GB2152707A - Storage heater control apparatus - Google Patents

Abstract

Relates to an apparatus controlling the supply of heat charge to storage heaters. A storage heater (6) located within a room includes a thermostat (2) responsive to the room temperature. The thermostat has a switch (3) operable at pre-selected higher temperatures, which can be set back to lower temperatures on activation of heater (4). A power control (1) connects power to the storage heater (6) under control of clock (13). During a first period the output of a ramp generator (12) is compared with the output of an outside temperature sensor (11) and is arranged by gates (9) and (8) to activate set back heater (4) until they are equal when, provided the room is cold, the switch (3) opens to cause closing of a circuit breaker (5) connected between the power control (1) and storage heater (6). During a second period clock 13 continuously energises the set back heater (4) and the supply of power to the storage heater (6) is under the control of thermostat (2). Consequently, the storage heater charging is responsive in the first period to outside temperature and responsive in the second period to room temperature. <IMAGE>

Description

SPECIFICATION Storage heater control apparatus This invention relates to apparatus for controlling the supply of heat charge to one or more storage heaters provided within an enclosure.

Known storage heaters, for example electric storage heaters, employ off-peak electricity to charge the heater with heat. The off-peak interval is a result of low consumer demand and occurs typically between midnight and 7 a.m. The cost for consumption of electricity during this interval is generally lower than the cost levied during other time intervals. Consequently efficient use of the off-peak electricity can reduce the costs resulting from the use of the heater. Heat stored in the heater can be given out, under user control, during the interval between off-peak intervals. Consequently heat is stored for future use.

Electric storage heaters are typically employed within an enclosure, for example a room. The amount of heat from the heater required to heat the room is dependent upon a number of parameters, for example residual heat charge already in the heater, the size of the heater and the room, external temperature and residual heat within the room. It is particularly important that sufficient heat is stored within the heater to ensure that adequate supplies of heat are available for the room between the off-peak intervals.

Known storage heater thermostat controllers are reactive to small differences in late evening room temperature, immediately prior to the off-peak interval, and large differences in heater input charge can occur particularly in cold weather when a high room temperature prevents the heater taking in sufficient charge.

Alternativeiy one can delay the input of the electric charge dependent on the heater and room size. Nevertheless, such delay charges can still cause insufficient or over charging to occur as a result of external temperature changes and residual charge in the heater.

It is an object of the invention to provide a storage heater control apparatus for controlling the supply of heat charge to one or more storage heaters provided within an enclosure, which apparatus is responsive to temperatures internal and external to the enclosure.

According to the invention there is provided an apparatus for controlling the supply of heat charge to one or more storage heaters provided within an enclosure comprising: supply means operable to supply heat charge to the one or more storage heaters; and control means arranged during one time interval to be responsive to external enclosure temperature and adapted to operate the supply means to supply heat charge in response to the external temperature being less than or equal to a selected reference external temperature, and arranged during another time interval to be responsive to internal enclosure temperature and adapted to operate the supply means to supply heat charge in response to the internal temperature being less than or equal to a selected internal temperature.

In this way the storage heater responds in the said one interval to external enclosure temperature and responds in said another time interval to the internal enclosure temperature. Consequently, if the another time interval is arranged to follow the said one time interval then changes in external temperature are reflected in the duration of supply of charge to the heaters followed by a duration of supply of charge to the heaters which is responsive to the internal temperature. Consequently the supply of charge is well regulated against variations in external and internal temperature.

Preferably the control means is also adapted during said another time interval to operate the supply means not to supply heat charge in response to the internal temperature being greater than or equal to a further selected reference internal temperature. Thetefore, the supply of charge is terminated during the another time interval, if the enclosure internal temperature becomes too high, thereby further regulating the supply of heat charge to the heaters.

Conveniently the control means is arranged such that the end of said one interval preceeds the end of said another time interval and preferably the said one time interval overlaps said another time interval. Therefore the supply of charge is initially determined with reference to the external temperature and subsequently with reference to the internal temperature, thereby allowing for variation in heater size and variation in retained heater charge. In use, the said one time interval can be arranged to begin when the off-peak heat charge interval starts.

In one embodiment the control means includes means to increase reference internal temperature by a predetermined amount during said overlap only in response to the supply means supplying heat charge during said overlap. In this way the effect of a high enclosure temperature before said one interval, as a result of use of the enclosure say.

does not result in early temination of charge supply.

In another embodiment the control means includes means to time dependently increase the reference external temperature during the said one interval. In this way the supply of heat charge allows for change in external temperature and delays charging according to the external temperature change characteristic.

Conveniently the control means includes a clock control defining said one time interval and said another time interval, and the supply means comprises an electrical switch connectable to a source of electrical power.

Examples of the present invention will now be described with reference to the accompanying drawings. in which: Figure 1 illustrates an embodiment of the invention in use.

