GB2627005A

GB2627005A - Heating device and method of controlling a heating device

Info

Publication number: GB2627005A
Application number: GB2302025.8A
Authority: GB
Inventors: Moreira Novais Bianco Da Silva Gabriel; Dexter Jones Oliver; Stuart Woolley Iain; Philip John Carver Christopher; Hendrik Du Plessis Johan
Original assignee: Tepeo Ltd
Current assignee: Tepeo Ltd
Priority date: 2023-02-13
Filing date: 2023-02-13
Publication date: 2024-08-14
Also published as: GB202302025D0; WO2024170874A1

Abstract

A heating device for use in a heating system, the heating device comprising a heat source, a first control circuit board 20, and a second control circuit board 30. The heat source is configured to receive a supply of power that is controlled by the first circuit board. The first control circuit board comprises a first safety circuit 23 configured to interrupt the supply of power to the heat source upon detection of an interruption in operating the first control circuit board. The second control circuit board is configured to control the heating device. The second control circuit board is spatially separate from the first control circuit board. The second control circuit board comprises a second safety circuit 33 configured to interrupt operation of the first control circuit board upon detection of an interruption in operating the second control circuit board. Upon detecting the interruption of the operation of the first control circuit board, the first safety circuit is configured to cascade the interruption to interrupt the supply of power to the heat source. Further third 40 and fourth 50 circuit boards may also be used.

Description

Heating Device and Method of Controlling a Heating Device

Field of the disclosure

The present disclosure relates to heating devices. In particular, the present disclosure relates to a safety system for a heating device.

Background

Heating devices, typically comprise some form of heat source and also some form of control circuitry.

One known type of heating device is a storage heating device. Storage heating devices may also be referred to as dry core thermal storage devices, thermal storage boilers, dry core storage boilers, heat banks, heat batteries, storage boilers or zero emission boilers.

Storage heating devices convert electrical energy into heat using electrical heating elements or resistive heating elements and store the heat in a heat storage volume.

Typically, the storage heating devices consume electrical power at times of low demand (or excess generation) across an electricity grid or network, such as during the night, when it has a lower cost. Increasingly this can occur at any time of day due to the increase in generation from renewable sources.

Typically the heat storage volume comprises some form of core material. One such storage heating device is disclosed in WO-A-2021037865. In the storage heating device of WO-A- 2021037865, the heat is usually transferred from the core material by a fan driving a transfer fluid, such as air, between the core and a heat exchanger in a closed loop. The heat exchanger transfers the heat to a water and/or central heating system for delivering heated water as required.

In the storage heating device of WO-A-2021037865 the core material in the heat storage volume is operated up to a very high temperature. A normal operating temperature may be up to 800°C for example.

The present disclosure aims to provide an improved, or at least a commercially relevant alternative, heating device.

Summary

According to a first aspect of the disclosure, a heating device for a heating system is provided. The heating device comprises a heat source, a first control circuit board, and a second control circuit board. The heat source is configured to receive a supply of power. The first control circuit board is configured to control the supply of power to the heat source. The first control circuit board comprises a first safety circuit configured to interrupt the supply of power to the heat source upon detection of an interruption in operating the first control circuit board. The second control circuit board is configured to control the heating device. The second control circuit board is spatially separate from the first control circuit board. The second control circuit board comprises a second safety circuit configured to interrupt operation of the first control circuit board upon detection of an interruption in operating the second control circuit board. Upon detecting the interruption of the operation of the first control circuit board, the first safety circuit is configured to cascade the interruption to interrupt the supply of power to the heat source.

Thus, according to the first aspect circuitry for controlling the heating device may be distributed across a plurality of control circuit boards. In particular, a first control circuit board is provided which controls the supply of power to the heat source. In the event of an interruption in the operation of one or more of the control circuit boards, for example due to a power failure or a fault on one of the control circuit boards, the heating device of the first aspect cascades the interruption in order to prevent the supply of power to the heat source.

Thus, the heating device of the first aspect is configured to "fail safe" by way of a cascading arrangement of the first and second control circuit boards to ensure that the supply of power to the heat source is interrupted in the event of a fault in the heating device.

The first and second control circuit boards according to the first aspect are spatially separate. By providing some circuitry for controlling the heating device on a second control circuit board, separate from the first control circuit board, in the event of an interruption of the operation of the first control circuit board, it may be desirable for the second control circuit board to continue operating. For example, in some embodiments, the second control circuit board may include circuity configured to control a cooling system of the heating device. Thus, the first and second control circuit boards are interconnected in a hierarchical manner such that an interruption in the operation of the first control circuit board may not cascade (upward) to interrupt the operation of the second control circuit board.

By providing a plurality of control circuit boards, rather than a single control circuit board, the various control circuit boards may be designed or tailored for specific functions or form factors. For example, the first control circuit board may be configured to operate at a higher voltage than the second control circuit board, and therefore require a different construction to a control circuit board which is configured to operate at a lower voltage. For example, where the control circuit boards are provided as printed circuit boards, lower voltage circuit boards may benefit from reduced gauge wiring and lower heat sinking requirements. That is to say, the electronic controls for the heating device may be distributed across the plurality of control circuit boards in a cost-effective manner relative to providing the electronic controls in a single control circuit board.

According to this disclosure, a heat source may comprise a heating element configured to convert electrical energy into heat energy. As such, the supply of power may comprise a voltage supply. In some embodiments, a heat source may comprise a burner configured to convert chemical energy (e.g. gas) into heat energy. Thus, the supply of power in some embodiments may comprise a gas supply or other form of power supply. As such, where the first safety circuit of the first control circuit board is configured to interrupt the supply of power to the heat source, this may comprise interrupting the supply of electrical power to a heating element, or the supply of chemical power (e.g. gas flow) to a burner depending on the nature of the heat source.

In some embodiments, the heating device may be a boiler. That is to say, the heating device may be configured to heat water for use in a heating system and/or hot water.

In some embodiments, the heating device further comprises a heat storage volume configured to store heat output by the heat source. As such, the heating device may be a storage heating device (storage heating boiler), or heat battery. That is to say, the heating device may be configured to generate and store heat for use in a heating system. For example, the heat battery may be configured to generate and store heat for the purpose of heating water for use in a heating system. As such, in some embodiments, the heating device is configured to heat water for the heating system. That is to say, the heating system may comprise a hot water heating system, a central heating system and the like.

