ARCH 502-3 BUILDING UTILITIES - 01 Electrical Systems

Bus

A heavy conductor, usually in the form of a solid copper bar, used for collecting, carrying and distributing large electric currents. Also called a busbar.

Transformer

Used by medium-sized and large buildings to step down from a high supply voltage to the service voltage.

Motor

Used for converting electrical energy to mechanical energy.

Transformer

Used for converting one voltage to another, from lower to higher or from higher to lower.

Direct Burial Cable

Used for residential service connections.

Dry-Type Transformers

Used in small- and medium-sized buildings may be replaced together with a disconnect switch and switchgear in a unit substation.

Storage Battery

Used to supply emergency lighting circuits for hallways, stairways, exits and to energize police and fire alarm systems and certain types of signal systems.

Watt

Unit of electric power or the rate of doing electrical work.

Coulomb

Unit of electricity comprising approximately 6.25 x 10 18 electrons.

Fuse

A device containing a strip or wire of fusible metal that melts under the heat produced by excess current thereby interrupting the circuit.

Lightning Arrester

A device for protecting electric equipment from damage by lightning or other high-voltage currents, using spark gaps to carry the current to the ground without passing through the device.

Transformer Vault

A fire-rated room housing a transformer and auxiliary equipment for a large building.

Electricity

A form of energy generated by friction, induction or chemical change, having magnetic, chemical and radiant effect. The motion of free electrons through a solid conductor.

Unit Substation

A freestanding enclosure housing a disconnect switch, a step-down transformer and switchgear.

Three-Phase Electrical System

A Triple Circuit where lighting and outlet loads are connected between any phase leg and a neutral line. While machineries and other bigger loads are connected to the phase leg only.

Panel

A board on which are mounted the switches, fuses and circuit breakers for controlling and protecting a number of similar branch circuits installed in a cabinet and accessible from the front only. Also called a panelboard.

General Purpose Circuit

A branch circuit that supplies current in a number of outlets for lighting and appliances

Appliance Circuit

A branch circuit that supplies current in one or more outlets specifically intended for appliances

Individual Circuit

A branch circuit that supplies current only to a single piece of electrical equipment

Series Circuit

A circuit where components are connected in tandem. All separate loads of the circuit carry the same equal current and the total resistance, R, is the sum of the resistances around the circuit.

Parallel Circuit

A circuit where components or loads are so arranged that the current divides between them. Each outlet has a live wire connected to the current carrying wire of the circuit and also a neutral wire or grounded wire connected to the return wire of the circuit. The total current flowing through the circuit is the sum of the current flowing through each outlet.

Ground Wire

A conductor connecting electric equipment or a circuit to a ground connection. Also called a grounding conductor.

Grounding Electrode

A conductor, as a metal ground rod, ground plate or cold-water pipe, firmly embedded in the earth to establish a ground connection.

Direct Current

A current which flows at a constant time rate and in the same direction.

Alternating Current

A current which is periodically varying in time rate and in direction. It rises from zero to maximum, falls to zero, reverses its direction and again returns to zero.

Conductor

A material which allows the free flow of electrons through them.

Watt-Hour Meter

A meter for measuring and recording the quantity of electric power consumed with respect to time.

Distribution Panel

A panel for distributing power to other panels or to motors and other heavy power-consuming loads. Controls, distributes and protects a number of similar branch circuits in an electrical system.

Spark Gap

A space between two terminals or electrodes across which a discharge of electricity may pass at a prescribed voltage.

Circuit Breaker

A switch that automatically interrupts an electric circuit to prevent excess current from damaging apparatus in the circuit or from causing a fire. A circuit breaker may be reclosed and reused without replacement of any components. Also called a breaker.

Sub-Panel Board

Also called cut-outs.

Automatic Instantaneous Demand Control (Rate Control)

An automated version of the demand metering alarm system, where it automatically disconnects or reconnects loads as required.

