GB2578425A

GB2578425A - Infrared heaters and infrared heater control

Info

Publication number: GB2578425A
Application number: GB1815848.5A
Authority: GB
Inventors: Peat Simon
Original assignee: Curv360 Ltd
Current assignee: Curv360 Ltd
Priority date: 2018-09-28
Filing date: 2018-09-28
Publication date: 2020-05-13
Anticipated expiration: 2038-09-28
Also published as: GB2578425B; WO2020065346A1

Abstract

An infrared heater control system 1 comprises a controller 7 configured to determine the electric power to be delivered to a heating element of an infrared heater 3. The determination comprises selecting from among no power and a plurality of alternative positive powers to be delivered in dependence on the values of one or more control parameters. The control parameters may comprise one or more of a set temperature, an ambient temperature, the rate of change of the ambient temperature or a surface temperature of the heater. The selectable electric power may be continuously variable and may be delivered to the heating element by a first switch 19 such as a thyristor. An override mode may be provided to discontinue power delivery to the heating element if it is detected that an aperture, such as a door or window of a heated room or space, is open. A wireless module may be provided via which the controller may receive values of control parameters from a remote device.

Description

INFRARED HEATERS AND INFRARED HEATER CONTROL

TECHNICAL FIELD

The present disclosure relates to infrared heaters and particularly, but not exclusively, to infrared heater control. Aspects of the invention relate to an infrared heater control system, to an infrared heater, to a heating system, to a method of determining the electric power to be delivered to a heating element of an infrared heater, to a computer program, to a non-transitory computer readable storage medium and to a signal.

BACKGROUND

Infrared room heaters have been known for many years and can provide benefits over conventional convection heaters in terms of efficiency and perceived warmth through direct radiation. Nonetheless, existing infrared heating systems can be relatively inaccurate in terms of room temperature control. A further difficulty may arise from risk of scalding in view of the surface temperature of infrared heaters.

Control mechanisms for heat adjustment may also be relatively inconvenient. Finally, as with other heating systems, energy may be wasted where an aperture in the heated room is opened.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided an infrared heater control system comprising a controller configured to determine the electric power to be delivered to a heating element of an infrared heater, the determination comprising selecting from among no power and a plurality of alternative positive powers to be delivered in dependence on the values of one or more control parameters. The use of dynamic temperature control (i.e. the availability and use of power settings in addition to 'on' and 'off') may provide benefits in terms of reduced power and therefore energy consumption. The finer control potentially offered may also lead to improved accuracy (i.e. fewer and less severe instances of set temperature over and undershoot).

In some embodiments the selectable electric power is continuously variable. By increasing the granularity of electric powers that may be selected, the accuracy with which a set power is approached and maintained may be increased.

In some embodiments current delivered to the heating element is alternating current and the determination of the electric power comprises sending driving signals configured to adjust a first switch, the adjustment controlling the proportion of the alternating current signal which is delivered to the heating element and therefore the electric power delivered, the timing of the driving signals corresponding to a proportion of the alternating current to be supplied in accordance with the selected power. In order to determine the timing for the driving signals such that the proportion of the alternating current signal delivered is controlled, the controller may determine the zero-crossing time for the alternating current signal. In this way synchronisation of the switching points with the phase of the alternating current signal may be achieved. The first switch driven by the switching signals may be a thyristor (e.g. a semiconductor-controlled rectifier). The driving of the first switch determines the proportion of the available alternating current that reaches the heating element and so the electric power delivered. In some embodiments the first switch forms part of the infrared heater control system and in others it does not.

In some embodiments the controller is configured to adjust a second switch, the adjustment switching electric power delivery from occurring via the first switch, to instead occurring directly to the electric heating element from an alternating current supply. The adjustment to the second switch may be undertaken in accordance with a user input and/or in dependence on values of one or more of the control parameters. Direct supply of current in this manner may be more efficient for periods for which maximum heating is determined by the controller.

In some embodiments the second switch forms part of the infrared heater control system and in others it does not.

In some embodiments the control parameters comprise one or more of: - a set temperature; -an ambient temperature; -the rate of change of the ambient temperature; -a surface temperature of the infrared heater; - override set; -the time and/or day and/or season.

