Portable air conditioning or heating apparatus suitable for use in a hazardous environment

Abstract

A controller (10) for use in controlling a portable air conditioning apparatus (100, fig 5) or portable heater apparatus (200, fig 8) for use in a hazardous environment. The controller comprises a pro

Description

FIELD 5 This relates to a controller for use in controlling a portable air conditioning apparatus or portable heater apparatus suitable for use in a hazardous environment, to a portable air conditioning apparatus or portable heater apparatus comprising said controller, and to associated methods of heating or cooling using said portable air conditioning apparatus or portable heater apparatus. 10 BACKGROUND Air conditioning and heating equipment is used in a wide variety of environments to control, either by cooling or heating, the temperature of the air in an enclosed space. 15 Many industrial applications involve the use of air conditioning and / or heating equipment in hazardous environments e.g. environments in which the presence of substances such as gases, vapours, mist or dust in the air can, in the event of an ignition, cause an explosion. 20 There are, however, significant challenges with the use of conventional air conditioning and / or heating equipment in such hazardous environments. Given their safety critical nature, equipment used in hazardous environments 25 must comply with strict safety requirements. In the European Union, for example, equipment used in hazardous environments must comply with European Union Directive 2014 / 34 / EU (commonly known as The ATEX Equipment Directive) with similar certification being provided via lECEx and UKEx certification. 30 The design and build requirements to satisfy ATEX, lECEx and UKEx or equivalent certification standards results, amongst other things, in existing air conditioning and / or heating equipment being relatively large, and thus unsuitable for many industrial applications. 35 08 10 24 SUMMARY Aspects of the present disclosure relate to a portable air conditioning apparatus or portable heater apparatus, and to associated methods of heating or cooling using said portable air conditioning apparatus or portable heater apparatus. 5 According to a first aspect, there is provided a portable air conditioning apparatus according to the appended claims. Beneficially, the provision of a controller which combines one or more 10 intrinsically safe circuits and one or more non-intrinsically safe circuits within the same programmable logic controller obviates the requirement for components that have to be installed in large and heavy protective enclosures while providing the same level of functionality as conventional equipment. This in turn means that the apparatus may be significantly more compact and / or have less mass, facilitating its use in portable air 15 conditioning or portable heater equipment while at the same time meeting the ATEX certification requirements for hazardous environments. As described above, the controller comprises or takes the form of a programmable logic controller (PLC). The controller may comprise or take the form of a 20 Zone 1 programmable logic controller. Beneficially, the provision of a Zone 1 programmable logic controller allows the controller to operate safely in an explosive environment i.e. an area in which an explosive gas atmosphere is likely to occur in normal operation. 25 Beneficially, the programmable logic controller may be capable of operating efficiently and reliably in the challenging operating and / or environmental conditions present in industrial air conditioning and heating applications. 30 The programmable logic controller may be configured and / or operable to be infallible, i.e., the programmable logic controller and components thereof may be configured and / or operable so that in the event of a fault the components exhibit high resistivity. 08 10 24 The first circuit board may define a main circuit board of the programmable logic controller. 5 The first circuit board may be encapsulated. The programmable logic controller may comprise a second circuit board. The first circuit board may define a master circuit board of the programmable 10 logic controller and the second circuit board may define a slave circuit board of the programmable logic controller. The second circuit board may be encapsulated. 15 The programmable logic controller may comprise one or more electrical isolation devices. The one or more electrical isolation devices may be configured to electrically isolate e.g. galvanically isolate, the first circuit board from the second circuit board. 20 The one or more electrical isolation devices may comprise one or more transformers and / or one or more optocouplers. Beneficially the provision of one or more electrical isolation devices provides isolated power and communications to the second circuit board. This in turn means the 25 second circuit board can be galvanically isolated to the requirements of I EC 60079-11. The controller may comprise, may be coupled to or operatively associated with a detector arrangement. 