Review, Teardown: Legrand E2 Edgelight LED Exit Sign (684731)

Emergency exit lighting is not the first thing that comes to mind when the word “lighting” is mentioned, but it is one very important type of lighting especially in larger residential and commercial buildings. Such lighting is regulated by AS2293 which informs the design and requirements, its main purpose is to ensure safe egress of people should the power fail and reduce the potential for panic situations arising. It might seem strange that I’m reviewing an emergency exit sign, but I have familiarized myself a long time ago with AS2293 in my internship with the Government Architect Office of NSW Department of Commerce, where simulating emergency exit lighting and verifying lux levels was part of my role.

There are many cases where new emergency lighting can be justified. Older emergency signs may be aesthetically lacking in their bulky size, not have replacement parts available and could be failing too often, not meeting required run-times or costing too much in maintenance and wasted energy. Maybe the signs are really old and renovations require the replacement of signs with Running Man style signs as opposed to the formerly used “EXIT” wording, or you might be interested in streamlining compliance testing by opting for networked self-testing features.

Just as LEDs have made big strides in normal lighting, LED technology is also creating waves in emergency lighting. Unlike incandescent lamps with low efficiencies, LED lamps are more efficient, thus allow for significant reductions in battery size and cost for the same run-time. Because of their robust characteristics, failure of the “globe” is eliminated reducing the ongoing maintenance cost. Also, as LEDs operate off low-voltage DC, the need for complex inverters with high-voltage components as in fluorescent based signs is eliminated.

In this review, we take a look at the Legrand E2 Edgelight LED Exit Sign, specifically, model 684731 which is a surface mounted, 1W LED maintained/non-maintained configurable single-point unit (SPU) with Running Man legend compliant with AS/NZS2293.3. The series includes other models to suit various needs, with Axiom wireless test features, recessed mounting, special decals, and (low-illuminance) theatre decals being standard options.

Thanks to Voltimum Australia for providing the initial contact, and Legrand for supplying the review sample.

Unboxing

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The sign arrived inside a medium sized cardboard box with the Legrand logo on the side.

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Its contents are detailed on a label on the side. It is Model Number 684731, a surface mounted maintained/non-maintained configurable E2 Edgelight LED exit sign with 1W LED light source and two-rate Ni-Cad battery charging. I suspect the 4RM code indicates the presence of four Running Man type decals (left, right, straight ahead and blank), and Wh indicates white body.

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Within the box, you will find the exit sign. The sign consists of an upper housing portion in white containing all the electronics, and a hinged lower section containing the light source, light guide and decals. The decals are housed within a clear plastic outer cover, which is removable, allowing for the reconfiguration of the decals.

The pictorial itself is approximately 150mm high, being one of the preferred heights in the AS2293, and the decals are marked with 8mm high letters indicating maximum viewing distance (24m) as compliant with the standard. As required, a circular logo indicating emergency exit luminaire is visible from the front side, of approximately 15mm diameter. Discreet branding can be seen in the upper right frame of the sign, in grey.

The sign comes pre-fitted with the exit-straight-ahead decal on one side, and a white blanking decal on the rear.

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The hinged segment is “supported” in place by two spring-loaded plastic bumps. This hinged arrangement allows for easy installation of the base on a wall above an exit, leaving the sign to “hang” vertically in either orientation. On one side of the hinge, windows for LED indicators and a recessed test button is present.

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In this particular model, only one red LED is used to indicate the charging status – flashing indicates “high rate” 70mA charging, and steady indicates “low rate” trickle charge at 17mA.

Above, the sign was shipped with the plastic cover on the sign not securely clipped into place. Metal retention clips slide into slots in the plastic cover to hold it in place and secure firmly with a positive click. These clips can be released with a small bladed screwdriver. The cover itself is made of two plastic parts glued together – one flat window on one side, and the rest of the sides, making it a little less rigid than expected when handling. The glue seam is visible in the above photo. It was found that this particular cover was a tight fit, and was able to clip in place only when placed in one orientation.

It is a good feature to see that the covers are replaceable, and can be re-ordered (P/N: 685735) in case of vandalism or damage. Other accessories are available, including a replacement battery pack (P/N: 686240), various mounting blocks and recessing plates, individual decals and conversion kits for upgrading from the discontinued Optica Bladelight Recessed fluorescent exit sign.

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Because of the risk of battery damage with inventory sitting in the channel being slowly depleted by the quiescent current of the onboard electronics, the batteries are shipped disconnected from the main board and need to be connected prior to installation.