The set temperature may be a target ambient temperature for the infrared heater in the environment in which it is located. It may be input or sent to the controller by a user or another system or else generated by the controller itself (e.g. in accordance with trend data for previous use).

The ambient temperature may be the temperature in the environment of the infrared heater, e.g. the air temperature as measured in a room in which the infrared heater is situated.

The surface temperature of the infrared heater may be the temperature of an outer surface of the infrared heater (e.g. the temperature as measured at a point on a cover thereof).

The ambient temperature and surface temperature of the infrared heater may be measured using respective temperature sensors or else determined or inferred by other measurements/data received and/or held by the infrared heater control system (e.g. a thermal model, prior use data and/or ambient temperature records). As will be appreciated, in some embodiments any such temperature sensors form part of the infrared heater control system and in others they do not.

The rate of change of the ambient temperature may be calculated in accordance with the ambient temperature recorded over time.

The enforcement of a set override may result from a manual override input of a user, a condition existing in which such an override is automatically triggered, or perpetual enforcement of the set override. Example set overrides are discussed further below.

In some embodiments the infrared heater control system is operable in a nominal mode whereby the controller determines the electric power in a manner so that the ambient temperature approaches the set temperature and so that the set temperature is then maintained. The nominal mode may be based on suitable control logic such as proportional control or PID control. The model used for power delivery in nominal mode may be determined so that the rate at which the ambient temperature is increased to reach the set temperature is a desirable/acceptable compromise between energy efficiency and time required for reaching the set temperature. The model used for power delivery in the nominal mode may utilise the various power settings available to more accurately approach and maintain the set temperature than might be achieved with simple on/off control.

In some embodiments, in the nominal mode, the controller controls the electric power so that the ambient temperature approaches the set temperature in a substantially asymptotic manner. This may minimise any temperature overshoot and yet give rise to a relatively rapid approach to the set temperature.

In some embodiments, in the nominal mode, the controller controls the electric power so that the ambient temperature approaches the set temperature whilst oscillating about the set temperature. Where a degree of overshoot is acceptable, permitting converging oscillation about the set temperature may allow a temperature approximating the set temperature to be approached more quickly.

In some embodiments the nominal mode is overridden by one/or more override modes in dependence on the values of one or more of the control parameters. The override modes may allow exceptions to the nominal mode to be acted upon in particular situations.

In some embodiments an override mode is an aperture open detected mode, where an aperture open detection determination is made in dependence on the values of one or more of the control parameters and electric power delivery to the heating element is discontinued by the controller for a pre-defined period and/or until such time as an aperture closed determination is made in dependence on the values of one or more of the control parameters. It may be for instance that aperture open detection determination is made where the rate of decrease of the ambient temperature is higher than a pre-defined threshold (e.g. 0.3degress per minute). Further, the aperture closed detection determination may be made where the rate of increase of the ambient temperature is higher than a predefined threshold. The pre-defined period may serve as a back-stop, ensuring that even where no temperature rise indicative of the aperture being closed is determined, power delivery is eventually recommenced. In this case the time period may be relatively long (e.g. 45-50 minutes). As will be appreciated the aperture might for instance be a door or window.

Deactivation of the heating element whilst an aperture is open may save unnecessary energy wastage.

In some embodiments an override mode is a maximum surface temperature mode, where power delivery is limited in order that a maximum surface temperature for the infrared heater is not exceeded. In some embodiments the maximum surface temperature is pre-set whereas in others it is settable by a user or another system. This override mode may be beneficial particularly in environments where those less aware of the possibility for scolding or less able to avoid scolding from radiators may be present (e.g. schools/nurseries/hospitals). In such cases a pre-set maximum surface temperature (for instance set at a level in accordance with legislation) may be appropriate (e.g. between 400 and 50°C).

In some embodiments an override mode is a defrosting mode, where any set temperature above a pre-determined level is overridden and a lower set temperature is set. This may help to avoid condensation of water vapor in the environment occurring where heating from low temperatures is undertaken.

