Lighting Plant

Understand how the lighting plant works. Explore system overviews, measurement steps, and additional resources.

Overview

A lighting plant consists of the electrical distribution system and one or more light fixture systems. The electrical distribution system provides power to the light fixture system, which provides the actual illumination to indoor spaces, emergency evacuation routes, and outdoor areas. The electrical distribution system receives electricity from the power grid, which then is distributed through switchgear and panelboards. A lighting plant and associated systems are shown in Figure 1. Measurements may be taken at the electrical distribution or light fixture system levels.

Systems

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Light Fixture System

Comprised of luminaires, lamps, and controls. Controls can be manual such as wall switches within a space or electrical disconnects (circuit breakers) at the panelboard, or automatic via control panel and sensors.

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Electrical Distribution System

Comprised of main and secondary switchgear, panelboards and electrical switches. The switchgear distributes electricity to the panelboards, and the panelboards provide electricity to light fixture and other systems.

info Panelboards

Panelboards typically serve light fixture systems in multiple spaces across a facility and are generally broken down by floor or smaller spaces on a floor. Sometimes multiple electric panelboards are required to provide power to a single space such as a warehouse, gymnasium, or garage. Panelboards can have mixed loads or be dedicated just to lighting. Mixed panelboards serve the light fixture systems and other electrical loads such as receptacles, office equipment or miscellaneous plug loads. Dedicated panelboards exclusively serve light fixture systems including interior, exterior, and emergency lighting.

How do I…

Assess Plant Energy Usage

The main energy consuming components of lighting plants are the fixtures themselves. The power draw of each unit is typically consistent enough that only a portion of the fixtures need to be measured in order to estimate the consumption of the entire plant. Units should be grouped by model for power measurements and grouped by operating schedule for duration measurements.

Quantify Electricity Usage (kWh)

Determine the total amount of electricity used to operate the fixtures.

Equipment to Measure

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Lighting fixtures and automatic controls

What to Measure:

Average hourly true RMS power draw (kW) of the light fixtures
Total operating time (hours) of the light fixture system.