30 The detector arrangement may comprise one or more detector configured to detect dust levels, e.g. within the portable air conditioning apparatus or the portable heater apparatus. 08 10 24 The detector arrangement may comprise one or more detector configured to detect vibration, e.g. within the portable air conditioning apparatus or the portable heater apparatus. 5 The detector arrangement may comprise one or more detector configured to detect orientation, e.g. of the portable air conditioning apparatus or the portable heater apparatus. The detector arrangement, or one or more detector of the detector 10 arrangement, may be disposed within the encapsulation of the first circuit board and / or the second circuit board. The programmable logic controller may be configured and / or operable to ensure isolation of low voltage power for use in hazardous environments. 15 The programmable logic controller may comprise a processor. The processor may comprise or take the form of a central processing unit (CPU). The programmable logic controller may comprise an input / output module. 20 The input / output module may be configured and / or operable to send and receive data from external components, such as a sensor arrangement and / or components of the air conditioning apparatus or heater apparatus. 25 The programmable logic controller may comprise a memory unit. The memory unit may be configured and / or operable to store data and / or one or more programs to be executed by the processor. 30 The programmable logic controller may comprise a communication module. The communication module may be configured and / or operable to store data and / or one or more programs to be executed by the processor. 35 The programmable logic controller may comprise a power supply. 08 10 24 The power supply may be configured and / or operable to supply power to components of the controller. 5 Beneficially, the air conditioning apparatus is configured to meet the requirements of ATEX, lECEx and UKEx certification for zones 1 &2 (gas) and zones 21 and 22 (dust), providing highly effective cooling for hazardous areas with potentially explosive atmospheres in a portable and compact unit. 10 Moreover, the air conditioning apparatus is configured to withstand harsh environmental conditions, such that the air conditioning apparatus may be utilised in locations and / or applications which are otherwise inaccessible for conventional air conditioning equipment. 15 The air conditioning apparatus may comprise a power supply unit. The power supply unit may comprise or take the form of a Zone 1 power supply unit. 20 Beneficially, the provision of a Zone 1 power supply unit allows the air conditioning apparatus to operate safely in an explosive environment i.e. an area in which an explosive gas atmosphere is likely to occur in normal operation. 25 The power supply may be configured and / or operable to be infallible, i.e., the power supply and components thereof may be configured and / or operable so that in the event of a fault the components exhibit high resistivity. The power supply unit may comprise one or more inputs and one or more 30 outputs. The power supply unit may comprise one or more electrical isolation devices. The one or more electrical isolation devices may be configured to electrically isolate e.g. galvanically isolate, the one or more inputs of the power supply unit from the one 35 or more outputs of the power supply unit. 08 10 24 The one or more electrical isolation devices may comprise one or more transformers and / or one or more optocouplers. 5 Beneficially the provision of one or more electrical isolation devices provides isolated power to the controller. This also means the power supply unit can be galvanically isolated to the requirements of IEC 60079-18. The power supply unit may be configured and / or operable to ensure isolation of 10 low voltage power for use in hazardous environments. Beneficially, the power supply according to the present disclosure has smaller dimensions in comparison to conventional power supply units. 15 The air conditioning apparatus comprises one or more solid state relay (SSR) devices. Beneficially, the provision of one or more solid state relay devices obviates the requirement for mechanical contact and moving parts, which may otherwise represent 20 an ignition source, and thus permits their use in explosive atmospheres. Solid state relay devices also have comparatively long electrical and mechanical life expectancy and have improved shock and vibration resistance. Moreover, the one or more solid state relay devices according to the present 25 disclosure are relatively compact and / or lightweight compared to conventional solid state relay (SSR) devices, while providing the functionality of larger, conventional, devices. The air conditioning apparatus may comprise a condenser. 30 The air conditioning apparatus may comprise a compressor. The air conditioning apparatus may comprise an evaporator. 35 The air conditioning apparatus may comprise an expansion valve. 