In some embodiments an override mode is a boost mode in which electric power is delivered at increased levels in order that the set temperature is reached in less time than would otherwise be the case in nominal mode. The boost mode may be automatically deactivated once the set temperature is reached, once the set-temperature is approached to within a pre-determined magnitude and/or alternatively after elapse of a pre-determined time. The boost mode may give more rapid increases in ambient temperature towards the set temperature at the expense of energy efficiency.

In some embodiments at least one of the nominal and/or override modes have models used for electric power delivery that avoid delivery of particular electric powers. It may be for instance that particular electric powers are known to cause audible noise above a predetermined threshold level where they are delivered to the heating element. These electric powers may be avoided. In particular, where the heating element is silicon gold, audible noise above pre-determined levels may be prevented where particular electric powers are not delivered.

In some embodiments the infrared heater control system comprises a wireless module via which the controller is configured to receive values of one/or more of the control parameters from a remote device. The remote device may be a user input device and/or a sensor unit. It may be for example that the controller receives the set temperature from a user input device and an ambient temperature from a sensor unit. In some embodiments the remote device forms part of the infrared heater control system and in some embodiments it does not. The wireless module may facilitate control of the infrared heater from locations remote from the infrared heater.

In some embodiments the remote device is a mobile device, a thermostat and/or a remote control. It may be for instance that control parameter values are input by a user via an application of a mobile phone which then sends the values to the controller via the wireless 30 module.

In some embodiments the infrared heater control system is configured to send one/or more status updates to the remote device for display thereon. It may be for instance that the status update indicates the operational state of the infrared heater and/or the ambient temperature and/or power used within a given period. This may inform current and future decisions concerning control of the infrared heater.

In some embodiments the infrared heater control system comprises a memory in which the controller is configured to store data on power delivered to the heating element. The power delivered may be determined by detecting current and voltage with the circuit delivering the electric power to the heating element. Storing this data may allow its subsequent retrieval and review to better inform a system and/or user.

According to a second aspect of the invention there is provided an infrared heater comprising and controlled by the infrared heater control system according to the first aspect.

In some embodiments the infrared heater has a cover which is also the heating element of the infrared heater.

In some embodiments the heating element comprises silicon. Silicon may be more flexible than an alternative such as carbon, facilitating easier shaping of the cover.

According to a third aspect of the invention there is provided a heating system comprising an infrared heater and the infrared heater control system according to the first aspect.

In some embodiments the heating element comprises silicon.

In some embodiments the heating system comprises a remote device configured to allow user input of one or more values for one or more of the control parameters. The remote device could for instance be a mobile device, a thermostat and/or a remote control.

According to a fourth aspect of the invention there is provided a method of determining the electric power to be delivered to a heating element of an infrared heater, comprising selecting from among no power and a plurality of alternative positive powers to be delivered in accordance with the values of one or more control parameters.

According to a fifth aspect of the invention there is provided a computer program that, when read by a computer, causes performance of the method of the fourth aspect.

According to sixth aspect of the invention there is provided a non-transitory computer readable storage medium comprising computer readable instructions that, when read by a computer, cause performance of the method of the fourth aspect. The non-transitory computer readable storage medium may be, for example, a USB flash drive, a secure digital (SD) card, an optical disc (such as a compact disc (CD), a digital versatile disc (DVD) or a Blu-ray disc).

According to a seventh aspect of the invention there is provided a signal comprising computer readable instructions that, when read by a computer, cause performance of the method of the fourth aspect.

Any controller or controllers described herein may suitably comprise a control unit or computational device having one or more electronic processors. Thus the system may comprise a single control unit or electronic controller or alternatively different functions of the controller may be embodied in, or hosted in, different control units or controllers. As used herein the term "controller" or "control unit" will be understood to include both a single control unit or controller and a plurality of control units or controllers collectively operating to provide any stated control functionality. To configure a controller, a suitable set of instructions may be provided which, when executed, cause said control unit or computational device to implement the control techniques specified herein. The set of instructions may suitably be embedded in said one or more electronic processors. Alternatively, the set of instructions may be provided as software saved on one or more memory associated with said controller to be executed on said computational device. A first controller may be implemented in software run on one or more processors. One or more other controllers may be implemented in software run on one or more processors, optionally the same one or more processors as the first controller. Other suitable arrangements may also be used.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic view showing a heating system in accordance with an embodiment of the invention; and Figure 2 is a plot showing electric power delivery against time to infrared heaters of various heating systems each according to an embodiment of the invention.

