Lighting Controls for Code Compliance in Interior Spaces

by Craig DiLouie, Lighting Controls Association

Posted November 2007

With varying exceptions and requirements, IECC 2003 and 2006 and ASHRAE/IESNA Standard 90.1-1999, -2001 and -2004 all require interior automatic lighting shutoff controls as well as manual or automatic controls in interior enclosed spaces.

This whitepaper provides a code comparison and a guide to compliant controls options for the following interior controls provisions:

• Interior automatic lighting shutoff (IECC, 90.1)
• Interior space controls (IECC, 90.1)
• Interior light level reduction control (IECC)
• Display/Accent lighting control (90.1)

Several other controls provisions, including independent controls for non-visual lighting (such as for plant growth), demonstration lighting (lighting for sale or part of lighting education), and task lighting, are not covered here.

By the end of this whitepaper, you will have learned major controls provisions in IECC 2003/2006 and Standard 90.1-1999/2001/2004 and what control strategies can be used to comply with code requirements.

This whitepaper is an excerpt of EE203: Lighting & Commercial Energy Codes. To receive education credit, be sure to take the course and successfully complete the exam at the end.

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AUTOMATIC LIGHTING SHUTOFF

Automatic Shutoff of General Lighting

With varying exceptions and rules, Standard 90.1 and IECC require automatic shutoff to ensure that general lighting in a building is turned off when it is no longer needed. Three methods of compliance of interest include:

Scheduled Shutoff

Scheduling entails activating and deactivating controlled lighting loads automatically based on a schedule, usually normal business operating hours. It is a proven energy management strategy for which savings of 5-15% have been demonstrated. Scheduling can be achieved by using a lighting control panel that features a time-clock.

The general lighting in the below 10,000-sq.ft. floor of an office building can be controlled by an intelligent control panel as a single zone with its own programmed schedule per IECC and Standard 90.1. However, code override provisions require the ability for users to override the shutoff and turn on the lights in a maximum area—in this case, 2,500 sq.ft. per Standard 90.1—in turn requiring more granular zoning.

Scheduling is a time-based function and as a consequence it is most suited for facilities or spaces where the occupancy pattern is predictable and certain things happen at certain times. Typical applications include open offices, retail sales floors, hallways and common areas.

If the building needs more than one lighting control panel, one approach is to centralize the time clock in a single panel (master) and then data-network the panel to other panels in the system (slaves) to communicate scheduled events. Another is to decentralize the scheduling function in a series of panels connected to a common bus, with the benefit being a failure in a single point in the system will not affect the rest of the system. For centralized programming and monitoring, consider a system that operates on a PC with lighting control software.

Because “off-normal” conditions inevitably arise, codes require capability for occupants to override the shutoff and turn on local lighting for use, covered later in this whitepaper.

Occupancy-based Shutoff

Occupancy-based automatic switching entails using occupancy sensors to shut off controlled lighting loads automatically when these devices detect the absence of people. It is a proven energy management strategy for which savings of 10-50+% have been demonstrated. Typical applications include private offices, restrooms, classrooms, conference rooms, break rooms, etc.

This 10,000-sq.ft. office building footprint uses color to delineate conference rooms, private offices, a kitchen and a copy room from open office cubicle and other spaces. Occupancy in these spaces is intermittent and unpredictable, making them ideal opportunities for occupancy-based shutoff throughout the day.

Occupancy sensors are ideally suited for spaces:

• In which the lighting is not required to be operating all day for safety or security reasons. For example, occupancy sensors are not recommended for public spaces such as hallways and lobbies, where the lights must remain on even when the space is unoccupied
• That are intermittently occupied throughout the day or are otherwise left vacant for significant portions of the day, and where occupancy is less predictable
• Smaller projects
• Projects requiring more granular control

Timed Shutoff

Timer switches turn off the lights in a single load switch leg after a preset period of time once the lights have been switched on. These switches may be programmable electronic switches or spring-loaded, mechanical, twist-timer switches. The shut-off setting is determined by the user or the contractor, depending on the technology.

Small spaces with limited use, such as the utility room coded blue in this office building footprint, are ideal applications for timed shutoff.

