GB2563040A - Downlight assembly - Google Patents

Abstract

A fire-rated downlight assembly 111 comprises a heat sink 102 having a front surface 102a and a rear surface 102b and a lighting element 103 comprising one or more LEDs. The lighting element 103 is located on the front surface 102a of the heat sink 102 and a first portion of intumescent material 104 is located on the rear surface of the heat sink. The first portion of intumescent material 104 is configured to swell under heat from the heat sink 102 to cover a vulnerable portion of the rear surface 102b. This restricts penetration of the assembly 111 by a fire below the front surface 102a and achieves an improved fire rating of the downlight.

Description

Figure 6

Downlight assembly

Field ofthe invention

This invention relates to improvements in fire-rated downlight assemblies.

Background to the invention

LED downlights are used in buildings to provide light sources that can sit almost flush with a ceiling, thereby taking up a reduced amount of space compared to a traditional hanging light fitting.

LED downlights are typically installed into apertures in ceilings. Current building regulations typically require such surfaces to act as a fire barrier for an amount of time (typically at least 30 minutes). Therefore, LED lights must be designed to adhere to such regulations considering that they are installed in ceiling apertures that may provide a means for a fire to spread from a room below the ceiling.

In prior art devices, aluminium circuit boards are mounted below aluminium heat sinks in order to efficiently dissipate heat that is generated by the LED lights during operation. However such aluminium components typically have a melting point of around 660 degrees C. These components would not withstand temperatures of 1100 degrees C (as required by UK building regulations) for the required length of time.

GB2518534 discloses a lighting unit that incorporates a collar or sleeve of intumescent fireproof material mounted within a mounting ring and being adapted to expand and occlude the area below a heat sink in the event of a fire. However, providing an intumescent sleeve has several disadvantages. For example, it is costly and difficult to manufacture a sleeve of intumescent material to be situated within a mounting ring. Furthermore, the passive fire protection provided by the sleeve is confined within this mounting ring.

Existing lighting units also typically require bulky driver units for providing the correct electrical voltage to the LED. Often such driver units are complex to fit.

It is an object of the inventors to provide a downlight that overcomes such problems.

Summary of Invention

In a first aspect the invention provides a fire-rated downlight assembly comprising a heat sink having a front surface and a rear surface, a lighting element comprising one or more LEDs, the lighting element being located on the front surface of the heat sink; and a first portion of intumescent material located on the rear surface of the heat sink configured to swell when exposed to heat conducted through the heat sink to substantially cover a vulnerable portion of the rear surface of the heat sink in order to restrict penetration of the assembly by a fire wherein the heat is conducted from the front surface to the rear surface of the heat sink and is generated by a fire being located in front of the front surface.

The vulnerable portion of the rear surface may correspond to a vulnerable portion of the front surface being exposed directly to the fire. The vulnerable portion of the rear surface may be the entire rear surface.

The intumescent material provides for passive fire protection by swelling and creating a barrier to restrict the spread of fire through an aperture in a wall or ceiling within which a downlight assembly typically sits. It is particularly important to create a barrier to restrict penetration of the fire through gaps that may arise in parts of components that are vulnerable to the fire. For example, the heat sink may be made of aluminium in order to take advantage of the heat conductive properties of that metal. Aluminium melts at a lower temperature than steel (approx. 660 degrees C) and therefore any part of the front surface of the heat sink that is not protected by another element such as a steel cover is deemed vulnerable and is hereinafter referred to as a vulnerable portion of the front surface. Typically the corresponding portion of the rear surface (i.e. the portion affected if the vulnerable portion of the front surface falls away due to heat) is referred to as the vulnerable portion of the rear surface. The inventors have determined that a first portion of intumescent material can be placed on a rear surface of the heat sink (this may be above the heatsink if the downlight is inserted in a ceiling pointing towards a floor). Such placement has many advantages compared to for example placing the material on a front surface (e.g. below) the heat sink as will be discussed further below.

