GB2535738A

GB2535738A - A method of monitoring the usage of a boiler, a boiler and a boiler usage sensor

Info

Publication number: GB2535738A
Application number: GB1503153.7A
Authority: GB
Inventors: Shermer John
Original assignee: Lightwaverf Tech Ltd
Current assignee: Lightwaverf Tech Ltd
Priority date: 2015-02-25
Filing date: 2015-02-25
Publication date: 2016-08-31
Anticipated expiration: 2035-02-25
Also published as: WO2016135494A1; GB2535738B; GB201503153D0

Abstract

A boiler 100 comprises a combustion chamber 102 in which a fuel is combusted. An electrically powered pressure control means, ideally a fan 120, controls pressure in the combustion chamber. An electrical current supplied to the fan is monitored, thereby monitoring usage of the boiler. Preferably a sensor 126, which may be a transformer sensor, Hall effect sensor or iron vane sensor, is used to detect electrical current supplied to the fan from an external power transmission source 127. The sensor ideally sends readings of electrical current supplied to the fan to a processing unit 130 via a wireless transceiver 132 and the processing unit determines whether the boiler is in an on-state or an off-state based on the readings. Monitoring boiler utilisation by sensing electrical current to the fan requires only simple retro-fitting of a boiler compared with monitoring utilisation by detecting a quantity of fuel received from a fuel source 106 using, for example, a gas usage sensor.

Description

Intellectual Property Office Application No. GII1503153.7 RTM Date:29 December 2015 The following terms are registered trade marks and should be read as such wherever they occur in this document: Calor (page 6) Intellectual Property Office is an operating name of the Patent Office www.gov.uk /ipo A method of monitoring the usage of a boiler, a boiler and a boiler usage sensor The present invention relates to a method of monitoring the usage of a boiler, a boiler and a boiler usage sensor. The present invention is particularly applicable to a domestic or commercial combination boiler which is arranged to combust natural gas.

It is useful to collect information regarding the usage of a boiler so that the amount of gas used can be calculated and the efficiency of the boiler determined. This can be of particular use when evaluating the performance and efficiency of a central heating system. It may, for example, be useful to determine the amount of gas used to achieve a certain temperature within a building. Such information may however be difficult to obtain. It may be difficult to directly measure the amount of gas that has been combusted within the boiler in a certain time period. For example, existing boiler installations may not be equipped with any means that provides an indication of when the boiler is being used (i.e. when gas is being combusted by the boiler). Modifying an existing boiler installation to include such a gas usage sensor may require significant changes to the internal components of the boiler. Such a task is technically complex and can only be performed by a skilled technician because of the need to meet safety requirements when servicing or modifying a boiler.

in a first aspect, the present invention provides a method of monitoring the usage of a boiler, the boiler comprising a combustion chamber arranged to combust fuel; and an electrically powered pressure control means arranged to control pressure in the combustion chamber, wherein fuel is combusted in the combustion chamber when an electrical current is supplied to the pressure control means, the method comprising: monitoring the electrical current supplied to the pressure control means, thereby monitoring the usage of the boiler.

The inventor has realised that by monitoring electrical current supplied to the pressure control means an accurate, non-invasive, indirect determination of whether fuel is currently being combusted by the boiler can be made. The pressure control means is activated to provide a pressure gradient (e.g. a draught) within the combustion chamber while the fuel is being combusted. Therefore determination of whether electrical current is being supplied to the pressure control means will provide an indirect indication that the fuel has been ignited within the combustion chamber and is being combusted.

Optionally, the pressure control means may have an on-state in which electrical current is supplied to the pressure control means and an off-state in which electrical current is not supplied to the pressure control means. The pressure control means may therefore vary between two discrete states: an off-state in which substantially no current is supplied and the pressure control means is not activated; and an on-state in which a non-zero current is supplied and the pressure control means is activated. In other embodiments, the off-state may correspond to a current that is greater than zero, but low enough that the pressure control means is not activated.

