Part 5: Electrical Systems
Ground- is a safety conductor with a low impedance path to earth. It is often called the “ground wire” or safety ground. It is either bare or has green insulation.
Hot- is any conductor connected that has electric potential relative to electrical ground or neutral. In 110/220 volt systems this conductor is either black or red, and in some instances, blue. The hot conductor terminates on brass colored terminals.
Neutral- is also called the “grounded conductor” and is represented by the white insulated conductor. It will terminate on the silver terminal (longer slot on a receptacle face) of receptacles, and at the neutral bus bar in circuit breaker panels.
Leg-, as in “hot leg”, refers to one of multiple hot conductors in a circuit. Example: 240 volt circuits feature a neutral and two hot legs, 240 V to each other, and 120 V each to the neutral.
Line- is the “in” side of the device where the wires from the panel (or other equipment feeding the device) are connected.
Load- is the “out” side of the device where any items that are to be serviced by the device are connected.
Hard-wire- refers to directly wiring to an appliance’s terminal block or by wire nuts in a junction box instead of attaching it by using a receptacle and cord/plug assembly.
Ground Fault Circuit Interrupter (GFCI)- Disconnects a circuit when it detects that the electric current is not balanced between the energized conductor and the return neutral conductor. Could be caused by current leakage through the body of a person who is grounded and accidentally touching the energized part of the circuit.
A luminaire is a complete lighting unit consisting of a lamp or lamps together with the fixture (parts designed to distribute the light, to position and protect the lamps and ballast (where applicable), and to connect the lamps to the power supply). The overall performance of a lighting system is a combination of the quantity and quality of light the lamps produce. Light output is measured in lumens. The amount of energy used by a lamp type is measured in watts. Efficacy is an indicator of performance which is rated in LPW (lumens per watt). The higher LPW, the more efficient the light source is.
Lighting fixtures are designed to meet a variety of applications and aesthetic requirements. Each fixture comes with specific installation instructions provided by the manufacturer that should be red prior to installing the lighting fixture. Some can be both wall and ceiling mount, wile other fixtures may be designed for only one method or the other. Each fixture also comes with labeling listing installation restrictions pertaining to location, mounting requirements, and wiring methods. Always connect fixtures to the electrical system with the proper polarity.
Common information found on a lighting fixture label:
- For wall mount only or ceiling mount only
- Maximum lamp wattage
- Lamp type
- Suitable for operation in an ambient temperature not exceeding ____°F (°C).
- Suitable for use in suspended ceilings, damp locations, and/or wet locations.
- Suitable for mounting on low-density cellulose fiberboard.
- For supply connections, use wire rated at least ____ °F (°C).
- Thermally protected.
- Type *Non-IC or **Type IC (common to recessed ceiling fixtures that are often called “can” fixtures)
*Type NON-IC- Installed so the insulation is no closer than 3″ (75 mm) to any part of the fixture.
**Type IC- Designed to be in direct contact with thermal insulation.
Light is the visible portion of the electromagnetic spectrum. Lamp manufacturers are concerned with three factors: color temperature, color rendering, and lamp efficacy.
Color temperature of a light source is a measurement of its color appearance measured in degrees Kelvin (°K). Light at higher-temperature wavelengths (blue and white) is referred to as “cool”, whereas light from lower-temperature wavelengths is referred to as “warm”. These descriptions have nothing to do with temperature, but with the way the colors appear. Warm light sources are commonly used for residential applications because they make colors appear more natural and vibrant.
Incandescent- Relies on the resistance of a tungsten filament to create light. Least efficient as it produces more heat than light. Standard household incandescent bulbs are being phased out of production.
Florescent-Requires a magnetic or electronic ballast to provide voltage surge required to start the lamp and current control that allows the lamp to operate efficiently. Consists of a tube filled with inert gas like argon or krypton, and small amount of mercury. Electrons emitted from cathodes strike particles of mercury vapor, producing ultraviolet radiation causing a phosphor coating on the inside of the glass tube to glow and produce light energy. More efficient than incandescent lighting.
Compact Florescent- These bulbs were developed to save up to 75% in energy cost and last 10 times longer than incandescent models. CFLs have heavy metal environmental disposal concerns to include lead, zinc, copper and mercury.
Light-Emitting Diode (LED)- LEDs offer energy savings of 80% to 90% over incandescent lamps with a reported operating life of up to 100,000 hours. They are offered in most all bulb sizes and base configurations.