In normal use, the heat sink may be designed to conduct heat generated by the LEDs effectively in order that the heat is dissipated. Therefore, during a fire that is proximal to the downlight assembly, the intumescent material may be rapidly exposed to heat from the fire since the heat sink will conduct heat from the fire effectively. Due to exposure to this heat that has been conducted through the heat sink, the first portion of intumescent material will react thereby swelling to cover a vulnerable portion of the rear of the heat sink. The temperature at which the intumescent reacts and begins to swell may be referred to as the activation temperature. This temperature may be in the region of 200 degrees C - significantly higher than the temperature that might be reached during normal operation of the downlight assembly, but less than the temperature at which the heat sink begins to melt. It should be noted that the intumescent material relies on heat transfer through the heat sink to gain exposure to heat that causes it to react and swell. As a result of the swelling of intumescent material, a barrier is formed that restricts penetration of the fire through the assembly. This barrier is formed even if elements of the downlight assembly fall away or melt due to the fire. The claimed downlights may therefore be placed in walls or ceilings without unduly compromising the fire resistant properties of such walls or ceilings. In contrast, prior art devices typically have intumescent material mounted in front of the heat sink with the aim of preventing the heat sink from over-heating. In the present invention, the intumescent material reacts in anticipation of the heat sink from being damaged thereby allowing for advantageous placement of the intumescent material. Prior art devices also typically require direct flame contact of a fire with the intumescent material.

The downlight assembly may further comprise a connecting wire attached to the lighting element and passing through a channel in the heating element that extends from the front surface of the heat sink to the rear surface of the heat sink.

The downlight assembly may further comprise a second portion of intumescent material mounted within the channel. The second portion of intumescent material may be configured to swell when exposed to heat conducted through the heat sink to fill the channel in order to restrict penetration of the channel by the fire.

The downlight assembly may further comprise a third portion of intumescent material mounted on the heat sink and being substantially proximal to a rear portion of the connecting wire that extends beyond the rear surface of the heat sink. The third portion of intumescent material may be configured to swell when exposed to heat conducted through the heat sink to substantially block the channel in order to restrict penetration of the assembly by the fire.

It is possible for a fire to spread through the heat sink via the channel. Swelling of the first strip of intumescent material due to heat restricts spread of a fire through this channel. Swelling of the third portion of intumescent material due to heat further restricts the spread of fire. The second and third portions of intumescent material improve the passive fire protection properties of the downlight assembly.

The downlight assembly may further comprise a metal cover that covers a portion of the front surface of the heatsink and being configured to restrict flames from contacting the heatsink in the event of a fire. Both a lens and the metal cover may be supported on a bevel of a metal bracket.

The heat sink may comprise one or more fins pointing away from the rear surface configured in use to dissipate heat generated by the lighting element and to provide a mounting space for the portion of intumescent material.

The portion of intumescent material may be mounted at a central point of the rear surface of the heat sink. A central mounting location helps ensure that the intumescent material swells to substantially cover the rear surface that is vulnerable since the material may swell substantially evenly across its entire volume.

The one or more fins may be arranged to surround the intumescent material. The one or more fins may be arranged in one or more concentric rings surrounding the intumescent material. Any of the one or more fins may have a u-shaped cross section.

Locating the intumescent material at the rear of the heat sink (such as above the heat sink in the case of a ceiling downlight) provides for many advantages. There is improved design flexibility for parts of the downlight that are to the front of the heatsink. As an example, GB2518534 requires a ring or “sleeve” of intumescent material to be placed in front of the heat sink. This has implications and introduces limitations to the design of components of the downlight. For example, the intumescent material must be in the form of a sleeve for a particular size of LED circuit board. Such considerations are not relevant to claimed invention since the area to the rear of the heat sink is typically behind a ceiling or wall and there is usually a large amount of space in this area. Furthermore, the portions of intumescent material may advantageously be of any shape and size such as a horizontal disc, lump or irregular globule. The portions of intumescent material may be contiguous or non-contiguous. Manufacturing costs and difficulty are therefore reduced. The portion of intumescent material can be varied depending on the level of fire protection desired and is not limited based on the positioning and size of components located in front of the heat sink.

Further advantages may be realised due to the interaction of the portion of intumescent material with features of the downlight on or around the rear surface of the heat sink. For example, fins on the rear surface of the heat sink may be arranged to improve the effectiveness of the intumescent material. Placing fins in a circular formation around the intumescent material may serve to restrict the swelling of intumescent material so that it does not increase in volume to such a degree that the density of intumescent material reduces below levels acceptable to provide passive fire protection. Furthermore, the fins may prevent any drafts in the region at the rear of the heatsink (i.e. typically behind a wall/ceiling) unfavourably affecting the intumescent material as it swells. For example, a draft may blow swelling intumescent material that is exposed away from the intended surface that it is supposed to protect if no fins were present.

