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FENTONS LTD.

Introduction

ELECTRICAL DIVISION

Since 1921 the division undertakes contracts in the entire field of electricalpower engineering.

SUPPLY / INSTALL / MAINTENANCE

• Electrical installation of industrial, commercial & domestic buildings.

•Lighting Control Systems.

•Design, implementation and maintenance of Mini-Hydro projects.

• HT and LT electrical projects.

•Design and build solutions on electrical installation.

•Industrial generators.

•Consultancy on all aspects of electrical installations and applications.

•Electronic lighting control systems.

•Lightning / surge protection system. Repairs to electrical appliances.

•Capacitor banks.

•Rewinding & repairs of industrial motors.

•Electric fences.

The Report on Specialized Industrial Training 1



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About Fentons


2 . F e n t o n s

( P v t ) L t

1 . E n e r g y

S u b s i d i a r

P a g i n g

3 . T e l e c

D i v i s i o

2 . F i r e &

D i v i s i o

1 . E l e c t r i c

D i v i s i o

1 . T h e P a

C o m p a

J o i n t V e

F e n t o n



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2.1 TOOLS

Combination pliers

This pliers used for cutting wires, gripping operation by hand, twisting wires & a number

of other operation required in electrical works.

Fig 2.1 Combination pliers

Long snipe nose pliers

This tool is useful for forming the eyes of the wires which are to be used where they are

held fast under the screw.

Fig 2.2 Long snipe nose pliers

Roll pen hammer

This tool is required for driving nails in to wooden batten or for cutting wall plaster &

bricks when it is necessary to take the wiring from one room to another.

Screw drivers

The screw drivers are available in different blade sizes.

Fig 2.3 Screw drivers




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2.2 CABLES

2.2.1 Classification of cables.

The wide range of cables use in electrical work .Cables for under ground service may be

classified in two ways according to;

(1) The type of insulating material used in there manufacture

(2) The voltage of which they are manufactured.

How ever, the latter method of classification is generally preferred, according to which

cables can be divided in to the following groups;

1) Low - tension (L.T) cables - up to 1000V

2) High - tension (H.T) cables - up to 11,000V

3) Super - tension (S.T) cables - from 22KV to 33KV4) Extra high - tension (E.H.T) - from 33 to 66 KV

5) Extra super voltage cables - beyond 132KV

METRIC MM2 AMP IMP

1/1.13

1/1.38

7/0.50

7/0.677/0.85

7/1.04

7/1.35

7/1.70

7/2.14

19/1.35

19/1.53

19/1.78

19/2.1437/1.78

37/2.03

37/2.25

37/2.52

61/2.25

61/2.52

61/2.85

61/3.20

1

1.5

1.5

2.54

6

10

16

25

25

35

50

7095

120

150

185

240

300

400

500

12

14

14

1729

37

51

66

87

87

106

125

160195

220

260

295

360

410

457

520

1/044

3/029

3/036

7/0297/036

7/044

7/052

7/064

19/044

19/052

19/064

19/073

19/08337/072

37/083

37/093

37/103

61/093

61/103

-

91/103




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2.2.2 Cable Paths used for Workstation

Following cable paths is used in work station

1. Conduit – Steel Conduit

PVC Conduit

Flexible Conduit

2. Trunking

3. Tray

4. Trench

5. Duct

1. Conduit

Steel conduit

The most common form of conduit used today is screwed steel with a welded seam or

solid drawn (used in hazardous areas where there is a high risk of fire and explosion). A

light gauge conduit is also available with its use restricted to providing protection for

flush PVC cable installations. Two finishes for conduit are: black enamel (dry situations)and galvanized (for out doors and situations where dampness is present).

The main advantages of steel conduit include its ability to give conductors good

protection against mechanical damage; it allows easy rewiring; fire risks are minimized;

and the conduit can be used as a circuit protective conductor (CPC), through it is

common practice to run a separate CPC in the conduit.

PVC Conduit:

Where appropriate, PVC conduit is a popular, and inexpensive alternative to steel

conduit. It is available in both light and heavy grades and does not need to be threaded

unless so specified by the job. The conduit is available as rigid, semi-rigid, flexible round

(for surface and embedded work) and in an oval shape (for switch drops). Grades of PVC

conduit include super high impact, standard impact, and high temperature (up to 850C)

Because the expansion rate for PVC conduit is around five times that of its steelequivalent, expansion couplers are needed in long runs (at every 8m). Where the conduit

is to be used in damp situations, a special temperatures etc.




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Flexible conduit:

Flexible metallic or PVC conduit is often used to make a suitable connection between

rigid conduit systems and, for example, a motor which may be required to be moved for

belt tensioning, a separate circuit protective conductor is needed, run either inside the

conduit or externally.

2. Trunking

Trunking is a fabricated casing for conductors and cables, generally rectangular in shape

with a removable lid which allows the conductors to be laid in rather than be drawn in as

is the case with conduit it is used where a large number of conductors are to be carried, or follow the same route. Both steel and PVC Trunking are available, with a wide range of

such accessories as bends, T’s ,flanged adaptors, risers and reducers.

The variety of trunking includes plain section, compart mented , skirting, bench, floor

trunking, and busbar trunking. Trunking is not necessarily a complete wiring system in it

self and is thus associated with conduit and MI cables to allow connection to wiring

accessories and their mounting boxes.

Finishes on steel trunking include gray enamel, galvanized and silver enamel on zinc-coated mild steel.

Compartmented trunking: Is allows wiring at different voltages to be segregated but

carried within the same unit run. This prevents services at one voltage accidentally

becoming live to a higher voltage in the event of a fault.

Skirting trunking: Is used in offices where the services (socket outlets, switches, etc.)

can be sited on the perimeters of rooms.

Bench trunking: Is commonly found in school and laboratories where access to a large

number of socket outlets is required. As the name implies, the trunking units are mounted

on benches.

Floor trunking: Is an alternative to skirting trunking. There are three types: under floor

(where the trunking is set in a concrete floor with flush with the floor surface), and flush

duct trunking (where the lid is mounted flush with the screen) and a finish (such as

parquet wood or tiles) are placed directly on to it.




