NEPAL NATIONAL BUILDING CODE
NBC 207 : 2003

ELECTRICAL DESIGN REQUIREMENTS
for(PUBLIC BUILDINGS)

Government of Nepal

Ministry of Physical Planning and Works
Department of Urban Development and Building Construction
Babar Mahal, Kathmandu, NEPAL

Reprinted : 2064

NBC108V2.RV9

7 December 1993

NEPAL NATIONAL BUILDING CODE
NBC 207 : 2003

ELECTRICAL DESIGN REQUIREMENTS
for(PUBLIC BUILDINGS)
This publication represents a standard of good practice and therefore
takes the form of recommendations. Compliance with it does not confer
immunity from relevant legal requirements, including bylaws
tTsflng >L % sf] ;/sf/ -dlGqkl/ifb\_ sf] ldlt @)^).$.!@ sf] lg0f{ofg';f/ :jLs[tGovernment of Nepal

Ministry of Physical Planning and Works
Department of Urban Development and Building Construction
Babar Mahal, Kathmandu, NEPAL

Reprinted : 2064

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i

PrefaceThis code has been prepared having considered the provisions of Electricity Act 2049
and Electricity Rule 2050 up to date. This includes general guidances for Electricalwiring installation. Prevention of short-circuiting has been emphasized. Utmost
importance should be given in the installation of electrical wiring while preplanningand exchanging information among all concerned agencies from the earlier stages ofthe building works. Due to the limited technical manpower the country's constructionindustry, the code has been simplified for the ease of use and implementation. It is
hoped that with the development of the manpower and modernization of construction
processes, it will be possible to release more sophisticated set of electrical wiring
installation guidelines in future.

Principal input to this code came from :Mr. Purna P. Kadariya , DG, DUDBC
Mr. Kishore Thapa, DDG, DUDBC
Mr. Mani Ratna Tuladhar, Sr. Div. Engineer, DUDBC
Mr. Jageshwar Mahaseth, Electrical Engineer, DUDBC
Mr. Kalu Bhattarai, Electrical Engineer, Dept. of Electricity Developement, New
Baneswor
Mr. Ladhu Ram Tamang, General Secretary, SEEN
Mr. Amrit Man Tuladhar, Engineer, DUDBC

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TABLE OF CONTENT
S.NO.

Particulars

Page No.

1

1. General Requirement12

2. Power Factor Improvement in Consumer's Installation

1

3

3. Planning of Electrical Installation

1

4

4. Distribution of Supply & Cabling35

5. Rating of Cables & Equipment

56

6. Wiring

67

7. Earthing

98

8. Inspection and Testing of Installation

109

9. Lightning Protection of Building

1210

10. Telecommunication and other services

12

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1.

2.

3.

General Requirements
1.1

The installation shall generally be carried out in conformity with theElectricity Act 2049 as amended up to date and the Electricity rules 2050
framed thereunder and also the relevant regulations of Electricity supply
authority concerned as amended from time to time.

1.2

For practices of electrical wiring, definitions, design & construction andinspection & testing of installation, IS 732, 732 (part 1) 1982, 732 (part 2) and
1982, 732 (part 3) 1982 shall be referred to respectively.

Power Factor Improvement in Consumer's Installation
2.1

Condition of supply of Electricity authority or licensees stipulate the lower
limit of power factor which is generally 0.8 and consumer is obliged to
improve and maintain the power factor of his installation to conform to thiscondition

2.2

Execution of work: Unless otherwise exempted under the appropriate rule ofelectricity rules the work of and electrical installation shall be carried out by
an electrical contractor licensed and under the direct supervision of a person
holding a certificate of competency and by persons holding valid permit
issued and recognized by the government.

2.3

For graphical symbols, power factor improvement, safety procedures andpractices IS 8270 (Part 1) 1976 & IS 2032; IS 7752 (Part 1) 1975 & IS 52161969 shall be referred to respectively.

Planning of Electrical installations
3.1

General – The design and planning of an electrical wiring installation involve
consideration of all prevailing conditions, and is usually influenced by thetype and requirement of the consumer. It is recommended that the advice of acompetent electrical engineer be sought at the planning stage with a view toproviding for an installation that will prove adequate for its intended purpose,and safe and efficient in its use.

3.2

Co-Ordination-Proper co-ordination and collaboration between the architect,civil engineer, electrical, communication and mechanical engineer shall beeffected from the planning stage of the installation. The provisions that will
be needed for the accommodation of substation, transformer, switchgear,
service cable ducts, rising mains and distribution cables, sub-distribution
boards, openings and chases in floors and walls for all required electricalinstallations, etc, shall be specified in advance.