In some embodiments, the heating device may be a dry-core storage heating device. As such, the heat storage volume may comprise one or more different heat storage materials.

For example in some embodiments, at least approximately 25%, or at least 50% of the volume of the heat storage volume core may comprise the same heat storage material. The heat storage volume may comprise an oxidising material and may be solid. Alternatively, the heat storage volume may comprise a phase change material. The heat storage volume may comprise a metal and may comprise at least one of an iron oxide and/or a ferrous metal or iron alloy (preferably with at least 90 wt% or 95 wt% iron content and/or up to 4 wt% carbon content). The iron oxide may comprise magnetite (Fe304), hematite (Fe2O3), wustite (FeO) and/or any other suitable iron oxide.

In some embodiments, the heating device may comprise a heat extraction system configured to extract heat from the heat storage volume, wherein circuitry configured to control the heat extraction system is provided on the second control circuit board. As such in the event of an interruption of the operation of the first control circuit board, the second control circuit board may remain operational in order to continue to control the heat extraction system. Thus, the heat extraction system may remain operational in order to cool the heat storage volume. In particular, operation of the heat extraction system may increase the rate at which the heat storage volume cools such that the heat storage volume may be safe for access by an engineer.

In some embodiments, the heat extraction system comprises a motor which is configured to cause a heat transfer fluid to circulate through the heat storage volume in order to extract heat from the heat storage volume, wherein circuitry to control the motor is provided on the second control circuit board. For example, in some embodiments, the heat transfer fluid may comprise air which is circulated through the heat storage volume by a fan connected to the motor.

In some embodiments, the first control circuit board comprises a first circuit breaker circuit configured to isolate the heat source from the supply of power upon detection of an interruption in operating the first control circuit board. In some embodiments, the first circuit breaker circuit comprises a first relay configured to isolate the heat source from the supply of power. In some embodiments, the first relay may be a normally open relay, such that in the event of a power failure to the first circuit breaker circuit, the first circuit breaker circuit will "fail safe" and prevent the operation of the heat source.

In some embodiments, the heating device further comprises a temperature sensor located in the heat storage volume and configured to detect a temperature of the heat storage volume. In some embodiments, the first control circuit board further comprises a safety temperature circuit configured: to receive a signal indicative of the temperature of the heat storage volume from the temperature sensor; to compare the signal indicative of the temperature of the heat storage volume to a safety temperature threshold; and to interrupt the supply of power to the heat source if the temperature of the heat storage volume exceeds a safety temperature threshold.

Thus, the first control circuit board may also include a circuit configured to detect overheating of the heat storage volume and subsequently isolate the heat source from the supply of power. In such cases, the operation of the second control circuit board may not be interrupted due to the hierarchical arrangement. Thus, the second control circuit board may continue to operate, for example to provide cooling for the heat storage volume.

By temperature sensor, it is understood that the temperature sensor is a device configured to sense or detect a temperature and output and/or modulate a signal in response to the sensed/detected temperature. As such, a temperature sensor according to this disclosure may comprise a thermocouple, or a bi-metallic temperature switch (i.e. a thermal cut-out switch). For example, the temperature sensor may provide a signal indicative of a temperature of the heat storage volume, or a signal indicating that a temperature of the heat storage volume exceeds a safety temperature threshold. The first control circuit board may be configured to receive the signal and compare the signal to a safety temperature threshold, which may include comparing whether the signal indicates that the safety temperature threshold is exceeded.

In some embodiments, the second safety circuit comprises a second circuit breaker circuit, wherein the second circuit breaker circuit is configured to interrupt the operation of the first control circuit board upon detection of an interruption in operating the second control circuit board. In some embodiments, the second circuit breaker circuit may comprise a second relay configured to interrupt the operation of the first control circuit board. For example, the second relay may be configured to interrupt a supply of power to the first control circuit board. In some embodiments, the second relay may be a normally open relay, such that in the event of a power failure to the second circuit breaker circuit, the second circuit breaker circuit will "fail safe" and interrupt the operation of the first control circuit board.

In some embodiments, the first safety control circuit is configured to detect an interruption in operating the first control circuit board when an error in a first safety control signal of the first control circuit board is detected. In some embodiments, the second safety control circuit is configured to detect an interruption in operating the second control circuit board when an error in a second safety control signal of the second control circuit board is detected. In some embodiments, the first and/or second safety control signals are periodic signals, for example a square wave. By providing a safety control signal for each of the first and second control circuit boards, a fault, or an interruption in the operation of any firmware present on the circuit board may be indicated by an interruption to the respective safety control signal. The absence of the safety control signal, for example due to a power failure, also indicates an interruption in the operation of the circuit board. Thus, the first and second safety control circuits may be configured to operate in a fail-safe manner.

It will be appreciated that the first aspect may be provided with any number of control circuit boards arranged in a hierarchical manner. For example, in some embodiments, the heating device further comprises a third control circuit board for controlling the heating device, the third control circuit board being spatially separate from the first and second control circuit boards. The third control circuit board may comprise a third safety circuit configured to interrupt operation of the second control circuit board upon detection of an interruption in operating the third control circuit board. Upon detecting the interruption of the operation of the second control circuit board, the second safety circuit is configured to cascade the interruption to interrupt the operation of the first control circuit board which in turn cascades to interrupt the supply of power to the heat source.

Thus, in some embodiments, the first, second and third control circuit boards may be provided in a series chain, wherein an interruption in operating one of the circuit boards may cascade "down" the chain (i.e. in decreasing control circuit board number). It will be appreciated that any number of control circuit boards may be arranged in a series chain, wherein the first control circuit board is connected at the "bottom" of the chain to ensure that the supply of power to the heat source is always interrupted in the event of an interruption in operating one of the control circuit boards. In some embodiments, more than one series chain of control circuit boards may be provided, wherein the first control circuit board is connected at the "bottom" of each of the chains.