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3. Cable tray

Cable tray is used to carry sub main cables and multi runs of MI cables. It is widely used

in industrial installations. Where pipe work and other structural features may be done

normal cable runs the tray is basically a flat metal sheet with perforations and either a

simple turned flange of finishes are provided to meet installation conditions: galvanized,

primed with red oxide or yellow chromate, plastic-coated and coated with epoxy resins

(resistant to acids and virtually non-flammable). For large amount of heavy cables runs,

cable ladders are used.

4. Cable Trench

Cable trenches are building by Concrete. All cables run in trenches must be sheathed or

armoured. Main hall is building in to the trenches for entrance the cable trench inside.

5. Cable Duct

Ducts are simply passages provided by builders in the structure of a building to allow

cables to run from points of supply to their terminations. Ducts can be rectangular

channels covered by steel lids or bricks. All cables run in ducts must be sheathed or

armored and cable ladders are used to carry cables through the ducts. Cable ladders are

fixed to the duct wall using thread bars or anchor bolts.

2.2.3 Cable joints & Termination

Joint methods

The methods used to join conductors may be reduced to two definite groups. The first

group involves the use of heat to fuse together the surfaces of the joint (e.g. clamping,

bolting, riveting) the following are brief description of the types of jointing method in

each group.

1. Soldering

2. Welding

3. Clamping

4. Bolting

5. Riveting

6. Crimping

7. Mechanical connectors




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1. Soldering

This joint involves the use of molten metal introduced to the two surfaces to be jointed so

that they are linked by a thin film of the metal which has penetrated in to the surfaces.

The metal used for joining copper surfaces is solder, which is an alloy of tin and led. It

melts at a comparatively low temperature. The grade of solder most suitable for electrical

joints istinman’s solder (60% tin, 40% led; melting point is about 200 C). The

disadvantage of soldering is that it makes the joint a non-separable contact. Soldered

joints in bus bars must be reinforced by bolts or clamps.

2. Welding

This process is some times used for large-section conductors such as bus bars. Welding is

the joining of two metal surfaces by melting adjacent portions so that there is a definite

fusion between them to an appreciable depth. The heat is supplied by a gas torch or an

electric arc. Again the welding joint is a non-separable contact.

3. Clamping

A clamped joint is easy to make, no particular preparation being required, through the

extra mass of metal round. The joints of termination make a larger bulk. How ever the

joint or termination is cooler in operation. This method provides a separable contact.Surfaces must be clean and in definite mechanical coated. Precautions must be taken to

ensure that the bolt and nuts of the clamp are locked tight.

4. Bolting

This is method involves drilling holes in the material and has the obvious disadvantage of

reducing effectiveness of the material. Contact pressure also tends to be less uniformly

distributed in a bolted joint that in one held together by clamps. Spring washers are

needed to allow for expansion and contraction as the material temperature varies with thecurrent carried.

5. Riveting

If well made, riveted joints make a good connection. There is the disadvantage, however

that they cannot easily be undone or tightened in-service.




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6. Crimping

This is a mechanical method. For conductor joints a closely fitting sleeve is placed over

the conductor and crimped by a hydraulically or pneumatically operated crimping tool.

This method is very commonly used now days and provides connection which is

mechanically strong and virtually negligible in its electrical resistance.

7. Mechanical connectors

These consist of one-way or multi-way brass terminals contained in blocks made from

porcelain, bake-lite, nylon, polythene or PVC. Small screws are use to make the

connection. The operating temperature of the block material is important. Porcelain can

be used for high operating conditions, while PVC and polythene tend to become distorted

as the melting – point of 160 C approached in fact, polythene is not recommended for use

as connector- blocks in fixed wiring systems, accessories, luminaries and appliances.

Nylon has a good resistance to deformation at high temperatures.

Termination method

These generally accept a solid- core small diameter connection to accessories and current

using apparatus.

1. Punched and notched tabs

2. Screw head

3. Lug terminals

4. Line taps

1. Punched and notched tabs

These generally accept a solid- core small diameter conductor. The connection issoldered.

2. Screw head connection

The end of the conductor is formed in to an eye using round - hosed pliers. The eye

should be slightly larger than the shank of the screw, but smaller than the out side

diameter of the screw head, nut or washers. The eye should be so placed that the rotation

of the screw head or nut tends to close the joint in the eye. If the eye is put the opposite

way round, the rotation of the screw head or nut will tend to untwist the eye to make a

bud, inefficient contact. Sometimes saddle washers are used to titian the shape of the eye.




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3. Lug terminals

Connection between conductor end and the terminal’s socket is made by the crimping.

Crimping – select the correct terminal end. Strip the insulation from the cable end, insert

the wire in to the open socket end of terminal and crimp using a crimping tool.

4. Line taps

These are used for making non- tensioned service or T connection to over head lines.

They are available in a range of sizes suitable for copper conductors. A simple shroud is

provided to insulate the line tap when used on covered service cable. There are the

designs for use with aluminum conductors and for conductors. In these instances, the

shroud is filled with weather proof sealing compound, giving protection against climatic

attraction corrosion.

2.3 Voltage Drop for Copper Conductors

To calculate the voltage drop in volts the tabulated value of voltage drop (mv/A/m) has to

be multiplied by the length of run in meters(L), the design current of the circuit (1b), and

divided by 1000 (to current to volts)

The requirement of BS7671 are deemed to be satisfied for a 230V supply, if the voltage

drop between the origin of the installation and a socket outlet or fixed current using

equipment does not exceed 9.2V at full load


Voltage drop = (mv/Am ) x 1b x L

1000



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Cable Rating

Conductor

Cross- sectional

area

Two- core

Cables, dc

Two-core

cable, Single-

phase a.c.

Three-or four-

core cable,

three phase

Mm

1

1.5

2.5

4

610

16

25

35

50

70

95

MV/A/m

44

29

18

11

7.34.4

2.8

1.75

1.25

0.93

0.63

0.46

MV/A/m

44

29

18

11

7.34.4

2.8

1.75

1.25

0.93

0.63

0.47

MV/A/m

38

25

15

9.5

6.43.8

2.4

1.50

1.10

0.80

0.55

0.41




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3.1 ELECTRICITY SUPPLY

Electricity that is supplied to homes under specific conditions of current and voltage.

Voltage, measured in volts (V), causes electric current, measured in amperes (A), to flow

in a conducting material such as copper wire. For practical and commercial reasons a“harmonized” 230-V system is used in homes in member countries of the European

Union. In the United States, domestic voltage is 120 V. Various sizes of cable are used,

depending on the circuit requirements. Typically these are: 6 A for lighting; 16 A for

water heaters; 32 A for sockets (the “ring main”); 40 A for ovens; 63 A for showers.