Optionally, determining whether the pressure control means is in the on-state may comprise determining whether the electrical current is equal to or above an 'on' threshold value. An 'on' threshold current may be set between the current corresponding to the off-state and the current corresponding to the on-state. Determining whether the current is equal to or above the 'on' threshold advantageously provides a reliable indication that the pressure control means is in the on-state.

in some embodiments, the 'on' threshold may be set at one of 0. I A, 0.5 A, 1 A, 5 A, 10 A, 15 A or may be in a range defined between any one of those values. In some embodiments, the 'on' threshold may be set at a proportion of the maximum current (or power) supplied to the pressure control means. This maximum value may vary depending on the specific boiler with which the invention is implemented. The 'on' threshold may for example be set as 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 99% of the maximum, or any range defined between any one of those values.

Optionally, determining whether the pressure control means is in the off-state may comprise determining whether the electrical current is less than or equal to an 'off threshold value. An 'off' threshold current may be set between the current corresponding to the off-state and the current corresponding to the on-state. The 'off' threshold current may be less than or equal to the 'on' threshold current. Determining whether the current is equal to or less than the 'off' threshold advantageously provides a reliable indication that the pressure control means is in the off-state.

in some embodiments, the 'off' threshold may be set at one of 0.1 A, 0.5 A, 1 A, 5 A, 10 A, 15 A or may be in a range defined between any one of those values. in some embodiments, the 'off' threshold may be set at a proportion of the maximum current (or power) supplied to the pressure control means. This maximum value may vary depending on the specific boiler with which the invention is implemented and the threshold can be calibrated uniquely for the particular boiler in question. The 'off' threshold may for example be set as 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 99% of the maximum, or any range defined between any one of those values. The maximum value of the current supplied to the pressure control means may be determined uniquely for each boiler with which the invention is implemented and the 'on' or off threshold set accordingly.

Optionally, the method may further comprise determining boiler usage information, which comprises the duration or proportion of time that the pressure control means is in the on-state, the-off state, or both. Using the boiler usage information, the duration or proportion of time that fuel is combusted in the boiler may be indirectly determined because the boiler is arranged to allow combustion of fuel when the pressure control means is in the on-state. Using the duration or proportion of time that the fuel combusted, along with knowledge of the rate at which fuel is combusted per unit time (which is dependent on the boiler in question and is information that is available to the skilled person) the total amount of fuel combusted in a given time can be determined. Such information is particularly useful to monitor the efficiency and performance of the boiler. The duration of time in which the pressure control means has been running may also be determined and may be useful for deciding when the boiler should be serviced and the pressure control means replace due to wear.

Optionally, the electrically powered pressure control means may be arranged to operate at variable rates to vary the rate of combustion in the combustion chamber, and wherein the electrical current comprises a variable electrical current and the method further comprises determining the magnitude of the electrical current supplied to the pressure control means. By measuring the magnitude of the current supplied to the pressure control means, an indirect measurement of the rate of combustion of fuel in the combustion chamber may be determined. The rate at which fuel is combusted may be related to the current supplied to the pressure control means by a known relationship. The relationship is dependent on the particular boiler in question. Such information may be available to the skilled person (e.g. from a technical specification of the boiler).

Optionally, the current may vary continuously or in discrete steps. In some embodiments the current may be 0.1 A, 0.5 A, 1 A, 5 A, 10 A, 15 A or any range defined between any one of those values. The current may for example vary between discrete proportions of the maximum current. The possible discrete current values may for example be approximately 10%, 20%, 30%, 35%, 40%, 50%, 60%, 75%, 80%, 90% of the maximum, or any range defined between any of these values.

Optionally, the method may further comprise determining boiler usage information, which comprises information on the current supplied over a proportion or duration of time. By determining the current supplied, which provides an indirect determination of the rate at which fuel is combusted in the boiler, the total amount of fuel combusted in any given period of time can be calculated.

Optionally, the combustion chamber and the pressure control means may be contained within a sealed housing, and wherein monitoring the electrical current supplied to the pressure control means may comprise detecting if power is being supplied via an external power transmission means outside of the sealed housing. By detecting current being supplied via a power transmission means outside of the sealed housing the method is non-invasive and does not require any access to the sealed housing. This means that the method can optionally be carried out on an existing boiler with minimal modifications.

