HEATING SYSTEM

Abstract: A heating system having a common boiler for supplying heated water to a number of apartments or offices. Each apartment has a thermal store (48) which is rechargeable with hot water when the temperature therein falls. An integrated store controller (40) controls heating requests as well as calculating the heat usage. It also has access to a prepayment unit (55) which allows credit to be provided. Requests for heat from the integrated store controller (40) can be sent to the common central controller (45) operating the boiler via a bus (42). A hand held unit (56) allows access by authorised persons to the integrated controller (40) and prepayment unit (55) for set up and checking purposes.

Description: HEATING SYSTEM The invention relates to heating systems and more specifically to the type used to supply a number of apartments, offices of the like, in a building from a common boilerhouse. According to the invention there is provided a heating system having a common boiler for supplying heated water to a number of apartments or offices and including a water storage device within each apartment or office heated with water supplied by the common boiler, temperature sensing means, and an integrated control device in each location associated with the water storage device having means for controlling heating requests in the system and means for calculating heat usage dependent on volume of water utilised and sensed temperatures. Further according to the invention there is provided an integrated control device for a heating system including means for controlling heating requests in the system and means for calculating heat usage dependent on the volume of water utilised and sensed temperatures. Further according to the invention there is provided a heating system having a common boiler for supplying heated water to a number of apartments or offices and including a water storage device within each apartment or office and heated with water supplied by the common boiler, and first and second temperature sensing means within the water storage device and arranged to request recharging of the water store when both the first and second sensed temperatures are below a threshold. The invention will now be described by way of example with reference to the accompanying drawings in which; Figure 1 shows a heating system the subject of our copending application; Figure 2 shows the heating system of the invention with a sophisticated thermal store controller; Figure 3 shows in more detail aspects of the Figure 2 system; Figure 4 shows in more detail the display and other aspects of the thermal store controller; and Figures 5 to 10 show flow charts for various functions. Figure 1 shows a system, the subject of our copending patent application, which includes a heating arrangement 10 for an apartment which is supplied from a common boiler system 12 which supplies similar arrangements in other apartments via outgoing pipe 13 and return pipe 14. A water store 15 is provided with an electronic controller 30 which is connected to two thermostats (SI and S2) to allow the water store temperature (S2) to be determined as well as that of the incoming water (SI) from the boiler 12 via valve 24. The electronic controller 30 can supply control information to the boiler by cable connection 33 thereto. Solenoid valves VI and V2 are provided and controlled by controller 30. The system includes a pump 32 for the main pipe circulation. Radiator 17 receives water via pipe 19 which returns via pipe 20. A water coil 35 receives a supply of cold water at inlet 36 and coil 35 acts as a heat exchanger to heat the water which passes from outlet 37 to taps for basins, baths and so on. A manual or thermostatic mixer 38 can adjust the heated water temperature to a desired user temperature. A meter 21 records the heat supplied and/or water supplied to the store. When the water store temperature drops (when water is being drawn, for example) this will be sensed by S2 and a signal sent to the boiler to pump water to the tank. SI senses the incoming water temperature and only allows VI to open if this incoming water temperature is sufficiently high. V2 operates under the controller 30 to return this water should it be too cold via pipe 22 and valve 23. Whilst the arrangement is an improvement on earlier systems giving fairer metering of usage, the system now described has additional advantages and features. In the arrangement shown in Figure 2 a bus system can be utilised to increase control flexibility and share wiring requirements and the additional components allow a sophisticated diagnostic and metering system to be incorporated. The electronic controller 30 of Figure 1 is now replaced by a sophisticated thermal store controller 40 mounted in thermal store 48 which controller is microprocessor based and capable of a number of functions including system control and metering and display. The display 41 can display the function selected via push button switches 43. The controller is linked to a common bus 42 (for all apartments) via appropriate socket outlets 46 in each apartment which allows each access to the bus on a time sharing basis and hence to the central controller 45 associated with the shared boiler as before via switching box 47. The thermal store controller 40 will have access to a metering sensor and temperature sensors to allow control and measuring functions to be