Substation

An auxiliary power station where electrical current is converted or where voltage is stepped up or down.

Uninterruptible Power Supply

An emergency system designed to provide power automatically and instantaneously.

Forecasting Systems

Computerized systems which continuously forecast the amount of energy remaining in the demand interval, then examine the status and priority of each of the connected loads and decide on the proper course of action.

Grounded Conductor

Any conductor of an electrical system intentionally connected to a ground connection.

Lightning Rod

Any of several conducting rods installed at the top of a structure and grounded to divert lightning away from the structure. Also called air terminal.

Feeder

Any of the conductors extending from the service equipment to various distribution points in a building.

Single-Phase Electrical System

Can either be 2-wire or 3-wire and composes two hot legs and a neutral wire.

Battery Equipment

Central storage batteries are mounted in individual racks and always provided with automatic charging equipment.

15-20 Amperes

Circuit load limits for lighting, small appliances, and current devices.

Control Devices and Systems

Collective term for the following: 1. Load shedding control 2. Peak demand control 3. Peak regulation control 4. Power use control

Electrical Circuit

Complete conducting path carrying current from a source of electricity to and through some electrical device or load and back to the source

Switchgear Room

Contains the service equipment for a large building.

Individual Branch Circuit

Designed to supply a single specific item, such as a motor load or a unit air-conditioner.

Volt

Electromotive force or potential difference between two points in an electric field which will move a charge of one coulomb between these points.

Service Equipment

Equipment necessary for controlling, metering and protecting the electric power supply to a building.

Service Conductors

Extend from a main power line or transformer to the service equipment of a building.

Appliance Branch Circuit

Supplies outlets intended for feeding appliances. Fixed lighting is not supplied.

Grounding Rod or Electrode

Firmly embedded in the earth to establish a ground connection.

Rotary Converter

For changing alternating current to direct current and vice versa.

Standby Generator

For providing emergency power during a power outage.

Direct Current Generator

Furnish electrical energy for elevators, escalators, intercommunicating telephone systems, control of signal systems, and clock systems.

Ohm's Law

I (amp) = V (Volts) / R (Ohms) The current, I, that will flow in a d-c circuit is directly proportional to the voltage ,V, and inversely proportional to the resistance , R, of the circuit.

Demand Metering Alarm

In conjunction with a duty cycle controller, demand is continuously metered and an alarm is set on when a predetermined demand level is exceeded.

Service Equipment

Includes a main disconnect switch and secondary switches, fuses and circuit breakers for controlling and protecting the electric power supply to a building. It is located in a switchgear room near the entrance of the service conductors.

Riser Diagram

Is a vertical line diagram of the major electrical components of the buildings electrical system presented showing the spatial relations between components.

Utilization Equipment

Lighting, power and motor loads and wiring devices which are directly handled and utilized by users.

Sub-Feeder Circuit

Line extensions of a feeder, fed through a panel board or cut-out, or from one distributing center to another and having no other circuit connected to it between the two distributing centers.

Engine-Generator Set

Machines intended to produce electricity and composed of three components: the machine and its housing (if any), fuel storage tank and the exhaust facilities.

Service Switch

Main disconnect for the entire electrical system of a building, except for any emergency power systems.

Watt-Hour Meter

Measures and records the quantity of electric power consumed with respect to time. Supplied by the public utility, it is always placed ahead of the main disconnect switch so that it cannot be disconnected.

KWH Meters

Measures energy by introducing factor of time with power. AC electric meters are small motors, whose speed is proportional to the power being used. The number of rotations is counted on the dials which are calibrated directly in kilowatt-hours.

2-20 Amperes

Minimum amperage required by the Code to appliance branch circuits for feeding all small appliance outlets in the kitchen, pantry, dining and family room.

Two-Wire Circuit

Most elementary of all wiring systems, consists of a live wire carrying the current to the various power consuming devices in the circuit and a neutral or grounded wire which is the return wire carrying the circuit back to the source of supply.

