Building Services Unit 1

Definition:

Electricity is a form of energy that can be

easily changed to other forms.

What is Electricity?

Where does Electricity come from?

Mainly 2 sources:

1) Power Stations

- Supply a lot of electricity

- Used in many electrical appliances

2) Electric Cells (batteries)

- Supply a little electricity

- Portable

- Safe

The electrical current that goes into our home comes from the electricity supply company's distribution network, usually in the form of overhead cables running on concrete poles or using cables buried one meter below the ground.

When the cables reach a residential house, they usually enter the house through the front entrance and connect to a meter panel.

Together with the meter on the panel is also a cut-out fuse and a neutral link. The meter and the fuse usually belong to the supply company.

The electric supply company would only install the meter if the owner or the tenant of the unit submits the supply application form and pay the necessary connection fees and deposit.

ELECTRICITY IN A BUILDING

All electrical cables must be insulated. Otherwise the conductor part (the copper part of the cable, or the aluminum part if it is an aluminum cable) can be exposed to touch and cause danger of electric shocks. Without insulation, a short circuit between electrical parts or components can easily occur which will damage the components and also cause fire to the house.

EARTHING

The view inside of a lighting

and power DB for an office

building.

Internal wiring of an electrical DB

A house electrical panel or Distribution Board

Basically it is a box in a house that controls the

distribution of electricity to the whole house.

Miniature circuit

Switches

A switch is used to open or close a circuit.

Main Switch used in buildings

Switches used on circuit boards

Switches

Open Circuit

Bulb does not light up

when the switch is open.

Close Circuit

Bulb will light up

when the switch is closed.

AC / DC current

• The AC Current it´s better to transmit through long distances.

• If the electric power is produced 500km away from where

it´s going to be consumed, the technique to "keep the power

through the distance" is to high the voltage of the lines, so

this gives more strength to cross the distance.

• Then, when the current arrives through the lines, the voltage

is dropped again and then distributed to the different

consumers in the appropriate values.

• This cannot be done with DC Current.

What voltages are dangerous?

• A wide range of voltages can be dangerous for different

reasons. A very low voltage (such as that produced by a single

torch battery) can produce a spark powerful enough to ignite

an explosive atmosphere. Batteries (such as those in motor

vehicles) can also overheat or explode if they are shorted.

• If a person comes into contact with a voltage above about 50

volts, they can receive a range of injuries, including those

directly resulting from electrical shock (problems with

breathing, heart function etc); and indirect effects resulting

from loss of control (such as falling from height or coming into

contact with moving machinery). The chance of being injured

by an electric shock increases where it is damp or where there

is a lot of metalwork

SAFETY DEVICES FUSE :-

·

Electric Fuse is a Safety device. It works on the principle of Joule’s law of heating. It consists of a fuse wire made of an alloy of tin and lead, which melts and breaks the circuit whenever current in the circuit exceeds safe limits due to overloading or short circuit. The thickness and length of the fuse wire depends on the maximum current allowed through the circuit It is connected in series in the beginning of the electric circuits.

An electric fuse is a device which is used to limit the current in an electric circuit. The fuse safeguards the circuit and the electrical appliances from being damaged.

Electric fuses are always connected in series in an electric circuit. Why? When the circuit current exceeds a specified value due to voltage fluctuations or short-circuiting, the fuse wire gets heated and melts. Thus it breaks the connection and no current flows. This prevents damage to the appliance.

Domestic circuits may be damaged due to the following conditions:- Overloading , Short-circuiting , Earthing of electrical appliance Overloading : If too many electrical appliances of high power rating (like electric iron, water heater etc) are switched on at the same time, they draw an extremely large current from the circuit. This condition is called overloading and it can cause overheating of the wiring and lead to a fire. It can also happen due to an accidental hike in the supply voltage. Do t o erload the

socket

Short-circuiting : In an electric circuit a short - circuit occurs whenever the live wire and the neutral wire come in direct contact. The wires touch each other due to faulty connection or sometimes due to the wearing off the insulation. This condition leads to overheating of the wires and causes a fire.

Our nerves also have protective coverings called myelin sheath. When neuropathy happens, this nerve insulation is slowly stripped which exposes our nerves that are very sensitive. This is where the numbness and pain of a neuropathy patient come from. Although there are many kinds of neuropathy, all of them have to do with degeneration of the nerves.