Optionally, the power transmission means may be an electrical cable and the method may comprise attaching a sensor to the outside of the electrical cable. This allows the sensor to be optionally fitted to an existing boiler without any modification to the power transmission means. In some embodiments, the power transmission means may be an electrical cable and the sensor may be advantageously fitted around an outside insulation layer of the electrical cable without requiring any electrical connection.

Optionally, the method may further comprise communicating the boiler usage information from the sensor to a processing unit arranged to process the boiler usage information. This advantageously allows boiler information to be collected at a central unit. In some embodiments, the processing unit may be in communication with a plurality of sensors at a plurality of boilers and therefore allows a number of boilers to be monitored efficiently.

Optionally, the sensor may communicate wirelessly with the processing unit. This allows the communication to take place without the need for installing a wired connection from the boiler to the processing unit.

Optionally, the processing unit may be part of a central heating control system. This allows the central heating system to determine the amount of fuel that is being consumed by the boiler in a particular period of time and allows the heating control system to determine the amount of fuel that is required to achieve a particular temperature.

In a second aspect, the present invention provides a boiler comprising: a combustion chamber arranged to combust fuel; an electrically powered pressure control means arranged to control the pressure in the combustion chamber, wherein fuel is combusted in the combustion chamber when an electrical current is supplied to the pressure control means; a sensor arranged to monitor the electrical current supplied to the pressure control means, thereby monitoring the usage of the boiler.

In a third aspect, the present invention provides a boiler usage sensor arranged to be used in the method described herein.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a boiler according to an embodiment of the invention.

A boiler 100 according to an embodiment of the present invention is shown schematically in Figure 1. in a preferred embodiment, the boiler is a combination boiler arranged to provide domestic hot water and central heating. In other embodiments it may be any boiler arranged to combust fuel to provide heat energy. It is to be understood that Figure 1 shows a schematic representation indicating the features necessary to implement the invention, and that the boiler may therefore comprise additional, or fewer, components as would be apparent to the skilled person in this field. The boiler 100 comprises a combustion chamber 102 arranged to combust fuel such as natural gas, including for example methane, butane and propane, or a mixture of these gasses (e.g. Calor gas). In other embodiments, the fuel may be another gaseous fuel such as coal gas, hydrogen gas, biogas, or like, as would be apparent to the skilled person. in yet other embodiments, the fuel may be a liquid fuel such as petroleum, gasoline or alcohol for example. The combustion chamber 102 comprises a burner 104 having at least one fuel outlet at which the fuel is ignited (six are shown in Figure 1). The burner 104 is connected to a fuel source 106, which in the preferred embodiment is arranged to provide a source of natural gas from a mains supply or gas cylinder. The supply of fuel to the burner is controlled by a gas supply valve 108 shown in Figure 1.

The combustion chamber 102 further comprises a heat exchanger 110 arranged to transfer heat, created by the combustion of the fuel, to a water supply. In the described embodiment, the heat exchanger comprises tubing 112 through which a supply of water is circulated. The water supply enters the tubing through an inlet 114 and exits at a higher temperature at an outlet 116. The flow of water through the heat exchanger is controlled using valves 118 according to the demand for heated water. Once the water is heated it may be used for example in a domestic central heating or hot water supply. in other embodiments, any other arrangement of heat exchanger may be provided, as would be apparent to the skilled person.

The boiler 100 further comprises an electrically powered pressure control means 120 arranged to control the pressure in the combustion chamber. The pressure control means is arranged to decrease the air pressure within the combustion chamber compared to the surrounding air pressure. This provides a flow of air out of the combustion chamber 102 and into a flue 122 through which waste gases produced by combustion of the fuel are allowed to escape from the boiler 100. The outlet of the flue 122 is connected to the outside of the building in which the boiler 100 is located to allow the waste gases to escape into the atmosphere. in the described embodiment, the pressure control means 120 comprises a fan located in the outlet of the flue 122, but in other embodiments, may be any means suitable to draw air out of the combustion chamber 102.