Another advantage is that the frontal surface of downlights (i.e. the surface that emits light and is exposed to users) may become degraded over time due to actions such as cleaning, accidental damage or redecoration. It is possible for components in front of the heat sink to drop out and these may not be replaced if for example a building is left unoccupied. Placing intumescent material to the rear of the heat sink ensures that the passive fire protection provided by the intumescent material is maintained in such instances. It is also possible to easily secure the intumescent material to the rear of the heat sink (for example using a screw). It is also clearly obvious to an installer that a portion of intumescent material is present if it is visibly located on the rear of the heat sink in order to reassure the installer that there is no manufacturing defect.

Another advantage is the risk of the portion of intumescent material “activating” and swelling due to the heat generated by the lighting element in normal use is minimised since the intumescent material is not placed within a common space with the lighting element as is the case in some prior art devices.

The third portion of intumescent material may be mounted on the one or more fins.

The heat sink may be manufactured from aluminium and the metal cover may be manufactured from steel.

The downlight assembly may further comprise a driver housing configured to receive one or more electricity cables and provide an output voltage to the connecting wire. The driver housing may be attached to the rear surface of the heat sink. The driver housing may be attached to the rear surface of the heat sink using attachment points located on the ends of one or more attachment fins extending from the rear surface of the heat sink. The driver housing may be supported by tips of the one or more fins and the driver housing may substantially cover the rear surface of the heat sink. A rear planar surface area of the rear surface of the heatsink may be substantially equivalent to a front planar surface area of the driver housing.

Attaching the driver housing to a rear surface of the heat sink advantageously provides for the downlight assembly unit to be compact and easy to install. The tips of the fins may provide mounting points for the driver unit. The positioning of the driver unit may further improve the effectiveness of intumescent material by restricting the amount of swelling that takes place in a rearward direction thereby ensuring that the material covers substantially the entire rear surface of the heat sink that is vulnerable.

The downlight housing may further comprise a lid having a plurality of toothed openings wherein closure of the lid engages teeth of the toothed openings with one or more electricity cables thereby ensuring that the one or more electricity cables are secured within the plurality of toothed openings.

Any portion of intumescent material may be configured to swell due to heat conducted through the heat sink. In other words, any portion of intumescent material may be configured to swell prior to flames of a fire being in direct contact with intumescent material.

Any portion of intumescent material may be configured to swell due to exposure of an activation temperature that is less than the temperature at which the heat sink begins to melt.

In a second aspect, the invention provides a fire-rated downlight assembly comprising: a heat sink having a front surface and a rear surface; a lighting element comprising one or more LEDs, the lighting element being located on the front surface of the heat sink; and a portion of intumescent material located on the rear surface of the heat sink configured to swell when exposed to heat to substantially cover a vulnerable portion of the rear surface of the heat sink in order to restrict penetration of the assembly by a fire in front of the assembly due to damage to the heat sink caused by the fire.

Embodiments of the second aspect may comprise any features of the embodiments of the first aspect as set forth above.

Brief Description of the Drawings

Figure 1 shows a cross-sectional view through a downlight assembly including a driver housing according to an embodiment of the present invention.

Figure 2 shows a cross-sectional view through a downlight assembly according to an embodiment of the present invention.

Figure 3 shows an exploded perspective view of a downlight assembly including a driver housing according to an embodiment of the present invention.

Figure 4 shows a perspective view of a downlight assembly including a driver housing according to an embodiment of the present invention.

Figure 5 shows a perspective view of a downlight assembly including a driver housing wherein a lid of the driver housing is partially open, according to an embodiment of the present invention.

Figure 6 shows a view of the rear surface of a downlight assembly having been heat tested so that intumescent material has swelled, in accordance with an embodiment of the present invention.

Detailed Description

With reference to Figures 1 to 3 there is shown a fire-rated downlight assembly 101 according to an embodiment of the present invention. The downlight assembly may be attached to parts of a building such as ceilings and walls (not shown). In the example shown, the downlight faces downwards as would be the case for when it is mounted in a ceiling.