08 10 24 In use, the air conditioning apparatus may be configured to extract heat from warm or hot air within a building or other enclosed area located in a hazardous environment by circulating a working fluid - in particular a refrigerant - between the 5 evaporator, the compressor, the condenser and expansion valve. On exposure to the warm or hot air, the working fluid passing through the evaporator evaporates at low pressure, during which evaporation process the working fluid absorbs heat from the surrounding air. The working fluid then passes through the compressor which reduces its volume and increases its temperature. The working fluid then passes to the 10 condenser where it condenses, during which process stored heat is released to the air passing through the condenser. The working fluid then returns to the evaporator via the expansion valve. The air conditioning apparatus may comprise a fan operatively associated with 15 the evaporator. The fan operatively associated with the evaporator may be configured and / or operable to draw air over the evaporator. 20 The fan operatively associated with the evaporator may comprise an ATEX certified fan. The air conditioning apparatus may comprise a fan operatively associated with the condenser. 25 The fan operatively associated with the condenser may be configured and / or operable to direct air over the condenser. The evaporator fan may comprise an ATEX certified fan. 30 The air conditioning apparatus may comprise a sensor arrangement. The portable air conditioning apparatus may be configured to operate using a 3 phase electrical supply. 08 10 24 The portable air conditioning apparatus may be configured to operate using a 400 Volt to 440 Volt supply voltage. The portable air conditioning apparatus may be configured to operate using a 440 Volt supply voltage. The portable air conditioning apparatus may be configured to operate using a 400 Volt supply voltage. 5 According to a second aspect, there is provided a method of cooling using the portable air conditioning apparatus of the first aspect. According to a third aspect, there is provided a portable heater apparatus 10 according to the appended claims. The portable heater apparatus may comprise a power supply unit. The power supply unit may comprise or take the form of a Zone 1 power supply 15 unit. Beneficially, the provision of a Zone 1 power supply unit allows the portable heater apparatus to operate safely in an explosive environment, i.e. an area in which an explosive gas atmosphere is likely to occur in normal operation. 20 The power supply unit may be configured and / or operable to be infallible, i.e., the power supply and components thereof may be configured and / or operable so that in the event of a fault the components exhibit high resistivity. 25 The power supply unit may comprise one or more inputs and one or more outputs. The power supply unit may be configured to convert the mains power supply from three phase AC into a regulated DC power supply to drive the controller. The 30 power supply unit may be configured to step down, and maintain at a constant level, the voltage of the mains power supply to e.g. to 24V, which may result in a nominal current and voltage level which is sufficiently low to be considered intrinsically safe. The power supply unit may comprise one or more electrical isolation devices. 35 The one or more electrical isolation devices may be configured to electrically isolate 08 10 24 e.g. galvanically isolate, the one or more inputs of the power supply unit from the one or more outputs of the power supply unit. The one or more electrical isolation devices may comprise one or more 5 transformers and / or one or more optocouplers. Beneficially the provision of one or more electrical isolation devices provides isolated power to the controller. This also means the power supply unit can be galvanically isolated to the requirements of IEC 60079-18. 10 The power supply may be configured and / or operable to ensure isolation of low voltage power for use in hazardous environments. Beneficially, the power supply according to the present disclosure has smaller 15 dimensions in comparison to conventional power supply units. The portable heater apparatus comprises one or more solid state relay (SSR) devices. 20 Beneficially, the provision of one or more solid state relay devices obviates the requirement for mechanical contact and moving parts, which may otherwise represent an ignition source, and thus permits their use in explosive atmospheres. Solid state relay devices also have comparatively long electrical and mechanical life expectancy and have improved shock and vibration resistance. 25 Moreover, the one or more solid state relay devices according to the present disclosure are relatively compact and / or lightweight compared to conventional solid state relay (SSR) devices, while providing the functionality of larger, conventional, devices. 