Switchboard

One or a group of panels on which are mounted switches, overcurrent devices, metering instruments and buses.

Main Switchboard

Panel on which are mounted switches, overcurrent devices, metering instruments and busbars for controlling, distributing and protecting a number of electric circuits.

Low-Voltage

Pertaining to a circuit in which alternating current below 50 volts is supplied by a step-down transformer form the normal line voltage used in residential systems to control doorbells, intercoms, heating and cooling systems and remote lighting fixtures. Low-voltage circuits do not require a protective raceway.

Emergency System

Provides electric power and illumination essentially for life safety and protection of property during an emergency, such as, electricity for exit lighting, elevators, fire alarm systems, fire pumps and the like.

Standby System

Provides power to selected loads not directly involved with life safety, such as, water and sewage treatment plants and industrial machines for manufacturing processes.

Ampere

Represents a rate of flow of one coulomb or 6.25 x 10 18 electrons/second through a given cross section.

Oil-Filled Transformers

Require a well-ventilated, fire-rated vault with two exits and located on an exterior wall adjacent to the switchgear room.

Panel Board

Serves to control and protect the sub feeders and branch circuits.

Sub-Feeder

Serves to distribute power from the main feeders to smaller local panel boards, called sub-panel boards.

Feeder Circuit

Set of conductors which extends from the main switchboard to a distributing center (panel board) with no other circuits connected to it between the source and the distributing center.

General Purpose Branch Circuit

Shall be rated at 20 amperes wired with No. 12 AWG minimum. may be No. 14 AWG if the lighting load permits.

Branch Circuit

Shall be sufficient to supply a load of 30 watts per square meter (3 watts per square foot) in buildings excluding porches, garages and basements.

Convenience Receptacle

Shall be wired to at least two different circuits so that in case of failure in any one of the circuits, the entire area will not be deprived of power.

Branch Circuit

Small capacity conductors which deliver energy to lamps, motors and other loads within the circuit.

Alternating Current Generator

Source of bulk electrical energy utilized today, including energy for power and lighting.

General Purpose Branch Circuit

Supplies outlets for lighting and appliances, including convenience receptacles.

Line Drop

The decrease in voltage between two points on a power line, usually caused by resistance or leakage along the line.

Electric Load Control

The effective utilization of available energy by reducing peak loads and lowering demand charge.

Load Scheduling and Duty Cycle Control

The installation's electric loads are analyzed and scheduled to restrict demand by shifting large loads to off-peak hours and controlled to avoid coincident operation.

Service Switch

The main disconnect for the entire electrical system of a building except for any emergency power systems.

Service Drop

The overhead portion of service conductors extending from the nearest utility pole to a building.

Service Entrance

The point of delivery of electricity to a building by a public utility company.

Service Entrance Conductor

The portion of a service conductor extending from a service drop or service lateral to the service equipment of a building

Service Entrance Conductor

The portion of a service conductor extending from a service drop or service lateral to the service equipment of a building.

Branch Circuit

The portion of an electrical system extending from the final overcurrent device protecting a circuit to the outlets served by the circuit

Ohm

The resistance which will allow one ampere of current to flow when one volt is impressed upon it.

Service

The supplying of utilities required or demanded by the public.

Service Lateral

The underground portion of service conductors extending from a main power line or transformer to a building.

Watt-Hours

The unit of energy or the capacity for doing work.

Ideal Curve Control

This controller operates by comparing the actual rate of energy usage to the ideal rate, and controls KW demand by controlling the total energy used within a metering interval.

Edison System

Three-wire single-phase DC electrical system.

Single-Line Diagram

When electrical symbols are used in lieu of the blocks.

Main Switchboard

Where the service entrance conductors in the form of bus bars terminates and connects to the distribution panel boards by means of feeder circuits protected by circuit breakers; serves for the control, protection and metering of the main feeders.