For example, a user enters a room, activates the lights and the timer, and when the timer expires, the lights shut off. When the lights are about to shut off, a warning signal may be emitted. This makes the timer switch both an occupancy- and time-based strategy to save energy that can be available for less than one-third the cost of an occupancy sensor.

However, timer switches typically save less energy than occupancy sensors, and may experience nuisance switching, as the lights will shut off at the end of the period unless the user restarts the timer. For this reason, timer switches are typically used in storage rooms, mechanical and electrical rooms, supply closets and janitorial spaces.

SPACE CONTROLS

Lighting Controls in Enclosed Spaces

With varying exceptions and rules, codes require additional controls in spaces enclosed by ceiling-height partitions. This enables users to override automatic shutoff events for a period of time while activating only localized lighting. Depending on the space and code in effect, this may be accomplished using manual switches, occupancy sensors or multi-scene controls such as dimmers. Two methods of compliance of interest include:

Control Panel with Timed Override Switches

As stated on a previous page, lighting control panels are a highly suitable automatic lighting shutoff strategy for spaces with high usage and regular schedules.

This 10,000-sq.ft. floor of an office building utilizes a combination of scheduling and timed override switches for control of open office areas and public spaces. After a maximum period of time allowed by code, the switches receive a signal from the control panel to turn the lights off. Per Standard 90.1, the maximum space control zone for a space this size is 2,500 sq.ft., leading to its division into four primary zones and a fifth zone centered on the elevator lobby and area around the stairs because this space has a different use. (IECC recognizes maximum coverage for each control as 5,000 sq.ft. for this building/space type, meaning there could be three zones in this floor.)

Panels can be networked with automatic control switches to provide local override capability to users. These switches are essentially manual ON/OFF switches. However, because the shutoff override is limited to 2-4 hours or longer depending on the code in effect, these switches can also receive signals from the control panel to turn controlled lighting loads on or off—enabling a timed override.

Occupancy Sensors

As stated on a previous page, occupancy sensors are a highly suitable automatic lighting shutoff strategy for spaces that are intermittently occupied and left unoccupied for periods of time throughout the day.

The kitchen, copy room and private offices are intermittently occupied, left vacant for significant portions of the day, and represent a highly granular group of control zones, making them highly suited for occupancy sensors both for shutoff and override. The conference rooms in this building utilize multi-scene dimming controls in addition to occupancy sensors.

One advantage of occupancy sensors is that they contain their own override (they turn off the lights when the space is unoccupied for a designated period of time). They are particularly suitable for smaller enclosed spaces, which require a high degree of control granularity or resolution.

LIGHT LEVEL REDUCTION CONTROL

Light Level Reduction Control

With several exceptions, IECC 2003 and 2006 require that occupants be able to reduce lighting load in the space in a reasonably uniform pattern by at least 50%. There is a notable exception for spaces controlled by occupancy sensors. NEMA estimates that bi-level/multi-level switching can generate 10-15% energy savings.

In our office building example, the dark blue-shaded open office areas do not qualify for exceptions and therefore must adopt some form of light level reduction control (in this case, an additional override switch that controls alternate lamps in the ceiling lighting system, matching the control panel and override zones). The conference rooms, shown as lighter blue-shaded areas, are covered not only because occupancy sensors qualify these space as exceptions, but because multi-scene dimming controls are used, which qualify as a suitable light level reduction control.

IECC recognizes four methods of light level reduction control:

• Controlling all lamps or fixtures (e.g., dimming)

• Dual switching alternate rows, fixtures or lamps

• Switching middle lamp independent of outer lamps (3-lamp fixtures)

• Switching each fixture or each lamp

Suitable solutions include dimming controls, manual switches and daylighting controls.

DISPLAY/ACCENT LIGHTING CONTROL

Standard 90.1-1999, -2001 and -2004 require that display/accent lighting be controlled independently of the general lighting. This can be accomplished, for example, with lighting control panels and programmable switches.

By separately controlling display/accent lighting from general lighting in a store, for example, display lighting can be scheduled to operate only during shopping hours, while the general lighting can operate during the store’s full operating hours.

LEARN MORE ABOUT CODES

Want to learn more about commercial energy codes? Take the Lighting Controls Association's EE203: Lighting & Commercial Energy Codes course. Click here to register and take the course.

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