30 According to a fourth aspect, there is provided a method of heating using the portable heater apparatus of the third aspect. The invention is defined by the appended claims. However, for the purposes of 35 the present disclosure it will be understood that any of the features defined above or CM 00 described below may be utilised in isolation or in combination. For example, features described above in relation to one of the above aspects or below in relation to the detailed description below may be utilised in any other aspect, or together form a new aspect. BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects will now be described by way of example with reference to the accompanying drawings, of which: Figure 1 shows a system block diagram of a system for use in a portable air conditioning apparatus or portable heater apparatus suitable for use in a hazardous environment; Figure 2 shows a detailed block diagram of the system shown in Figure 1; Figure 3 shows an exploded perspective view of the controller shown in Figure 1; Figure 4 shows an exploded perspective view of the power supply unit shown in Figure 1; Figure 5 shows a front perspective view of a portable air conditioning apparatus comprising the controller and power supply unit shown in Figure 1; Figure 6 shows a rear perspective view of the portable air conditioning apparatus shown in Figure 5, with enclosure removed; Figure 7 shows a detailed block diagram of the controller of the portable air conditioning apparatus shown in Figure 5 and its external connections; Figure 8 shows a front perspective view of a portable heater apparatus comprising the controller and power supply unit shown in Figure 1; Figure 9 shows a side elevation view of the portable heater apparatus shown in Figure 8; and Figure 10 shows a detailed block diagram of the controller of the portable heater apparatus shown in Figure 8 and its external connections. DETAILED DESCRIPTION OF THE DRAWINGS Referring first to Figure 1 of the accompanying drawings, there is shown a system block diagram of a system 1 comprising a controller, generally denoted 10, and power supply unit, generally denoted 12, the system being for use as a portable air conditioning apparatus 100 (shown in Figures 5 to 7) or a portable heater apparatus 200 (shown in Figures 8 to 10), suitable for use in a hazardous environment. As will be described further below, the controller 10 comprises or takes the form of a programmable logic controller configured to communicate to and / or from one or more intrinsically safe circuits, generally denoted 14, and one or more non-intrinsically safe circuits, generally denoted 16. Beneficially, the provision of a controller 10 which combines communication to and / or from one or more intrinsically safe circuit 14 and one or more non-intrinsically safe circuit 16 within the same controller 10 obviates the requirement for components that have to be installed in large and heavy protective enclosures while providing the same level of functionality as conventional equipment. This in turn means that the controller 10 may be significantly more compact and / or have less mass, facilitating its use in portable air conditioning or portable heater equipment while at the same time meeting the ATEX certification or equivalent certification requirements for hazardous environments, and more particularly in a Zone 1 hazardous environment i.e. an area in which an explosive gas atmosphere is likely to occur in normal operation.. Moreover, the controller 10 is capable of operating efficiently and reliably in the challenging operating and / or environmental conditions present in industrial air conditioning and heating applications. As shown in Figure 1, the controller 10 comprises a first PLC, generally denoted 18, and a second PLC, generally denoted 20. The first PLC 18 defines a main PLC of the controller 10 and the second PLC 20 defines a mini PLC of the controller 10. The controller 10 is configured so that the first PLC 18 functions as a master PLC and the second PLC 20 acts as a slave PLC, although in other embodiments the first PLC 18 and second PLC 20 may alternatively not be configured in a master and slave arrangement. As shown in Figure 1, the power supply unit 12 is coupled to a mains power supply, generally denoted PS. The mains power supply PS takes the form of a 3-phase AC power supply, and more particularly a 440V AC power supply. However, it will be recognised that the power supply unit 12 may be configured and / or operable to use any suitable power supply. The controller 10 is coupled to the mains power supply PS via the power supply unit 12. Referring now to Figure 2 of the accompanying drawings, which shows a detailed block diagram of the system of Figure 1. As shown in Figure 2, power supply unit 12 comprises a 3-phase rectifier 22, switching circuitry which comprises a transformer 24, one or more optocouplers 26, and a voltage regulator 28. The power supply unit 12 further comprises a shunt voltage limiter or voltage clamp not shown in Figure 2 for clarity. The power supply unit 12 is configured to convert the mains power supply PS from three phase AC into a regulated DC power supply to drive the controller 10. The power supply unit 12 is also configured to step down, and maintain at a constant level, the voltage of the mains power supply PS to e.g. 24V, which results in a nominal current and voltage level which is sufficiently low to be considered intrinsically safe. As described above, the controller 10 comprises first PLC 18. The first PLC 18 is coupled to, and receives power from, power supply unit 12. As shown in Figure 2, the first PLC 18 comprises an input / out