DETAILED DESCRIPTION

Referring first to Figure 1, an infrared heater control system is generally shown at 1 and is configured to control an infrared heater generally shown at 3. The infrared heater 3 has an infrared heating element comprising a silicon gold cover (not shown) for the heater 3. The infrared heater 3 also has a power input 5 via which the infrared heating element receives powering alternating current.

The infrared heater control system 1 has a controller 7 (in this case a processor) having various inputs and outputs. The controller 7 is configured to send, via a power signal output 9 thereof, power signals to a power signal input 11 of a driving unit 13. The driving unit 13 is configured to generate driving signals corresponding to the power signals from the controller 7. The driving unit 13 is further configured to send the driving signals via a driving signal output 15 thereof, to a driving signal input 17 of a first switch 19 of the control system 1. In this case the first switch 19 is a semiconductor-controlled rectifier, and the driving signal input 17 is a gate electrode thereof. Further electrodes of the first switch 19 are connected to the power input 5 of the infrared heater 3 and selectively to an alternating current power source 21 via a second switch 23, when the second switch is in a first configuration. When the second switch 23 is in a second configuration, the first switch 19 is bypassed, so that the alternating current power source 21 is connected directly to the power input 5 of the infrared heater 3 by the second switch 23. The configuration of the second switch 23 is controlled by the controller 7.

A zero-crossing time detector 25 has an alternating current signal input 27, which receives an alternating current signal from the alternating current power source 21 via alternating current signal output 29 of the second switch 23. The zero-crossing time detector 25 has a zero-crossing time output 31 in communication with a zero-crossing time input 33 of the controller 7.

A power detection suite 35 comprising means for detecting voltage and current delivered to the heating element via the second switch 23 has a power data output 37 connected to a power data input 39 of the controller 7.

A rectifier 41 is connected to the alternating current power source via the second switch and is also connected to the controller 7.

A clock 43 has a clock signal output 45 in communication with a clock signal input 47 of the controller 7.

The controller 7 is also connected to a memory 49 via a memory input/output 51 at the memory 49 and a memory input/output 53 at the controller 7.

A temperature detection suite 55 comprises an ambient temperature detector and a heater surface temperature detector. The temperature detection suite 55 has a temperature data output 57 in communication with a temperature data input 59 of the controller 7.

The infrared heater control system 1 has a wireless module 61 comprising a wireless transceiver. The wireless transceiver is connected to the controller 7 via a for wireless setting input/output 63 of the wireless transceiver and a for wireless setting input/output 65 of the controller 7. The infrared heater control system 1 also has a radio frequency module 67 comprising a radio frequency transceiver. The radio frequency transceiver is connected to the controller 7 via a radio setting input/output 69 of the radio frequency transceiver and a radio setting input/output 71 of the controller 7. The infrared heater control system 1 has a user interface 73 On this case a touch screen display, though other user interfaces e.g. utilising push buttons, may alternatively/additionally be used). The user interface 73 is connected to the controller 7 via a local setting input/output 75 of the user interface 73 and a local setting input/output 77 of the controller 7.

In use the infrared heater 3 is used to adjust the ambient temperature of a room or space in which the infrared heater 3 is installed. The controller 7 receives a set temperature (one of a number of control parameters) input by a user or else stored in and retrieved from memory 49 (e.g. in accordance with a heating program). Where the set temperature is input by a user, it can be: a) input on user interface 73 and received via local setting input/output 75 and local setting input/output 77; or b) input on a user interface of a thermostat or remote control and received via the radio setting input/output 69 and radio setting input/output 71; c) input on a user interface of a wireless device such as a mobile phone (e.g. using a dedicated application) and received via the for wireless setting input/output 63 and the for wireless setting input/output 65.