effected as described in more detail below. The system also includes a prepayment unit 55 connected to controller 40 to allow a mechanism for advanced payment of the heat utilised. The prepayment unit can be charged via a prepayment charger 50 mechanism with printer 58. A hand held unit 56 allows the utility operator to visit the apartment and set up operation of the system, run diagnostic tests or read the meter. Access to the prepayment unit for reading can also be achieved by the hand held unit 56 using optical device 60. If required remote access to the central controller can be given using remote console 57 which has a communication link via telephone line 61 for example. The prepayment unit 55 includes a display 62 and keypad 63 and is designed to allow customers to prepay and receive heat tokens from the landlord or local store, for example, who will use the prepayment charger 50 to generate a unique code via printer 58. This number is entered by the customer into prepayment unit 55 using the keypad 63. Thus the number is a 'one off which only applies for that particular purchase of credit. Remaining credit is normally displayed on display 62. The thermal store controller 40 monitors the heat utilised and when heat credit is used up will shut off the supply of hea . An alarm giving warning of low credit can be incorporated. A further purchased heat token will allow credit to be restored. The heating system employing the controller 40 is now described in more detail in Figure 3. The system controller 45 is connected to bus 42 which is common to all apartments and a polling system allows access on a sequential basis. In each water heating system arrangement 10 in each apartment, additional temperature sensors S4 (for room ambient temperature) and S3 (for water temperature at the bottom of the thermal store 48) are provided as well as incoming water sensor SI and upper water thermal store sensor S2. They are connected to the controller 40 for operational control as now described, which can send signals via the bus 42 to the controller as well as operate motorised valves VI and V2 and the pump 32. The sensors SI and S3 are used both for controlling the system utilisation and also for measuring heat utilised so as to give accurate heat metering. The control arrangement with the by¬ pass prevents negative utilisation hence the heat meter will give an accurate consumption value. S3 sensor is also used in combination with S2 . to adjust utilisation. In this embodiment, both S2 and S3 must call for heat before water is allowed to pass into the store. S2 and S3 may be set at different temperatures . S2 will need to initiate the recharging of water (not S3) . Even if S3 indicates a low temperature this alone will not suffice to request recharging. As the hot water enters the store, S2 will be satisfied first but the water is allowed to continue to enter (so heating the lower part of the store) such that S3 will eventually be satisfied. At this point the store controller 40 will halt the receipt of further heating water. This charging to the bottom of the store allows a larger store to be used more effectively. Requiring S2 to be the initiating temperature avoids heating the store just because a small amount of cold water is present in the region of sensor S3. The store controller system also uses the sensors S1-S3 for diagnosis programs and can check valve operations, etc. for determining correct system functioning. The controller 40 receives information on the amount of credit from the prepayment unit 55 and will count pulses from the metering sensor 65. This controller 40 can determine the amount of utilisation and when credit is exhausted can isolate the supply by activating the motorised valves to prevent further utilisation. The temperature from sensor S4 can also be used to determine room temperature to act as a frost protection mechanism when this temperature falls below a predetermined value. The heating can then be automatically initiated. The thermal store controller 40 is shown in more detail in Figure 4 and includes a liquid crystal display 41 with a number of functions including current water temperature display 63 and heat consumption display 62. A number of display indicia 64 show other display functions such as status of operation and day of week. A particular selected display or operation can be selected via controls 43. Hence the time of day can be selected as an alternative to heat consumption display. Room temperature can be selected as an alternative to water temperature. The controller 40 also acts as a timer device for programming purposes to select periods of operation for heating radiators for example. Diagnosis tests can also be effected. External sensors S1-S4 (e.g. platinum resistance devices) allow various temperatures to be determined. The controller 40 can control valves VI, V2 and pump 32. Two way communication between bus 42, prepayment unit 55 and hand held unit 56 is available. The controller includes a CPU 70 with real time clock 71 and associated memory 72 on the bus which allows receipt and outputting of information via interface 74. The temperatures for tl through to t4 can be preset and each temperature will have an OFF setpoint and an ON setpoint. Such temperatures can be as follows. able 1: Control sensor factory set points The controller 40 can compute the heat utilised by employing pulses from the metering sensor indicative