Neuropathy and Short Circuit of Electrical Wires

Neuropathy is the damage of nerves. Neuro means nerves while pathy means a disease or disorder

SINGLE PHASE AND 3 PHASE

• With single-phase current, the voltage rises to a peak in one direction of flow, subsides to zero, reverses, rises to a peak in the opposite direction,

subsides to zero, and so on.

• The cycle repeats itself 60 times every second, which is where we get the term 60-cycle or 60-hertz

alternating current.

• Single-phase current requires the use of one

transformer.

SINGLE PHASE AND 3 PHASE

• In the case of three-phase current, the same pattern exists,

except that there are three separate and distinct single-phase

currents, which are combined so they can be transmitted over

three or four wires.

• The three currents rise to a peak in one direction, subside,

reverse, and so on; however they do not peak at the same

time.

• Each phase reaches its peak 120 degrees apart from the

others.

• Three-phase current requires two or three transformers.

Earthing of electrical appliance To avoid the risk of electric shocks, the metal of an electrical appliance is 'earthed'. Earthed means to connect the metal case of the appliance to the earth (at zero potential) by means of a metal wire (copper) called the earth wire. One end of the earth wire is buried deep in the earth; the other end of the wire is connected to the three pin socket. When the electrical appliance is switched on, the metal casing of the appliance will remain at zero potential as it is in contact with the earth wire in the three pin socket. It thus prevents us from an electric shock even if we touch it accidentally

Usually an electric appliance such as a heater, an iron, etc. are fitted with all the 3 wires namely live, neutral and earth. The earth wire is connected to the metallic body of the appliance. This is done to avoid accidental shock. Suppose due to some defect, the insulation of the live wire inside an electric iron is burnt then the live wire may touch the metallic body of the iron.

When the iron is in use, the metallic body will also be increased to 110V. If we accidentally come in contact with such a metallic body we are sure to get an electric shock. If the earth wire is properly connected to the metallic body it protects us from an electric shock

EARTHING THE BUILDING

Dig a hole. Put some nassaddar

Put the copper plate and wire. Connect the

wire to the MSB

Add some charcoal

Water it well. And you are ready. Fill up

the whole

Methods of Earthing:

• The important methods of earthing are the plate earthing and

the pipe earthing. The earth resistance for copper wire is 1

ohm and that of G I wire less than 3 ohms. The earth

resistance should be kept as low as possible so that the

neutral of any electrical system, which is earthed, is

maintained almost at the earth potential. The typical value of

the earth resistance at powerhouse is 0. 5 ohm and that at

substation is 1 ohm.

• Plate earthing

• Pipe earthing

• Plate Earthing

• In this method a copper plate

of 60cm x 60cm x 3.18cm or a

GI plate of the size 60cm x

60cm x 6.35cm is used for

earthing. The plate is placed

vertically down inside the

ground at a depth of 3m and

is embedded in alternate

layers of coal and salt for a

thickness of 15 cm. In

addition, water is poured for

keeping the earth electrode

resistance value well below a

maximum of 5 ohms. The

earth wire is securely bolted

to the earth plate. A cement

masonry chamber is built with

a cast iron cover for easy

regular maintenance.

Pipe Earthing

Earth electrode made of a GI

(galvanized) iron pipe of 38mm

in diameter and length of 2m

(depending on the current) with

12mm holes on the surface is

placed upright at a depth of

4.75m in a permanently wet

ground. To keep the value of the

earth resistance at the desired

level, the area (15 cms)

surrounding the GI pipe is filled

with a mixture of salt and coal..

The efficiency of the earthing

system is improved by pouring

water through the funnel

periodically. The GI earth wires

of sufficient cross- sectional

area are run through a 12.7mm

diameter pipe (at 60cms below)

from the 19mm diameter pipe

and secured tightly at the top as

shown in the following figure.

TRANSFORMERS

• Transformers are used at power stations to increase the

voltage and decrease the current of the electricity being

supplied across the National Grid.

• This is to reduce power loss, as high currents cause higher

power losses.

• At local stations, transformers are used again to reduce the

voltage to a safe level.

• Transformers only work with ac current, so AC current allows

electricity to be distributed over long distances more

efficiently.

Transformer

An A.C. device used to change high voltage low

current A.C. into low voltage high current A.C. and

vice-versa without changing the frequency

In brief,

1. Transfers electric power from one circuit to another

2. It does so without a change of frequency

3. It accomplishes this by electromagnetic induction

4. Where the two electric circuits are in mutual

inductive influence of each other.

