# Observations On The Use Of LEDs For Emergency Lighting Systems.



## Ken_McE (Mar 29, 2007)

Background:

Almost all commercial emergency lighting units made or sold at this time use incandescent bulbs. There are a few units available that will power a four-foot fluorescent tube. At this time no one seems to make serious LED emergency lights, and there seems to not even be literature on the subject. This is odd since in this situation LEDs are clearly superior to incandescent bulbs in every way except initial cost. Accordingly, I have put down a few observations in the hope that they may be of some slight use to others.


Why LED?:

First, efficiency. An LED will routinely produce more lumens/watt than a
comparable incandescent bulb. When you are running off a battery you have a limited amount of power available and will want to get as many lumens out of it as possible. Commercial units are normally designed to run for a minimum of ninety minutes. By converting from incan. to LED you can either get more light out of the same size battery, or switch to a smaller (cheaper) battery while maintaining run time.

Second, reliability. Incandescent bulbs will break or wear out more quickly
than LEDs. To kill an LED you need to overdrive it, something that is hard to do with a battery, or beat it with a hammer until something breaks. Since emergency lighting systems usually run no more than a few hours a year you would expect the bulbs to last for decades. My experience has been that the common PAR-36 four-and-a-half inch type incandescent bulbs fail much more often than you would expect, usually for no visible reason.

Third, esthetics. Emergency lighting units are usually big ugly boxes that are hung with a callous disregard for the esthetics of the building. This is not necessarily a fault of the technology, Americans do this with everything. LED lights have a much smaller physical size than incandescent bulbs and I have found that with a minimum of care they can be built into a public space to the point where you will not notice them unless you specifically search.

Fourth, safety. Incandescent units normally have bulbs mounted in pairs. When they come on they cast powerful cones of light on whatever the installer wanted you to see. This leaves the rest of the area in shadow, and if you should look towards the light you will promptly be blinded. Multiple small LEDs will look like a string of dots if you look at them directly, but they will not harm your vision.


Colors:

LEDs are of course available in all the primary colors and a few of the
secondaries. I feel that colors are usually inappropriate for emergency
lighting. Green could have an advantage because we are sensitive to it, but in a public place I feel you risk confusing or distracting people. I have settled on cool-white as consistently having the highest lumens/watt ratio and use only that color for emergency lighting. Warm-white is a more attractive color, but costs more per foot and has a lower lumens/watt ratio.

Products:


I consider the Superflux (AKA spider, piranha) type LEDs superior for general lighting purposes. They are specifically designed to produce a broad hemisphere of light rather than a narrow beam. You can run them without lenses or diffusers or heatsinks, which simplifies fixtures nicely.

I have purchased 50-Led light strips from a company called acolyteled.com out of New York City. The name is annoyingly hard to spell, but I find myself taken by their product. They make a long slim circuit board, populate it with SuperFlux LEDs, attach a lead cord and encase it in resin. This appears to be one of the most powerful LED lighting products on the market that does not need cooling.

One of theses strips, containing fifty SuperFlux LEDs, mounted facing down over a doorway will light the door clearly and distinctly, create an arc of well lit floor within three or four feet of the door, and cast weaker light out about ten or twenty feet, making it possible to navigate to the doorway from across the room without falling on things.

They are skinny, weatherproof, easy to mount, and almost invisible when not lit. They can often be conveniently mounted in the frame around the door. You do not need any kind of frame or fixture or housing. Anything that will secure it above the door will do. A variety of U shaped straps and clamps available at hardware stores.


Rope Lights:

I have been testing LED rope lights. There are three or four vendors on eBay who sell LED ropelight in one-hundred and fifty foot rolls. Prices run around $2.00 (US) per foot with shipping. They don't seem to ever go on sale. I have observed no real differences from one vendor to the next. Properly installed, the ropes are essentially invisible, or just look like part of the trim. They have a disadvantage in that the light is weak and does not project far.

Rope light track:

The ropelights need to be mounted somehow. Tracks are available in four-foot lengths. The track is just a clear piece of plastic with a flat side and a channel. You mount the flat side against whatever you want the lights on and then pop the rope into the channel. This will keep the rope straight and makes it possible to swap it out easily if something breaks, or a better rope comes along. The channels may come with a glue strip along one side. This glue will affix the track while you are mounting it, but will not hold the weight of the rope by itself. You will need to add mechanical fasteners or your own glue to make it stay put.

I have worked with taking wood screws and driving them into the base of the channel. If you drive them too far they will tear out through the plastic. If you don't drive them far enough the head will stick up in the channel and you will have a permanent bump in the light. The screws also need to be fairly close (no less than one per foot) or the track will sag between screws.

Both tracks and ropes come in different sizes, usually three or four eighths of an inch, and the size of the rope must be matched to the size of the track. If you try to mix sizes you will get only misery. The smaller rope in the larger track will fall out after you go away, the larger rope must be hammered to get it in the smaller track, and hammering will kill sections of the rope.

When running the tracks you use tracks for straight runs and leave a gap between pieces where you want to change direction, go around a corner, change levels or something. Then as you string the rope you follow the track, use just the rope to make the bend, and then mount it in the next piece of track to keep it straight again. If need be you can add a U shaped clamp to the open run to steady the rope. The finished product is perhaps an inch high by an inch wide and looks a bit like an unusually large bead of silicone sealant.

The individual LEDs inside the rope all face in the same direction. I like to
light the rope while I install it so I can easily see the LEDs and aim them so they face directly at what I want lit. I also prefer that they aim through the opening at the top of the channel. This avoids transmission losses that happen when you aim through the side of the channel. It is easy to twist the rope this way and that while installing it. This is fine for decoration, but I normally aim for maximum function.


Observations

Room one:

Thirteen foot by thirteen foot office, eight foot ceiling. ten feet of LED rope light leading to exit door. Rope mounted eight feet up and aimed at floor. Room is poorly lit, occupant can find exit door. Deep shadows in corners. Room is very lightly used, so no plans to upgrade.

Room Two:

Thirteen foot by twenty-six foot room, forty feet of rope light mounted eight feet up, pointing at floor. (rope runs full length of one narrow and one long side.) Room is dim and light has greyish appearance. Light adequate to navigate room. I consider lighting minimal and may double it.

Stair one:

Fourteen steps, one landing, four feet wide. ~ fourteen feet of blue-white LED sign modules mounted under handrails pointing at steps. Stairs are clearly lit and easy to use.

Stair Two:

Decorative rather than emergency light.

Thirteen steps three feet wide, one landing. ~ fourty-four feet of amber LED rope lights (a line on either side and some decorative bits) were used with the thought that yellow would compliment the wooden stair, be much cheaper than warm white. thought was wrong, amber on wood is a nothing combo. Amber also turns out to be extremely dim. Stair is safe and easy to use, but nothing special. 

Conclusion:

LEDs are suitable for emergency lighting.  Installed along the lines above (rope lights around perimeter and a superflux strip over each door) you will get a high-cost, high-performance system. A fair amount of time and effort is required, more than for a standard incan. unit. LED rope lights are sold for decorative purposes, the vendors will have absolutely no idea how to use them for emergency lights. You will have to design each installation, decide on a termination/connection system and install your own connections on everything. Local contractors can install it, but they will need very clear and detailed instructions, because neither they nor anybody they know has every worked with this stuff.


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## Opto-King (Mar 30, 2007)

Here you have a link to a company that makes LED signs;

http://www.ledolight.se/avd_produkter/ledosafe/index.html


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