In some embodiments, the heating device further comprises a heat exchanger configured to be connected to the heating system, and a fourth control circuit board configured to control the heat exchanger, the fourth control circuit board being spatially separate from the first, second, and third control circuit boards. The fourth control circuit board may comprise a fourth safety circuit configured to interrupt the operation of the third control circuit board upon detection of an interruption in operating the fourth control circuit board. Upon detecting the interruption of the operation of the third control circuit board, the third safety circuit is configured to cascade the interruption to interrupt the operation of the second control circuit board which in turn cascades to interrupt the operation of the first control circuit board which in turn cascades to interrupt the supply of power to the heat source. As such, in some embodiments, the heating device may continue to operate a heat exchanger to supply heat to a heating system in the event of an interruption to the supply of power to the heat source. Such an operating state helps to cool the heating device more quickly and also provides additional functionality for a user.

In some embodiments, the first, second, third, and/or fourth safety control circuits are configured to detect an interruption in operating the respective first, second, third and/or fourth control circuit board when a temperature associated with the respective circuit board is exceeded, and/or when a fault condition is detected.

According to a second aspect of the disclosure, a method of controlling a heating device for a heating system is provided. The heating device comprises a heat source, a first control circuit board, and a second control circuit board being spatially separate from the first control circuit board. The method comprises: in normal operation of the heating device the first control circuit board controls the supply of power to the heat source, and the second control circuit board controls the heating device; where the operation of the first control circuit board is interrupted: a first safety circuit of the first control circuit board detects the interruption and interrupts the supply of power to the heat source; and where the operation of the second control circuit board is interrupted: a second safety circuit of the second control circuit board detects the interruption and interrupts operation of the first control circuit board causing the first safety circuit to cascade the interruption to interrupt the supply of power to the heat source.

As such, the heating device of the first aspect may be operated to perform the method of the second aspect. Any of the optional features and associated advantages of the first aspect may be applied to the method of the second aspect. In particular, the method of the second aspect may be performed using a heating device comprising a plurality of control circuit boards arranged in a cascading, hierarchical manner.

Brief description of the figures

By way of example only, embodiments of the present disclosure are now described with reference to, and as shown in, the accompanying figures, in which: - Fig. 1 shows an isometric drawing of a heating device according to an embodiment of the disclosure; - Fig. 2 shows a cross-section of the heating device of Fig. 1; Fig. 3 shows a schematic circuit diagram of the control circuit boards of the heating device of Fig. 1; and - Fig. 4 shows a circuit diagram of a first safety control circuit for a first control circuit board.

Detailed description

According to an embodiment of the disclosure, a heating device 1 is provided. An isometric drawing of the heating device 1, including a cut-away portion is shown in Fig. 1. It will be appreciated that the heating device 1 of Fig. 1 is a storage heating device.

As shown in Fig. 1, the heating device 1 comprises a heat storage volume 11. The heat storage volume 11 comprises a medium capable of storing thermal energy, principally by sensible heat storage (or antiferromagnetic and eutectoid transition effects), for extraction at a later time. In some embodiments, the heat storage volume 11 may comprise different heat storage materials. For example in some embodiments, at least approximately 25%, or at least 50% of the volume of the heat storage volume 11 may comprise the same heat storage material. The heat storage volume 11 may comprise an oxidising material and may be solid. Alternatively, the heat storage volume 11 may comprise a phase change material. The heat storage volume 11 may comprise a metal and may comprise at least one of an iron oxide and/or a ferrous metal or iron alloy (preferably with at least 90 wt% or 95 wt% iron content and/or up to 4 wt% carbon content). The iron oxide may comprise magnetite (Fe304), hematite (Fe2O3), wustite (FeO) and/or any other suitable iron oxide. Further details of suitable heat storage volumes 11 may be found in at least WO-A-2021037865.

As shown in Fig. 1, the heating device 1 comprises a plurality of heating elements 15 which provide the heat source for the heating device 1. The heating elements 15 are provided within the heat storage volume 11 and configured to supply thermal energy to the heat storage volume 11. For example, in the embodiment of Fig. 1, the heating elements 15 may be resistive heating elements which are configured to convert electrical energy into thermal energy.

The heating device 1 may further comprise a core housing 130 wherein the heat storage volume 11 is defined by the core housing 130. The heat storage volume 11 may be a sealed chamber, in particular sealed from the environment external to the heat storage volume 11 and/or heating device 1 such that gas cannot be communicated into or out of the heat storage volume 11. The core housing 130 preferably comprises a non-oxidising material, such as stainless steel. As illustrated, the core housing 130 may be substantially cuboidal such that the heat storage volume 11 is also substantially cuboidal and may comprise an open core main housing 134 and a lid 136 to seal the opening of the core main housing 134. The lid 136 may be removable for access to the heat storage volume 11 for maintenance. However, the core housing 130 and heat storage volume 11 may have any other suitable shape and/or construction.

The heating device 1 may also comprise: a base 101, wherein the heat storage volume 11 may be connected to the base 101; a heat extraction system 103 extending through the heat storage volume 11 and base 101 for heating a transfer fluid in the heat storage volume 11 and for circulating the heated transfer fluid between the heat storage volume 11 and the base 101. The heating device 1 may be configured to provide heat to a heating system. In the embodiment of Fig. 1, the heating device is configured to provide heat to an external heat demand system 105. As such, the heat extraction system 103 is configured to extract the heat from the heat storage volume 11 via the transfer fluid to transfer the heat to the external heat demand system 105 via heat exchanger 133. The external heat demand system 105 may comprise a domestic hot water circuit, domestic central heating system or hot air system or any other heat demand system.

In some embodiments, the heating device 1 may be a storage boiler wherein the external heat demand system 105 may comprise a domestic hot water circuit or domestic central heating system, wherein the heat from the transfer fluid is used to heat water.

The base 101 of the heating device 1 may comprise a base housing 111 defining an internal base chamber through which the heat extraction system 103 may extend. The base housing 111 may be connected to a base mounting plate 117, provided towards the heat storage volume 11. Fig. 2 shows a further cross-section of the heating device 1 of Fig. 1.