The controller 7 also receives an ambient temperature (another control parameter) as sensed by the ambient temperature detector and sent to the controller 7 via the temperature data output 57 and temperature data input 59. The ambient temperature detector is positioned at a location within the room away from the immediate vicinity of the infrared heater 3, so that the sensed temperature data is not unduly influenced by proximity to the infrared heater 3. In this case the ambient temperature detector forms part of a thermostat.

The controller 7 also receives a heater surface temperature (another control parameter) as sensed by the heater surface temperature detector and sent to the controller 7 via the temperature data output 57 and temperature data input 59.

The controller 7 is configured to determine the electric power to be delivered to the heating element of the infrared heater 3 at any given time. Assuming that the controller 7 does not determine that exercise of an override mode (discussed further below) is appropriate, the controller 7 operates in a nominal mode. In the nominal mode the controller 7 determines the electric power in a manner so that the ambient temperature approaches the set temperature and so that the set temperature is then maintained. The nominal mode is based on proportional integral derivative (PID) control logic implemented by the controller 7. In this way the controller 7 adjusts the electric power delivery over time in dependence on variation in the ambient temperature by reference to the set temperature in a manner such that the ambient temperature approaches the set temperature in an asymptotic manner.

The source of the electric power delivered to the heating element is the alternating current power source 21, which is connectable to the heating element via the first switch 19 and second switch 23.

The electrical power deliverable to the heating element is continuously variable under the control of the controller 7. The controller 7 controls the first switch 19 to determine the proportion of the alternating current signal from the alternating current power source 21 that is delivered to the power input 5 of the heating element. The controller 7 achieves this by determining the periods for which the first switch 19 is open for the delivery of alternating current. This in turn is achieved by outputting a power signal via output 9 to power signal input 11 of the driving unit 13. The driving unit 13 is configured to generate driving signals corresponding to the power signals from the controller 7. The driving unit 13 is further configured to send the driving signals via the driving signal output 15 thereof, to the driving signal input 17 of the first switch 19.

In order to determine the periods for which the first switch 19 is open for delivery of alternating current, the controller 7 monitors the zero-crossing time for the alternating current signal. In this way the controller 7 can ensure that the switching of the first switch 19 can be timed so as a proportion of each alternating current pulse can be supplied to the heating element, the proportion corresponding to the desired electric power to be delivered. The zero-crossing time for the alternating current signal is monitored by the controller 7 via the zero-crossing time detector 25. This receives the alternating current signal at an alternating current signal input 27 from the alternating current power source 21 via alternating current signal output 29 of the second switch 23. The zero-crossing time detector 25 has a zero-crossing time output 31 in communication with a zero-crossing time input 33 of the controller 7.

Where full electric power is determined to be required by the controller 7, it may send a signal to the second switch 23 causing it to be switched from a first configuration in which alternating current is delivered to the first switch 19, to a second configuration in which the first switch 19 is bypassed. In this manner the alternating current power source 21 is connected directly to the power input 5 of the infrared heater 3 by the second switch 23.

The controller 7 also monitors the electric power delivered to the heating element over time.

The power detection suite 35 sends voltage and current delivered to the heating element data via the power data output 37 to the power data input 39 of the controller 7. The controller 7 calculates cumulative power delivered for given periods based on the voltage and current data and stores the results in the memory 49.

Regardless of whether user input is received to provide the set temperature, and the route via which it is received, each of the communication paths described above is used by the controller 7 to send status updates comprising the operational state of the infrared heater 3, the ambient temperature and power used within a given period for display via a screen of the relevant remote device.

The controller 7 itself is also powered via the alternating current power source 21, but the alternating current is converted by the rectifier 41 into direct current so as to be suitable for the controller 7.

The clock signal delivered by the clock 43 to the controller 7 via the clock signal output 45 and clock signal input 47 is used to control the timing of signals and electronic circuits in the controller 7.

In dependence on the values of one or more of the control parameters, the controller 7 modifies or overrides the nominal mode and operates in an override mode. In some cases a user input (e.g. via the user interface 73, user interface of a thermostat or remote control or user interface of the wireless device) triggers an override mode. In this case the override set itself constitutes a control parameter. For other override modes, the controller 7 automatically adjusts in accordance with other control parameters.