Figure 2 illustrates the internal and external temperature variation and the charging for the embodiment shown in Fig. 1.

Figure 3 illustrates the operation of the embodiment shown in Fig. 1.

The embodiment illustrated in the drawings describes electric storage heaters wherein cheap electricity is available between midnight and 7 a.m. It will be apparent that different forms of heat charge could be used for the storage heaters and different time intervals employed for the supply of heat.

Referring to Fig. 1 a storage heater 6 is provided within an enclosure to be heated, for example a room in a house, Typically the enclosure is to be heated by the storage heater for a time after the expiration of possible supply of heat charge.

A thermostat 2 is provided which is responsive to the temperature of the room in a manner to open or close a switch 3 provided therein dependent on preselected internal reference thermostat temperatures Toff and Ton.

The thermostat 2 includes a setback heater 4, which when energised causes switch 3 to have the above preselected reference temperatures. If the setback heater is de-energised, the preselected temperatures are raised by a known temperature, say 5"K, to new temperatures Tioff and Tlon for the opening and closing of the switch 3 respectively.

The heat charge for the storage heater 6 is provided from a power supply 15, for example mains a/c, through a power control 1 and on lines L, N and E to the storage heater 6, the indication of letters L, N and E will he apparent. The availability of power on a circuit between lines L to N is controlled by application of clock pulses to the power control 1 from outputs A and B of a clock control 13.

The setback heater is connected from the line N through a triac 7 to a 240 volt supply.

The gate of triac 7 is connected to the output of an OR gate 8 so that when the gate output is high, triac 7 is short circuited so that setback heater 4 is energised and when gate 8 output is low triac 7 becomes open circuit so setback heater 4 is de-energised. The purpose of this circuit will be apparent hereinafter.

Notwithstanding the clock control operation of power control 1, a circuit breaker 5 is interposed on the line L between the power control 1 and the storage heater 6. The circuit breaker 5 can move to an open circuit or a closed circuit state in acordance with whether its associated coil 5a is energised. The coil F is connected from line N through switch 3 to the power controller along line L. Therefore when switch 3 is open, as illustrated by position X, coil 5a is de-energised to open circuit breaker 5 and when switch 3 is closed, as illustrated by position Y, coil 5a is energised to open circuit breaker 5.The switch 5 is therefore operable to supply heat charge to the heater 6 during time intervals defined by clock control 1 3 and in accordance with the preselected thermostat temperatures, which may be raised by de-energisation of the setback heater 4.

An external temperature sensor 11 is provided external to the enclosure where the storage heater 6 is located, in this case outside the house. The output of the sensor 11 is directly proportional to the temperature sensed and is relayed to a comparator 10 for comparison with an output from a ramp generator 1 2. The output of the comparator 10 is fed to an input of an AND gate 9, the other input of this gate is connected to the output B of the clock control 1 3. The output of the comparator 10 is high provided the output from temperature sensor 11, corresponding to the external temperature, is greater than the output from the ramp generator. The output of gate 9 is connected to the OR gate 8 input, the other input of this gate is connected to the output A of the clock control 1 3.

Referring now to ali the drawings, immediately prior to midnight the room temperature is T, and the external temperature is To; no clock pulses are produced at outputs A and B of the clock control 1 3 and therefore the output of OR gate 8 is low. Consequently the triac 7 is open circuit to de-energise the setback heater 4 so that the switch 3 has thermostat temperatures T > off and T'0 as shown in Fig. 3. Power is not available for supplying heat charge to the storage heater 6 notwithstanding the state of the circuit breaker 5.

At midnight a first time interval until 3.30 a.m. begins. In response to the start of the first time interval, output B of the clock con trol produces clock pulses which operate on power control 1 to make power available so that supply of heat charge to the storage heater 6 is directly controlled by the circuit breaker 5. The clock pulses from output B also initiate ramp generator 1 2 to produce an output signal for application to comparator 10 which is equivalent to a temperature T, as produced by sensor 11. Assuming the external temperature To is greater than the temper ature T, then the comparator output 10 is high to open gate 9 to allow clock pulses from output B to pass to and through the gate 8 to energise setback heater 4. Consequently the thermostat 2 assumes thermostat temperatures Toff and Ton. Therefore the circuit breaker 5 closes to supply heat charge to the storage heater 6 only if the room temperature is below Ton This is unlikely, however if this is the case then the room is very cold and does in fact need the heat to be supplied to the storage heater.

The output of the ramp generator 1 2 is arranged to increase in a time dependent proportional manner until at 3.30 a.m. its output at this time corresponding to a temperature T2 from sensor 11. If the external temperature To is still greater than temperature T2 then at no time during this first interval is the setback heater 4 de-energised. However, referring to Figs. 2 and 3, at approximately 1.45 a.m. the external temperature To becomes less than the temperature represented by the output of the ramp generator 1 2.