The heating device 1 may further comprise an insulation arrangement 120 located between and mounted to the base 101 and heat storage volume 11 for insulating the components in the base 101 from the heat of the heat storage volume 11. The insulation arrangement 120 may be mounted to and between the base housing 111, preferably to the mounting plate 117 thereof, and the core housing 130. Preferably the insulation arrangement 120 comprises at least one insulation block comprising a thermal insulating material, for example, calcium silicate or microporous board. Preferably the insulation arrangement 120 encases the heat storage volume 11 on all sides of the heat storage volume 11 (i.e. the insulation arrangement surrounds the heat storage volume 11 on all sides of the heat storage volume 11). As shown in Figs. 1 and 2, insulation passageways 125 may extend through the insulation arrangement 120, preferably entirely therethrough, to allow the communication of fluid between the core 11 and the base 101. In other embodiments the heat storage volume 11 may be mounted directly to the base 101.

The heat extraction system 103 defines a fluid circulation circuit for the transfer fluid to circulate between the heat storage volume 11 and the base 101. The heat extraction system 103 is preferably a closed loop, constant volume system. The transfer fluid is preferably air. The heat extraction system 103 may comprise a heat exchanger 133 and a fan 135, which may be mounted inside the base 101, particularly the base housing 111 thereof. The heat exchanger 133 may be located downstream of the heat storage volume 11 and upstream of the fan 135. The heat exchanger 133 is configured to extract heat from the heated transfer fluid and transfer the heat to the external heat demand system 105. The external heat demand system 105 may comprise, for example, at least one pipe circulating a fluid, such as water or air, through the heat exchanger 133 as shown in Fig. 2. The heat exchanger 133 may be of any suitable type, such as fin and tube, or material, such as brazed copper.

The fan 135 is configured to direct the transfer fluid around the heat extraction system 103. The fan 135 may be located upstream of the heat storage volume 11 and downstream of the heat exchanger 133. The fan 135 may comprise a fan inlet (not shown) for receiving cooler transfer fluid from the heat exchanger 133. For example, the fan inlet may be mounted substantially directly at the exchanger outlet (not shown). The fan 135 may comprise a fan outlet 137 out of which it drives transfer fluid towards the heat extraction system 103 and the heat storage volume 11. The fan 135 may be driven by fan motor 145, such as an electronically commutated (EC) motor. The fan motor 145 may be variable to drive the fan 135 to provide a variable flowrate and thus control the power output from the heat storage volume 11.

The heat extraction system 103 further may comprise a cooled fluid passageway 151 extending from the heat exchanger 133 to the core 11, core fluid passageways 153 extending through the core 11 and a heated fluid passageway 155 extending from the core 11 to the heat exchanger 133. The cooled fluid passageway 151 may diverge into and be connected to the core fluid passageways 153 and the heated fluid passageway 155 may be connected to and converge from the core fluid passageways 153. The cooled and heated fluid passageways 151, 153 may be located in the base 101 and, if present, insulation arrangement 120. Each core fluid passageway 153 may be provided by a fluid conduit through the heat storage volume 11. The fluid conduits extend, preferably entirely and continuously, heat storage volume 11 for enabling the transfer of heat from the heat storage volume 11, through the fluid conduits and to the transfer fluid in the core fluid passageways 153 by forced convection. The core fluid passageways 153, and the transfer fluid therein, are sealed from the core chamber 32 by, for example, the fluid conduits being sealed and mounted to the core housing 130. As a result, the transfer fluid passes through the heat storage volume 11 without contacting the heat storage volume 11.

Preferably, the fluid conduits comprise a conductive material such that heat from the heat storage volume 11 can be effectively transferred to the transfer fluid. Preferably the fluid conduits comprise a metal, for example steel, stainless steel, an Incoloy (RTM) alloy or an Inconel (RTM) alloy, or a ceramic, such as silicon carbide. Although not illustrated, the fluid conduits may comprise at least one fin on their exterior walls for improving heat transfer with the heat storage volume 11.

The heating device 1 shown in Figs. 1 and 2 comprises a plurality of control circuit boards (not shown in Figs. 1 and 2) configured to control the various components of the heating device 1. Fig. 3 shows a schematic circuit diagram of an arrangement of a plurality of control circuit boards for a heating device 1 according to an embodiment of the disclosure.

Thus, the following description of the plurality of control circuit boards shown in Fig. 3 may be used to control the various components of the heating device 1 shown in Figs 1 and 2 according to an embodiment of the disclosure. It will be appreciated that the arrangement of control circuit boards shown in Fig. 3 is not limited to the heating device of Fig. 1, and that the principle of cascading control circuit boards may also be applied to other heating

devices according to this disclosure.

As shown in Fig. 3, the heating device 1 comprises a first control circuit board 20, a second control circuit board 30, a third control circuit board 40, and a fourth control circuit board 50. Each of the first, second, third and fourth control circuit boards 20, 30, 40, 50 are spatially separate from each other. As such, each of the first, second, third and fourth control circuit boards 20, 30, 40, 50 may be located in a different region of the heating device 1. For example, the first, second, third and fourth control circuit boards 20, 30, 40, 50 may each be configured to control a different part (or parts), or system, of the heating device 1, wherein each control circuit board 20, 30, 40, 50 may be located proximal to the associated part/system of the heating device 1. In some embodiments, such as in Fig. 3, each control circuit board 20, 30, 40, 50 may comprise a printed circuit board (PCB) or other electronics substrate wherein, the various electronic circuits, and electronic components are provided on the PCB.

As shown in Fig. 3, the first control circuit board 20 is configured to control the supply of power to the heating elements 15. As shown schematically in Fig. 3, the first control circuit board comprises first firmware circuitry 21, a safety temperature circuit 22 (core over-temp), a first safety circuit 23, and a first power supply circuit 24. As shown in Fig. 3, the first control circuit board 20 also comprises a heating element circuit 25.

The first firmware circuitry 21 may be configured to perform various control functions of the heating device 1. In some embodiments, the first firmware circuitry 21 may comprise a first safety control signal generation circuit (not shown in Fig. 3). The first safety control signal generation circuit may be configured to generate a first safety control signal for the first control circuit board 20. In some embodiments, the first safety control signal may be a periodic signal. The first safety control signal may be generated by the first firmware circuitry 21 in order to indicate that the first firmware circuitry is operating normally.

