the selected period keyed in.

These steps may be repeated to provide as many such periods in the 24-hour day as desired, some of which may commence and terminate simultaneously.

The remaining zones are programmed in a similar manner.

All keyed in values are stored at predetermined address in RAM.

A typical program might be as follows: Zone 1-Office Accommodation Heating On 08.00 Off 18.00 Temp 20"C On 18.00 Off 08.00 Temp 8"C [Offices wil be warm for staff arriving at 9.00 am and remain so until cleaner leaves at 7.00 pm. Low heat is maintained through the night to prevent condensation and ensure frost protection].

Zone 2-Machine Shop Heating On 06.00 Off 24.00 Temp 18"C On 24.00 Off 06.00 Temp 5"C [Factory space heated for two shift working and protected against frost overnight].

Zone 3-Hot Water Supply On 06.30 Off 23.000 Temp 60"C [Hot water available whenever staff present].

The ROM of the micro-processor contains software to cause the following operations: 1. During each period of one second to send coded pulses through line 31 to actuate circuitry 43 to access ports 42 in turn to receive through line 31 temperature data from each of the three zones.

2. To compare the received data with the required data in RAM.

3. Whenever the programmed time settings and sensed temperature for any zone both call for heat to send a coded signal through line 31 to actuate circuitry 22 to operate switch means 21 to open the associated zone control valve.

4. Whenever either the programmed time settings or the sensed temperature for any zone calls for no heat to send a coded signal through line 31 to actuate circuitry 22 to operate switch means 21 to close the associated zone control valve.

The zone control valves 13, 15 and 17 include switch means adapted to apply mains voltage to line 10a to fire the boiler 10 whenever any one of them is open and also to apply mains voltage to line 1 8a to operate pump 18 whenever either valve 16 or valve 17 is open.

The LED indicators 53 can be illuminated (under control of the micro-processor) to show which parts of the system are operating at any time, whilst the LCD display 52 can be used allow the user to examine any of the preset values by actuation of the appropreaite sequence of function buttons 51.

It will be appreciated that it is not intended to limit the invention to the above example only, many variations, such as might readily occur to one skilled in the art, being possible, without departing from the scope.

Thus, for example, the micro-processor may use coded tones or other signals instead of the coded pulse signals referred to, and may have more extensive user programming faciliteis enabling different timings and temperatures for different days of the week, for example.

Additional buttons may be provided on the control panel to set any zone to a permanently on or permanently off condition.

All systems should have an overide to call for heat in frost conditions.

Claims (5)

1. A control arrangement for a central heating or cooling system of the kind referred to including a user-programmable micro-processor adapted to receive temperature data and transmit control instructions through a data transmission line, said micro-processor being connectable with said line by means of a simple plug and socket arrangement local to the position where the micro-processor is to be used.

2. A control arrangement according to claim 1 wherein said micro-processor is designed to be free-standing.

3. A control arrangement according to claim 1 or claim 2 wherein the micro-processor is transportable between a variety of different operational locations, there being a socket entry to said line at or adjacent each said location.

4. A control arrangement according to any preceding claim wherein the micro-processor has a battery reserve to ensure that memory is not lost through temporary interruption of power supply.

5. A control arrangement for a central heating system substantially as described herein with reference to the figures of the accompanying drawings.