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MEEF - Middle East Economic Engineering - Articles    previous page

 

INTRODUCTION TO LIGHTING CONTROLS

Introduction: Lighting controls play a critical role in electric lighting systems, providing the function of:

  • Turning the lights on and off using a switch; and/or

  • Adjusting light output up and down using a dimmer

In recent decades, technological development has increasingly automated these functions and allowed integration of devices into larger, more flexible systems. The result is significantly expanding energy-saving opportunities, flexibility, reliability and interoperability between devices from different manufacturers.

 

The Lighting Control System: Lighting control systems contain three components linked by communication wiring, which is used to transmit control signals, and power wiring, which supplies power.

Component

Sensing Device →

Logic Circuit →

Power Controller

Function

Provides information to logic circuit

Decides whether to supply lighting, and how much

Changes the output of the lighting system

We can therefore view a lighting control system or device as an apparatus that 1) receives information, 2) decides what to do with that information, and 3) changes the operation of the lighting system. In other words, we can look at lighting control devices based on inputs and outputs. Below are three examples.

Control

Input

Decision-making

Output

Occupancy sensor

Sensor detects presence or absence or people

Decide whether to turn on or shut off lights

Sends signal to relay, which closes or opens circuit

Control station and dimming panel

User presses button to recall preset scene

Control station recalls scene from memory and sends signal to dimmer at dimming panel

Dimmer adjusts light output to desired level

Dimmable ballast

Controller provides signal to dim

Ballast is instructed to dim, and by how much

Ballast alters the current to the lamps, dimming them

Below is an example of a robust lighting control system with a control station, occupancy sensor, photosensor and time switch or centralized switching system providing a variety of inputs to the master lighting controller. The lighting controller can be a switching panel, dimming panel or both linked together. The controller in turn controls the lighting load with a variety of outputs based on decisions made by the logic circuits. Since different control strategies may have overlapping device requirements, control synergies can be gained by building a system of simple components.

Purpose of Lighting Controls: In many applications, the overall purpose of the lighting control system is to eliminate waste while providing a productive visual environment. This entails:

  • Providing the right amount of light

  • Providing that light where it’s needed

  • Providing that light when it’s needed

The Right Amount of Light … Control systems provide the right amount of light. This lighting decision is based on the type of tasks being performed in the space. Lighting controls support this goal in two ways.

Lighting controls provide flexibility in adapting the lighting system to different uses. For example, a school auditorium, which is home to a diverse range of activities, would need different light levels for these activities.

Lighting controls provide the ability for users to adjust light levels based on changing needs or individual preference, either through dimming or through bi- or multi-level switching. Dimming provides the greatest amount of flexibility in light level adjustment.

By enabling the lighting system to deliver the right amount of light to the task, the control system can eliminate energy waste while providing a productive visual environment.

… Where It’s Needed … Lighting controls support the lighting system putting light where it’s needed. This entails establishing control zones, which is a light fixture or group of fixtures controlled simultaneously as a single entity by a single controller. Zones are typically established based on types of tasks to be lighted, lighting schedules, types of lighting systems, architectural finishes/furnishings, and daylight availability.


The greater the resolution of the control zones—that is, the smaller they are—the greater the precision the control system can provide. For example, a control system can turn the lights on automatically when a person enters a building during non-operating hours. Only the areas to be used should be lighted, however, and not the entire floor. A zone can also be as small as single ballast or light fixture, which enables the greatest amount of control resolution. For example, each user in an open office can be given capability via PC or handheld remote to dim his or her own lighting to personal preference.

Generally, the smaller the control zone, the greater the control resolution and potential utility cost savings and the greater the opportunity to enable the lighting system to support visual needs.

… And When It’s Needed: An effective control system ensures that the lighting system operates—and consumes energy which costs the owner money—only when it’s needed. Determining when the lighting system should be operating depends on how the space is occupied. This will entail whether a time-based or a threshold event should be the deciding factor in whether the lights should be turned on or shut off.

If occupancy is predictable, a time-based strategy can be considered. For example, a switching system can be scheduled to automatically shut off the lights by area, by floor or in an entire building if a building’s occupancy is predictable.

If occupancy is not predictable, a threshold-event-based strategy can be considered. For example, occupancy sensors can be used to automatically turn on and shut off lights in areas depending on whether the sensor detects the presence or absence of people in the monitored area.

By ensuring the lighting system provides light only when it’s needed, the control system can significantly reduce wasted energy and generate utility cost savings for the owner.

Energy Management: Advanced lighting control devices and systems can be used to reduce ongoing costs for the owner and thereby increase profitability and competitiveness. According to the New Buildings Institute, lighting controls can reduce lighting energy consumption by 50% in existing buildings and by at least 35% in new construction.

  • Lighting energy: Controls can reduce the amount of power drawn by the lighting system during operation and also the number of operating hours, thereby reducing utility energy charges.

  • Lighting demand: Controls can reduce the amount of power drawn by the lighting system, reducing utility demand charges—particularly during peak demand periods, when demand charges are highest.

These cost savings can produce a short payback and a high rate of return for the investment in the new controls. In new construction, the rate of return is often higher because only the premium, not the total installed cost, will be recouped before positive cash flow is realized.

Visual Needs: The project may be driven by business benefits other than energy savings by providing increased performance and flexibility:

  • Adapt the lighting for multiple uses of a space, such as a conference room or gymnasium.

  • Adapt the lighting to evolving space needs resulting from employee churn and office strategies such as hoteling and hot-desking.