3.3

While planning an installation, consideration should be taken of the
anticipated increase in the use of electricity for lighting, general-purpose
socket-outlet, kitchen heating, room heating etc.
Arrangement of Substation and switchgear rooms :3.4

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a)

b)

c)

Total Plinth (covered) Area: Electrical substations may normally berequired in case of office buildings with a total plinth (covered) area of5000 m2; even buildings with smaller plinth (covered) areas with large
loading or under local regulations may require a substation. Separate
substation building is generally not required it total load is less than
100 kVA. However, a suitable size of lockable space should be
earmarked for installing control switchgear in buildings.
Load Centre and Centre of Gravity of Buildings : The ideal location for
an electrical substation for a group of buildings would be at the load
centre and shall be located on the ground floor. In multi-storeyedbuildings, the substation shall preferably be installed on the lowest
floor level, but direct access from the street for installation or removalof the equipment shall be provided. The floor level of the substation or
switchroom shall be above the highest flood level of the locality. In
this case the load centre would be somewhere between the geometricl
centre and the air conditioning plant room, if provided. The sub station
should preferably be located in a separate building and should be
adjacent to the generator room, if any. Location of substation in thebasement floors should be avoided, as far as possible, In case electric
substation has to be located within the main building itself forunavoidable reasons, then it should be located on ground floor witheasy access from outside.
Layout of Substation : In allocating the area of substation, it is to be
noted that the flow of electric power is from supply company's room to
HT room, then to transformer and finally to the low voltage switchgear
room. The layout of the room shall be in accordance with this flow.
The capacity of a substation depends upon the area of the building andits type. The capacity of transformers may be determined based on thefollowing load requirements:

Load Requirement
Per Plinth Area
(Watts/m2)
Normal lighting
20.0Lighting with lifts, pumps but without
central air-conditioning
30.0
Additional capacity for technical buildings
like laboratories, hospitals, etc
11.0
Additional capacity for airconditioning
100(of air-conditioned area)
After calculating the electrical load on the above basis, a load factor of
70 percent is to be applied to arrive at the minimum capacity of
substation. The area required for substation and transformer room fordifferent capacities is given in standard Table.

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d)

e)

4.

High & Low Voltage Switch Room: Incase of substation having one
transformer and one source of supply, the owner is required to provide
one high voltage switch. In case of single point supply with two or
more transformers the number of switch required will be one forincoming supply and one for each transformer. In case of duplicate
supply two switches shall be provided with mechanical/electricalinterlocking arrangement where necessary in cables with switches. In
case the number of incoming and outgoing switches exceed five, bus
coupler of suitable capacity should invariably be provided. The floorarea required in case of a single switch is roughly 4mX4m and forevery additional switch the length would be increased by 1m. The floorarea required in respect of low voltage switchgear room may be
determined keeping in view the number and type of incoming/outgoingbus coupler switches including likely expansion in future.
Room For Stand By Generator: The capacity of standby generating set
shall be chosen on the basis of essential light load, essential airconditioning load, essential equipment load and essential services load,such as one lift out of the bank of lifts, one or all water pumps, etc.
Having chosen the capacity and number of generating sets, a space
may be provided for their installation from the Standard Table. The
generating set should invariably be housed in the substation building toenable transfer of electrical load quickly as well as to avoid transfer ofvibration and noise to the main building. The generator house shouldhave proper ventilation, firefighting equipment, etc.

Distribution of Supply & Cabling
4.1

In case of connected load of 100KVA and above, the relative advantage ofhigh voltage three-phase supply should be considered.

4.2

Switchgear and fuse gear shall have adequate breaking capacity in relation to
the capacity of the transformers ultimately to be connected. Isolation andprotection of outgoing circuits forming main distribution system may beeffected by means of circuit-breakers, or fuses or switch and fuse units
mounted on the main switchboard.

4.3

Control at point of commencement of supply: There shall be a circuit-breakeror miniature circuit-breakers or a load break switch fuse on each live
conductor of the supply mains at the point of entry. The wiring throughout the
installation shall be such that there is no break in the neutral wire in the formof a switch or fuse unit. The neutral shall also be distinctly marked. The main
switch shall be easily accessible and situated as near as practicable to thetermination of service line. On the main switch, where the conductors include
an earthed conductor of a two-wire system or an earthed neutral conductor,
which is to be connected thereto, an indication of a permanent nature shall be
provided to identify the earthed neutral conductor.

4.4

Energy Meters: Energy meters shall be installed in residential buildings at
such a place which is readily accessible to the owner of the building and the
Authority. These should be installed at a height where it is convenient to noteNBC108V2.RV9

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the meter reading; it should preferably not be installed below one meter fromthe ground. The energy meters should either be provided with a protective
covering, enclosing it completely except the glass window through which thereadings are noted or should be mounted inside a completely enclosed panel
provided with hinged or sliding doors with arrangement for locking. Energy
Meter along with Switch disconnector such as MCCB, MCB & Fuse ismandatory.
4.5

Marking of Apparatus: Where a board is connected to voltage higher than 250
V in a three Phase system, all the apparatus mounted on it shall be marked on
the following colours to indicate the different poles or phases to which theapparatus or its different terminals may have been connected:
Alternating Current
Three-phasesRed, yellow, blue
1 Neutral-black
Earth green

Direct Current
Three-wire system-2outer wire, positive red andnegative blue.
1 Neutral-black

Where four-wire three-phase wiring is done, the neutral cable shall be in black
colour and the other three wires in red, yellow and blue.