Electric current flows when a circuit is continuous and unbroken—for example, when a

switch is closed to the “on” position, enabling an electrical appliance to be operated.

Because conductors carry electric current, they must be insulated in order to prevent

potentially fatal contact with them. The usual insulating material is PVC(polyvinylchloride), a plastic that is flexible and mechanically strong, and can be made

thick enough to prevent a short-circuit between the conductor and any adjacent metal

parts.

For identification purposes, insulation is colour-coded. In the permanent “hidden” house

wiring, “live” cables are coloured red and are used for the supply to the appliance.

Neutral cables are coloured black and are used to complete the circuit from the appliance

back to the supply. A third cable, identified by green and yellow stripes, is used to

connect the exposed metallic parts of the appliance to earth, so that if a fault develops in

the appliance, any small fault current will flow to earth, and the exposed parts will remain

at earth potential. If there is a more serious fault, the current flowing to earth will operate

a protective device. The three cables are grouped together and further insulated by a grey

PVC outer covering. Flexible cables running from an appliance to its plug are also

colour-coded. The live cable is brown, the neutral one is blue, and the earth is again green

and yellow.

Electric current can cause fires in property, and electric shock to human beings and

animals. Fires are caused by overloading circuits attempting to take more current from

the circuit than it is designed to support. Electric shock is experienced when current passes through a living body. The result is, at best, an unpleasant experience; or burns

(which can be both external and internal), or death.

While a current of a few amperes is sufficient to cause a fire, voltages in excess of 50 V

and current in excess of 50 mA (1 mA, or milliampere, is one-thousandth of an ampere)

can prove fatal to human beings. (A 25-V shock for domestic pets can be fatal.)

Consequently, the electrical installations in homes require some form of protection to

safeguard property and lives. This is the function of the consumer unit, which is used to

divide the incoming electrical current between circuits, each carrying an appropriatecurrent, and to provide protection in each individual circuit against the hazards of shock




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and fire. Protection devices are designed to sense the development of a dangerous

situation and operate to cut off the electrical supply to that circuit before the danger

reaches an unacceptable level.

Such protective devices include miniature circuit-breakers (MCBs), which prevent

circuits from being overloaded; and residual-current devices (RCDs), which protectagainst earth faults, which can cause an electric shock. An earth fault is a condition in

which current flows to earth through a conducting pathway, which could be a human

body.

Consumer units with these protective devices have superseded outdated fuse boards,

although many older properties still have fuse boards

Some appliances do not include an earth wire. This is because the appliances are double-

insulated to prevent accidental contact with the live parts inside. It is a legal requirement

in the United Kingdom for appliances to be supplied with a 13 A plug connected. These plugs have rectangular pins and are fitted with a fuse in order to protect the appliance

from damage. It is essential that the correct rating of fuse is used.

The power used by an appliance (the rate at which it consumes energy) is measured in

watts (W). The amount of power used by a particular appliance must be shown on it.

Appliances rated up to 720 W must be protected by a 3-A fuse; between 720 W and

1,200 W by a 5-A fuse; and from 1,200 W to 3,000 W by a 13-A fuse.

Fuse

Safety device used to protect an electrical circuit from the effect of excessive current. Its

essential component is usually a strip of metal that will melt at a given temperature. A

fuse is so designed that the strip of metal can easily be placed in the electric circuit. If the

current in the circuit exceeds a predetermined value, the fusible metal will melt and thus

break, or open, the circuit. Devices used to detonate explosives are also called fuses.

A cylindrical fuse consists of a ribbon of fusible metal enclosed in a ceramic or fiber

cylinder. Metal end caps fastened over the cylinder make contact with the metal ribbon.

This type of fuse is placed in an electric circuit so that the current must flow through the

metal strip to complete the circuit. If excess current surges through the circuit, the metallink will heat to its melting point and break. This action will open the circuit, stop the

current flow, and thus protect the circuit.

Recent fuse developments include types that will permit a momentary overload without

breaking the circuit. These are necessary for circuits that are used to power air

conditioners, because initial surges of power can be expected with such appliances.

Another recently developed type of fuse contains several links that can be selected by the

flip of a switch. If the fuse is blown, another link can be switched in without replacing the

fuse.In high-voltage circuits, subject to frequent interruptions, and increasingly in residential

wiring, protection is provided by circuit-breakers instead of fuses.




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Circuit-Breaker

Switch designed to control an electrical power system by switching power on or off,

under conditions of either normal or excessive load, in order to protect the electrical

system in which it is connected. It is easier to break an alternating current (AC) than a

direct current as an AC current passes through zero twice in each cycle. The circuit- breaker may be controlled manually or automatically.

Operating conditions are unusually demanding, as a circuit-breaker may on the one hand

be called upon to open under conditions of a short circuit on the load, requiring it to break

a current that is many times the normal load current, and on the other may be required to

close on to a short-circuited system in order to confirm that a fault exists. The circuit-

breaker must therefore be reliable under static conditions, yet must operate virtually

instantaneously when called upon to do so after a long quiescent period.

When switch contacts open an arc is formed in the medium between the contacts. Thismedium is often air, but may be oil, a high-pressure gas, or a vacuum. To prevent damage

because of arcing, an air breaker may have a main set of flat contacts held together under

pressure when the switch is closed; a secondary set where the arc forms, because they are

arranged to open after the main contacts; and an arc chute, consisting of insulated parallel

metal plates, to spread and extinguish the arc.

A mechanical system of levers serves as a latch to keep the switch closed under

mechanical pressure, and a sensitive trigger, operated mechanically or electrically, is used

to release it. Electrical operation may be controlled by an electromagnet, using either the

load current itself, or some other electrical signal derived from the network, to trip the

trigger. In this way the switch can act as an overload trip.

Alternatively, the circuit-breaker can be arranged to use some other electrical quantity,

such as an imbalance in current between the load connections, which might represent

leakage to earth. In this case the circuit-breaker becomes a residual current device (RCD),

which can provide protection against serious electric shock. Miniature circuit-breakers

and RCDs have largely replaced fuses and conventional isolating switches in domestic

consumer units because they are much more accurate and reliable.