The downlight assembly comprises a lens holder 112 that is secured within an aperture in a wall, ceiling, or comparable structure of a building. Typically the downlight assembly will be secured so that light emitted by lighting element 103 shines in a desirable direction. For example this may be downwards, if the downlight assembly is secured in a ceiling. For the purposes of this description, the downlight assembly will be referred to as being secured in a horizontal ceiling and facing downwards towards a floor. However downlights may be secured in different structural features and in different orientations. For example a downlight may be secured in a vertical wall so that light shines at a right-angle to the vertical wall. The term “front” refers to the side of the downlight assembly that faces users (i.e. from which light is emitted). The term “rear” refers to the side of the downlight assembly that faces in the opposite direction to the front faces. Rear facing surfaces may be hidden behind a ceiling or wall (not shown).

In use, flange 112a of the lens holder 112 will abut with a ceiling/wall (not shown) on a rear side of the flange. Spring-biased lugs 113 will bias the lens holder 112 in a rearward direction. In other words, the rear surface of the flange 112a is pressed into a ceiling/wall due to the biasing force of the lugs 113. In this way, the downlight assembly is held in position. The lens holder may also include bezels 112b and 112c upon which components of the downlight assembly rest, namely lens 109, metal cover 110, lens cover 114, and heat sink 102. Bezels 112b and 112c of the lens holder may have a silicone (or similar) layer to provide for an airtight or watertight seal. An aluminium frame 115 may be attached to a frontal surface of bezel 112a.

Metal cover 110 and the lens holder 112 may be made from steel and have a melting point in excess of 1000 degrees C. The Heat sink 102 and bezel 113 may be made from aluminium and have a melting point of approximately 660 degrees C. Aluminium may be used to manufacture the heat sink since it has good heat conductive properties which are necessary in order to ensure that in use, heat generated by the light element 103 is conducted away to ensure that the assembly does not overheat.

Light element 103 (see figure 2) is attached to heat sink 102 on a front surface 102a of the heat sink. Front surface 102a is a vulnerable surface, for reasons that will become apparent from the discussion below. Light element 103 may comprise one or more LEDs mounted on a PCB board that in use, generate heat. Heat sink 102 dissipates some of this heat by transferring the heat to the air at the rear of the wall/ceiling via fins 108. This may be necessary in order to ensure that electrical components do not overheat and damage the assembly.

In the event of a fire in a room, it is necessary for the ceilings and walls to be fire resistant for a certain period of time as stipulated in building regulations. For example, UK regulations state that in some cases, walls and ceilings must be fire resistant for 30 minutes in order to provide time for evacuation. Downlight assemblies may be mounted within apertures in such walls and ceilings, and it is possible for these apertures to be points of weakness with regards to the fire resistance of the wall or ceiling. For example, if a downlight assembly is destroyed in a fire, then fire may spread via the resulting open aperture.

In the event of a fire that is in danger of penetrating a wall/ceiling having downlight assembly 101 installed, the heat from the fire may eventually melt or damage components such as the lens 109, lens cover 114, and aluminium frame 115. These components will eventually drop away from the downlight assembly and the lighting element 103 will be directly exposed to the fire. After a period of time, the heat due to the fire will also melt the lighting element 103 causing it to fall out. A vulnerable portion of the front surface 102a is defined as the portion that is not covered by steel metal cover 110 and lens holder 112. The vulnerable portion of the front surface will be susceptible to melting or destruction due to a fire at a substantially quicker rate than other “non-vulnerable” portions of the front surface. After the lighting element 103 falls out, the vulnerable front surface 102a of the heat sink 102 will now be directly exposed to the fire. Heat from the fire will conduct through the heat sink 102. This heat will cause the intumescent material to react and start to swell. . A first portion of intumescent material 104 is mounted on the rear surface of the heat sink 102bThe first portion of intumescent material will swell to substantially cover the rear surface of the heat sink 102b that corresponds to the vulnerable front surface 102a of the heat sink. At this point, the fire is restricted from penetrating the assembly 101 even though vulnerable parts of the heat sink may melt after the intumescent material has reacted. The intumescent material 104 reacts at around 200 degrees C (i.e. the activation temperature), and the aluminium heat sink 102 reacts at around 660 degrees C. Therefore the intumescent material will react and swell before parts of the heat sink start to melt ensuring that there is an effective fire barrier to areas that are to the rear of the assembly. It should be noted that the invention may ensure that intumescent material is activated and swells before it is directly exposed to flames of a fire.

