Six Questions to Guide Tunable White Decisions

Constant changes to LED technology can make keeping up with LED developments seem like a full-time job. Color tuning, and specifically tunable white, is one of today’s most intriguing control opportunities, but where do you start to ensure you’re making the best fixture and control decisions? Historically, fixtures have been purchased with a specific color temperature; however, emerging studies are confirming the human centric benefits of being able to change, or tune, a fixture’s correlated color temperature (CCT). Tunable white applications use more sophisticated LED drivers and light engines to control both the color temperature and the intensity of a fixture. The right solution for any project begins with asking the right questions. 
We have identified six key questions, along with a short explanation about why each question is so important
to achieve a successful tunable white installation. Explore these issues early in the project process to help guide you to the right decision, starting with the type of fixture you’re using. 
1. What are the control inputs to the fixture?
There are two types of fixture control: Warm & Cool control, and Intensity & CCT control. In all cases, we recommend the latter – tunable white fixtures that have one control input for intensity and one control input for CCT.
Fixtures with Intensity and CCT inputs are easy to integrate into a smart lighting system, while fixtures with Warm and Cool control are much more difficult to integrate. If the system’s sequence of operations requires specific intensities and CCTs, as well as automated dimming, daylighting, or user control, it is vital to know if the fixture can be integrated into the design. For applications where advanced control methods are required, only fixtures with intensity and CCT control will deliver the desired results.
2. What are the maximum and minimum CCTs for all fixtures in the space?
It is important to know if the fixtures offer the necessary CCT range for the application. For example, in a given space there may be multiple fixture types with different CCT ranges. If the defined sequence of operations includes a situation where tunable white control is desired simultaneously in all fixtures, the system performance will be constrained to operate within the overlapping range of ALL the fixtures in a space. In other words, if one set of fixtures has a CCT range of 3000-5000K, and another set of fixtures has a range of 2000-4000K, the functional tunable white range for the combined fixtures in that space is 3000-4000K. For proper design, it’s critical to understand these limitations up front.
3. Some fixtures may produce many more lumens at the high CCT than at the low CCT. What are the achievable lumen outputs at the highest CCT and the lowest CCTs?
As with the functional CCT range, the maximum light output across the range of CCTs determines how much light can be delivered in the application. If the design needs to meet a certain illumination level at a certain CCT, it is critical to know if the fixture, or combination of fixtures, can achieve that illumination level.
4. What are the x,y chromaticity coordinates for the maximum and minimum CCTs for each fixture in the space?
Different people in a space may experience different visual perceptions of the source color in multiple fixtures, despite the fact that the CCT is the same. Space occupants may become frustrated because they are unable to make the variety of fixtures match one another. This is a problem with fixture selectio