Have you installed brand new LED light fixtures only to find that a room is overlit, causing discomfort or other difficulties for the occupants? You could certainly reduce the quantity of installed fixtures, but removing fixtures can make the ceiling space look odd as well as cause the room to be unevenly lit. Rearranging fixtures requires re-wiring the line voltage which can get costly.
Read on for a possible solution to this problem for under $50 and a little time.
We didn’t want the space too dark!
It’s a well-known fact that LED based light fixtures produce a higher lumen output per watt than incandescent, fluorescent or CFL lighting. The amount of light produced compared to how much electricity it consumes is referred to as the fixtures EFFICACY. An easy analogy for this would be the Miles Per Gallon you get in your car – fuel in, miles out.
Another major element in a fixture is the design of the housing, reflector, lens and trim, all of which play a part in either trapping the light inside the fixture, or directing it from the point source out into the space. This is referred to as the fixtures EFFICIENCY. The higher the efficiency, the more usable light you actually get from fixture.
LED lighting is not only more efficacious, but the small point source and better lens techniques also direct the light out of the fixture body better, making the entire fixture more efficient.
The outcome of a new LED lighting installation often surprises professionals designing the space, especially if they are working in an existing building and retrofitting the lighting on a 1 to 1 basis. Generally speaking, a 1,000 lumen LED fixture appears brighter than a 1,000 lumen fluorescent fixture, primarily because the larger surface area of the fluorescent tube makes it hard to direct all the light out of the fixture.
Adding to the problem, particularly in retrofit situations, many owners and specifiers want to “upgrade” the light level from the original build. As a result, the lumen packages selected are actually raised to an even higher lumen output than before, raising the overall brightness considerably. The end result can be a room that is perceived as “too bright” and difficult to work in.
If you did not already include a means of dimming the lights as part of your design, the easiest way to reduce the light output of an overlit room is to use an inexpensive wall box dimmer as a means to “trim” the high-end, setting the luminaires in a slightly dimmed state for lower output. This can be done without cutting a hole in the wall or having to re-route power through the dimmer.
1. Determine if your fixtures are capable of dimming
A benefit of most commercial LED lighting is the fixture drivers often come with 0-10v dimming capability built-in as a standard option. The industry often refers to this as “free” dimming since, in the past, fluorescent and other fixture types required a more expensive ballast in order to dim and therefore had to be selected with the intention of dimming the space from the beginning.
Obtain the part number of the fixtures that were installed in the space and search the Internet for a spec sheet detailing the available options in that fixture. In many cases, you are likely to find that the fixture comes with a 0-10v dimming driver as a standard part of the base model.
Another way to confirm if the fixture has 0-10v dimming built-in is to check for the presence of purple and grey wire leads coming from the LED driver itself. You may have to open the driver compartment of the fixture to find them as they were likely tucked away during installation.
If purple and grey wires are present, you’re in luck! Verify the fixture actually dims down by shorting the purple and grey wire together. You should see immediate, visible results in the light level as the fixture dims to it’s lowest state.
2. Run a control wire to each fixture
0-10v dimming operates using (2) #18 gauge control wires connected to the purple and grey leads from the driver and daisy chained from fixture to fixture, eventually connecting to the dimming device. The dimmer uses this control wire as a dedicated channel to signal the fixtures to dim down.
Running this wire between fixtures is the most difficult and time-consuming step of this process, but if you have access to the ceiling space, it’s much easier than working with the line voltage or moving fixtures around. For one, #18 gauge wire is light and easy to manipulate. Since it’s carrying low voltage, it’s considered Class 2 which means it can be run free-air above the ceiling tile and does not have to be installed in conduit (This is true for most locations in the U.S., but check your local code authority to be sure).
Class 2 does not require an electrician, so the control wire can often be installed by an on-staff maintenance person with a ladder, a spool of #18-2 wire and a couple of hours of time.
3. Connect a wall box dimmer
At a very basic level, 0-10v dimmers are simply variable resistors which “sink” the current on the purple control wire to the grey common in order to signal the fixture to dim down and back up. There are 2 primary types: mechanical and digital. Ideally, you will want a slide dimmer which is strictly mechanical as these do not require line voltage to power the dimmer itself. Digital versions on the other hand often have more advanced functionality such as touch sensitive controls and dim level indicator LEDs, but require a connection to a 120v or 277v power source to operate.
Here are 2 recommended models I have known to work well for this application:
Simply connect the 0-10v purple and grey control wires coming from the fixtures to the dimmer and slide the dimmer up and down to test the dimming capability. You can then “set” the level you want the lighting at by leaving the dimmer in a specific position.
You just created a high-end trim for your lighting zone! Simply leave the dimmer laying in the ceiling or install it in a box if you want to make it more permanent. No need to run wires down the wall or mess with line voltage whatsoever!
For $50 in a dimmer and some low voltage wiring, not only have you solved the problem of your fixtures putting out too much light, but the lower light levels will reduce energy usage even further as well as extend the life of the LED fixtures by not driving them as hard.
A note: most dimmers support sinking up to 20mA and the average driver produces .5mA of current on the dimming wires. While this is getting into the technical aspect of how 0-10v works, at a high level this means a good rule of thumb is to daisy chain no more than 40 fixtures together on the same dimming control wire.
If your project is still in the design phase, you can avoid this issue in the first place by having a professional lighting layout done by your local lighting manufacturer rep. Most of the top agencies in each state around the country will offer this service free of charge to their local specifying community.
A shout out to Kirk Roth for coming up with this solution and implementing in his own office!
Image by Miranda MyIne