module comprising a number of inputs and outputs. The inputs and outputs are coupled to one or more non-intrinsically safe circuits 16 which comprise suitably certified devices e.g. indicators within an Ex-d enclosure. In the described controller 10 the non-intrinsically safe circuits 16 comprise non-IS analogue and digital inputs, and digital outputs. However, it will be understood that any combination of suitably certified devices may be used. The first PLC is further coupled to one or more solid state relays 30. The solid state relays 30 are coupled between main power supply PS and one or more powered devices 32 e.g. a fan, heater or compressor. However, it will be understood that any suitably powered device may be used. In this way, second PLC 20 can control power to the powered devices whilst remaining galvanically isolated from main power supply PS. As described above, the controller 10 further comprises a second PLC 20. The second PLC 20 is coupled to, and receives power from, power supply unit 12 via transformer 36. In this way second PLC 20 is galvanically isolated from power supply unit 12. The second PLC 20 is also coupled to the first PLC 18 via one or more optocouplers 38. In this way second PLC 20 is also galvanically isolated from first PLC 18. The second PLC 20 comprises an input / out module comprising a number of inputs and outputs. The inputs and outputs are coupled to one or more intrinsically safe circuits 14 which comprise suitably certified devices or simple apparatus. In the described controller 10 the intrinsically safe circuits 14 comprise one or more temperature sensors, low pressure control switches, low pressure safety switches, high pressure safety switches, belt tension switches and LEDs. However, it will be understood that any combination of suitably certified devices may be used. Referring now to Figure 3 of the accompanying drawings, which shows an exploded perspective view of the controller 10. As shown in Figure 3, the controller 10 comprises a housing 40, which in the illustrated controller 10 is constructed from Aluminium alloy having less than 7.5% magnesium, titanium and zirconium by mass. Although not shown in Figure 3, the housing 40 is connected to earth. The housing 40 is configured to receive the first PLC 18 and the second PLC 20. In the illustrated controller 10, the first PLC 18 and the second PLC 20 are encapsulated by an encapsulation material 38, which in the illustrated controller 10 takes the form of a resin, e.g. a polyurethane or epoxy resin. In the illustrated controller 10, the controller 10 comprises terminals 42. However, it will be understood that in other embodiments of the controller 10 terminals 42 may not be present. When located in the portable air conditioning apparatus 100 or portable heater apparatus 200, the controller 10 is disposed within an Ex-e enclosure 46. Referring now also to Figure 4 of the accompanying drawings, which shows an exploded perspective view of the power supply unit 12. As shown in Figure 4, the power supply unit 12 comprises a housing 52, which in the illustrated power supply unit 12 is constructed from Aluminium alloy having less than 7.5% magnesium, titanium and zirconium by mass. In the illustrated power supply unit 12, the housing 52 is not an Ex-e enclosure but is coupled to an Ex-e enclosure via wiring tube 54. As shown in Figure 4, the housing 52 is configured to receive a PCB 56. In the illustrated power supply unit 12, the PCB 56 is encapsulated by an encapsulation material 58, which in the illustrated controller 10 takes the form of a resin, e.g. a polyurethane or epoxy resin. The power supply unit 12 further comprises a thermal interface which in the illustrated power supply unit 12 takes the form of thermally conductive tape or sheet 62 (two thermally conductive tapes or sheets are provided in the power supply unit 12). As described above, the controller 10 and power supply unit 12 are configured and / or operable for use in a portable air conditioning apparatus 100 and referring now also to Figures 5 to 7 of the accompanying drawings, there is shown a portable air conditioning apparatus 100 comprising the controller 10 and the power supply unit 12. Beneficially, the air conditioning apparatus 100 is configured to meet the requirements of ATEX, lECEx and UKEx certification for zones 1 &2 (gas) and zones 21 and 22 (dust), providing highly effective cooling for hazardous areas with potentially explosive atmospheres in a portable and compact unit. Moreover, the portable air conditioning apparatus 100 is configured to withstand harsh environmental conditions, such that the air conditioning apparatus 100 may be utilised in locations and / or applications which are otherwise inaccessible for conventional air conditioning equipment. As shown, the portable air conditioning apparatus 100 comprises an enclosure 102. The enclosure 102 is disposed on castors 104, which facilitate manoeuvring of the apparatus 100. The air conditioning apparatus may comprise an evaporator 106, a compressor 108, a condenser 110, and an expansion valve 112. In use, the air conditioning apparatus 100 is configured to extract heat from warm or hot air within