Sizing out and specifying lighting for dwellings, including guest rooms and suites in hotels and motels, is a simple, intuitive process, even for fledgling electricians. This is because we have lived our entire lives in dwellings and know by experience the amount of incandescent lighting required for various work and living areas.

It is a simple matter to provide three volt-amps per square foot of dwelling area, place one or more ceiling lights in each room with receptacles spaced according to applicable codes. With the addition of some modest kitchen task lighting a residential design is almost complete.

A few features make for a better job. In new construction and remodeling, it is said that premium upscale lighting is the least expensive way to add value to a building. Consider what the addition of a few high-end outdoor fixtures can do for an otherwise nondescript building! Then there is the whole concept of low voltage landscape lighting.

But notwithstanding these extras, residential lighting is not a big issue in the life of a practicing electrician. But when you get into the world of commercial and industrial lighting, let's say beware of pitfalls.

In many of these venues, for example in the case of a passive storage warehouse, lighting comprises a major fraction of the total connected load. If you did the electrical design for such an occupancy only to find after the building was put into service that for whatever reason the lighting was insufficient, it might be necessary to put in a bigger service and rework the entire electrical structure. Similarly, it is not at all good to overbuild because in that instance the owners are not getting good value for their money.

The larger the building, the more removed it is from everyday experience, especially in terms of lighting design. We cannot all become lighting design engineers overnight. But as we peruse the literature and become familiar with the terminology (lumens, color rendition and the like) and sizing conventions, a good plan is simultaneously to enter this type of work in an incremental fashion, beginning with small retail operations and office situations before attempting a large manufacturing operation with high bay areas, telecom rooms and office space.

We have to recognize the fact that the electrician will not always influence the entire building design. Ideally, a new industrial location will have extensive skylights. Besides cutting energy costs, these simple architectural units provide a high quality diffuse light which has been found to vastly increase worker comfort and productivity. Employee accidents and errors are reduced while morale and loyalty increase. Unfortunately, by the time the electrician comes on the job, the building has exited the design stage. But it is still possible to influence certain other aspects of the finished product. One of these is interior painting. Ceiling and walls should be white -- use matte instead of high gloss to minimize glare. The floor should be light colored, low gloss. These seemingly minor building decisions can greatly augment good lighting choices to create a more comfortable and productive workplace.

Interior industrial lighting is conveniently divided into low bay and high bay, each of these requiring different design approaches.

If the ceiling height is less than 25', with the fixtures typically hanging three feet lower, it is considered a low bay workspace, while greater heights are high bay. High intensity discharge fixtures come in high bay and low bay versions. Low bay fixtures provide a wider spread of light, usually 65 to 100 degrees. The spacing is generally equal to the mounting height.

The other solution in a low bay setting is to use linear fluorescent fixtures. In a remodeling job, if the old fluorescent fixture has T-12 bulbs, change them over to the more efficient T-8s. This involves changing the ballast. Ignore the old wiring and follow the wiring diagram on the new ballast. The sockets are the same and don't need to be changed.

As a fluorescent bulb ages, it makes less light and more heat. It also draws more current, which burns out the more expensive ballast. Therefore, fluorescent bulbs should be changed well before they fail completely. Large facilities have a fixed schedule for bulb replacement. A sign of aging is that the bulbs begin to blacken at the ends. They should be changed before that becomes very pronounced.

Besides fluorescent, 250-watt metal halide low bay open reflector and prismatic glass reflector are appropriate for under 25' ceiling heights.

The high bay setting is a whole different world. Because of the greater distance, task lighting assumes a greater significance both in terms of cost saving and from the point of view of worker comfort and productivity. What this means is individual lighting, usually fluorescent strips, directly above or behind glare defeating valances at each workstation.

Lighting types used in a high bay setting are 400-watt and 250-watt metal halide, prismatic reflector, or four-foot, two-lamp T-8 fluorescent pendant reflector, or four-foot, one-lamp T-5 HO fluorescent pendant reflector.

T-12 fluorescent with magnetic ballast, because of its lesser efficiency (less light per watt) and 60-Hz hum and flicker, and mercury vapor with poor color rendition, are mostly obsolete for interior lighting.

Metal halide, developed in the 1960's, achieves excellent color rendition and is appropriate for both interior and exterior work.

Of course a key design objective is to provide comfortable, productive light at minimum cost to the owner. Proper switching and dimming capability are important ways to minimize energy use. Other strategies are resisting the impulse to overbuild and using the most efficient lighting available. (While we have not yet entered the LED era, there is no doubt that it will be the wave of the future.)

In approaching a new design, the first step is to ascertain the light level required. A careful survey of contemplated usage is in order. What type of work will be done at the facility? A machine shop or art restoration studio requires much higher light levels that a warehouse for storing boxed appliances. Ambient daylight via windows or skylights, while greatly reducing artificial light needs and thus energy usage at times, cannot reduce the amount of lighting that must be provided if the enterprise will at times operate during hours of darkness like late cloudy afternoons in winter.

In figuring the number and placement of light fixtures, local conditions must be considered. Special prismatic fixtures are available when the workplace is divided into longitudinal aisles, for example.

A great impediment to worker comfort and productivity is glare. This condition occurs when areas of excessive brightness impinge upon the field of vision, reducing perceptive functionality and, over a period of time, causing actual physical pain. The remedy is controlling glare by means of light placement and sizing and/or adjusting workstation positioning. Sometimes it is possible to defeat glare by reducing fixture wattage. Computers and control panels should be located so that the screens face away from light sources including windows. Bright light fixtures can be raised so that the light is not directed into the workers' eyes. A certain percentage of the light should be directed upward toward a light-colored ceiling so that it diffuses downward.

HID ballasts can create a strobe effect which is extremely uncomfortable and hazardous to some individuals. Additionally, it can make rotating machinery appear to stand still, which could cause worker injury. One remedy is to power adjacent lighting from different legs of a three-phase system so that the pulses cancel out. Another approach is to introduce T-8 fluorescent lighting, which is powered by higher frequency electronic ballasts.

If the organization has a safety officer, this individual should become familiar with lighting technology and be able to implement solutions to worker discomfort on a case-by-case basis.

Specific occupancies require individualized approaches when it comes to lighting design. Health care facility, classroom, retail store, manufacturing location and hazardous area all present different needs and challenges in terms of lighting design.

In the classroom, lighting specifications and layout are of great importance to the health and safety of teachers and students alike. Color rendition and elimination of glare are prime objectives. The ubiquitous recessed parabolic 2' X 4' or 2' X 2' fluorescent panels are not ideal in this setting since often distracting shadows are generated where they are least desirable -- right on the desktop. At least some of the lighting should focus on the front of the room where teacher and board are located, and this lighting will also help to minimize shadows.

In the classroom it is helpful to use more fixtures of less intensity so as to create a diffused, relaxing ambience. Large variations in light cause fatigue and detract from the learning experience.

Lighting control is a whole area of expertise that needs to be incorporated into the lighting design. Occupancy sensors and timers are highly effective alternatives to manual switching, which can be neglected so that expected savings are not realized.

Do not neglect the emergency lights -- these are sometimes excluded in the initial design and left to the installer. Location is of great importance. All public areas and means of egress should be generously lighted, with particular attention to any stairways or changes of floor level. Since a power outage and presence of dense smoke may accompany a fire, it is of essential that abundant light from redundant fail-safe unit emergency lights be provided. Exit lights should be installed and never positioned so as to mislead individuals in an emergency.

Good lighting design enhances worker comfort and productivity and contributes toward cost savings. Accident prevention and worker and public safety are moral imperatives as well.
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