Before ignition of the fuel takes place, the pressure in the combustion chamber must be lowered in order to ensure that waste gases can escape and a flow of fuel is drawn out of the burner 104. The pressure control means 120 is in communication with a controller 124 arranged to control the pressure control means. When the pressure control means is activated the valve 108 is operated by the controller 124 to allow the gas to enter the burner and ignition to occur. it is important that the supply of gas is not ignited before the activation of the pressure control means 120 because without the reduction in pressure within the combustion chamber 102, the waste gases produced by the combustion process will not be drawn out of the flue 122 and allowed to escape into the air outside of the building. if waste gasses or un-combusted fuel are allowed to build up within the boiler they may escape from the boiler into the building in which it is located. The controller 124 is arranged to control the pressure control means 120 by controlling the supply of electrical current to the pressure control means 120. When a current is supplied to the pressure control means 120 it is activated and the pressure in the combustion chamber 102 is lowered.

Once the pressure control means is activated (i.e. a current is supplied to it), the combustion of gas can occur. The gas supply valve 108 and burner 104 are also in communication with the controller 124 which is arranged to control the flow of gas to the burner by operation of the valve 108. Once the fuel escapes from the burner outlets it is ignited for example using a pilot light (not shown in Figure I) or other suitable source of ignition as would be apparent to the skilled person. In some embodiments, the pressure control means is active before the combustion of fuel begins in order to allow the pressure to fall in the combustion chamber. The pressure control means 120 may also remain activate for some time after the combustion of fuel has stopped to ensure all waste gases have left the combustion chamber. These delays are however small compared to the duration of time that both the pressure control means and the fuel combustion occur together and so have little effect on the determination of usage of the boiler. For efficiency, this invention assumes that combustion of fuel takes place when there is a current supplied to the pressure control means 120 and stops when a current is no longer supplied to the pressure control means 120.

The inventor has realised that by detecting the current supplied to the pressure control means 120, a non-invasive indication that the fuel is being combusted is provided. The boiler 100 therefore comprises a sensor 126 arranged to monitor the electrical current supplied to the pressure control means. The sensor of the present invention advantageously provides an indirect measure of the usage of the boiler compared to directly measuring the flow of gas supplied to the burner.

in some embodiments, the pressure control means has an on-state in which it is supplied with an electrical current and an off-state in which it is not supplied with electrical current. The pressure control means therefore varies between two discrete states: the on-state in which it is activated and the pressure within the combustion chamber is reduced, and an off-state in which it is not activated and the pressure within the combustion chamber is the same as the surrounding ambient pressure. In order to detect when the pressure control means is in the on-state the sensor is arranged to determine whether the electrical current is equal to or above a threshold value. Conversely, the sensor is arranged to determine whether the pressure control means is in the off-state by determining whether the electrical current is less than or equal to a threshold value.

in the off-state, the current supplied to the pressure control means may be substantially zero. In other embodiments, the current supplied in the off-state may be greater than zero, but not large enough to activate the pressure control means 120 (e.g. it may be a small current value that is close to zero). In the on-state the current supplied to the pressure control means 120 is non-zero, or great enough to activate the pressure control means. In the on-state, the current supplied may be significantly greater than in the off-state. The 'on' threshold current may be set between the current corresponding to the off-state and the current corresponding to the on-state. Determining whether the current is equal to or above the 'on' threshold advantageously provides a reliable indication that the pressure control means is in the on-state. In some embodiments, the 'on' threshold may be set at one of 0.1 A, 0.5 A, 1 A, 5 A, 10 A, 15 A or may be in a range defined between any one of those values.

Similarly, determining whether the pressure control means is in the off-state may comprise determining whether the electrical current is less than or equal to an 'off' threshold value. The 'off' threshold current may be set between the current corresponding to the off-state and the current corresponding to the on-state. The 'off' threshold current may be less than or equal to the 'on' threshold current. In some embodiments, the 'off' threshold may be set at one of 0.1 A, 0.5 A, I A, 5 A, 10 A, 15 A or may be in a range defined between any one of those values.