Switch

Part of an electronic or electric circuit that controls the flow of electric current. In its

simplest form, a switch consists of two metal contacts that are held together so that

current flows through them from, for example, a battery to a bulb (for example, in a

torch). In this case, as current flows through the bulb and back to the battery, the bulb is

illuminated. When the metal contacts are not held together there is a gap in the circuit and

so current cannot flow.

The mechanical contacts may be held together in different ways, depending on the

purpose of the switch and the way in which it has been designed. For example, when a




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door-bell button is pushed, contacts are pressed together and current flows, working a

bell or buzzer. When the button is released, a spring forces the contacts apart again. This

is called momentary action. In a household light switch, the contacts are held together

after the switch is flicked to the on-position. They are released when the switch is pushed

to the other position. This is called toggle action.

Some switches have more than one set of contacts, and may be used to control current

flow in a number of different circuits (multiple-pole switches), or to control the current

flow to different parts of a circuit (multiple-way switches). A typical example of a

multiple-way switch is the two-way arrangement used to control a single light from the

top and bottom of a staircase.

The switch contacts are not always operated by a person's finger. Specialized switches

are designed with contacts that close when there is a change in temperature, pressure, or

humidity.

3.2 CIRCUIT PROTECTION SYSTEM

3.2.1 Type of protective devices

The consumer unit (or distribution board) contains devices for the protection of the final

circuit against:

1. Over load2. Short-circuit

3. Earth fault

Over load and short- circuit are carried out usually by one device, a fuse or circuit

breaker.

Earth fault may be carried out by the fuse or circuit breaker provided for over load &

short- circuit or by and RCD.

Over load protection

Over load protection is given by the following devices:

Fuses to BS88 part 2 or part 6; BS1361 and BS 3036; miniature circuit breakers to BS

3871 Types 1,2,3 and circuit breakers to BS EN 60898 types B,C and D.

Fault Current Protection

When a consumer unit to BS EN 60439-3 or BS 5486:

Part 13, or a fuse board having fuse links to BS88 part 2 or part 6 or BS1361 is used, then

fault current protection will be given by the over load protective device.




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For other protective devices the breaking capacity must be adequate for the prospective

short- circuit current at the point.

Protection against Electric Shock

Direct Contact:

Electrical insulation and enclosures and barriers give protection against direct contact.

Non-sheathed insulated conductors must be protected by conduit or trunking or be with in

a suitable enclosure. A 30A RCD may be provided to give supplementary protection

against direct contact, but must not to be relied upon for primary protection.

Indirect contact:

Protection against indirect contact is given by limiting to safe values the magnitude and

duration of voltages that may appear under earth fault conditions between simultaneously

accessible exposed- conductive parts or earth. This may be effected by the:

(a) Co-ordination of protective devices and circuit impedances, or

(b) Use of RCD’s to limit the disconnection time, or

(c) Use of class 2 equipment or equivalent Insulation.

SELV and PELV

Separated Extra Low Voltage (SELV) system

(a) Are supplied from isolated safety sources such as a safety isolating transformer

to BS 3535

(b) Have no live part connected to earth or the protective conductor of another

system.

(c) Are enclosed in an insulating sheath additional to their basic insulation(d) Have no exposed-conductive parts or protective conductors of other systems

or extraneous-conductive parts.

Protective Extra- Low Voltage (PELV) system

PELV systems must meet all the requirements for SELV except that the circuits are not

electrically separated from earth.

For SELV and PELV systems protection against direct contact need not be provided if

voltages do not exceed the following.




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Location SELV PELV

Dry areas Swimming

pools, Bath rooms, saunas

other area

25V a.c or 60V d.c

12V a.c or 30V d.c

12V a.c or 30V d.c

25V a.c or 60V d.c

Not allowed

6V a.c or 15V d.c

Application of RCDs

Regulation 314-01-01 required installations to be divided in to circuits to avoid danger

and minimize inconvenience in the event of a fault and takes account hazards that might

arise from the failure of a single circuit, e.g. a lighting circuit.

30mA RCDs installed to provide protection to socket outlets likely to feed portable

equipment outdoors should protect only those sockets,

where an RCD is fitted only because the earth loop impedance is to high for shock

protection to be provided by an over current device, for example in a TT system, the rated

operating current should not be less than 100mA.

If two RCDs are installed they should preferably control separate circuits or a time delay100mA.

The enclosures of RCDs or consumer units incorporating RCDs in TT installations

should be of an all insulated or class 2 constructions. Other wise additional precautions

need to be taken to prevent faults to earth on the supply side of the RCDs.

3.3 POWER SUPPLY CIRCUIT PROTECTION ACCESSORIES

Following protection devices using for power distribution panel & consumer units.

1. Molded case circuit breaker (MCCB)

2. Miniature circuit breaker (MCB)

3. Residual current circuit breaker(RCCB)

4. Earth fault Relay (EFR)

5. Earth leakage relay (ELR)

6. Phase failure relay (PFR)




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1. Molded Case Circuit Breaker (MCCB)

Molded case circuit breakers have two tripping mechanism

1. Normal tripping

2. shunt tripping

2. Miniature Circuit Breaker (MCB)

MCB’s have two tripping mechanism

(a) The Bi-metal over load trip

(b) The electromagnetic short-circuit trip

The Bi-metal over load trip

The over load tripping depends on the operation of the thermally operated bi-metal strip,

which consists of two different metals rolled on each other. Due to the different

coefficient of thermal expansion, the two metals expand differently when heated (for

instance by an electric current flowing through), which results in a deflection. The

deflection depends directly on the duration. After a predetermined deflection (or

temperature), the bi-metal will activate the tripping mechanism. Normally the bi-metal is

selected to carry the line current and can be directly heated, for lower current ratings itmight be necessary to use indirect heating via a heater tape which is wound around the bi-

metal.

Some older designs of miniature circuit breakers still in use, extend the function of the bi-

metal tripping system to trip on short- circuit conditions as well as to support the bi-metal

for faster bending on high short- circuit current, an iron core is attached to the bi-metal.