A first override mode is an aperture open detected mode. This override mode is triggered by detection of a rate of drop of the ambient temperature that is larger in magnitude than a first pre-determined threshold. In this override mode, the controller 7 interrupts the delivery of electric power to the element of the infrared heater until one of the following conditions is met: the detected ambient temperature is rising at a rate larger in magnitude than a second pre-determined threshold; ii) a time elapse since initiation of the aperture open detected mode reaches 48 minutes.

This mode may prevent unnecessary waste of energy while an aperture such as a door or window is open. The rate of drop of the ambient temperature above the first pre-determined threshold may be indicative of an aperture being open. The rise of the detected ambient temperature at a rate larger in magnitude than the second pre-determined threshold may indicate that the aperture has been closed and that modest heating from another source (e.g. the heating of an adjacent room or thermal energy stored in the room itself) is therefore more obvious.

Once one of the conditions is met, the controller 7 returns to the nominal mode.

A second override mode is a maximum surface temperature mode. This override mode is triggered by user selection of the mode. The maximum surface temperature mode operates in a similar manner to the nominal mode, but electric power delivery at or above a level causing the surface temperature of the infrared heater to exceed a pre-determined threshold is prevented. A user may wish to trigger this mode in environments where the risk of discomfort and/or scolding associated with touching the cover of the infrared heater is higher (e.g. in schools or hospitals).

A third override mode is a defrosting mode. This mode is triggered by detection of an ambient temperature that is below a pre-determined threshold. In the defrosting mode, any set temperature above a pre-determined level is overridden for a pre-determined interval and a lower set temperature is set at a pre-determined level. This may help to avoid condensation of water vapor in the environment occurring where heating from low temperatures is undertaken.

A fourth override mode is a boost mode. This mode is triggered by user selection of the mode. In the boost mode, electric power is delivered at increased levels in order that the set temperature is reached in less time than would otherwise be the case in nominal mode. The boost mode is automatically deactivated in favour of the nominal mode once the set temperature is approached to within a pre-determined magnitude. The boost mode may give more rapid increases in ambient temperature towards the set temperature at the expense of energy efficiency.

Multiple override modes may be active at the same time. Where different modes indicate different electric power level delivery at any one time, the conflict is resolved in accordance with a hierarchy. Specifically, electric power delivery in accordance with the maximum surface temperature mode takes precedence over the aperture open detected mode, which takes precedence over the defrosting mode which takes precedence over the boost mode.

As will be appreciated the conflict may be resolved in accordance with a different hierarchy order or by another means (e.g. a policy such as lowest electric power delivery demand wins).

Each mode (be it nominal or an override mode), has an additional constraint within its control logic such that electric power delivery at a particular pre-determined magnitude is precluded. The pre-determined electric power magnitude is known to cause vibrations giving rise to audible sound when delivered to the silicon-gold heating element.

Figure 2 shows traces for electric power delivery to infrared heaters of respective heating systems over a time period, those heating systems being located in different rooms. As can be seen, the electric power delivery in each case is delivered in a continuously variable manner (as for instance contrasted with on-off control). This may allow significantly closer adherence to a set ambient temperature.

It will be appreciated that embodiments of the present invention can be realised in the form of hardware, software or a combination of hardware and software. Any such software may be stored in the form of volatile or non-volatile storage such as, for example, a storage device like a ROM, whether erasable or rewritable or not, or in the form of memory such as, for example, RAM, memory chips, device or integrated circuits or on an optically or magnetically readable medium such as, for example, a CD, DVD, magnetic disk or magnetic tape. It will be appreciated that the storage devices and storage media are embodiments of machine-readable storage that are suitable for storing a program or programs that, when executed, implement embodiments of the present invention. Accordingly, embodiments provide a program comprising code for implementing a system or method as claimed in any preceding claim and a machine-readable storage storing such a program. Still further, embodiments of the present invention may be conveyed electronically via any medium such as a communication signal carried over a wired or wireless connection and embodiments suitably encompass the same.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. The claims should not be construed to cover merely the foregoing embodiments, but also any embodiments which fall within the scope of the claims.