Steel metal cover 110 and lens holder 112 cover portions of the heat sink that are not covered by the lighting element 103. Therefore these parts are not referred to as being vulnerable. The skilled person would recognise that even these non-vulnerable portions would eventually be destroyed by a fire that is maintained for a certain period of time. However the invention is concerned with delaying the penetration of fire and therefore it is necessary to ensure improved fire resistance for the so-called vulnerable portions of the heat sink.

The lighting element 103 is connected to an LED driver (or driver housing) 111 or the like using connecting wire 105. The LED driver takes in an electrical supply connection (not shown) and provides an appropriate voltage to power LED lights on the lighting element. Connecting wire 105 passes through channel 107 in the heat sink 102. A second portion of intumescent material 106a may be placed within channel 107 adjacent to the connecting wire 105. In the event of a fire as discussed above, the second portion of intumescent material 106a will swell to fill this channel and help restrict penetration of fire through the assembly. Similarly, there may be a third portion of intumescent material 106b that swells to further help fill channel 107 and cover rear surface 102b of the heat sink. The second and third portions of intumescent material may have the same properties as the first portion of intumescent material discussed above.

It should be noted that the device provides for a delay in fire penetration as required by relevant building regulations. For example, a fire may be prevented from penetrating a wall/ceiling containing assemblies as described above for 30 minutes.

Referring to Figures 1, and 3 to 6, there is shown an LED driver (or driver housing) 111 that may be attached to a rear surface of the heat sink 102. In the shown example, the front surface of the LED driver 111 is attached to tips of fins of the heat sink 102. The LED driver 111 has a lid 301 (proximal to a rear portion of the LED driver) and a base 302. The lid and base are linked via a hinge 305 so that the lid may be opened in order to connect electricity supply cables to a bus (not shown) within the driver module. The lid may be snapped in a closed position using clips 306. The lid may further be secured in a closed position using one or more screws (not shown). Typically the LED driver 111 is substantially manufactured from plastic. The LED driver 111 may be sized such that the cross sectional areas of the lid and base, as viewed from the front or rear of the assembly, are substantially similar. The cross sectional areas of the lid and base may also be substantially similar to the surface area of the rear surface of the heatsink. The connecting wire 105 connects the driver unit to the lighting element 103 in order to provide an electrical supply for LEDs mounted on the lighting element 103.

With further reference to Figures 3, 4 and 5 toothed openings 303 and strips 304 are shown for securely retaining electricity cables (not shown). In the shown embodiment, closure of the lid causes the teeth of said toothed openings/strips to engage with electricity cables. There may be no lid, and the electricity cables may be retained by a tooth strip alone.

Figure 6 shows a downlight assembly substantially as described above after a heat test. It can be seen that first and third portions of intumescent material 803/804 has swelled and covered the vulnerable portion of the rear surface of the heat sink. It can be seen that the U shape of the fin ensures that the third portion of intumescent material swells to substantially cover the channel (not shown in Figure 6). The second portion of intumescent material has also swelled, however this cannot be seen in Figure 6.

With reference to Figure 6, it can also be seen that the heat sink 802 may comprise multiple fins 801. These fins may be arranged in a concentric formation around the first portion of intumescent material. As can also be seen, a third portion 106b of intumescent material may be mounted on a fin. The third portion of intumescent material 106b will react similarly to the second portion of intumescent material 106a as discussed above and further restrict the spread of a fire through the assembly. There may be multiple concentric formations. For example, Figure 6 shows an embodiment where there are two such formations. The fins may have a U shaped cross section as can be seen by the outer formation shown in Figure 6. A concentric fin formation provides for the swelling of the intumescent material to be restricted in order that its density does not reduce to such a great degree that any fire resistance qualities are hindered. Figure 6 also shows attachment points for the driver housing located at the end of fins 801. These connections provide for the driver housing to be mounted conveniently directly on the rear side of the assembly 101, as shown in Figures 1, 3, and 4.

Claims (25)

1. A fire-rated downlight assembly comprising:

a heat sink having a front surface and a rear surface;

a lighting element comprising one or more LEDs, the lighting element being located on the front surface of the heat sink; and a first portion of intumescent material located on the rear surface of the heat sink configured to swell when exposed to heat conducted through the heat sink to substantially cover a vulnerable portion of the rear surface of the heat sink in order to restrict penetration of the assembly by a fire; wherein the heat is conducted from the front surface to the rear surface of the heat sink and is generated by a fire being located in front of the front surface.