Such systems normally cause the bi-metal to be over heated and result in an over

stretching. After the fault has been cleared, the bi-metal does not return to its next fault

situation the miniature circuit breaker will trip much earlier than it was design for,however the distortion is irreversible such circuit breakers may comply with standards

like NEMA (American standards) or JIS (Japanese standards), but would not pass the

more stringent requirements of standards like IEC (International standards), SS

(Singapore standards) and EN (European standards)




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(a) The electromagnetic short-circuit trip

For server over load or short-circuit conditions, miniature circuit breakers should provide

an instantaneous tripping facility.

The electromagnetic tripping system consists essentially of a solenoid coil through which

the load current flows. The coil has a fixed iron core plus a movable armature. If the

current exceeds a predermined value the coil produces sufficient electromagnetic force to

attract the movable armature against the for of the re-set spring. The switching

mechanism is activated by the tripping liver to open the contacts

This classical method is used in the so called zero point extinguishing MCBs (ZPE).

ZPE MCBs operate with an arc voltage which is much lower than the supply voltage.

This allows the short-circuit current to flow practically uninfluenced or impeded for the

first half wave of the a.c. cycle only just near the zero or cross over point of the a.c. sine

wave, the arc can be extinguished, in some cases it may even re-ignite. Electromagnetic

short-circuit trip shown in

3. Residual Current Circuit Breaker (RCCB)

RCCB’s have a two pole and 4 poles. Phase and Neutral going through the 2 pole RCCB.

3 phase and neutral go through the 4 pole RCCB.

Residual current devices provide the functions of isolation switching and earth leakage protection of electrical circuits (no over load and short-circuit protection).

They have a residual current operated electromechanical release which operates without

any auxiliary source of supply to open a circuit automatically in the case of an earth

leakage fault between phase & earth greater than or equal to a threshold of 30,100 or

300mA.

Mechanism of the RCCB

A residual current device (RCD) is a measurement device connected to a torrid sensor

surrounding the active conductors of a circuit, it’s function is to detect a difference

incurrent, i.e. a residual current caused by in insulation fault between an active conductor

and the frames or earth, and to automatically interrupt the supply with in a delay that is

compatible with people safety.

4. Earth Fault Relay (EFR)

Earth fault relay suitable for protection of all electrical circuit. This relay is extremely

accurate easy to set, compact and easy to install with rear terminal connection.




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EFR’s have a following special features

1. Mechanical fault indicator to indicate the tripping of relay

2. Manual reset push button for the relay

3. Built-in delay timer with adjustable range of 0 sec to 1.0 sec

4. Its reliability and stability arc excellent and performance is

extremely high compared with conventional induction relays

5. Highly resistant to electrical induction and external mechanical

shock.

6. Its unique circuit design and electronic parts ensure stable operation

over a wide range of temperature, humidity, voltage and frequency

fluctuation

7. Specially made transparent plastic cover for sealing of the setting

knob.

5. Earth leakage relay (ELR)

The earth leakage relay has the very best diagnostic (and auto diagnostic) never seen on

the previous generation of earth leakage relays. Particularly, it has three types of tests,

two of which are made automatically by the relay it self.

1. manual test (trough test button)

2. automatic test of the torrid/relay circuit (watch)

3. automatic test of the internal electronic functionally

Every two second the microprocessor checks all the electronic circuit between the input

and output terminals. The test doesn’t generate any interference with the normal relay

operation in case of fault the out put relay trips and the fault LED light-on steady.

6. Phase Failure Relay (PFR)

PFR’s have a three-phase voltage control for three phase networks without neutral. The

voltage to be controlled is applied to terminals L1, L2, L3, N and feeds the unit too

(green “ON” LED). “Max voltage” and “Min voltage” potential meters establish a control

window around the line rated voltage which value is selected by the rotary switch “Ue”

on the front.

The unit trips when only one of the line voltages (L1-L2, L2-L3, L1-L3) exceeds the set

limits.

i. Normal condition




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If the voltage is with in the control window, both out put relays are energized, the “Min”

and “Max” LED’s are off.

II. Maximum voltage trip

When the voltage exceeds the “Max voltage” limit of the control window and the over

voltage remains for more that time “Delay max” the “Max” out put relay de-energizesand the “Max” out put relay energizes and the “Max” LED switch off.

III. Minimum Voltage trip

When the voltage exceeds the “Min voltage” limit of the control window and the under

voltage remains for more than time “Delay min”, the “Min” out put relay de-energizes

and the “Min” LED switches on. When the voltage returns to a value more than “Min

voltage” +3% (hysterics). The reset is automatic, the “Min” out put relay energizes and

the “Min” LED switches off.

3.4 EARTHING

Every exposed-conductive-part (a part which may become live under earth fault

conditions) shall be connected by a protective conductor to the main earthing terminal

3.4.1Types of earthing system

1. TT system

2. IT system

3. TN-C system

4. TN-S system

5. TN-CS system

The correct selection of protective devices and their current/voltage ratings depend on,

among other factors, the earthing arrangement of the electrical installation system. The

distribution systems ate classified according to IEC 60364-3 by the method of systemearthing. The basic definition of the system is denoted by using two letters. An addition

of one or two letters may be necessary to indicate neutral and protective conductor

arrangements as well.

The first letter indicates the relationship of the power source and earthing.

T- Direct connection to earth

N- All live parts isolated from earth or one point earthed through impedance

The second letter indicates the relationship of the exposed conductive parts of theinstallation and the earthing.




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T- Direct connection to earth

N- Direct connection of exposed conductive parts by protective conductors to the

earthed.

In the TN- system an additional code using one or two letters defines the arrangement of

the neutral and protective conductors.

C- Neutral and protective conductor combined in a single conductor

S- Separate conductors for neutral and protective functions

CS- Neutral and protective conductors combined in part of the system only

In the TT system, all exposed conductive parts of an installation are connected to an earth

electrode which is electrically independent of the earth all the supply source.

Effective earth connection is some times difficult as the fault loop impedance may not be

as low as required. The fault current limitation in the IT- system is obtained by the

absence of an earth connection from the supply (is obtained neutral) or by in serration of

an impedance between the neutral path and earth.

In the TN- system the fault loop is entirely constituted of conducting elements, so that

high earthing resistances can be avoided. The star point at the power source is directly

earthed, the exposed conductive parts of the installation may be connected to a separate

protective conductor and neutral (as in the TN-C or the TN-CS- system)

3.4.2 Earth Electrodes

The following types of earth electrode are recognized for the purposes of the regulations.