The sensor 100 is arranged to determine boiler usage information for the boiler 100. The boiler usage information comprises the duration or proportion of time that the pressure control means is in the on-state, in the off-state, or both. The usage information may therefore include the period of time that the current supplied to the pressure control means 120 is above the 'on' threshold, therefore indicating the period of time for which the pressure control means is in the power-on state. The usage information may alternative or additionally include the period of time that the current supplied to the pressure control means 120 is below the 'off' threshold, therefore indicating the period of time for which the pressure control means is in the power-off state. Using this information, the period of time in which the fuel will have been combusted is determined because it is known that whenever the pressure control means is activated the combustion of fuel occurs. The fuel is combusted at a known rate depending on the properties of the burner 104 and fuel supply (information which is available to the skilled person). From this information the total amount of gas combusted by the boiler in any given period of time can be calculated. The amount of time in which the boiler has been in use can also be recorded. This information can be particularly useful to determine when the boiler next needs to be serviced (for example, the boiler can be serviced after accurately measuring 1000 hours of use).

In another embodiment, the powered pressure control means 120 is arranged to operate at variable rates to vary the rate of combustion in the combustion chamber. In order to increase the rate at which the fuel is combusted within the combustion chamber, the rate at which the pressure control means 120 is operated is increased.

Conversely, if the rate at which the fuel is combusted is reduced, the rate at which the pressure control means 120 is operated is decreased. In order to vary the rate at which the pressure control means 120 is operated, the electrical current with which it is supplied is varied. in this embodiment, the sensor is further arranged to determine the magnitude of the electrical current supplied to the pressure control means. If the dependence of the fuel combustion rate on the pressure control means operation rate is known, this gives an indirect indication of the rate at which fuel is combusted in the combustion chamber 102. In this embodiment, the sensor 126 is arranged to determine boiler usage information which comprises information on the current supplied over a proportion or duration of time. This information allows the calculation of the amount of fuel combusted by the boiler in any given period of time.

In some embodiments, the current supplied to the pressure control means 120 varies continuously. The power supplied to the pressure control means may for example vary between substantially zero and a maximum of approximately 270 W. In other embodiments, the current may vary between a subset of the maximum range. The maximum value of the current (or power) may vary depending on the particular boiler to which the invention is implemented and can be determined by measurement of the current for each unique boiler. in other embodiments the current (or power) varies in discrete steps. The current (or power) may for example vary between discrete proportions of the maximum current (or power). The possible discrete current (or power) values may for example be approximately 10%, 20%, 30%, 35%, 40%, 50%, 60%, 75%, 80%, 90% of the maximum, or any range defined between any of these values.

In the embodiment shown in Figure 1, the boiler 100 comprises a sealed housing 128.

The sealed housing 128 contains the combustion chamber 102 and the pressure control means 120. The scaled housing helps to contain the combusting fuel and to prevent the components of the boiler 100 from being tampered with once the boiler is installed. The sealed housing 128 is surrounded by an outer housing 129 which contains other components of the boiler, including the controller 124. In this embodiment, the sensor 126 is arranged to monitor the electrical current supplied to the pressure control means 120 by detecting if power is being supplied via an external power transmission means 127 arranged to provide electrical current to the pressure control means. The external power transmission means is therefore external to the sealed housing as shown in Figure 1. In the described embodiment, the external power transmission means 127 enters the outer housing to supply power to the boiler (by connecting to a mains electrical supply, for example). The external power transmission means then runs through the controller and enters the sealed housing 128. At this point it becomes an internal power transmission means which continues to the pressure control means 120 (as shown in the dotted line in Figure 1). It is to be understood that the path of the power transmission means shown in Figure 1 is only a schematic representation and in some embodiments in may follow a more complicated path or pass through additional components (it may for example supply power to other processes within the controller). in some embodiments it may not pass through the controller 124, but may run directly to the pressure control means 120.

As shown in Figure 1, the sensor 124 is provided on the external power transmission means and is therefore outside of the scaled housing 128 and so can be installed and accessed without requiring access to the interior of the sealed housing 128. This is particularly advantageous because it means that the sensor can optionally be installed to an existing boiler without a technician requiring access to the inside of the scaled housing. The sensor can therefore be easily fitted without interfering with the operation of the boiler.