For example, in some embodiments, the first safety control signal may be a square wave, a sine wave, or a saw tooth wave. In the embodiment of Fig. 3, the first safety control signal is a 1 kHz square wave, alternating between a "high" voltage of the first control circuit board 20 (i.e. indicative of a logic vale of 1) and ground (i.e. indicative of a logic value of 0), although any suitable periodic signal may be used. The first safety signal may be generated by a microprocessor, or microcontroller provided as part of the first firmware circuitry 21, or a dedicated pulse generating circuit provided as part of the first firmware circuitry 21. The first safety signal is intended to provide an indication that the first firmware circuitry 21 is operating normally. As such using a periodic signal is preferable as it may provide a positive indication that the first firmware circuitry 21 (e.g. a microprocessor of the first firmware circuitry 21) has not entered an unintended state.

In an alternative embodiment, the first firmware circuitry may be configured to output a first safety signal to a watchdog timer integrated circuit. The watchdog timer integrated circuit may be provided as part of the first firmware circuitry, or as part of the first safety circuit 23. The watchdog timer integrated circuit may be configured to output an interrupt (i.e. interrupt the operation of the first control circuit board 20) if a first safety signal is not received within a predetermined period of time. For example, the watchdog timer integrated circuit may be configured to expect to receive a first safety signal every 500 ms.

The first firmware circuitry 21 is configured to communicate the first safety control signal to the first safety circuit 23. Where the normal operation of the first firmware circuity is interrupted, the first safety control signal may not be generated. For example, a high value (logic 1) or a low value (logic value 0) may be output by the first firmware circuitry instead.

The first safety circuit 23 is configured to detect the interruption in operating the first control circuit board 20. Upon detecting an interruption, the first safety circuit is configured to interrupt the supply of power to the heating elements 15. For example, as shown in Fig. 3, where an interruption in the operation of the first firmware circuitry 21 is detected (first firmware circuitry 21 is depicted schematically in Fig. 3 as a switch), the first safety circuit 23 is configured to interrupt (i.e. break) a circuit configured to supply power to the heating elements 15.

For example, as shown in Fig. 3, the first safety circuit 23 may comprise a first circuit breaker circuit comprising a relay or similar circuit breaker. The first circuit breaker circuit is configured to isolate the heat source from the supply of power upon detection of an interruption in the operation of the first control circuit board 20. For example, in Fig. 3, the relay is configured to allow or prevent the supply of power to heating elements 15 in response to the first safety control signal. In some embodiments, the relay may be a normally open relay.

The first safety control circuit 23 is configured to detect an interruption in the operation of the first control circuit board 20 when an error in the first safety control signal is detected. That is to say, in the absence of the first safety signal, the relay may be configured to prevent the supply of power to the heating elements 15. Where the relay receives the first safety signal from the first firmware circuitry 21, the relay allows power to be supplied to the heating elements.

Where the first safety signal is a periodic signal, the first safety control circuit 23 may be configured to detect the periodic signal in order to allow power to be supplied to the heating elements 15. Where the periodic signal is not detected by the first safety control circuit 23 (e.g. a high value (logic 1) or a low value (logic value 0) is output by the first firmware circuitry 21 for an extended period of time, e.g. 0.1 s) the first safety control circuit 23 is configured to interrupt the flow of power to the heating elements 15.

An example of a suitable first safety control circuit 23 is shown in Fig. 4. In Fig. 4, the first safety control circuit 23 is configured to detect a 1 kHz square wave as the first safety control signal Vs. The first safety control signal Vs is input into the first safety control circuit 23. When the first safety control signal is present, the relay 26 (first circuit breaker circuit) shown in Fig. 4 is configured to allow power to flow to heating elements 15 by connecting terminals VH. The relay 26 may also control the flow of power to at least some of the circuitry on the first control circuit board 20 via connecting terminals Vi. As such, the relay 26 may be a double pole relay. As such, the relay 26 may be configured to prevent the flow of power to the heating elements 15 and other circuitry associated with the first control circuit board 20 when an interruption in the operation of the first control circuit board 20 is detected. In some embodiments, for example as shown in Fig. 4, the first safety control circuit 23 may comprise a charge pump circuit which is configured to receive the periodic signal (Vs) and to output a high voltage (i.e. a logic value of 1) to a switching element (e.g. a transistor) upon receipt of the periodic signal. Where the periodic signal is not received, the charge pump circuit is configured to output a low voltage (i.e. a logic value of 0) to the switching element, causing the relay 26 to open. One advantage of using a charge pump circuit to detect the periodic signal is that the charge pump circuit shown in Fig. 4 may be implemented with discrete electronic components (e.g. the charge pump circuit of Fig. 4 comprises diodes, resistors and capacitors), rather than relying on software-based control.

The implementation of a charge pump in the first safety control circuit provides an additional layer of protection to the overall operation of the safety loop. The circuit is comprised of capacitors and diodes that time the input signal Vs in order to exploit the charge transfer properties of the capacitors, alternating the charging and discharging of the first-stage series capacitor.

The rapid charging and discharging of the first-stage capacitor transfers its charge to a second-stage capacitor, causing the voltage on the second-stage capacitor to increase. When the voltage reaches a certain threshold, this switches the transistor, allowing the relay to be activated.

If the input signal Vs were held either HIGH or LOW, the DC blocking characteristics of the series capacitor would interrupt the charge transfer process, depleting the second stage capacitor and the relay would not be activated. This is a critical aspect of the fail-safe mechanism provided by the charge pump, as it ensures the protection of the system even in the event of a failure in the microcontroller, whether it be due to a hardware or firmware fault.

It will be appreciated that the relay of the first safety circuit 23 may not be the only means of controlling the flow of power to the heating elements 15. For example, the first firmware circuitry 21 may comprise a controller (not shown) which is configured to control the heating element circuit 25 in order to provide additional control of the heating elements 15 under normal operation of the heating device 1. That is to say, it will be appreciated that the first safety circuit 23 is provided in order to provide a means for interrupting the flow of power to the heating elements 15 when the normal operation of the heating device 1 is interrupted.

In some embodiments, the first control circuit board 20 may also comprise a safety temperature circuit 22. The safety temperature circuit 22 may provide a fail-safe method of preventing overheating of the heat storage volume 11. The safety temperature circuit 22 may be configured to receive a signal indicative of the temperature of the heat storage volume 11 from a temperature sensor (not shown in Fig. 3) located in the heat storage volume 11 and configured to detect a temperature of the heat storage volume. The safety temperature circuit 22 may be configured to compare the signal indicative of the temperature of the heat storage volume 11 to a safety temperature threshold and to interrupt the supply of power to the heating elements 15 if the temperature of the heat storage volume 11 exceeds a safety temperature threshold.