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Also included in the box are a cardboard drilling template, which eases installation significantly when it comes to drilling the necessary holes, and two plastic Running Man decals for exit to the left, and exit to the right.

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Finally, there is a fold-open installation guide with pictorial illustrations, which is easy to follow, and an insert sheet with “installation instructions” that contain information about commissioning and testing the unit. Key points include the use of a switched active to control sign illumination and unswitched active for battery charging allowing for maintained or non-maintained operation. Where 24/7 maintained operation is required, both are to be bridged together. Both switched and unswitched active must be on the same phase.

The product requires a minimum of 16 hours of charging before full discharge testing is performed. On long periods of interruption, battery damage may occur due to excessive discharge (to be disconnected if stored for >3 months). Do not subject the units to high number of charge/discharge cycles as can occur on temporary (construction) power supply. All these warnings are fairly standard and to be expected.

Further information is available online from Legrand or by directly contacting Legrand.

Consulting their datasheet, it is also found that the sign carries an IP21 rating, suitable for indoor installations with an ambient temperature of 10 to 40 degrees Celsius. Best of all, it’s Australian designed and manufactured. Way to go!

Internals and Configuration

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Opening the unit reveals the first feature, namely a separating base plate. This allows for easy installation, as you can drill the necessary holes, screw it in, wire it up to the terminal block and then snap the sign in. It also eases field service by allowing easy whole-unit removal and replacement. The base plate itself has moulded within it the information about wire stripping depth and connections, a further convenience feature. A loop terminal is provided as well as an Earth, although as we will see later, the Earth terminal is not actually used by this model of sign. The cable entry hole is also covered by a plastic guard, which stops potential cable interference with the internal circuitry and should limit entry of vermin.

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The top housing of the sign is seen in the photo above. Mating terminal blocks and pins can be seen on the left, which interface with the block on the baseplate, and three wires are bought into the main PCB – active, neutral and switched active. The battery can be seen in the bottom, clipped into the side of the enclosure with some separation from the PCB to enhance lifetime by managing heat more effectively. Two sets of connections are made to the sign underneath – a grey and white cable which provides power to the LEDs, and a multi-pin header which connects the status LEDs and test button. The battery connector is disconnected, as supplied.

Examining the main PCB, we can see it is a neat quality PCB with green solder resist and silk screened top. The green terminal block has a plastic frame support, and right behind it, is a MOV surge protection element over active and neutral. Inductor and capacitor filter of the primary is provided for transient protection, which is all in good practice. Electrolytic capacitors used throughout the product are highly recognizable Nippon Chemi-Con capacitors, Made in Japan, of very high quality. The primary side switching controller is a Power Integrations TNY274GN energy-efficient off-line switcher. Additional connections can be seen, which are not used, and may be related to the Axiom wireless networking feature, which needs to be specified when ordering.

The primary to secondary isolation can be seen with optoisolator feedback and even a nice “channel” cut into the PCB near the unused pads to ensure isolation. On the secondary side, there are a few SMD ICs which I didn’t get a close look at, although I suspect it is related to the power-loss LED switching supply from the battery and battery charging logic.

Within the unit, we can see the appropriate regulatory marks (C-tick), quality control markings and a warning not to use a Megger on the unit (likely as it degrades the surge protective elements if improperly set).

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A quick peek at the underside of the PCB shows no components mounted there, with mostly shiny, regular solder joints with smooth appearance – as it should be. The one exception is on the multi-pin header on the leftmost side of the image – the second and third row of pins have irregular appearance and flux residue indicating they have been touched up post-manufacture. However, this is inconsequential, as these connections are not used by the consumer. They are likely programming or test contacts used during manufacture.

An additional benefit of the design is the use of connectors, terminal blocks and screwless internal design, which minimises the time required for field service, should actual replacement of PCB, battery be undertaken.

Overall, it appears the design and physical construction of the unit is very good, and the components used are appropriate.

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The included battery is a BYD branded D-AA700HX4/HB00043TA: BT AA4 with catalog number 686240. This is a 4xAA series string of 700mAh “high temperature” tolerant Ni-CD cells. There is a space on the label to record commissioning date.

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The cells are Made in China, which seem pretty “standard”, although BYD is the largest Ni-CD manufacturer in the world, so quality is probably as good as anything else out there. According to the label code, it appears this unit is Week 52 of 2015, so relatively fresh.

The positive side is soldered within the heatshrink to the positive tab, but the negative is connected with a quick connect spade lug which avoids the need to solder the negative connection. The lug is a good match and makes good contact, and interestingly, provides an ideal location for me to observe the battery performance. More on that later.