1. Earth rods or pipes

2. Earth tapes or wires

3. Earth plates

4. Under ground structural metal work embedded in foundations

5. Welded metal reinforcement of concrete (except pre-stressed concrete)embedded the earth,

6. Lead sheaths and other metal coverings of cables

7. Other suitable under ground metal work.

Generally we were used earth pipe for my work station. But earth plate is used for the

lighting arrestor.




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Method of the installing earth pipe

At first we should dig a hole. Then insert the galvanized pipe in to the hole. And attack to

the top of the pipe, till come to the ground level. Then insert the sold or chemical in to the

earth pipe, for good resistance to the pipe & ground.

3.6 LIGHTING ARRESTER

Buildings are protected from lightning by metallic lightning rods extending to the ground

from a point above the highest part of the roof. These rods form a low-resistance path for

the lightning discharge and prevent it from traveling through the structure itself. Power

lines and radio sets with external aerials are protected against lightning by lightning

arresters that consist of a small gas-filled gap between the line and ground wire. This gap

offers a high resistance to ordinary voltages, but a lightning discharge, which has a

potential of tens of millions of volts, causes the gas in the gap to ionize, providing a low-

resistance path to earth for this discharge.

There are several types of lighting arresters in general use. They differ only in

constructional details but operate on the same principle which providing low resistance

path for the surges to the ground. Following are kinds of lighting arresters.

1. Rod gap arrester

2. Horn gap arrester 3. Multi gap arrester

4. Expulsion type lighting arrester

5. Valve type lighting arrester

Assembling the lighting arrester

First one fixed lighting arrester then fixed the copper tape to the arrester and termination

to earth plate to the other side of the copper tape.

Safety measures to be taken when installing lighting arrester

1. The lighting arrester must be at last 2 meters higher than any other point on

the structure it is intended to protect.

2. Check that the down conductor is attacked tightly to the lighting arrester tip

by the arrester adaptor / down conductor.

3. Make sure that there is perfect electrical continuity between the lighting

arrester and its earthing point.




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4. The resistance of the earthing points must be no greater than 10. this value

should be taken at an earthing point insulated from all other conducting

elements.

4.1 INTERNATIONAL ELECTRICAL ENGINEERING REGULATION (IEE

REGULATION)

We must always attach phase(live) wires to the right side of the switch

Phase wire of the socket outlet must be attached to the right.

Fuse is not attach to a neutral wire

The equipments protected by circuit must be clearly noted in the distribution

board

All the socket out let of a room must be connected to a single phase

If there are more than one sub circuits, they must be connected to a distribution

board.

Each equipment of a low voltage must be noted in the distribution board.

The neutral wire of distribution board must be connected neatly according to

their circuit.

On, off switch must be placed closed to its motor.

When wires are sent through mettle cover rubber-bush must attach to the end

of them.

When doing a wires joint with aluminium conductors and copper conductors

they must not be mixed.

If must not good enough to keep a P.V.C wires in an heat of more than 60C.

Equipments with oil in a building must be kept a part from other to avoid

accidents.

More than flexible wire must not be attached to the sealing rose.

Socket must not be fixing in the bath rooms.

All the earth joint must be welded together to end earth wire.

Insulation and resistance must be move than mega ohm.

A socket must be fixed in a height of 150mm from the floor.

The voltage drop of a sub circuit must not be more than 2.5%

The distance between the main switch and its permanents cookers must be less

than 2mm




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5.1 WORK STATION SAFETY PROCEDURE

1. Site cleaning

2. Protective wear

3. Safety access

4. Scaffolding / platform

5. Prevention of accident due to falls

6. Prevention of due to electrical failure

7. Prevention of accident due to misuse of machineries

8. Prevention of fire

9. Safety sign

10.First aid

11. Activities for safety

1. Site cleaning

At heights safe scaffolding / platform shall be always kept clean.

Dustbins shall be provided at appropriate interval for small garbage with

indication by signboard.

Garbage dumping area shall be arranged at site with indication by

signboard. All garbage shall be collected to this area and collected garbage

shall be disposed to out side of site periodically.

2. Protective wear

Helmet - all workers / staff shall wears helmet at site.

Shoes-all workers / staff shall wear gumboots at required places.

Other protective wears.

Safety belt shall be worn for following works structural steel erection,

scaffolding erection etc at high places.

Goggles shall be worn for following works chipping, grinding, etc in case

small particles could be emitted.

Welding hoods shall be worn for following works-welding etc in case

harmful ray could be emitted.




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Mask shall be worn for following works-grinding / cutting concrete, etc in

case small particles could be emitted.

3. Safety access

Safety access to work place shall be always secured and cleaned.

Signs for safety access shall be provided lighting to safety access shall be

provided at night.

4. Scaffolding / Platform

Damaged, deformed, corroded materials shall not be used for scaffoldings.

Scaffoldings shall be erected in either of following systems.

Prefabricated scaffolding system, consisting of frame, brace, catwalk

panel, etc

G.I.pipe scarffolding, consisting of vertical, horizontal, bracing G.I.pipes

tightened by cramps.

Scaffolding which is more than 5m in height shall be tide to permanent

structure at appropriate interval. Top of scaffolding platform shall be equippedwith handrail.

5. Prevention of accidents due to falls.

In case of works, be provided.

In case it is physically difficult to provide safe scaffolding / platform

form for work at heights, workers must use safety belt.

Opening which may cause fall shall be closed, or barriered. Work at heights in strong wind and heavy rain is prohibited.

In case heights in strong wind and heavy rain is prohibited.

In case height / depth of working platform are more than 1.5m, safe

facilities for going up and down shall be provided.

6. Prevention of accidents due to electrical failure.

Insulated wire shall be used for wiring of temporary

power supply.




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Nothing shall be put on cable.

Nothing shall be in front of distribution board.

Circuit bracer shall be provided to each circuit.

7. Prevention of accidents due to misuse of machineries.

Max speed within the site shall be 15km/h

No entry in to the radius of operation of crane, backhoe, ect.is allowed.

Inspection before commencement of work of basic mechanical items such

as brakes and clutch shall be carried out by operators.

Periodical inspection for entire machineries shall be established (detail will

be submitted later) and in effect.

Signals for hoisting shall be unified, and signalman shall be stationed at

hoisting works.

8. Prevention of fire.

Contact Tel.No. of nearest fire station shall be displayed at site office.