  • Mood-setting for restaurants and similar applications.

  • Increasing worker satisfaction by providing personal control of their lighting systems in office and other environments.

  • Enhanced aesthetics and image, greater space marketability, and pollution prevention.

These business benefits are often more difficult to calculate than energy savings, but tangibly contribute to the bottom line.

Studies, for example, have shown that personal lighting control can increase worker satisfaction, a major contributor to productivity, while providing energy savings. According to the Building Owners and Managers Association (BOMA), energy costs run about $2/sq.ft. in a typical commercial building while worker salaries and benefits can run to $130/sq.ft. or more. While reducing energy costs by a large percentage can be profitable, increasing productivity by even a very small percentage can be much more profitable.

Defining the Application Goals: The first step in determining the right control strategy is to thoroughly define and understand the application goals.

 

2003 Ducker Research/ Watt Stopper Lighting Automation Study

2004-2005 ZING Communications/ LCA Dimming Study

2005 Square D Bulls Eye Study

Methodology

Telephone interviews of 158 facility managers, electrical engineers and architects

Email survey to 4,317 lighting designers, architects, engineers, distributors and contractors with 6.7% response

Direct mail survey

Study Focus

Automatic Switching

Dimming

Lighting Controls

Research Question

What are the top five factors driving the use of automatic lighting controls?

What are the top five reasons for specifying dimming systems?

What are the most important benefits of lighting control?

Average Respondent Answer

1. Increasing energy savings

2. Complying with owner requests

3. Compliance with state and national energy codes

4. Providing occupant control capability

5. Obtaining utility rebates and incentives

1. Ability to light space for different uses (flexibility)

2. Client request

3. Energy savings

4. Add value to the design

5. Mood setting

1. Reduce energy costs

2. Worker safety

3. Occupant convenience

4. Prolong equipment life

5. Meet state energy codes


Switching or Dimming?
The first primary decision after defining the load and the application goals is whether to switch or dim the load. Switching and dimming are stand-alone strategies but are often used in the same facility, and may be integrated in the same control system.

Method

Switching

Dimming

Primary Use

Energy management

Visual needs

Basic Function

Turn lights on or off

Change light output with smooth transitions between light levels

Benefits

Utility cost savings

Occupant satisfaction, flexibility, utility cost savings

Advantages

Relatively inexpensive and simple to commission

Can set light output at any level within available range, greater user acceptance due to smooth transitions between light levels

Disadvantages

Lower user acceptance in occupied spaces with stationary tasks due to abrupt, noticeable changes in light level

Higher installed cost, and can require more sophisticated commissioning


Local or Central Control?
The next step is to determine the amount of local vs. central control that is needed from the lighting control system.

Control Method

Divide the building into series of control zones, each zone constituting a lighting load controlled by a single controller

Localized

Centralized

Each zone operated by its own point of control independently of other zones

All zones operated by single point of control

Lower cost, less sophisticated commissioning

Greater capabilities, flexibility, potential cost savings

The control scheme can be designed with local systems and a centralized system working together as layers. Both local and centralized systems can be integrated into building automation systems for control of lighting and HVAC.


What Degree of Automation Is Required?
Manual lighting controls range from a single switch to a bank of switches and dimmers that are actuated by toggles, rotary knobs, push buttons, remote control, and other means. Manual controls can be cost-effective options for small-scale situations. However, as the size of the lighting system grows, manual controls lose their cost-effectiveness. In addition, manual controls often waste energy because the decision to shut off the lights when they are not needed is based entirely on human initiative.

Method

Strategy

Manual vs. Automatic

Switching

Occupancy sensors

Turn the lights on or off automatically based on whether space is occupied

Scheduled automatic shut-off at end of workday switching panels, time-clocks or building automation system

Turn selected lights on or off automatically based on schedule when space is predictably unoccupied

Scheduled automatic shut-off of select loads (bi-level switching) during peak demand periods, time-clocks or building automation system

Turn off one or two lamps in each fixture or checkerboard fixtures automatically for load shedding during peak demand periods

Bi-level switching using wall switches controlling lighting system layered as two separate circuits

Turn selected circuit on and off manually to achieve ON, 50% light level, and OFF

Multilevel switching using photosensor and low-voltage relay

Turn the lights off automatically based on available ambient daylight

Dimming

Dimming control of smaller loads using wall-box and remote dimmers

Adjust light output manually based on space need or personal preference

Dimming control of larger loads using control stations and dimming panels

Adjust light output manually based on space need or personal preference

Daylight harvesting using photosensor, controller and dimmable ballast

Adjust light output automatically to maintain target light level as daylight enters space

Adaptive compensation using dimming panels and scheduling device such as time-clock

Adjust light output automatically to provide lower light levels at night based on studies about human lighting preferences

Peak shaving and load shedding using dimming panels and scheduling or control device

Adjust light output automatically during peak demand periods and/or manually based on utility request to curtail load


Example Strategies:
Below are six sample strategies defined according to whether they are dimming or switching, local or centralized, and manual or automatic.


What Degree of Control Accuracy Is Required?
A key step in designing a lighting control system is to determine the degree of control over the lighting system, which means breaking the load up into zones. A control zone is a fixture or group of fixtures controlled simultaneously as a single entity by a single controller. Zones are typically established based on types of tasks to be lighted, lighting schedules, types of lighting systems, architectural finishes/furnishings and daylight availability. Establishing smaller zones increases control accuracy and flexibility but also increases cost.

See also:

Occupancy Sensors
Intelligent Control Panels

 

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