Principle of operation

It is based on

principle of MUTUAL

INDUCTION.

According to which

an e.m.f. is induced

in a coil when

current in the

neighbouring coil

changes.

Cut view of transformer

Working of a transformer 1. When current in the

primary coil changes being

alternating in nature, a

changing magnetic field is

produced

2. This changing magnetic

field gets associated with

the secondary through the

soft iron core

3. Hence magnetic flux

linked with the secondary

coil changes.

4. Which induces e.m.f. in the

secondary.

Electrical Switchgear

Definition of Switchgear • A switchgear is used for

switching controlling and protecting the electrical circuits and equipment's.

• A switchgear or electrical switchgear is a generic term which includes all the switching devices associated with mainly power system protection.

• It also includes all devices associated with control, metering and regulating of electrical power system.

• Assembly of such devices in a logical manner forms a switchgear. This is very basic definition of switchgear.

Electrical Switchgear Elements of a substation A:Primary power lines' side B:Secondary power lines' side 1.Primary power lines 2.Ground wire 3.Overhead lines 4.Transformer for measurement of electric voltage 5.Disconnect switch 6.Circuit breaker 7.Current transformer 8.Lightning arrester 9.Main transformer 10.Control building 11.Security fence 12.Secondary power lines

SUBSTATION

30

. What is a substation?

An electrical

substation takes

electricity from a

very high voltage

and lowers it to the

voltage we use in

our homes &

businesses

.

Electricity is made

at a very high,

powerful voltage. A

substation safely

changes the

electricity from very

high voltage to

lower voltage we

can use.

What does a substation do?

. How does a substation work?

• Tra sfor ers step do the electricity from the high voltage

needed to

economically transmit

the electricity.

• There are also complex

circuit breakers,

switches, relays, and

capacitors. • Substations have HUGE

power poles to bring in

the high voltage

electricity. These

would be more than

200 feet tall.

33

. How does a substation work?

• Substations operate

without any workers on-

site.

• Substations are monitored

by remote control.

• Because these are very

dangerous activities and

no workers are present,

they have automated

emergency gear.

• There are detectors for

fire and line breaks.

• There is automatic fire

suppression.

34

A quick picture of how substation works

35

. Can a substation harm me?

The short answer is YES!

That s hy there are fe ces around them. They can

electrocute people.

Poisonous and corrosive

chemicals are inside the

substation.

All substations emit invisible

electrical waves. Some

scientists believe these waves

harm us.

. So why do we have substations?

We need them to cheaply

transfer electricity.

Substations are a part of what

we call essential

infrastructure.

Types of wiring according to the Uses.

1. Domestic Wiring.

2. Commercial Wiring.

3. Industrial Wiring.

Introduction of wiring.

Use of electricity

1. In industries : Heating, welding, electroplating.

2. Domestic : Light, fan, heater, washing machine.

3. Commercial : Cinema, Lift, water pump, lighting,

advertising display.

POWER CIRCUITS

When deciding on the number of circuits for a house, a useful rule is; one power circuit for every 100m2 of floor

area. In larger houses this means that two circuits can be

used for power socket outlets, in a two-storey house this would be one circuit for upstairs and one for downstairs.

In some larger houses a separate power circuit is also installed for the garage / utility area

• Ring circuits are used as a safe and economic method of distribution of electricity to socket outlets.

• Many consumer unit manufacturers produce 8 way and 12 way units.

The electrical distribution system in high rise flats and office

buildings uses a busbar system.

A busbar is a solid copper bar that carries the electrical

current.

The busbars run vertically inside trunking and are supported

by insulated bars across the trunking chamber.

The electrical supply to each floor is connected to the rising

main by means of tap-off units.

To balance electrical distribution across the phases,

connections at each floor should be spread between the

phase bars.

To prevent the spread of fire and smoke, fire barriers are

incorporated with the busbar chamber at each compartment

floor level.

The chamber must also be fire stopped to the full depth of

the floor.

Distribution in High-rise Buildings

Factors Affecting choice of wiring

Safety

Duration

Appearance

Accessibility

Maintenance

Cost

Surface Switch Flush Switch

Pull /Ceiling Switch

Push Button Switch

Iron Clad Water tight Switch

Rotary Snap Switch

Types of Wiring 1. Cleat Wiring

2. Batten Wiring

(i) PVC Batten wiring.

(ii)TRS/CTS Wiring.

(iii)Lead Shed Wiring.