The safety temperature circuit 22 may comprise a comparator in order to compare the signal indicative of the temperature of the heat storage volume to a predetermined safety temperature threshold. In some embodiments of the storage heating device of Figs. 1 and 2, the safety temperature threshold may be at least about 850 °C, and may be no greater than about 1400 °C. It will be appreciated that the safety temperature threshold will depend on the materials used in the heat storage volume 11. In the embodiment of Fig. 3, the safety temperature circuit 22 is depicted schematically as a switch. As such, the safety temperature circuit 22 may be configured to cause the first safety circuit 23 to interrupt the flow of power to the heating elements 15 upon detecting a temperature of the heat storage volume 11 that exceeds the safety temperature threshold. For example, the safety temperature threshold circuit 22 may be configured to interrupt the first safety signal, or the supply of power on the first control circuit board 20 in order to cause the first safety circuit 23 to open the relay 26.

As shown in Fig. 3, the first power supply circuit 24 is shown schematically as providing power for the first firmware circuitry 21, the safety temperature circuit 22, and the first safety circuit 23. As will be appreciated from the above description, any interruption in the flow of power around the first control circuit board 20 will cause the first safety circuit 23 to interrupt the flow of power to the heating elements 15. It will be appreciated that the first power supply circuit may supply power at a lower voltage than the voltage supply used to power the heating elements 15. As such, it is preferable for the first safety circuit to use a relay to interrupt the flow of power to the heating elements 15, such that the voltages used on the first control circuit board 20 are electrically isolated from the higher voltage circuit used to power the heating elements 15.

The first power supply circuit 24 may be connected to a common voltage power supply (not shown) which is common to all of the control circuit boards 20, 30, 40, 50. The common voltage supply may be provided to all the control circuit boards 20, 30, 40, 50 via a bus (not 10 shown).

The heating element circuit 25 shown schematically in Fig. 3 comprises the heating elements 15. The heating element circuit 25 is also configured to be connected to a supply of power for the heating elements 15. The heating element circuit 25 may comprise power supply circuitry (not shown in Fig. 3) configured to receive the supply of power from an external source and transmit the power to the heating elements 15. Typically, the heating elements 15 may be supplied with alternating mains voltage (e.g. 230 V or 110 V alternating voltage). The heating element circuit 25 may also comprise additional control circuitry to allow the operation of the heating elements 15 to be controlled during normal operation. For example, one or more thyristors, or other suitable power electronics component/circuit may be provided to allow a controller to control the operation of the heating elements 15 (i.e. software-based control of the heating elements 15).

As shown in Fig. 3, the first control circuit board 20 is electrically connected to the second control circuit board 30. It will be appreciated that the circuit boards are physically separate, but connected to each other by one or more wires, or a bus or other suitable connection.

The second control circuit board 30 is configured to control the heating device 1. In the embodiment of Fig. 3, the second control circuit board is configured to control the heat extraction system 103 of the heating device 1. Specifically, the second control circuit board may comprise second firmware circuitry 31, motor circuitry 32, and a second safety control circuit 33.

The second firmware circuitry 31 may be configured to perform various control functions of the heating device 1. In some embodiments, the second firmware circuitry 31 may comprise a second safety control signal generation circuit (not shown in Fig. 3). The second safety control signal generation circuit may be configured to generate a second safety control signal for the second control circuit board 30 in a similar manner to the first safety control signal generation circuit discussed above. In some embodiments, the second safety control signal may be a periodic signal, for example a 1 kHz square wave.

The motor circuitry 32 may be configured to control the motor 145 which powers the fan 135 of the heat extraction system 103. As such, operation of the motor 145 allows the heat extraction system 103 to cause the transfer fluid to circulate through the heat storage volume 11 in order to extract heat from the heat storage volume 11. Accordingly, in the event of an interruption of the operation of the first control circuit board 20, it may be desirable for the second control circuit board to remain operational so that the motor 145 can be operated in order to utilise the heat extraction system 103 to cool the heat storage volume 11.

The second safety circuit 33 is configured to interrupt operation of the first control circuit 20 board upon detection of an interruption in operating the second control circuit board 30. It will be appreciated that the second safety circuit 33 may be provided in a similar manner to the first safety circuit described 23 above, wherein the second safety circuit 23 is configured to interrupt the operation of the first control circuit board 20. As such, the second safety circuit 33 may comprise a second circuit breaker circuit (e.g. a circuit comprising the double pole relay shown in Fig. 3) configured to interrupt the operation of the first control circuit board 20 upon detection of an interruption in operating the second control circuit board 30.

For example, as shown in Fig. 3, where an interruption in the operation of the second firmware circuitry 31 is detected (second firmware circuitry 31 is depicted schematically in Fig. 3 as a switch), the second safety circuit 33 is configured to interrupt (i.e. break) the operation of the first control circuit board 20. For example, as depicted schematically in Fig. 3, the second safety circuit 33 may be configured to interrupt the supply of power from first power supply circuit 24 to the first firmware circuitry 21 and/or the first safety circuit 23 in order to cause the first control circuit board 20 to no longer operate normally. Accordingly, the first safety circuit 23 will in turn detect an interruption in the operation of the first control circuit board 20, wherein the first safety circuit 23 cascades the interruption in order to interrupt the supply of power to the heating element 15 in the manner as described above.

As shown in Fig. 3, the second power supply circuit 34 is shown schematically as providing power for the second firmware circuitry 31, the motor circuitry 32, and the second safety circuit 33. As will be appreciated from the above description, any interruption in the flow of power around the second control circuit board 30 will cause the second safety circuit 33 to interrupt the operation of the first control circuit board 20. Similar to the first power supply circuit 24, the second power supply circuit 34 may be connected to a common voltage power supply (not shown) which is common to all of the control circuit boards 20, 30, 40, 50.