Flammable gas cylinder shall be kept at well ventilated place.

9. Safety signs Following signs shall be provided at appropriate places according to site situation

/ progress

Safety first

Wear helmets

Watch your head

Dust bin

Max. load

Other sings as required

10. First aid

First aid box equipped with a first-aid kit, etc. shall be

provided

Contact Tel.No. for calling ambulance shall be displaced

at site office.




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11. Activity for safety

Monthly safety meeting - safety meeting for all workers

shall be held monthly in order to educate workers for improvement of safety at

site.

Daily meeting - at daily meeting for tomorrow’s

activities, what to take care for safety shall be discussed.

6.0 Specification

Specification generally consisted of two sections, one being the requirements for

Stranded of workmanship and the other being a specific requirement for the electrical

wiring of the installation. Particular requirements were detailed in individual clauses.

The Electrical Consultant had the responsibilities of ensuring that the Specification

correctly identified and details the work that the electrical contractor was to undertaken;

there be clauses requiring him to accept responsibility for the satisfactory design of the

installation, as well as clauses requiring him to point out any alleged deficiencies or error

in the design at the tender stage of the project. In addition to this, was the general

responsibility upon the electrical installation were safe and designed to a satisfactory

standard.

It some times happens that the client changed the requirement about some aspect of the

work being undertaken or that an incorrect detail was discovered on a drawing or in the

specification. Such variance (as they were called) were generally advised by the

consulting engineer to the architect who then issued an architect’s instruction to the main

contractor who in turn informs the electrical contractor to carry out the extra work in

accordance with terms and condition.

The permanent site staff consists of project Manager, Engineers, Assistant EngineersQuantity Surveyors, Administrative Officer, & Storekeepers. Duties and responsibilities

of these officers at the work site distribute as follows.

6.1 DUTIES & RESPONSIBILITIES OF PROJECT MANAGER

He should responsibilities for around all section of the site administration,

technical and other parts.

He should prepare programs & progress charts for the site organization.

He should co- ordinates between head office and site and also between the client& contractor




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He must select who are the best for each work and who can do hard works.

He should co-coordinate with different sub contractor agencies to maintain the

speed of construction project work.

He should attend site meetings, preparation of proceeding for tomorrow; discuss

the difficulties, suggestions taken out the meeting.

He should give instructions to the engineers, assistance engineers & officers as it

required by the site conditions.

Complete the project with in given time & cost also good quality must there.

6.2 DUTIES OF ENGINEERS

Keeping overall watch on working of all the supervisors & workers to obtain

maximum out put from them.

To control wastage & details provided by the consultants & explain to supervisors.

To prepare reinforcement schedules of the project.

To work out the requirement of different material necessary for work involved.

6.3 DUTIES & RESPONSIBILITIES OF ADMINISTRATIVE OFFICER

Security services should be careful checked on daily basis & report promptly all

shortcomings to project manager.

Maintenance & movements of machineries, vehicles & arrangement it requirementin time.

All transfers of employers from one work site should be organized an in order to

prepare the transfer documents. ( gate passes )

All the copies of attendance sheet & any other document pertaining to site

employee’s from; be care fully packed and dispatched to teed office at the end

every month.

The passes must be issued all sub contractors employees & re-new or alter each 6

months.

Every personal accident looks after the purpose of employees & he should takeaction to over come problems as soon as possible.

6.4 STORE MANAGEMENTS

To get good store handling without wasting the materials or working hours of labors due

to the finishing of materials, the site manager should keep close associated with store

keepers. Main stores managed site stores.

Storekeepers should maintain the following records;




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Material requisition

Goods Received note

Stores requisition

Gate pass

Transfer voucher

Issue receipt voucher

Material Requisition

This is used to issue the material to the workers from the site office. Officers have to fill

this form & sign it & worker give it to stores and store keeper was issued request quantity

for the worker.

Goods Received Note

When the requested materials are supplied to the site, the store keeper prepares the

“Goods Received Note” by checking quantity of the goods received thoroughly. The

project manager must give the final approval.

Purchase Requisition

If any material is not available or not on sufficient quantities in the site the store keeper

should inform the project manager about the stock levels when a requirement arises a

“Purchase Requisition” is prepared stating the required materials, quantities etc. and

forwarded to the site manager for approval.

Store Requisition

If a material purchasing through the head office stores requisition is prepared. Thencertified it by site manager and forwarded to the head office.

Transfer voucher

To transfer any equipment, material from one site to another site or head office stores to

the site transfer voucher is issued. This is consisting of four copies.

Original - to receive place

Duplicate - to certify that goods received and return it to the siteTriplicate - to the security book copy




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Gate pass

If some thing is taken out from the site the gate pass is issued. Especially for the sub

contractors

6.5 DUTIES AND RESPONSIBILITIES OF CONSULTANT

Consultant has to design and prepare the details of the project to the satisfaction of the

client has to administer the work till its completion.

In this task consultant has to give details and certification where ever necessary. If all of

his responsibilities be has,

1. Closely supervises the work

2. Review the progress and propose remedial action

3. Check and certify the bills

4. Check and approve the new rates, day works, variation orders

5. Supervise the rectification work during maintenance period6. Issue as certificate of completion at the end of the project

7. Check the quality of the work that client wishes

8. Complete project within given time period and given cost by the client.




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7.0 C-Bus Lighting Control system

Introduction

C-Bus is a microprocessor-based control and management system for buildings and

homes. It is used to control lighting and other electrical services such as pumps,

audiovisual devices, motors, etc. Whether simple ON/OFF control of a lighting circuit, or

variable (analogue) type control, such as electronic dimmable fluorescent ballasts, C-Bus

can be used to easily control virtually any type of electrical load..

To ensure fast and reliable operation, each C-Bus device has its own in-built

microprocessor and “intelligence”, allowing units to be individually programmed.

C-Bus uses a patented method for updating the status of units. This method does not

require a central computer or central controller to handle databases or lookup tables tooperate. The status of each C-Bus unit is initiated at specific time intervals, without the

need of a central controller. Each device is allocated a specific time frame to broadcast its

status, synchronized by a self- generated system clock pulse. This allows large amounts

of data to be transmitted in a very small time frame, effectively and reliably on the

network, leading to low processing overheads and low bandwidth requirements.