Consequently the comparator 10 output becomes low to close gate 9 and setback heater 4 is consequently de-energised so that the thermostat 2 assumes its thermostat temperatures T'off and Tlon. The most likely result is that the thermostat temperature Tlon is above the room temperature T1. Therefore the circuit breaker 5 closes and heat charge is supplied to storage heater 6. Naturally if T1 should become greater than T10ff, then the circuit breaker 5 opens to stop the supply of heat charge to the storage heater 6.

Therefore during the first time interval the heat charge is supplied to the storage heater in response to the external temperature falling below a time dependently increasing selected reference external temperature, It will be apparent that the apparatus illustrated could be arranged to supply heat charge in response to the external temperature falling below a constant or otherwise time varying selected reference external temperature. It will also be apparent that the apparatus illustrated could be arranged so that the thermostat values of thermostat 2 are not shifted upwards in the first interval during intervals of supply of heat charge to the storage heater 6.

At 3.30 a.m. the second time interval begins and continues until 7.00 a.m. The clock control 1 3 switches the clock pulse output production from output B to output A, thereby closing gate 9 to any output from comparator 1 0. The ramp generator 1 2 is effectively reset by the cessation of pulses from output B, so that the next application of pulses from output B causes the ramp generator to produce its ramp output corresponding to a temperature T1 The pulses from output A are applied to power control 1 so that power remains available, so that supply of heat charge to the storage heater 6 is still controlled by the circuit breaker 5.The clock pulses from output A pass through OR gate 8 to energise the setback heater 4 so that the thermostat 2 assumes its thermostat temperatures Toff and Ton. If the room temperature T, is greater than To then the circuit breaker 5 opens and no heat charge is supplied unless during the second interval the room temperature T1 falls below Ton. The most likely situation is that the room temperature T, is less than Toff SO that as shown in Figs. 2 and 3, the circuit breaker 5 remains closed and heat charge continues to be supplied to the storage heater 6. As illutrated in Figs. 2 and 3, at approximately 6.00 a.m. the room temperature T assumes a value greater than Toff SO that circuit breaker 5 opens.

Therefore during the second time interval the heat charge is supplied in response to the internal temperature falling below a selected reference internal temperature. It will be apparent that the apparatus illustrated could be arranged to not have an upper swtach off thermostat temperature on the thermostat 2 and would therefore continue to supply heat charge until termination of the second time interval.

The embodiment of the invention illustrated is one example only and a person skilled in the art could produce different circuits having essentially the same function. Furthermore the apparatus could be arranged such that the first and second time intervals occur in a different order and are completely separate so that they do not overlap.

In the example described it is envisaged that a normal thermostat differential of about 2K between Toff and Ton would be satisfactory, with a setback increment of 5K. It will be apparent that the apparatus illustrated would be suitable for controlling a number of storage heaters with the considerable advantage that heater size and controller setting up are not critical, and room by room adjustment would be possible.

Although the circuit illustrated shows a thermostat operating at mains voltage, it would be quite feasible for the setback heater and the thermostat contacts to operate at low voltage.

Claims (9)

1. Apparatus for controlling the supply of heat charge to one or more storage heaters provided within an enclosure comprising: supply means operable to supply heat charge to the one or more storage heaters; and control means arranged during one time interval to be responsive to external enclosure temperature and adapted to operate the supply means to supply heat charge in response to the external temperature being less than or equal to a selected reference external temperature, and arranged during another time interval to be responsive to internal enclosure temperature and adapted to operate the supply means to supply heat charge in response to the internal temperature being less than or equal to a selected internal temperature.

2. Apparatus as claimed in claim 1 wherein the control means is also adapted during said another time interval to operate the supply means not to supply heat charge in response to the internal temperature being greater than or equal to a further selected reference internal temperature.

3. Apparatus as claimed in claim 1 or 2 wherein the end of said one interval preceeds the end of said another time interval.

4. Apparatus as claimed in claim 3 wherein said one interval overlaps said another time interval

5. Apparatus as claimed in claim 4 wherein the control means includes means to increase reference internal temperature by a pre-determined amount during said overlap only in response to the external enclosure temperature causing the supply means to supply heat charge during said overlap.

6. Apparatus as claimed in any one of claims 1 to 5 wherein the control means includes means to time dependently increase the reference external temperature during the said one interval.

7. Apparatus as claimed in any one of claims 1 to 6 wherein the control means includes a clock control defining said one time interval and said another time interval.

8. Apparatus as claimed in any one of claims 1 to 7 wherein supply means comprises an electrical switch connectable to a source of electrical power.

9. Apparatus for controlling the supply of heat charge to one or more storage heaters provided within an enclosure substantially as herein described with reference to the accompanying drawings.