In the described embodiment, the sensor 124 is attached to the external power transmission means 127 after it has passed through the controller 124, and before it enters the sealed housing 128. in other embodiments, the sensor may be attached to the external power transmission means 127 at a point within the controller (it may be, for example, attached to or included on, a circuit board within the controller). In other embodiments, the sensor may be attached to the external power transmission means 127 at a point before it passes through the controller, but still within the outer housing 129 of the boiler. In yet another embodiment, it may be attached at a point on the external power transmission means 127 before it enters the outer housing 129. Advantageously, in this embodiment, the sensor can be fitted without the need to access the outer housing 129. In yet another embodiment, the sensor may alternatively be attached to the internal power transmission means at a point within the sealed housing.

The power transmission means 127 may be an electrical cable along which current is supplied to the pressure control means 120. The electrical cable may comprise a current carrying element and a surrounding insulating layer as is well known in the art. The sensor 126 is advantageously attached to the outside of the electrical cable by, for example, wrapping or clamping around at least part of the insulating layer. in order to attach to the electrical cable the sensor may comprise a fixing means such as a clamp or the like. The sensor is arranged to detect current flowing through the electrical cable without the requirement of an electrical connection to the current carrying dement. This means that the sensor is non-invasive and can optionally be retro-fitted to an existing boiler without having any effect on the operation of the boiler. in other embodiments, the sensor may be alternatively connected so that it forms an electrical contact with the current carrying dement.

The sensor may be chosen from any sensor suitable for detecting a current within an electrical cable without requiring a direct connection to the current carrying element. The sensor may be, for example chosen from a transformer sensor, Hall effect sensor, or iron vane sensor. In particular, the sensor may be a current transformer (CT) clamp.

In some embodiments, the sensor may be arranged to determine the magnitude of an AC or DC current transmitted by the power transmission means 127.

The sensor 100 is arranged to communicate the boiler usage information to a processing unit 130 arranged to process the boiler usage information. In order to communicate with the processing unit, the sensor comprises a wireless transceiver 132. in the described embodiment, the wireless transceiver is separate from the body of the sensor 126, with a wired link provided between them. This allows the transceiver to be located outside the outer housing 129 of the boiler, which may provide improved wireless signal coverage. By including a separate transceiver, the body of the sensor attached to the power transmission means 127 may be made smaller. In other embodiments the sensor may comprise a single unit with the transceiver provided within that unit.

The processing unit 130 may be, for example, part of a central heating control systcm.

The processing unit may make use of the boiler usage information in controlling a central heating system. For example, the boiler usage information can be useful to monitor the efficiency of the central heating system, by for example measuring the amount of fuel combusted to reach a desired ambient temperature. The boiler usage information can also be useful for charging a customer for the amount of fuel they have used. Furthermore, the boiler usage information may be useful as a safety indication that the fuel supply is being combusted.

The present invention also relates to a method of monitoring the usage of a boiler using the sensor described above. The method comprises monitoring the electrical current supplied to the pressure control means 120 of the boiler 100, thereby monitoring the usage of the boiler.

Various modifications may be made to this invention without departing from its scope, as defined by the claims. For example, other uses of the usage information may be envisaged by the skilled person. For example, the usage information may be fed into a larger energy monitoring system. Such an energy monitor system may be suitable for an industrial building or block of separate dwellings (e.g. an apartment building) having a plurality of boilers, in which energy use is monitored in order to efficiently provide desired environmental conditions.

