Essentials of designing with LED

Posted by Advanced Controls & Distribution on May 22, 2019 9:41:00 AM

ESSENTIALS OF DESIGNING WITH LEDThe era of LED lighting has given designers several wide-ranging advantages over legacy systems, which they may incorporate within end-products for their clients. However, in order to ensure these benefits are reaped by the end-user, the design phase must be given due importance along with special considerations.   

First and foremost, lighting designers must gain an in-depth understanding of their clients’ requirements. Each project should be treated differently, depending on its size, shape and geographical location. Moreover, the clients’ opinions with respect to the look and feel of their efficiency goals must be taken into account during the design phase to ensure the project’s suitability and sustainability.

Energy efficiency is an embedded benefit of LED technology compared to legacy lighting solutions. The advances in semi-conductor and embedded hardware design have made continuous efficiency improvement possible, making today’s LED boards & drivers superior to older technologies, both in terms of lumens and wattage ratings. Most manufacturers are now able to design products rated at 100+ lumens/W which are becoming more prevalent as lighting regulations become increasingly stringent.

Daylight harvesting

The higher energy efficiency of LEDs doesn’t mean designers should neglect the worth of natural light. Easy access to daylight can greatly contribute to energy savings within a building. Photosensors can be used to monitor real-time light levels, sending control signals to fixtures that adjust accordingly. Correspondingly, the LEDs can be dimmed, leading to lower amperage and thus energy savings.

LEDs follow a linear energy consumption trend, meaning reducing the current by 50% would lead to approximately 50% dimming, depending on the quality of the LED driver. Furthermore, incorporating daylight harvesting can also improve the lifespan of the fixtures. Another benefit of this is reduced heating in wiring that leads to lower chance of premature failure. Compared with legacy fluorescent, HID and incandescent systems, savings upwards of 35% can be achieved, making LED lights vital for project sustainability.

Project sustainability is defined either by the client or by regulatory codes and standards established by governing bodies.

Codes and Standards

The International Building Code, International Energy Conservation Code and ASHRAE 90:1 define the relevant codes for lighting design. There may be variations within each guideline, all of them clearly define the LPD metrics, minimum lighting control strategies and emergency & egress light levels. These regulations usually follow a 3-year cycle after which they are updated. The version of code used depends on the starting year and local regulations, with some countries following stricter codes. An example of this is California’s Title 24 that makes it necessary for companies to stay updated with lighting requirements.

Next, a design that is in line with the U.S. Green Building Council’s LEED guidelines has to be taken into account. The LEED system is basically a checklist of guidelines that can be incorporated within a design to get a certain level of certification. As a rule of thumb, the more strategies included, the higher the level of certification awarded.

Different projects have different checklists, but each defines common parameters such as control strategies, lighting fixture qualities and building LPD. Achieving the required levels is easier with LED technology rather than conventional systems.

Design Flexibility

LEDs offer greater flexibility in design, particularly in terms of corelated color temperature or CCT, which defines the color of light emitted by a fixture. Since LED technology is available in a number of CCTs, the program itself can drive the ultimate decision.

Projects that belong to the hospitality genre usually follow a warmer CCT, with a range falling between 1800 – 2700K. Corporate commercial spaces use 3000 – 4000K while residential applications follow 2700 – 3000K. Requirements for educational projects vary, usually following CCT ratings between 3000 – 5000K, depending on pupils’ age.

In recent years, manufacturers have put in considerable effort to design dynamic CCT fixtures, which unlike older technologies would allow the output to be governed by the current level. Several manufacturers are already offering “tunable white” and “warm dim” products, allowing a single fixture to provide a range of colors. Many, high-end fixtures also provide a full color-changing range that gives the end-user near-limitless control.

Finally, color rendition can play a vital role in the selection of lighting technology. Compared to fluorescent and incandescent lighting, LEDs offer improvements in color rendition, quantified through color-rendering index. Selecting optimum CRI can greatly improve the appearance of objects and the perceived color of materials.

A higher CRI will lead to greater vibrance, with colors matching closely with natural lighting conditions while lower CRI will lead to distortion. Typical LED fixtures deliver a CRI over 80, which is a decent rating, however, if required, products with rating as high as 97 are also available.

Color Rendering

The way in which LEDs create light is challenging the conventional techniques through which good color rendering was defined. The chemical mix that leads to creation of “white” light can now be adjusted to provide more vibrance and intensive saturation. A comprehensive approach to color rendition is provided by the Technical Memorandum 30-15.

Unlike traditional technologies, LEDs can provide colored light in addition to white light, depending on the build processes. Furthermore, hues of red, blue, green and yellow can also be mixed to provide an illusion of white light to the observer. Another technique commonly used to produce white light is phosphor coating.

All this can be combined with effective control from touch screens or cloud-based apps, giving floor managers the ability to change lighting parameters at the push of a button.

LED Sizing

Another benefit of LED technology is its size. Incandescent, fluorescent and HID lighting have higher heat-dissipation and hence housing requirements compared to LEDs. With every passing year, fixtures are becoming smaller, combined with low heat emission and smaller wattage, making them ideal for all form factors.

LEDs are also directional making them efficient for applications that require directed light. For instance, a raw LED sitting on a circuit board has a 120-degree range of uniform operation. For targeted operation, optical changes need to be made to the fixtures, e.g. reflectors, lenses and total internal reflection optics.

Due to their smaller size, LED fixtures have also replaced linear fluorescent lamps, with modules varying in size and shape. This has allowed customizable dimensions to be followed, giving designers “to the inch” precision while at the same time providing energy efficiency.

The driver is generally the first component of the LED to fail. The fixtures will either fail at startup or follow a linear trend of diminishing with the passage of time. An LED module’s life is expressed as its L70 value, i.e. the output in terms of hours it will have when it is operated at 70% of its rated value. Regardless, the lifespan of LEDs is economically sustainable compared to other technologies and can be extended through periodic driver maintenance.

Coordination and Integration

The need for coordination is often sidelined during project design that leads to a loss of productivity and deviation from original requirements. Each part of the design, whether its mechanical, electrical, architectural, etc. must coordinate with each other, in order to ensure the project’s success.

As LEDs have become popularized, creative options have also grown in number along with flexibility. This has given rise to a new set of coordination needs since there are design aspects that were never considered in conventional sources due to their large size and inability to deal with heat. Close collaboration between different teams can help ensure that clients’ requirements are met, irrespective of the form factor desired. Furthermore, there’s an increased need for coordination with ceiling-grid locations due to advancement in optical technologies.

Another vital coordination entity is dimming control, which requires special consideration to the coordination between driver and control device. Inability to do so can lead to a host of problems such as flickering, buzzing, reduced range of operation, flashing, etc. The driver’s dimming protocol should match with the controller’s so that they “speak” the same language. Commonly used protocols are DALI, 0-10V, DMX512 and TRIAC.

Finally, any wiring requirements must be understood with limitations such as maximum load limit, minimum load requirements, operation distance and voltage drop getting special consideration.

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Topics: LED Lighting

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