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MEEF - Middle East Economic Engineering - Articles    previous page

 

INTELLIGENT CONTROL PANELS  

Background: According to the California Energy Commission, scheduling a building’s lighting to automatically shut off at the end of the workday has been documented to result in 5-10 percent kWh savings and 0-5 percent peak kW savings. Scheduling the lighting to automatically shut off selected lighting during peak demand periods has been documented to generate 5-15 percent kWh savings and 5-15 percent peak kW savings.

 

Intelligent lighting control panels or lighting automation panels—lighting control panels that include an internal time-clock for scheduling capability—can be used to generate energy savings and satisfy the mandatory controls requirements in ASHRAE/IES Standard 90.1-2001.

Description: Lighting control panels have been the subject of increased interest within the electrical construction industry because of their energy-saving utility and also new energy codes enacted in recent years. The ASHRAE/IES 90.1 Standard, which was recognized by the Department of Energy as the minimum national energy standard, requires automatic shut-off in buildings larger than 5,000 sq.ft. except for buildings where it is critical that the lighting be operated continuously. There are basically three choices to satisfy this requirement: occupancy sensors, building automation systems, and lighting control panels.

Lighting control panels—also called switching or dimming panels, controllers, sequencers and automation panels—are typically installed in the electrical room near the electrical panel, although in some cases the electrical panel and the lighting control can be integrated into a single unit using controllable breakers.

The control panel houses high densities of switching modules, although some can also house dimming modules. Its processor assigns these modules to control zones—a fixture or group of fixtures that are to be controlled in unison. Otherwise, the control panel is a simple input/output device. Inputs can include signals from manual controls, photosensors, PCs and other devices. Outputs include switching or dimming of connected loads. Different sizes are available to manage various sizes of loads, from as few as two circuits up to 100+ circuits. While this traditional control panel performs its function well, it is not smart.

Intelligent control panels include an integrated time-clock that enables programmable scheduling for automatic shut-off of selected loads, and can provide monitoring and alarm features. Today’s intelligent lighting control panel has grown to a sophisticated system that can automatically switch lighting and other loads on and off from a time schedule, or in response to an occupancy sensor or a building automation system. The panels can also monitor the status of the branch circuit and various inputs and can alert the facility manager of a tripped breaker, a faulty sensor, or when the burn time of a lamp fixture exceeds a preset value. These alarms are generated from an embedded email server that allows the operator the ability to click on the email and go directly to the panelboard and view the status from a standard Web browser.

Advantages: Intelligent control panels are ideally suited to applications where the granularity of control stops at the branch circuit level, such as retail stores, warehouses, factories, transportation terminals and parking garages are ideal applications. Advantages include scheduling for energy savings, code compliance, and individual breaker control, which enables branch circuits to be individually controlled or grouped together and easy rescheduling and changing of control zones via a Web browser.

Distributed Control: Besides greater intelligence, other trends related to control panels include distributed control and distributed intelligence.

Traditionally, the control panel is centrally located in the electrical room, and houses multiple relays or contactors for economical control of larger numbers of loads. For example, to automatically switch the lights on and off on entire floors of a building based on a schedule, a centralized control scheme can be economical.

A new approach is distributed control, which can be more economical in applications that require more granularity of control zones. A distributed control system uses smaller panels with 2-4 outputs each, which are located closer to the loads they control, typically above the ceiling or in a closet. The local controls are wired back to the nearby distributed panel rather than all the way back to the electrical room, which can reduce wiring costs. For example, if each floor in a building contains multiple rooms that must be switched separately with different controls that must be wired back to a control panel, then a distributed control scheme can be more economical because the wiring between the control and the panel is shortened.

A distributed control scheme, in fact, can eliminate the central control panel. For scheduling, the distributed panels can be run back to a central time-clock.

Distributed Intelligence: Another trend is distributed intelligence, a subset of distributed controls. In a typical control panel, a processor provides the intelligence. If the processor fails, the control system fails because the intelligence is centralized.

In a distributed intelligence system, a processor is located in each connected control device, which increases reliability because if a processor fails, only that device fails instead of the entire control system. This scheme also allows control devices to be networked in virtually configuration.

see also:
Bi-Level Switching
Occupancy Sensors

 

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