Claims

Claims I. A method of monitoring the usage of a boiler, the boiler comprising a combustion chamber arranged to combust fuel; and an electrically powered pressure control means arranged to control pressure in the combustion chamber, wherein fuel is combusted in the combustion chamber when an electrical current is supplied to the pressure control means, the method comprising: monitoring the electrical current supplied to the pressure control means, thereby monitoring the usage of the boiler.
2 The method according to claim I, wherein the pressure control means has an on-state in which electrical current is supplied to the pressure control means and an off-state in which electrical current is not supplied to the pressure control means.
3. The method according to claim 2, wherein determining whether the pressure control means is in the on-state comprises determining whether the electrical current is equal to or above an 'on' threshold value.
4. The method according to claim 2 or claim 3, wherein determining whether the pressure control means is in the off-state comprises determining whether the electrical current is less than or equal to an 'off' threshold value.
The method according to any of claims 2 to 4, wherein the method further comprises determining boiler usage information, which comprises the duration or proportion of time that the pressure control means is in the on-state, the-off state, or both.
6. The method according to claim 1, wherein the electrically powered pressure control means is arranged to operate at variable rates to vary the rate of combustion in the combustion chamber. and wherein the electrical current comprises a variable electrical current and the method further comprises determining the magnitude of the electrical current supplied to the pressure control means.
7. The method according to claim 6, wherein the current varies continuously or in discrete steps.
8. The method according to claim 6 or claim 7, further comprising determining boiler usage information, which comprises information on the current supplied over a proportion or duration of time.
9 The method according to any preceding claim, wherein the combustion chamber and the pressure control means are contained within a sealed housing, and wherein monitoring the electrical current supplied to the pressure control means comprises detecting if power is being supplied via an external power transmission means outside of the sealed housing.
10. The method according to claim 9, wherein the power transmission means is an electrical cable and the method comprises attaching a sensor to the outside of the electrical cable.
11. The method according to any of claims 9 to 10, further comprising communicating the boiler usage information from the sensor to a processing unit arranged to process the boiler usage information.
12. The method according to claim 11, wherein the sensor communicates wirelessly with the processing unit.
13. The method according to claim 11 or claim 12, wherein the processing unit is part of a central heating control system. 30
14. A boiler comprising: a combustion chamber arranged to combust fuel; an electrically powered pressure control means arranged to control the pressure in the combustion chamber, wherein fuel is combusted in the combustion chamber when an electrical current is supplied to the pressure control means; a sensor arranged to monitor the electrical current supplied to the pressure control means, thereby monitoring the usage of the boiler.The boiler according to claim 14, wherein the pressure control means has an on-state in which electrical current is supplied to the pressure control means and an off-state in which electrical current is not supplied to the pressure control means.16. The boiler according to claim 15, wherein the sensor is arranged to determine whether the pressure control means is in the on-state by determining whether the electrical current is equal to or above a threshold value.17. The boiler according to claim 15 or claim 16, wherein the sensor is arranged to determine whether the pressure control means is in the off-state by determining whether the electrical current is less than or equal to a threshold value.1S. The boiler according to any of claims 15 to 17, wherein the sensor is further arranged to determine boiler usage information which comprises the duration or proportion of time that the pressure control means is in the on-state, the-off state, or both.19. The boiler according to claim 14, wherein the electrically powered pressure control means is arranged to operate at variable rates to vary the rate of combustion in the combustion chamber, and wherein the electrical current comprises a variable electrical current and the sensor is further arranged to determine the magnitude of the electrical current supplied to the pressure control means.20. The boiler according to claim 19, wherein the current varies continuously or in discrete steps.21. The boiler according to claim 19 or claim 20, wherein the sensor is further arranged to determine boiler usage information, which comprises information on the current supplied over a proportion or duration of time.22. The boiler according to any of claims 14 to 21, wherein the combustion chamber and the pressure control means are contained within a sealed housing, and wherein the sensor is arranged to monitor the electrical current supplied to the pressure control means by detecting if power is being supplied via an external power transmission means outside of the sealed housing.23. The boiler according to claim 22, wherein the power transmission means is an electrical cable and the sensor is attached to the outside of the electrical cable.24. The boiler according to any of claims 18 to 23, wherein the sensor is arranged to communicate the boiler usage information to a processing unit arranged to process the boiler usage information.25. The boiler according to claim 24, wherein the sensor communicates wirelessly with the processing unit.26. The boiler according to claim 24 or claim 25, wherein the processing unit is part of a central heating control system.27. A boiler usage sensor arranged to be used in the method of any of claims 1 to 14.28. A method, a boiler or a boiler usage sensor substantially as herein described with reference to any one or more of the accompanying drawings.