LED Lighting System Design
As a business owner, an LED lighting retrofit can be an important solution for your commercial space. These design basics can help you understand how LED fixtures can give you better quality lighting and a more efficient infrastructure
A new LED system typically results in energy savings of as much as 85 percent compared to traditional lighting systems? While there is an upfront installation cost, the return on investment is apparent almost instantly with ongoing energy savings.
When considering an LED retrofit of your space, have the engineer analyse the following items to ensure optimal LED lighting design.
- Thermal management
- Photometrics & 3D renderings
- Usage vs. longevity of LED fixtures
- Spacing of the fixtures
- Lumen requirements for code compliance and productivity needs
- Multiple lighting layouts to see what option fits your space best based on the tasks being performed
- What options for lighting control are available for the space(s)
LEDs can produce thousands of lumens, and even low-power LEDs are becoming more specialized. When you’re designing a space and need the lighting to reflect your style and light the space appropriately, consider these elements first:
- Colour temperature – This only applies to white light, and measure how cool (blue hue) or warm (red hue) the light appears. Warm temp LEDs tend to make food more appetizing and people look better, so it might be the right choice for restaurants or retail space. Cool whites are often used in office environments because they tend to mimic daylight and have been proven to make employees more productive.
- Wavelength – To get the specific colour you really want for your space, make sure you pay attention to the wavelength spec to see if you’re going to get a true green shade, for example, rather than a yellow-green.
- LED efficiency – Efficiency is measured in lumens per Watt. As a rule of thumb, customers tend to aim for 100 lumens per Watt from an entire system. This includes any losses due to heat, lensing, light guides, and power conversion.
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Some general principles to follow when reviewing requirements for a renovation lighting design project:
- Most spaces now require more lighting controls than a simple on/off toggle switch. There are many control systems available that make design and installation easier.
- To meet the LPD limits of the new ASHRAE 90.1 edition, IECC, you’ll most likely want to use LED fixtures instead of more energy-intensive lighting options.
- Over lighting a space can be as undesirable as underlighting a space. Aim to be within +/-10% of the target foot-candles typically found in the Illuminating Engineering Society (IES) Lighting Handbook.
- With so many options for LED lighting fixtures, even obscure architectural fixtures can be used and still meet codes.
- Minimize glare from intensive computer screen areas by looking at indirect and direct fixtures with shielding on the downlight side of the fixture.
- Clients appreciate rendered 3-D images of their new facilities showing the lighting within. With minimal effort, adding some small details and colour can look impressive. Three-dimensional-rendered models are not an option for all consultants.
Lighting Control Design Requirements
The following is an overview of the basic lighting control requirements and devices to consider during design and is by no means an exhaustive code review. There are many exceptions to certain control requirements including 24-hour operation and security or safety concerns, among others. Exceptions should be cleared with the client prior to removing them from the design. The control requirements and devices are:
- Occupancy sensors are mounted in the ceiling or on a wall switch, available in passive infrared (PIR) or “dual-technology,” which incorporates PIR plus either a microphonics or ultrasonic sensor. PIR is limited to line-of-sight movement only, so it is not a good choice in areas with lots of obstructions like tall cubicle walls, large equipment, or restroom stall doors. Microphonics uses a tiny microphone to detect sound, while ultrasonic sensors emit high-frequency sound waves to detect motion. The sensors operate by turning on the lights in the space upon occupancy to a level determined in ASHRAE 90.1 and turning them off automatically after 20 to 30 minutes when unoccupied. Most space types in a commercial application, aside from mechanical/electrical rooms, require occupancy sensors.
- Daylight sensors are mounted in the ceiling, ideally with lights between the sensor and a window. They operate by taking a reading of total available light in the space. Throughout the day, sensors dim the artificial lights to where the artificial light level plus the sunlight level in the space meets the programmed foot-candle either at the work surface (generally 30 in. above the floor) or on the floor, depending on space usage.
- Automatic receptacle control was introduced in ASHRAE 90.1-2010 and consists of a relay pack that controls 50% of the electrical receptacles in the space. Let’s consider two different ways how a private office with four duplex receptacles is controlled:
- Two full duplex receptacles will be controlled.
- The bottom (or top) receptacle on each of four duplex receptacles is controlled.
- Controlled receptacles shall be marked with the International Power Symbol. The receptacles can be tied to the operation of the occupancy sensor in the space or they can be incorporated into a scheduled time-of-day shutdown. In the case of occupancy sensor-controlled receptacles, they turn on upon occupancy and turn off after 20 to 30 minutes of being unoccupied. These receptacles are a good choice to plug in noncritical loads, such as a desk lamp that may inadvertently be left on. (per ASHRAE 90.1-2016). A best practice is to bring this up early in the design process so clients are not blindsided.
- Bilevel lighting control is a method of having at least two separate lighting-output levels for a space, one of which may be automatic upon entry while the second is manual. A smart switch with full dimming capabilities also meets this requirement, provided the automatic operation is no higher than 50%. When an occupant enters the space, the lights come on to 50% output automatically. If the occupant wants full light output, they manually hit the second-level button (or dimmer buttons) on the wall switch. This requirement is in place to prevent wasted energy on someone stopping in briefly and leaving immediately. For example, a janitor closet, where the janitor would open the door, grab a broom and leave, triggering the occupancy sensor. This requirement can be programmed into the system or be a pre-installed option on a relay pack.
- Automatic HVAC shutdown – Typically provided on a building management system (BMS) time-of-day schedule, another option is to integrate HVAC operation in spaces with lighting control occupancy sensors. Many lighting control systems offer options for this integration. If the lighting control system sensor is used, the lighting controls notify the HVAC/BMS to turn on in the space. When the occupancy sensor times out after 20 to 30 minutes, the signal is sent to the HVAC/BMS to turn off or lower HVAC to the space, saving energy from running HVAC in an empty room for extended periods. There are various interface protocol options, and the choice will depend on how the mechanical BMS is set up. A simple contact closure hard-wired to the BMS can be used from a per-room relay basis, or the preferred method is to use a BACnet (or other) interface module that resides on the lighting control system network that converts the signal to the correct protocol for the particular BMS. Then logic is used for input into the spaces for HVAC control. Always confer with your mechanical engineer on the project to confirm his or her preferred protocol. This strategy is typically used in most occupied spaces like offices, conference rooms, control rooms, and break rooms. Click here for more information on LED Lighting system design