There are many reasons to use C-Bus:

It is a highly robust and reliable control system, with a low cost per node. A wide range of tools is available, allowing third party companies to interface

with both PC based and embedded systems.

A single C-Bus cable connection can control many devices.

C-Bus offers the ultimate flexibility in switching and control. Functions can be

changed, added, removed, moved, reprogrammed, at any position on the network,

at any time — without any cumbersome hard-wiring.

C-Bus is simple to install and commission.

C-Bus can control any type of load, digital and analogue.

Electrical wiring practices have not changed much since the introduction of insulated




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multicore cabling. However, wiring requirements in commercial buildings have changed

rapidly since that innovation. The additions of fire and smoke detection, security and

energy management systems have placed high demands on electrical installations.

The need for central monitoring and control of these extra systems may result in massive

networks of wires emanating from the control area.

Conventional wiring practice requires current to flow through both a switch and its load.

This requires heavy conductors to run from the switchboard to the load and, from the

load to the controlling switches. These aspects add to wiring complexity, increasing

installation time, documentation control and overall system cost. Maintenance and

system flexibility can be problematic.

The C-Bus network overcomes these problems. It uses a twisted pair of wires such as

Unshielded Twisted Pair (UTP) Category 5 (Cat-5) Local Area Network (LAN) cable, to

communicate between a building’s light switches and load controlling devices. This same

cable pair also provides the DC supply voltage to the C-Bus devices.

This greatly reduces the number of heavy wires in an installation, while enabling easy

central monitoring and system control.

C-Bus can be expanded to control and monitor a building’s electrical appliances from a

personal computer. Security, air conditioning and other systems can be programmed to

turn on or off at specific times or events. Lighting and temperature can be variedaccording to ambient conditions. Inputs, switches and loads can be reconfigured without

reconnecting a single wire.

C-Bus Communications

When a button is pressed on an input unit, a measurement is made of its press duration.

This measurement influences the message that the unit issues in response to the button

press (depending on its programming). This is illustrated in Figure 1.




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The relevant C-Bus message is then transmitted over the C-Bus network as indicated by

the dashed line in Figure 2.

The C-Bus message is broadcast over the bus for all C-Bus units to read, as illustrated in

Figure 3. It contains information about the Group Address and the operation to be

performed, such as switch on or off. Only the C-Bus units with the same address will

respond.




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C – Bus Wiring

Figure 6 shows how the same two-way control is wired using C-Bus (pink wiring). Thecontrol circuitry is simpler than the conventional method. If a four or eight button switch

is used instead of the two button, the wiring remains the same. Just two conductors are

required to link the C-Bus control.

DESIGN PHILOSOPHY

There are several methods of designing and installing C-Bus. An overview of theinstallation approach is shown below.

Installation

Once the design phase has been completed, installation may

begin. Several

simple steps are typically followed:

• Implementation of Programming Requirements of the Design

on a Personal Computer (Build C-Bus Database).

• Unit Initialisation and Programming (One at a Time).

• Cabling and Electrical Installation of the Hardware.

• Finalization and Further Programming of Units on the Network as required.

The details of the design are first input into a personal

computer using the C-Bus Installation Software. Hardware

should then be initialised (on a Unit by Unit basis). This

involves the assignment of a Unit Address to each Unit, one ata time. In this way Units can be uniquely identified once

installed on the Network. It is recommended that each Unit be




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clearly labeled for easy identification before final electrical

fitting takes place. Testing and any further programming may

be undertaken at this time, or tackled once all

Units have been physically installed.

Commissioning

Subject to compliance with the specification, the system may

now be commissioned. Modifications or design review can be

undertaken at any time, often requiring programming changes

only. A well designed system should seldom call for the

installation of new hardware, except where revised

specifications dictate the necessity.

Programming Principles

All C-Bus devices require programming (with the exception of

Power Supplies).

This is achieved by dedicated software running on a Personal

Computer.

Unit programming is carried out to achieve the following

objectives:

• Create/Define Units on the C-Bus Network

• Identify each Unit using the C-Bus addressing convention

• Create/Define/Edit control relationships between Inputs and

Outputs

• Edit Unit operating parameters

The operating parameters vary from Unit to Unit, depending on it’s type.

They include:

• Key Functions

• Timer Functions• Dimming Functions

• Toggle (On/Off) Control

• Preset Levels

• Custom/Other Functions

• Output Switching Logic Assignments

• Power Fail Recovery Status

• Power Up Sequences

• Dimming Rates




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• Indicator Options

• Sensor Switching Conditions

• Override Controls (Enable/Disable)

• Error Status Options

Practical Wiring Considerations

The C-Bus is designed to operate at a safe, extra-low voltage of 36V DC, with optical

and/or galvanic isolation from mains voltages. The installer must ensure that acceptable

wiring practices for extra low voltage cabling are adopted with C-Bus.

In particular, the routing of the C-Bus cable near mains wiring, where physical separation

criteria between cables need to be satisfied. In this respect C-Bus is treated as a data

cable, and the same practices should be employed. The C-Bus, operating at the safe extra

low voltage of 36V DC, allows electrical work to be performed on the C-Bus side while

the system is powered on.




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The C-Bus side with short circuit protection ensures that the equipment will not be

damaged if the supply is shorted for an indefinite period. The installer needs to be aware

that shorting the C-Bus Network will disable operation of the C-Bus Network as long as

the short circuit persists. A benefit of the C-Bus method of wiring is that wiring of the C-

Bus Units may be accomplished in a number of ways. The C-Bus Units are all wired in

parallel on the Bus, and the Units may be daisy chained, or be part of a branch/star

structure or a combination of these. Closed loop ring structures are not recommended.

Installation of every Unit on the C-Bus Network requires connection to the Unshielded

Twisted Pair C-Bus Network Cable. This connection is polarity sensitive, and is clearly

marked on the terminal block of the Unit. Clipsal has Category 5 cable for use with C-

Bus (Catalogue Number 5005C305B). The cable features eight single core conductors

(four Unshielded Twisted Pairs (UTP), encased in a pink outer sheathing. Pink has been

chosen in order to distinguish between the C-Bus cabling in an installation. A second

feature is that the cable may for short runs be routed into a switchboard close to mains

cable. The outer sheath insulation resistance is suitable for this application. The following

illustration shows the recommended technique for cable termination giving optimum

performance, and immunity from electromagnetic interference (EMI).

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