It will be appreciated that in some embodiments, a heating device 1 may be provided with only two control circuit boards 20, 30, wherein control of the various components is split between the two circuit control boards 20, 30 with regard to the hierarchical arrangement of the two control circuit boards 20, 30. As such, in the event of an interruption in operating the first control circuit board 20, the second control circuit board may remain operational in order to perform, for example, cooling or monitoring functions for the heating device 1.

As shown in Fig. 3, a third control circuit board 40 may be provided for the heating device 1. The third control circuit board may be configured to control the heating device 1.

Similar to the second control circuit board 30, the third control circuit board 30 may be spatially separate from the first and second control circuit boards 20, 30.

The third control circuit board may comprise a third safety circuit 43 configured to interrupt operation of the second control circuit board 30 upon detection of an interruption in operating the third control circuit board 40. As will be appreciated from the above description, upon detecting the interruption of the operation of the second control circuit board 30, the second safety circuit 33 is configured to cascade the interruption to interrupt the operation of the first control circuit board 20 which in turn cascades to interrupt the supply of power to the heating elements 15.

As shown in Fig. 3, the third control circuit board 40 may comprise third firmware circuitry 41, which may comprise a third safety signal generation circuit (not shown in Fig. 3), similar to the first and second safety signal generation circuits discussed above. The third control circuit board 40 may also comprise a controller 42 configured to communicate with the (external) heating system. For example, the controller 42 may be configured to communicate with the heating system in order to control a water pump connected to the external heat demand system in order to control a water flow through heat exchanger 133.

As such, the controller 42 may assist in cooling the transfer fluid in order to promote the cooling of the heat storage volume 11 if desired.

As shown in Fig. 3, the third control circuit board 40 may also comprise a third power supply circuit 44. The third power supply circuit 44 is shown schematically as providing power for the third firmware circuitry 41 and the third safety circuit 43, and may also provide power for the controller 42. As will be appreciated from the above description, any interruption in the flow of power around the third control circuit board 40 will cause the third safety circuit 43 to interrupt the operation of the second control circuit board 30. Similar to the first and second power supply circuits 24, 34, the third power supply circuit 44 may be connected to a common voltage power supply (not shown) which is common to all of the control circuit boards 20, 30, 40, 50.

In some embodiments, a further control circuit board (fourth control circuit board 50) may be provided which provides additional controls for the heat exchanger 133. Similar to the other circuit control boards 20, 30, 40, the fourth control circuit board 50 may be spatially separate from the first, second, and third control circuit boards 20, 30, 40. The fourth control circuit board 50 may comprise a fourth safety circuit 43 configured to interrupt operation of the third control circuit board 40 upon detection of an interruption in operating the fourth control circuit board 50. Based on the above description, it will be appreciated that upon detecting the interruption of the operation of the third control circuit board 40, the third safety circuit 43 is then configured to cascade the interruption to interrupt the operation of the second control circuit board 30 which in turn cascades to interrupt the operation of the first control circuit board 20 which in turn cascades to interrupt the supply of power to the heating elements 15.

The fourth control circuit board 50 may also comprise fourth firmware circuitry 41, which may include a fourth safety signal generation circuit similar to the safety signal generation circuits discussed above.

-21 -As shown in Fig. 3, the fourth control circuit board 50 may also comprise a fourth power supply circuit 54 which may be provided in a similar manner to the first, second, and third power supply circuits 24, 34, 44.

The fourth control circuit board may also comprise a heat exchanger control circuit 52 (water over-temp). The heat exchanger control circuit 52 may be configured to receive a signal from a temperature sensor (not shown) associated with the heat exchanger 133. By temperature sensor, it is understood that the temperature sensor is a device configured to sense or detect a temperature and output and/or modulate a signal in response to the temperature. As such, a temperature sensor according to this disclosure may comprise a thermocouple, or a bi-metallic temperature switch (i.e. a thermal cut-out switch). For example, the temperature sensor may provide a signal indicative of a temperature of the water in the external heat demand system 105 leaving the heat exchanger 133, or a signal indicating that a temperature of the water in the external heat demand system 105 exceeds a temperature threshold. The heat exchanger control circuit 52 may provide a fail-safe method of preventing overheating of the external heat demand system 105 by the heat exchanger 133. The heat exchanger control circuit 52 may be configured to compare the signal indicative of the temperature associated with the heat exchanger 133 to a heat exchanger safety temperature threshold and to interrupt the operation of the fourth control circuit board if the temperature exceeds the heat exchanger safety temperature threshold.

As such, the operation of the heat exchanger control circuit 52 may be similar to that of the safety temperature circuit 22 described above. It will be appreciated that interrupting the operation of the fourth control circuit board 50 will cascade down the other circuit boards 40, 30, 20, such that the heating device 1 stops outputting heat to the external heat demand system 105.

The fourth control circuit board may also comprise one or more external temperature sensor circuits 55 (shown schematically in Fig. 3), or access panel microswitches (i.e. a switch indicative that an access panel of the housing 130 of the heating device 1 is open or closed). Each external temperature sensor circuit may comprise a temperature sensor (not shown) which may be connected to the core housing 130 or any other external panel of the heating device in order to detect the temperature of the core housing 130 or other external panel of the heating device 1. In the event that a core housing temperature threshold is exceeded, the external temperature sensor circuit 55 may be configured to interrupt the operation of the fourth control circuit board 50, similar to the heat exchanger control circuit 52.

In the embodiment of Fig. 3 the fourth control circuit board 50 has a plurality of circuits 52, 55 configured to detect a temperature associated with the fourth control circuit board 50. It will be appreciated that when a threshold temperature associated with the circuit 52, 55 is exceeded, the fourth safety control circuit 50 is configured to detect an interruption in the operation of the fourth control circuit board 50. It will also be appreciated that in other embodiments, any control circuit board 20, 30, 40, 50 may be provided with a similar temperature-sensing circuit. As such, a safety control circuit for a control circuit board may be provided which is configured to interrupt the operation of the control circuit board when a temperature associated with the control circuit board is exceeded.

With reference to the diagram of Fig. 3, it will be appreciated that a method of controlling the heating device 1 in order to provide heat for the external heat demand system 103 may be provided. The method comprises operating the heating device in a normal operation mode (normal operation). In normal operation of the heating device 1, the first control circuit board 20 controls the supply of power to the heat source (heating elements 15), and the second control circuit board 30 controls the heating device 1. With reference to Fig. 3, the third and fourth control circuit boards 40, 50 also provide for the control of the heating device and/or interface with the external heat demand system 103.