2. The downlight assembly of claim 1 wherein the vulnerable portion of the rear surface corresponds to a vulnerable portion of the front surface being exposed directly to the fire.

3. The downlight assembly of claim 1 wherein the vulnerable portion of the rear surface is the entire rear surface of the heat sink.

4. The downlight assembly of claim 1 further comprising:

a connecting wire attached to the lighting element and passing through a channel in the heating element that extends from the front surface of the heat sink to the rear surface of the heat sink.

5. The downlight assembly of any of claims 1 to 4 further comprising a second portion of intumescent material mounted within the channel;

wherein;

the second portion of intumescent material is configured to swell when exposed to heat conducted through the heat sink to fill the channel in order to restrict penetration of the channel by the fire.

6. The downlight assembly of any of claims 1 to 5 further comprising a third portion of intumescent material mounted on the heat sink and being substantially proximal to a rear portion of the connecting wire that extends beyond the rear surface of the heat sink wherein;

the third portion of intumescent material is configured to swell when exposed to heat conducted through the heat sink to substantially block the channel in order to restrict penetration of the assembly by the fire.

7. The downlight assembly of any preceding claim further comprising a metal cover that covers a portion of the front surface of the heatsink and being configured to restrict flames from contacting the heatsink in the event of a fire.

8. The downlight assembly of claim 7 wherein both a lens and the metal cover are supported on a bevel of a metal bracket.

9. The downlight assembly of any preceding claim wherein the heat sink comprises one or more fins pointing away from the rear surface configured in use to dissipate heat generated by the lighting element and to provide a mounting space for the portion of intumescent material.

10. The downlight assembly of any preceding claim wherein the portion of intumescent material is mounted at a central point of the rear surface of the heat sink.

11. The downlight assembly of claim 9 or of claim 10 when dependent on claim 9 wherein the one or more fins are arranged to surround the intumescent material.

12. The downlight assembly of any of claims 9 to 11 wherein the one or more fins are arranged in one or more concentric rings surrounding the intumescent material.

13. The downlight assembly of any of claims 9 to 12 wherein any of the one or more fins have a u-shaped cross section.

14. The downlight assembly of claim 6, or any of claims 7 to 13 when dependent on claim 6, wherein the third portion of intumescent material is mounted on the one or more fins.

15. The downlight assembly of any preceding claim wherein the heat sink is manufactured from aluminium.

16. The downlight assembly of any preceding claim wherein the metal cover is manufactured from steel.

17. The downlight assembly of claim 4 or any of claims claims 5 to 16 when dependent on claim 4 further comprising a driver housing configured to receive one or more electricity cables and provide an output voltage to the connecting wire.

18. The downlight assembly of claim 17 wherein the driver housing is attached to the rear surface of the heat sink.

19. The downlight assembly of claim 18 wherein the driver housing is attached to the rear surface of the heat sink using attachment points located on the ends of one or more attachment fins extending from the rear surface of the heat sink.

20. The downlight assembly of any of claims 17 to 19 wherein the driver housing is supported by tips of the one or more fins and the driver housing substantially covers the rear surface of the heat sink.

21. The downlight assembly of any of claims 17 to 20 wherein a rear planar surface area of the rear surface of the heat sink may be substantially equivalent to a frontal planar surface area of the driver housing.

22. The downlight assembly of any of claims 17 to 21 comprising a lid having a plurality of toothed openings wherein closure of the lid engages teeth of the toothed openings with one or more electricity cables thereby ensuring that the one or more electricity cables are securely retained within the plurality of toothed openings.

23. The downlight assembly of any of claims 17 to 22 comprising at least one toothed strip wherein one or more electricity cables engages with the at least one toothed strip in order to be securely retained.

24. The downlight assembly of any previous claim wherein any portion of intumescent material is configured to swell due to exposure to an activation temperature that is less than the temperature at which the heat sink begins to melt.

25. A fire-rated downlight assembly comprising:

a heat sink having a front surface and a rear surface;

a lighting element comprising one or more LEDs, the lighting element being located on the front surface of the heat sink; and

5 a portion of intumescent material located on the rear surface of the heat sink configured to swell when exposed to heat to substantially cover a vulnerable portion of the rear surface of the heat sink in order to restrict penetration of the assembly by a fire in front of the assembly due to damage to the heat sink caused by the fire.