3. Casing Capping wiring

(a) Wood Casing capping Wiring

(b) PVC Casing Capping Wiring.

4. Conduit Wiring

(a) Surface conduit wiring

Metal Conduit Wiring

PVC conduit wiring

(b) Consealed Conduit Wiring

Metal Conduit Wiring.

PVC Conduit wiring

• Introduction

The types of wiring to be adopted is dependent on

various factors, viz, durability, safety, appearance,

cost, consumer’s budget etc. • Cleat wiring

This System uses insulated Cables sub protected

in porcelain cleats.

CLEAT WIRING

• Cleat wiring is recommended only for temporary installations.

• The cleats are made in pairs having bottom and top halves.

• The bottom half is grooved to receive the wire and the top half is for cable grip.

• Initially the bottom and top cleats are fixed on the wall loosely according to the layout.

• Then the cable is drawn, tensioned and the cleats are tightened by the screw.

• Cleats are of three types, having one, two or three grooves, so as to receive one, two or three wires.

Cleat wiring is one of the cheapest wiring considering the initial cost and labor, and is most suitable for temporary wiring.

This wiring can be quickly installed, easily inspected and altered.

When not required, this wiring could be dismantled without damage to the cables, cleats and accessories

Fixing of cleats In ordinary cases, cleats shall be attached to wooden

plugs fixed to the walls

B.I.S. RECOMMENDATIONS FOR CLEAT WIRING

General • This system shall not be employed for wiring on damp walls

or ceilings unless precautions are adopted for effectively preventing dampness and thus the deterioration of the insulation of the conductors.

Accessibility • Cleat wiring shall be run, as far as practicable, so as to be

visible. • In positions where they would be liable to mechanical injury

and where they are less than 1.5 m above the floor, they shall be adequately protected.

Class of cables

Vulcanized rubber insulted cables, PVC and polythene insulted

cables, braided or unbraided insulted cables could be used

without any further protection.

Cleats

All cleats shall consist of two parts, a base piece and a cap.

Cleats shall be fixed at distances not more than 60 cm apart

and at regular intervals.

WOOD CASING WIRING SYSTEM

• This system of wiring is suitable for low voltage installation

where vulcanized rubber

• insulated cables, plastic insulated cables or other suitable

insulated cables shall be used in the wiring

• work and carried within wood casing enclosure. Wood casing

wiring system shall not be used in damp

• places or in ill-ventilated places, unless suitable precautions

are taken.

• All casing shall be of seasoned teak wood or any other

• approved hardwood, free from knots, shakes, saps, or other

defects, all sides planed with smooth

• finish, and ail sides well varnished ( both inside and outside )

with pure shellac varnish. The casing

• shall have grooved body with beaded or plain moulded cover

as desired.

• All casing shall be fixed by means of suitable

• Flat-head wood screws to plugs at an

interval not exceeding 90 cm for sizes up to

64 mm casing and not exceeding 60 cm for

sizes above 64 mm casing.

• All casing shall be spaced from the wall or

ceiling by means of porcelain disc insulators

not less than 6.5 mm thick.

• Casing shall be used only on dry walls and

ceilings avoiding outside walls, as far as

possible.

TOUGH RUBBER-SHEATHED OR PVC

SHEATHED WIRING SYSTEM • Wiring with tough rubber sheathed cables is suitable for low voltage

installations,

• and shall not be used in places exposed to sun and rain nor in damp

places.

• Wiring with PVC-sheathed cables is suitable for medium voltage

installation and may be installed directly under exposed conditions

of sun and rain or damp places.

• This system of wiring is suitable in situations where acids and alkalis

are likely to be present.

• Where attack from white ants (termite) is prevalent, anti-termite

treatment shall be-given.

• Sheathed cables on brick walls, stone or plaster walls and ceilings,

steel joists, or any structural steel work shall be run on well-

seasoned and varnished, straight teak wood battens finished.

• Prior to erection, these shall be painted with one coat of varnish or

suitable paint matching with the surroundings.

CONDUIT WIRING • An electrical conduit is an electrical

tubing used for protection and routing

of electrical wiring. Electrical conduit

may be made of metal, plastic, fiber,

or fired clay. Flexible conduit is

available for special purposes

The term "conduit" is commonly used by electricians to describe any

system that contains electrical conductors

Electrical conduit provides very good protection to enclosed conductors

from impact, moisture, and chemical vapors.