Performance Test Results

The following are some test results gained through informal testing performed by myself. It is important to remember that I am a hobbyist, volunteering my effort and time, and as a result, I am not equipped as well as a formal test laboratory would be. As a result, do not take the absolute figures to be entirely perfect, although the results are presented in good faith and are correct to the best of my knowledge and ability.

Because the role of emergency lighting is different to regular lighting, many of the tests performed for regular lighting are not very useful. Instead, the test suite and methodology has been varied to focus on what is most important. As the sign claims compliance with AS2293.3 and I am not fully equipped to test for this, my results should be taken as independent confirmation of some aspects regarding compliance and the provided datasheet values.

Visual Check

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With the power applied, non-maintained and maintained operation was verified. From the front with the default decal, a level of non-uniformity is visible at the top corresponding to the discrete LEDs used in the edge. It appears that the internal light-guide sheet may not be diffusing the LEDs too much at the top edge, resulting in the non-uniform “wavy” appearance.

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As the sign edges are not taped, the LED array is visible from the underside, and could in some very restricted circumstances looking straight up, contribute to glare. However, from an emergency lighting point of view, this light escaping the bottom of the sign could serve to provide some extra light to the escape pathway, and thus, may serve a useful purpose. I’m not an expert on this aspect, so I won’t pass judgement on this aspect.

A total of 16 LEDs can be seen, which means each LED is contributing 62.5mW to the total 1W output. As I did not find a way of accessing the LED array without compromising the sign’s structural integrity, I could not tell the type of LEDs that were used, however, this is considerably small amount of power to be expecting from the majority of SMD LEDs. This may be deliberate, so as to run the LEDs conservatively for better lifetime.

Measurement of the LED array voltage with an Agilent U1241B handheld DMM gave a reading of about 11.6v. This seems to indicate that the internal configuration is 4 parallel sets of 4 LEDs in series. Without further examination, I cannot be sure how these strings are managed, however, the choice of lower voltage may be a design choice to ease the difficulty of operating off battery power. If the LEDs are indeed operated conservatively, this may even allow for partial array failure without losing illumination completely, but this is just a hunch.

Power Consumption Test

According to the datasheet, the sign has a 3W maximum consumption, with a claimed 2.7W consumption during full rate charging, and 2.3W during trickle low-rate charging.

Testing using a Tektronix PA1000 Power Analyzer and variac to stabilize the input voltage to 230v (+/- 1%) showed the following results:

  • Full-rate charge, battery fully discharged, LED sign active
    • 2.764W, 0.530 power factor
  • Full-rate charge, battery fully discharged, LED sign switched off
    • 1.185W, 0.418 power factor
  • Full-rate charge, battery half-charged, LED sign active
    • 2.801W, 0.531 power factor
  • Full-rate charge, battery nearly fully charged, LED sign active
    • 2.861W, 0.533 power factor
  • Trickle-charge, LED sign active
    • 2.355W, 0.488 power factor
  • Self-test button pushed
    • 0.600W, power factor not recorded

On the whole, the results appear consistent with datasheet claims within about a 0.1W margin. Self-test button was provably working as intended, as the sign remain lit at full brightness, drawing only a fraction of the power otherwise drawn from mains.

The LED sign itself appears to consume 1.579W from the mains by mathematical subtraction. While the sign appeared to have a relatively poor power factor, this is not highly important overall as the reactive power contribution is very small, as the load itself is minuscule.

Mains Voltage Changeover

The mains voltage provided to the sign was varied using a variac and the power parameters recorded using a Tektronix PA1000 Power Analyzer.

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With an intended operating voltage range of 216.2 – 254.4v, the sign was able to exceed the range. Tested with a nearly depleted battery, the operating power varied slightly as a function of voltage. The unit survived operation at 274v, and operated on the mains down to 171v AC RMS. At this point, a seamless changeover to battery occurred.

As this is significantly below that of the expected range, it means that the sign is less likely in case of a small brown out to operate from batteries and cause wear to the batteries.

When the voltage was slowly ramped up from zero, the sign resumed mains operation and battery charging autonomously, as expected.

A requirement of the standard is that on application and removal of power, that the sign lights up within one second to minimise risk of panic. In order to assess this (in an informal way), a camera running at 50 frames per second (for a 20 ms time granularity) was pointed at the sign as it was subjected to 15 cycles of on-off switching through an automated script process using a wireless remote switch. The number of frames with the sign not fully lit at each transition was examined to determine the length of time that the sign was unlit at each transition.

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It was found that 80% of the tests with power returning resulted in no interruption to the sign output at all. In 20% of the cases, the interruption (a visible flicker) was about 0.24 seconds.