a building or other enclosed area located in a hazardous environment by circulating a working fluid - in particular a refrigerant - between the evaporator 106, the compressor 108, the condenser 110 and expansion valve 112. On exposure to the warm or hot air, the working fluid passing through the evaporator 106 evaporates at low pressure, during which evaporation process the working fluid absorbs heat from the surrounding air. The working fluid then passes through the compressor 108, which reduces its volume and increases its temperature. The working fluid then passes to the condenser 110 where it condenses, during which process stored heat is released to the air passing through the condenser 110. The working fluid then returns to the evaporator 106 via the expansion valve 112. As shown, the air conditioning apparatus 100 comprises a fan 118 operatively associated with the evaporator 106 and which is configured and / or operable to draw air over the evaporator 106. In the illustrated apparatus 100, the fan 118 operatively associated with the evaporator 106 is an ATEX certified fan. The air conditioning apparatus 100 comprises a fan 120 operatively associated with the condenser 110 and which is configured and / or operable to direct air over the condenser 110. In the illustrated apparatus 100, the fan 120 operatively associated with the condenser 110 is an ATEX certified fan. As shown in the block diagram of Figure 7 the Non-IS circuits 116 of the portable air conditioning apparatus 100 comprise 2 x digital inputs, an accelerometer interface, a serial interface and an LED. However, it will be understood that any combination of suitably protected devices may be used. As shown the IS circuits 114 of the portable air conditioning apparatus 100 comprise 2 x pressure safety switches, a belt tension switch, a pressure control switch and an LED. However, it will be understood that any combination of suitably certified devices may be used. As shown the portable air conditioning apparatus 100 comprises 2 x solid state relays 130 coupled to a fan 118 and a compressor 108. However, it will be understood that any combination of powered devices and associated solid state relays may be used. As described above, the controller 10 and power supply unit 12 are configured and / or operable for use in a portable heater apparatus 200 and referring now also to Figures 8 to 10 of the accompanying drawings, there is shown a portable heater apparatus 200 comprising the controller 10 and the power supply unit 12. As shown in Figures 8 and 9, the portable heater apparatus 200 comprises an enclosure 202. In the illustrated heater apparatus 200, the enclosure 202 is constructed from stainless steel and takes the form of a fully welded construction. However, it will be understood that the enclosure 202 may be manufactured from any suitable material and / or form of construction. As shown, the heater apparatus 200 comprises an outlet 204 for directed heated air from the heater apparatus 200. As shown, the enclosure 202 is coupled to end plates 206. In the illustrated heater apparatus 200, the end plates 206 are constructed from plastic. However, it will be understood that the end plates 206 may be manufactured from any suitable material and / or form of construction, and in some instances may be integrally formed with the enclosure 202. In the illustrated apparatus 200, the end plates 206 each comprise an aperture 208 to facilitate handling of the apparatus 200. The heater apparatus 200 further comprises a frame 210, which functions to protect the enclosure 202. The frame 210 also forms a handle portion to facilitate handling of the heater apparatus 200. As shown most clearly in Figure 9, the heater apparatus 200 comprises a motor 212, an impeller 218 and a heater assembly 220. In the illustrated heater apparatus 200, the heater assembly 220 is configured to operate using an AC 3 phase supply, e.g. 400V to 440V, and is an ATEX certified heater including a thermal cut-out mechanism. 08 10 24 As in the air conditioning apparatus 100, in the heater apparatus 200 a finger guard 222 is provided across the outlet 204 of the heater apparatus 200. In use, the motor 212 drives the impeller 218 to direct warm air heated by the 5 heater assembly 220 through the outlet 204. As shown in the block diagram of Figure 10 the Non-IS circuits 216 of the portable heater apparatus 200 comprise 2 x digital outputs, 8 x analogue inputs, a serial interface and an LED. However, it will be understood that any combination of 10 suitably protected devices may be used. As shown the IS circuits 214 of the portable heater apparatus 200 comprise 2 x digital inputs, an accelerometer interface, 3 x PT100 temperature sensors and an LED. However, it will be understood that any combination of suitably certified devices may be 15 used. As shown the portable heater apparatus 200 comprises 2 x solid state relays 230 coupled to a motor 212 and a heater 220. However, it will be understood that any combination of powered devices and associated solid state relays may be used. 20 Various modifications may be made without departing from the scope of the invention as defined in the claims. 08 10 24

