In this series we have looked at the "Why?" of a lighting system in Part 1, the "Where?" in Part 2 and the "When?" in Part 3. In this segment we want to look at "WHAT?" comprises a lighting system. We will describe the types of lighting systems, their function and the specific equipment used in those systems.Traditionally, there are two types of lighting systems: line voltage and low voltage. Let's examine each.Line Voltage SystemsA lighting system that utilizes a supply voltage of 120 volts (AC) and above is classified as a line voltage system. As a homeowner, you won't have to deal with commercial systems, therefore we'll only discuss lighting in the context of 120/240 volt single phase systems. Most residential fixtures require 120 volt input but may be labeled for inputs of 120 to 277 volts. Basically, anything that can be plugged into your wall outlet is considered a line voltage device (e.g. table lamps, floor lamps) or pre-existing devices which include your recessed lights, floodlights and hanging fixtures installed during the construction of your home. Wiring for line voltage systems runs directly to the fixtures which means that 120 volts are present at each fixture. Therefore the risk of shock is present at each fixture. This can be a risk for homes with small children since many of these fixtures are at ground level. Power can be removed from the system when it is not in operation by control devices that are installed at the head of a system in the form of timers, photocells or wireless devices.Line voltage outdoor fixtures are usually designed to illuminate larger areas by utilizing a high wattage lamp configured in a way (usually gas-filled) to produce a high lumen output. Many of these fixtures will implement a reflector system that directs the lamp output in a specific pattern. Some fixtures use a lamp that has the reflector built in as a part of the lamp itself. Parabolic Aluminized Reflector (PAR) lamps use a reflective material (usually aluminum) shaped in such a way as to distribute light in the desired area. Usually these distribution patterns are wide flood (WFL), narrow flood (NFL) and spot (very narrow concentrated light pattern). Reflecting systems can be configured to provide almost any pattern of light needed but these types of specialty reflector systems are generally used in commercial products.Several technologies are associated with line voltage systems for residential use. Along with PAR lamps using Halogen technology, other subtypes include Metal-Halide, Fluorescent, High Pressure Sodium and Light Emitting Diode (LED). If you would like more information about lamp technologies, you can find it in our Homeowner's Lighting Guide. Smaller scale line voltage fixtures including post lamps and wall sconces use some of these technologies also but have lamps with less output for smaller target areas. Many of these lamp styles are constructed to be more decorative since they are visible within the fixture. (e.g. flame shaped, antique lamps, etc.)Line voltage systems require a qualified installer since damage to person and property are real hazards if these systems are not properly installed.Low Voltage SystemsLighting systems that are powered by 30 volts or less (AC or DC) are categorized as low voltage. Most outdoor systems are 12VAC or 24VAC but some LED systems operate on direct current (DC). Power is supplied to the lighting system via a transformer that converts line voltage to the required low voltage. These systems are much safer, in fact, you can hold the wires supplying a 12VAC low voltage system without even feeling the current. Even though novice installers can install low voltage systems without fear of being shocked, the danger of improperly wiring a low voltage system can result in fire caused by supply wires getting so hot they melt the shielding off the wires. This results in the bare wires arcing or creating sparks which, in turn, can cause surrounding materials like mulch to flame up or smolder.Some transformers have built-in control devices which may include photocell/timer combinations which have regular timers or countdown timers. Regular timers allow a system to come on at a specific time and stay on until a specific time, both set by the user. The weakness of these control systems is that if power goes out the clock loses it's time and the system comes on at the wrong time. The user must also correct the timer twice per year due to Daylight Savings Time. The countdown timer alleviates the need for user input by letting the photocell determine when the system should come on by the level of darkness and when the system should go off by counting down from a preset number of hours. These control systems never need correcting since they reset when the photocell removes power from the system. There are several options for control of lighting systems available including wireless devices and those that work over Wi-Fi with several new technologies on the horizon including PoE and Li-Fi.Although the output of low voltage fixtures can rival line voltage fixtures, they generally are used to control the pattern of light output in a way to reduce light pollution. Light pollution results from light being cast into areas where it is unwanted. An example would be having light shining into your eyes while trying to go down a set of stairs or shining into a child's bedroom at bedtime. You don't need, or want, a light designed to cover a 1000 square feet on a target that is 100 square feet. The result will be the target details will be washed out and the effect will not be very appealing. The beauty of low voltage systems is the subtle effect that can be achieved through proper fixture selection and proper placement.