of flow rates of water. The flow chart for this activity is shown in Figure 5. The heat consumption q = F PcpCp (tj-t 3 ) . Where F is a scaling factor and Pc is based on the pulse count. p is the density of water - corrected for temperature and Cp is the specific heat of water corrected for temperature. t, is the temperature measured from SI and t 3 is the temperature measured from S3. The total is accumulated to give the current total. If a fault is detected the register in the microprocessor will generate the appropriate error flag. The controller also uses the same microprocessor to perform heating circulation control as shown in the flow chart of Figure 6. This operation takes into account the credit in the prepayment unit and temperature readings. DT 2 is a delay timer in the processor which allows a brief period to elapse to ensure system change has occurred and can be detected before the next step is carried out . FR7 and FR10 are fault registers for fault conditions with appropriate flags. When the temperature of the water thermal store 48 falls it needs recharging and the logic flow diagram for this control is shown in Figure 7(a) & (b) . As mentioned above, the system can operate in a frost protection mode and when selected will cause the controller 40 to operate as in the flow chart of Figure 8. The controller is also configured to carry out a periodic actuation of the pump 32 to avoid it 'sticking' as this is a common fault. Figure 9 shows the heating pump exercising flow chart. Preset time settings of the appropriate timers are shown in the table below. Table 2: Initial factory settings of timers Function Timers Factory set value Pump exercising interval DTI LTI = 48 h timer Pump on time - When T 2. , = 15 s exercising Pump on time - For frost DT2 LT 2.2 = 30 m protection Pump on time - For detecting LT 23 = 90 m pump failure Charge control fault timer - bypass valve and main pump/plant failure LT 3-1 = 300 s - main valve and pump/plant DT3 failure LT 32 = 300 s DT4 LT4 = Finally a fault status checking 'routine' is provided by the controller 40 and operates as shown in Figure 10. Errors will cause registers FR8 and FR9 to generate appropriate fault flags.

Claims: CLAIMS 1. A heating system having a common boiler for supplying heated water to a number of apartments or offices and including a water storage device within each apartment or office heated with water supplied by the common boiler, temperature sensing means, and an integrated control device in each location associated with the water storage device having means for controlling heating requests in the system and means for calculating heat usage dependent on volume of water utilised and sensed temperatures. 2. A system as claimed in claim 1 including prepayment means and wherein the integrated control device includes means for interacting with the prepayment means to allow heating requests to be controlled dependent on prepaid credits. 3. A system as claimed in claim 1 or 2 wherein the integrated control device includes means for carrying out diagnostic tests for the system. 4. A system as claimed in claim 1, 2 or 3 wherein the integrated control device includes means for periodically exercising a water circulation pump ensuring the device does not become inoperative due to prolonged non- utilisation. 5. A system as claimed in any one of claims 1 to 4 wherein the integrated control device includes means for automatically activating the system when a temperature approaching the freezing point of water is reached to prevent system damage. 6. A system as claimed in any preceding claim including a portable device configured to allow control and diagnostic functions to be effected by the integrated control device on instruction from an authorised operator. 7. A system as claimed in any preceding claim wherein the temperature sensing means include upper and lower temperature sensors within the water storage device and the integrated control means includes means for recharging the store with hot water following a fall in temperature detected by both the upper and lower sensor. 8. A system as claimed in claim 7 wherein the control device is configured to operate when a temperature on the upper sensor is higher than that of the lower sensor. 9. A system as claimed in any preceding claim wherein the integrated control device includes means for commissioning the system. 10. An integrated control device for a heating system including means for controlling heating requests in the system and means for calculating heat usage dependent on the volume of water utilised and sensed temperatures. 11. A heating system having a common boiler for supplying heated water to a number of apartments or offices and including a water storage device within each apartment or office and heated with water supplied by the common boiler, and first and second temperature sensing means within the water storage device and arranged to request recharging of the water store when both the first and second sensed temperatures are below a threshold. 12. A heating system substantially as described herein with reference to Figures 2 to 10 of the accompanying drawings. 13. An integrated control device substantially as described herein.

Inventors: GATAORA SANTOKH SINGH, GATAORA, SANTOKH, SINGH
Applicants: BRITISH GAS PLC, GATAORA SANTOKH SINGH, GATAORA, SANTOKH, SINGH
Application year: 1996
Main classification: F24D11
IPC codes: F24D11