Claims

1. A portable air conditioning apparatus for use in hazardous environments, comprising:5 a controller for use in controlling the portable air conditioning apparatus; andone or more solid state relay (SSR) devices;wherein the controller comprises or takes the form of a programmable logic controller configured to operate one or more intrinsically safe circuits and one or more non-intrinsically safe circuits.

102. The controller of claim 1, wherein the programmable logic controller comprises a first circuit board and a second circuit board.

3. The controller of claim 2, wherein the first circuit board and / or the second circuit 15 board are encapsulated.

4. The controller of any one of claims 2 or 3, wherein the first circuit board is configured to function as a master circuit board of the programmable logic controller and the second circuit board is configured to function as a slave circuit board of the 20 programmable logic controller.

5. The controller of any one of claims 2 to 4, wherein the controller further comprises one or more electrical isolation devices configured to galvanically isolate the first circuit board from the second circuit board.

256. The controller of claim 5, wherein the one or more electrical isolation devices comprise one or more transformers and / or one or more optocouplers.

7. The portable air conditioning apparatus of any preceding claim, further30 comprising a power supply unit.

8. The portable air conditioning apparatus of claim 7, wherein the power supply unit further comprises:one or more inputs and one or more outputs; and08 10 24one or more further electrical isolation devices configured to galvanically isolate the one or more inputs from the one or more outputs.

9. The portable air conditioning apparatus of claim 8, wherein the one or more 5 further electrical isolation devices comprise one or more transformers and / or one or more optocouplers.

10. A method of cooling using the portable air conditioning apparatus of any one of claims 1 to 9.1011. A portable heater apparatus for use in hazardous environments, comprising:, a controller for use in controlling the portable heater apparatus; and one or more solid state relay (SSR) devices;wherein the controller comprises or takes the form of a programmable logic 15 controller configured to operate one or more intrinsically safe circuits and one or more non-intrinsically safe circuits12. The controller of claim 11, wherein the programmable logic controller comprises a first circuit board and a second circuit board.2013. The controller of claim 12, wherein the first circuit board and / or the second circuit board are encapsulated.

14. The controller of any one of claims 12 or 13, wherein the first circuit board is 25 configured to function as a master circuit board of the programmable logic controller and the second circuit board is configured to function as a slave circuit board of the programmable logic controller.

15. The controller of any one of claims 12 to 14, wherein the controller further 30 comprises one or more electrical isolation devices configured to galvanically isolate the first circuit board from the second circuit board.

16. The controller of claim 15, wherein the one or more electrical isolation devices comprise one or more transformers and / or one or more optocouplers.

17. The portable heater apparatus of any one of claims 11 to 16, further comprising a power supply unit.

18. The portable heater apparatus of claim 17, wherein the power supply unit 5 further comprises:one or more inputs and one or more outputs; andone or more further electrical isolation devices configured to galvanically isolate the one or more inputs from the one or more outputs.10 19. The portable heater apparatus of claim 18, wherein the one or more furtherelectrical isolation devices comprise one or more transformers and / or one or more optocouplers.

20. A method of heating using the portable heater apparatus of any one of claims 15 11 to 19.CMCO

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