The design of lighting systems for Metropolitan’s water treatment plants, pump stations, and administration and maintenance buildings shall be in accordance with California Code of Regulations, Title 24, State Building Code. The Code provides performance and perspective compliance approaches for achieving energy efficiency in building lighting systems.
3.11.4 Luminaires
There are too many companies that manufacture luminaires to list them or the types of luminaire that they manufacture. In this section, some of the general types of luminaires available will be discussed and
STANDARD ELECTRICAL DESIGN PROCEDURES MWD Electrical Design Manual
Table 3-2. Recommended Illumination Levels
Task/Area Footcandles Office/Lab Areas General Close Work 50 100 Control Room 50 Process Areas 30 Storage Areas/Active 20 Storage Areas/Inactive 10 Outdoor Areas Filters Pump Stations Storage Areas Walkways Roadways 5 10 5 2 1
3.11.4.1 Fluorescent. Fluorescent luminaires used indoors shall be one
of four basic types:
x Recessed type with a lens; x Surface type with a lens; x Open-chassis type; x Enclosed and gasketed.
All lenses shall be specified to be 100 percent clear acrylic.
Recessed fluorescent luminaires with a prismatic acrylic lens shall normally be used in office areas, and lab areas. The luminaire specified must be coordinated with the type of ceiling being installed, because the luminaire to be recessed in a lay-in ceiling cannot be installed in a plaster board ceiling and vice versa. Two-lamp luminaires are preferred but three- and four-lamp luminaires shall be used where higher footcandle levels are required and/or two-level switching is desired. Where three- and four-lamp luminaires are installed in office areas, two-level switching shall be provided.
Surface-mounted fluorescent luminaires with a lens may be substituted for recessed luminaires in areas where plasterboard ceilings are being
installed.
used. High-angle brightness, better known as glare, must be controlled to avoid discomfort and fatigue. Proper selection of lighting units can
substantially reduce this brightness and thus improve the work environment. Lighting control systems that utilize a parabolic louver assembly of preanodized specular low-iridescent aluminum, Lithonia OPTIMAX, or equal, shall be used in all areas where VDT screens will be used.
Open-chassis fluorescent luminaires shall be specified for all industrial type areas in the plant where moisture is not a problem if they can be mounted at 15 feet or less. Higher mounting heights result in difficulties in relamping and the need for higher wattage luminaires. Again, two-lamp luminaires are the preferred type. Where more lamps are required to provide the footcandle levels required, higher wattage lamps should be considered. Open-chassis luminaires with reflectors shall normally be used. Where the luminaires are to be suspended, a minimum of
10 percent uplight shall be provided. In situations where surface mounting is necessary, no uplight is required and an open-chassis luminaire without the reflector may be used. All open-chassis luminaires specified shall be heavy duty type.
Enclosed and gasketed luminaires shall be specified for damp and wet locations. They shall be UL-listed as suitable for the type of area that they will be installed in. Luminaires shall be manufactured of molded, high- impact resistant ABS plastic or reinforced fiberglass with a diffuser of high- impact resistant acrylic.
3.11.4.2 High-Pressure Sodium. High-pressure sodium (HPS) lumi-
naires installed indoors shall be either open or enclosed and gasketed as best suits the needs of the area where they are to be installed. Open luminaires shall be installed in dry low and high bay areas where they will be suspended and uplight is required. They shall be installed in areas where the ceiling height exceeds 15 feet. Enclosed and gasketed HPS luminaires shall be installed in all damp and wet areas where the mounting height exceeds 12 feet. Luminaires shall be installed suspended and shall be constructed using an acrylic or glass refractor that totally houses the lamp.
High-pressure sodium lamps shall be used for all lighting applications outdoors except where decorative lighting is to be provided at the entrances of administration buildings.
Security lighting shall be provided on the outside of buildings and at entrances by wall-mounted HPS luminaires that use a prismatic glass or
STANDARD ELECTRICAL DESIGN PROCEDURES MWD Electrical Design Manual
luminaire shall put a minimum of 2.25 footcandles of light on the ground within a space of at least 10 feet in front of and at both sides of the luminaire when it is mounted at 10 feet above final grade.
Illumination shall be provided at parking areas and on roadways by pole- mounted luminaires. Mounting heights shall not exceed 25 feet, and lamp size shall be 150 watt. In most situations, IES Type II luminaires will provide the best illumination on roadways whereas IES Type IV or V luminaires provide the best lighting for parking areas. Parking area and roadway luminaires shall be wired for operation at 480 volts if the voltage is available.
3.11.5 Emergency/Standby Lighting
For the purposes of this section, the term "emergency lighting" shall mean those lighting systems that are required by NFPA 101 for the protection of human life when the normal power supply fails. The term "standby
lighting" shall mean those auxiliary lighting systems that are not required by code but are required for safety reasons should the normal power supply fail. The same equipment shall be used for both lighting systems. Emergency/standby lighting needs in office, lab, and control room areas shall be provided by either recessed emergency lighting units or
emergency lighting units that are supplied integral to the fluorescent luminaires. In either case, sufficient units shall be installed in all areas to provide adequate egress lighting for all occupants in the building. Units supplied shall provide a minimum of 90 minutes of light as required by UL 924.
Emergency/standby lighting needs in enclosed process areas of the plant shall be provided by 12-volt unitized lighting units. At least one unit shall be installed in each area where motors or other process equipment exist and one unit shall be installed in each electrical room that houses
switchboards, unit substation, or motor control centers. Lighting units may also be installed in other areas where the exitway may be blocked by equipment or materials and a hazard may exist. Each lighting unit shall be located to provide maximum illumination on the normal exitway.
The NEC requires that all unit type emergency lighting systems be supplied power from the circuit that normally supplies the lighting in the area where the unit is to be located. Where more than one circuit supplies the area, the one that supplies the largest part of the traveled area shall be selected as the source of power.