The method also comprises controlling the heating device 1 when operation of one or more of the first, second, third, or fourth control circuit boards 20, 30, 40, 50 is interrupted. For example, where the operation of the first control circuit board 20 is interrupted: the first safety circuit 23 of the first control circuit board 20 detects the interruption and interrupts the supply of power to the heating elements 15. Where the operation of the second control circuit board 30 is interrupted: the second safety circuit 33 of the second control circuit board 30 detects the interruption and interrupts operation of the first control circuit board 20 causing the first safety circuit 23 to cascade the interruption to interrupt the supply of power to the heating elements 15. A similar cascading principle may also be applied to the third and fourth control circuit boards 40, 50 when an interruption in the operation of the respective control circuit board 40, 50 is detected, as will be appreciated from the above description.

Thus, according to this disclosure, a heating device 1 is provided which provides a plurality of control circuit boards 20, 30, 40, 50. The heating device 1 is configured to cascade an interruption in the operation of one or more of control circuit boards 20, 30, 40, 50 in order to prevent the supply of power to the heating elements 15. Thus, the heating device 1 is configured to "fail safe" by way of a cascading arrangement of the control circuit boards 20, 30, 40, 50 to ensure that the supply of power to heating elements 15 is interrupted in the event of e.g. an unexpected power failure in the heating device 1.

Claims

CLAIMS: 1. A heating device for a heating system comprising: a heat source, the heat source configured to receive a supply of power; a first control circuit board configured to control the supply of power to the heat source, the first control circuit board comprising a first safety circuit configured to interrupt the supply of power to the heat source upon detection of an interruption in operating the first control circuit board; a second control circuit board configured to control the heating device, the second control circuit board being spatially separate from the first control circuit board, the second control circuit board comprising a second safety circuit configured to interrupt operation of the first control circuit board upon detection of an interruption in operating the second control circuit board, wherein upon detecting the interruption of the operation of the first control circuit board, the first safety circuit is configured to cascade the interruption to interrupt the supply of power to the heat source.
A heating device according to claim 1, further comprising a heat storage volume configured to store heat output by the heat source.
3. A heating device according to claim 2, further comprising a heat extraction system configured to extract heat from the heat storage volume, wherein circuitry configured to control the heat extraction system is provided on the second control circuit board.
4. A heating device according to claim 3, wherein the heat extraction system comprises a motor which is configured to cause a heat transfer fluid to circulate through the heat storage volume in order to extract heat from the heat storage volume, wherein circuitry to control the motor is provided on the second control circuit board.
5. A heating device according to any of claims 1 to 4, wherein the first control safety circuit comprises a first circuit breaker circuit configured to isolate the heat source from the supply of power upon detection of an interruption in the operation of the first control circuit board.
6. A heating device according to claim 5, further comprising a temperature sensor located in the heat storage volume and configured to detect a temperature of the heat storage volume, wherein the first control circuit board further comprises a safety temperature circuit configured: to receive a signal indicative of the temperature of the heat storage volume from the temperature sensor; to compare the signal indicative of the temperature of the heat storage volume to a safety temperature threshold; and to interrupt the supply of power to the heat source if the temperature of the heat storage volume exceeds a safety temperature threshold.
7. A heating device according to any of claims 1 to 6, wherein the second safety circuit comprises a second circuit breaker circuit, wherein the second circuit breaker circuit is configured to interrupt the operation of the first control circuit board upon detection of the interruption in the operation of the second control circuit board.
8. A heating device according to any of claims 1 to 7, wherein the first safety control circuit is configured to detect an interruption in the operation of the first control circuit board when an error in a first safety control signal of the first control circuit board is detected; and/or the second safety control circuit is configured to detect an interruption in the operation of the second control circuit board when an error in a second safety control signal of the second control circuit board is detected.
9. A heating device according to claim 8, wherein the first and/or second safety control signals are periodic signals.
10. A heating device according to any of claims 1 to 9, further comprising: a third control circuit board for controlling the heating device, the third control circuit board being spatially separate from the first and second control circuit boards, the third control circuit board comprising a third safety circuit configured to interrupt operation of the second control circuit board upon detection of an interruption in operating the third control circuit board, wherein upon detecting the interruption of the operation of the second control circuit board, the second safety circuit is configured to cascade the interruption to interrupt the operation of the first control circuit board which in turn cascades to interrupt the supply of power to the heat source.
11. A heating device according to claim 10, further comprising: a heat exchanger configured to be connected to the heating system; a fourth control circuit board configured to control the heat exchanger, the fourth control circuit board being spatially separate from the first, second, and third control circuit boards, the fourth control circuit board comprising a fourth safety circuit configured to interrupt operation of the third control circuit board upon detection of an interruption in operating the fourth control circuit board, wherein upon detecting the interruption of the operation of the third control circuit board, the third safety circuit is configured to cascade the interruption to interrupt the operation of the second control circuit board which in turn cascades to interrupt the operation of the first control circuit board which in turn cascades to interrupt the supply of power to the heat source.
12. A heating device according to any of claims 1 to 11, wherein The first, second, third, and/or fourth safety control circuits are configured to detect an interruption in the operation of the respective first, second, third and/or fourth control circuit board when a temperature associated with the respective circuit board is exceeded.
13. A heating device according to any of claims 1 to 12, wherein the heating device is configured to heat water for the heating system and/or hot water.
14. A heating device according to any of claims 1 to 13, wherein the heat source comprises one or more heating elements configured to convert electrical power into heat.
15. A method of controlling a heating device for a heating system, the heating device comprising: a heat source; a first control circuit board; and a second control circuit board being spatially separate from the first control circuit board, wherein the method comprises: in normal operation of the heating device the first control circuit board controls the supply of power to the heat source, and the second control circuit board controls the heating device; where the operation of the first control circuit board is interrupted: a first safety circuit of the first control circuit board detects the interruption and interrupts the supply of power to the heat source; and where the operation of the second control circuit board is interrupted: a second safety circuit of the second control circuit board detects the interruption and interrupts operation of the first control circuit board causing the first safety circuit to cascade the interruption to interrupt the supply of power to the heat source.