Claims

CLAIMS1 An infrared heater control system comprising a controller configured to determine the electric power to be delivered to a heating element of an infrared heater, the determination comprising selecting from among no power and a plurality of alternative positive powers to be delivered in dependence on the values of one or more control parameters.
2. An infrared heater control system according to claim 1 where the selectable electric power is continuously variable.
3 An infrared heater control system according to claim 1 or claim 2 where current delivered to the heating element is alternating current and the determination of the electric power comprises sending driving signals configured to adjust a first switch, the adjustment controlling the proportion of the alternating current signal which is delivered to the heating element and therefore the electric power delivered, the timing of the driving signals corresponding to a proportion of the alternating current to be supplied in accordance with the selected power.
4 An infrared heater control system according to any preceding claim where the controller is configured to adjust a second switch, the adjustment switching electric power delivery from occurring via the first switch, to instead occurring directly to the electric heating element from an alternating current supply.
5 An infrared heater control system according to any preceding claim where the control parameters comprise one or more of: -a set temperature which is a target ambient temperature for the infrared heater in the environment in which it is located; - an ambient temperature which is the temperature in the environment of the infrared heater; -the rate of change of the ambient temperature; -a surface temperature of the infrared heater; -override set; - the time and/or day and/or season.
6. An infrared heater control system according to claim 5 operable in a nominal mode whereby the controller determines the electric power in a manner so that the ambient temperature approaches the set temperature and so that the set temperature is then maintained.
7. An infrared heater control system according to claim 6 where the nominal mode is based on proportional control logic or proportional integral derivative control logic.
8 An infrared heater control system according to claim 6 or 7 where in the nominal mode, the controller controls the electric power so that the ambient temperature approaches the set temperature in a substantially asymptotic manner.
9 An infrared heater control system according to any of claims 6 to 8 where in the nominal mode, the controller controls the electric power so that the ambient temperature approaches the set temperature whilst oscillating about the set temperature.
10. An infrared heater control system according to any of claims 6 to 9 where the nominal mode is overridden by one/or more override modes in dependence on the values of one or more of the control parameters.
11 An infrared heater control system according to claim 10 where override mode is an aperture open detected mode, where an aperture open detection determination is made in dependence on the values of one or more of the control parameters and electric power delivery to the heating element is discontinued by the controller for a pre-defined period and/or until such time as an aperture closed determination is made in dependence on the values of one or more of the control parameters.
12 An infrared heater control system according to claim 10 or claim 11 where an override mode is a maximum surface temperature mode, where power delivery is limited in order that a maximum surface temperature for the infrared heater is not exceeded.
13. An infrared heater control system according to any of claims 10 to 12 where an override mode is a defrosting mode, where any set temperature above a predetermined level is overridden and a lower set temperature is set.
14. An infrared heater control system according to any of claims 10 to 13 where an override mode is a boost mode in which electric power is delivered at increased levels in order that the set temperature is reached in less time than would otherwise be the case in nominal mode.
15. An infrared heater control system according to any of claims 6 to 14 where at least one of the nominal and/or override modes have models used for electric power delivery that avoid delivery of particular electric powers.
16. An infrared heater control system according to any preceding claim comprising a wireless module via which the controller is configured to receive values of one/or more of the control parameters from a remote device.
17. An infrared heater comprising and controlled by the infrared heater control system according to any of claims 1 to 16.
18. An infrared heater according to claim 17 having a cover which is also the heating element of the infrared heater.
19. An infrared heater according to claim 17 or claim 18 where the heating element comprises silicon.
20. A heating system comprising an infrared heater and the infrared heater control system according to any of claims 1 to 16.
21. A heating system according to claim 20 comprising a remote device configured to allow user input of one or more values for one or more of the control parameters.
22. A method of determining the electric power to be delivered to a heating element of an infrared heater, comprising selecting from among no power and a plurality of alternative positive powers to be delivered in accordance with the values of one or more control parameters.
23. A computer program that, when read by a computer, causes performance of the method of claim 22.
24. A non-transitory computer readable storage medium comprising computer readable instructions that, when read by a computer, cause performance of the method of claim 22.
25. A signal comprising computer readable instructions that, when read by a computer, cause performance of the method of claim 22.