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Electrical Systems
Electrical Systems G8
| Term | Definition |
|---|---|
| parallel circuits | circuit that has two or more loads or branches that connected between the same two points |
| universal motor | AC or DC electrical current used- handheld appliances, such as construction tools |
| Direct Current - DC | The flow of electricity takes place at a constant time rate, voltage and in the same direction around the circuit. Often found in elevator work |
| Alternating Current - AC | The flow of electricity reverses direction and changes voltage. It operates at 60 Hz. |
| Electric Current | The flow of electrons through a conductor. Measured in amperes. |
| Gauge wire in construction | 14 gauge copper wire - minimum Gauge - diameter of wire. |
| Electrical HVAC | Simplest HVAC to install and operate. No space needed for pipes and duct work and temperature can be controlled with a separate thermostat in each room. Expensive.. |
| ohm's law | I Current= V Voltage/ R Resistance Current that will flow in a DC circuit is directly proportional to the voltage and inversely proportional to the resistance of the circuit |
| Ampere | I Current amps = W power watts/ V Volts |
| Direct current low voltage lamps | smaller filaments allow more precise control over light placement |
| Resistance | Resistance is the reciprocal of conductance and is a measure of the insulating quality of a material. conductivity measures a material's ability to conduct heat. Resistance increases as the thickness of a material increases. R= 1/C |
| Transformer | Device that changes the voltage in AC. Cannot be used in DC. Mounted on a concrete pad. Steps down voltage to 480V for building use. Transformer inside the building steps down to 120V for use at receptacles. |
| Generator | Converts mechanical energy into electrical energy(electricity) |
| Panel boards | A set of fuses or circuit breakers that is the central distribution point for electrical loading in the building |
| GFCI | An outlet receptacle used in wet areas to provide additional protection against electrical shocks |
| Fuse | Fusible link or wire with low melting point enclosed in a threaded porcelain cup or insulated fiber tube. |
| Circuit breakers | Same function as a fuse, but mechanism is enclosed in a molded plastic case. Manually switched on and off to protect or open the circuit. Visually indicates a trip and can be reset |
| Conductance | Number of BTUs that pass through one sq ft of material |
| Variable Voltage | DC Used before 1990. Low efficiency, high maintenance, high thermal loss and high noise level |
| Variable Voltage, Variable-Frequency AC | Elevator motor control- best system for high quality installation |
| AC Thyristor | High power transistors to make accurate speed control of AC squirrel cage motors |
| DC Thyristor | Greater rise and speed than AC version |
| Flexible Metal Conduit | Excellent for transformers, motors, ballasts, where acoustic and vibration isolation in important. When covered in plastic jacket, useful in wet locations. Also knows as Flex or Greenfield |
| PVS Plastic Conduit | Ideal for underground use |
| Electrical Equipment room location | At the center of the facility, because it allows minimum lengths of thermal and electrical distribution runs. |
| Conductor cable | Electrical panel to outlet = 10, 12, 14 AWG Appliance like range and dryer = 8, 10 AWG Smaller the AWG number- thicker the diameter. Thicker the wire- greater the current carrying capacity and longer the run distance |
| Conductors | Wire/ cable/ busbars that carry electrical. They range in size from 16 GA to 4/0000. |
| cable | Insulated 6 gauge or larger, or several smaller ones bound together in a single unit, referred to as cable |
| wire | 8 gauge or smaller is called wire |
| busbars | rectangular copper bars used to conduct high currents of electricity. power is transmitted through multiple bars, insulated from one another, and arranged in a metal housing called a busway |
| Critical distance | Maximum length of drain pipe between a trap and an air vent. can be no more than 48 times the pipe diameter. |
| 120/240 single phase | residences and small office building. |
| 277/480 three phase four wire | large commercial buildings |
| 2400/ 4160 three phase four wire | industrial |
| 120/208 three phase four wire | small and medium commercial |
| Service entrance equipment | transformers, service disconnect, fuses, meters, circuit breakers |
| Interior distribution equipment | conductors, raceways, subpanels, submeters |
| loads | power demand created by appliances and lights |
Created by:
rudolph.beukes
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