Varying numbers, sizes, and types of conductors can be pulled into a

conduit, which simplifies design and construction compared to multiple

runs of cables or the expense of customized composite cable. Wiring systems in buildings may be subject to frequent alterations.

Frequent wiring changes are made simpler and safer through the use of

electrical conduit, as existing conductors can be withdrawn and new

conductors installed, with little disruption along the path of the conduit.

Types of Conduits : Metal,Non-Metal,Flexible and Underground.

Types of Lighting

• Incandescents/Halogens.

• Fluorescents.

• High Intensity Discharge (HID).

• Inductive.

• Light Emitting Diode.

Incandescent Lamps • One of the oldest electric lighting

technologies.

• Light is produced by passing a current through a tungsten filament.

• Least efficient – (4 to 24 lumens/watt).

• Lamp life ~ 1,000 hours. • Inexpensive • Easily dimmed – no ballast

needed • Immediate off and on • No temperature concerns – can

be used outdoors • 100, 75, 60 and 40 watt lamps

will be going away per 2007 law beginning 2012

Fluorescent Lamps

• Most common commercial lighting technology.

• High Efficicacy: up to 100 lumens/watt.

• Improvements made in the last 15 years.

• T12: 1.5 inch in diameter.

• T8: 1 inch in diameter.

• ~30% more efficient than T12.

• T5: 5/8 inch in diameter.

• ~40% more efficient than T12.

Observations About Fluorescents

• They often take a few moments to turn on

• They come in several variations of white

• They are often whiter than incandescent bulbs

• They last longer than incandescent bulbs

• They sometimes hum loudly

• They flicker before they fail completely

HOW IS LIGHT PRODUCED

The fluorescent lamp produces light by the passage of an electric

current flowing through a vapor of mercury.

1.Electron emitted from electrode collides with mercury atom.

2.Impact produces ultraviolet rays

3.Phosphor converts ultraviolet to visible light.

This process is k o as fluoresce ce, he ce the a e fluoresce t lamp.

THE ELEMENTS OF A

FLUORESCENT LAMP

A fluorescent lamp contains the following basic elements:

• Bulb Electrodes Gases

• Base Phosphors Mercury

THE ELEMENTS OF A FLUORESCENT LAMP

THE BULB

•Most fluorescent lamps

are made in straight

tubular bulbs in various

diameters.

•Circline lamps are in the

form of a circle.

•U-Bent lamps are

essentially straight lamps

bent to form a U shape.

THE ELEMENTS OF A FLUORESCENT LAMP

THE BASE

The base provides the means of holding the lamp firmly in the

lamp holders or sockets and providing the electrical connections

for the lamp/ballast circuit. The basic types are:

•Bipin – Used on preheat and rapid start lamps.

THE ELEMENTS OF A FLUORESCENT LAMP

•Single Pin – Used on slimline lamps.

•Recessed Double Contact – Used on HO and VHO lamps.

THE ELEMENTS OF A FLUORESCENT LAMP

PHYSICAL DIMENSIONS

The significant dimensions of fluorescent lamps are:

•Bulb diameter

•Nominal overall length

Bulb Diameter – Expressed in eighths of an inch.

Diameter = 12 8 = 1 ½ inches

THE ELEMENTS OF A FLUORESCENT LAMP

Nominal Length – Unique to fluorescent lamps.

• Straight Lamps – Measured from the back of one socket or lampholder to the

back of the other socket. Pin to Pin.

THE ELEMENTS OF A FLUORESCENT LAMP

•U-Bent Lamps – Measured from the back of the socket to top of the lamp.

•Circline Lamps – Measured from the outside diameter of the lamp.

THE ELEMENTS OF A FLUORESCENT LAMP

THE ELECTRODES

•Coiled tungsten wires coated with an emission

material

•When heated, emit electrons

•Electrons bombard mercury atoms producing

ultraviolet rays.

THE PHOSHPORS

Phosphors are the coated powders on the inside of the bulb that convert the

ultraviolet rays to visible light. There are two basic types:

• Halophosphates

• Trichromatics or Triband Phosphors

Compact Fluorescent

•Excellent color available – comparable to incandescent

•Many choices (sizes, shapes, wattages, output, etc.)

•Wide Range of CRI and Color Temperatures

•Energy Efficient (3.5 to 4 times incandescent)

•Long Life (generally 10,000 hours –

lasts 12 times longer than standard 750 hour incandescent lamps)

•Less expensive dimming now available (0-10v dimming to 5%)

•Available for outdoor use with amalgam technology