On the tests where the mains were suddenly removed (rather than gradual ramp-down), light output interruption of between 0.06 seconds to 0.24 seconds was observed.

It seems likely, in light of these results, that the sign complies with the one-second requirement with significant margin. Further to this, the cycle testing was continued with the sign subjected to 5 seconds mains on, 5 seconds mains off cycles for four hours (1440 switching cycles) with no failure (as to be expected from a fully solid state design).

Battery Charger Performance

Battery charger performance was determined through interrupting the battery circuit at the negative spade terminal and inserting a Keysight U1461 Multimeter in series, with the current range set to 600mA (1 ohm burden resistance) to minimise impact on the operation of the equipment. The current was logged over time using the Keysight Handheld Meter Logger software and a USB IR cable.

The battery charge was performed on a depleted battery, and the current profile recorded and plotted.

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The full charge rate is advertised as 70mA, and was found to start just above 70mA and settled to a value just below, averaging out to 68.58mA. The trickle charge current is “pulsed” to optimize battery life, with a claimed average 17mA rate. The average of the readings is slightly higher, about 18.31mA. Total charge time from depleted was 16 hours, 7 minutes and 8 seconds, fairly close to the 16 hours minimum charge as recommended by Legrand’s datasheet.

The bulk charge current itself is approximately C/10 for the Ni-CD cell, and the trickle charge is about C/41 rate. The choice of C/10-rate charge allows for safe full-charge application with minimal monitoring logic, and even if it should fail stuck at that rate, it is likely that quality Ni-CD cells could maintain that rate of charge indefinitely without safety problems. The trickle rate, being even less, is also very appropriate. However, using such low rates will mean it takes longer to restore the batteries to charge after depletion by an extended power outage event.

Battery Only Operation Time

Current monitoring was also used to determine the battery-only operation time. The Australian Standards presently require 2 hours at commissioning and 1.5 hours duration at testing as a minimum.

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The Legrand E2 sample showed a current draw that increased over time to compensate for declining cell voltage, resulting in a constant power characteristic with a draw of approximately 1.096W or 228.46mA. The run-time was 3 hours 15 minutes and 9 seconds, indicating the battery has approximately twice the needed capacity which should result in a very good service life and replacement interval.

Battery Charger Safety

Another requirement of the standard is for the safety of the battery charging circuit. The unit was tested to see what happens in the case of battery removal and short circuit.

It was found that the sign was inoperative with the battery disconnected, with the sign remaining off. This provides a clear indication of failure of the battery.

On short circuit, the sign remained inoperative. The current measured peaked at 74.77mA, remaining in a relatively safe level with limited power. No permanent damage was sustained.

Removal of the multi-pin connector resulted in the loss of the side LED indication and test button, whereas removal of the grey and white plug resulted in a non-operating sign. In both cases, no damage was sustained.

Conclusion

The Legrand E2 Edgelight LED Exit Sign is an Australian made product, backed by a 1-year warranty. It claims compliance with AS/NZS2293.3 for use as emergency lighting. It has a simple visual design with discreet branding. The supplied unit is suitable for surface mounting on walls and ceilings with a hinged design, and is designed to operate as a single point unit with standard-compliant set of Running Man decals. Variations of the E2 are provided for recessed mounting, networked Axiom self-testing, and with low-illuminance/custom decals.

The design is highly modular, with a base-plate for easy installation and unit exchange, with replacement and special mounting parts available. The unit is supplied with a drilling template to make for speedy installation. Field repair is possible, especially with the use of terminal blocks and “clip in” components with connectors.

Testing confirmed that the unit exceeded expectations for runtime, operating voltage window, changeover from mains to battery and battery charger safety requirements. This implies that the unit will survive field conditions especially given the large reserve capacity in the battery and spacing between battery and electronics to aid in reducing heat-related stress. The battery charging algorithm is also optimized to prevent stressing the battery, with pulsed trickle charge and a limited full-rate charge. The internal electronics were found to utilize high quality capacitors, and possess the necessary mains filtering with surge protection to ensure longevity. The only potential drawback I could find was that the lighting was found to be a little non-uniform at the top edge, and the plastic sign cover was made from two-parts glued together rather than a single piece which may be slightly less rigid.

If you’re looking for an emergency exit sign for a retrofit or for a new installation, it is worth considering the Legrand E2 Edgelight LED series. Thanks again to Voltimum Australia and Legrand.

About lui_gough

I’m a bit of a nut for electronics, computing, photography, radio, satellite and other technical hobbies. Click for more about me!

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