4.6

Where a board has more than one switch, each such switch shall be marked toindicate which section of the installation it controls. The main switch shall bemarked as such and where there is more than one main switch, each suchswitch shall be marked to indicate which section of the installation it controls.
All markings shall be clear and permanent.
Protection against the short circuits :a) Cascading : Cascading is the techniqe by which circuit breakers withbreaking capacity lower than the prospective short circuit current may beinstalled downstream from a current limiting type of circuit breaker. The
breaking capacity of downstream breaker shall be enhanced by the limiting
capability of the breaker. Combination shall be applicable to all switchtear
down stream and capacity of upstream breakers should be greater or equal
to the prospective short circuit current at the point of installation.
b) Co-ordination : the characteristics of the two breakers must be coordinated in such a way that the energy let though by the upstream breaker
shall not be more than down stream breakers. Condition for co-ordinationof breakers shall be such that the downstream breaker having breaking
capacity less than the prospective shourt circuit current, shall be permited
as long as breaker installed upstream having breaking capacity greater thanor equall to prospective short circuit current at the point of installation
exists.
c) Discrimination : At the design stage of low voltage installation one mustbe sure that the co-ordination of automatic protecting devices like MCCB,MCB, ACB and other protective divice should be selected in such a waythat a fault opearing at a given point in any installation shall be cleared by
the protection device installed immediately above the point of occurrenceof fault. Where HRC type fuses are used for back-up protection of circuit-

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breakers, or where HRC fuses are used for protection of main circuits, andcircuit-breakers for the protection of sub-circuits derived thereform,in theevent of short-circuits protection exceeding the short-circuits capacity of
the circuit-breakers, the HRC fuses shall operate earlier than the circuitbreakers; but for smaller overloads within the short-circuit capacity of thecircuit-breakers, the circuit-breakers shall operate earlier than the HRC
fuse blows.

5.

Rating of Cables & Equipments:
5.1

The current-carrying capacity of different types of cables shall be chosen inaccordance with good practice IS 3961-1967, 1968 and IS 1534 (part 1) 1988
shall be referred to. Cable size shall be 1.5, 2.5, 4, 6, 10, 16, shall be 1.5, 2.5,
4, 6, 10, 16, 25, 35, 50, 70, 95, 120, 150, 185, 240, 300, 400, 500 mm2 .

5.2

The current ratings of switches for domestic and similar purposes are 5 A and
15A.

5.3

The current ratings of isolators and normal duty switches and composite unitsof switches and fuses shall be selected from one of the following values: 6, 10,
16, 25, 32, 63, 100, 160, 200, 320, 400, 500, 630, 800, 1000 and 1250 A. IS
13947-3 shall be referd.

5.4

The ratings of rewirable and HRC fuses shall be in accordance with goodpractice. IS 2086-1963 and IS 13703 shall be referred to.

5.5

The current ratings of miniature circuit breakers shall be chosen from thevalues given below: 6, 10, 16, 25, 32, 40, 63, 80 , 100, 125 A. IS 8828-1996

5.6

Lighting and levels of illumination: Lighting installation shall take into
consideration the many factors on which the quality and quantity of artificial
lighting depends. The modern concept is to provide illumination with the helpof a large number of light sources not of higher illumination level. Also muchhigher levels of illumination are called for than in the past, often necessitating
the use of fluorescent lighting suitably supplemented with incandescentfittings, where required.

5.7

For specific requirements for lighting of special occupancies, reference shallbe made to good practice. IS 2672-1966; 4347-1967; 8030-1967 shall bereferred to. Electric wiring installations in hospitals shall be done inaccordance with good practice. IS 7733-1975 shall be referred to. For
guidelines for electrical installation in residential buildings, reference may bemade to good practice. IS 4648-1968 shall be referred to.

5.8

Cables: The smallest size of the cable that shall be used, will depend upon themethod of laying cable, permissible maximum temperature it shall withstand,the prospective short-circuit current to which the cable may be subjected, thecharacteristics of the overload protection gear installed, load cycle and thermal
resistivity of the soil. IS 1255-1965 shall be referred to. Short-circuit rating
curves will serve as an approximate guide for selection of the size of cables.

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5.9

Residual current breaker should be used as to avoid electrocution and fire of
from electricity hazards in case of Hospital building.

5.10

Minimum standard size of wiring cable for light and power shall be specified
as follows:oo6.

Light circuit --- 2.5 sq.mm PVC insulated copper stranded cable
Power circuit - 4.0 sq.mm PVC insulated copper stranded cable.

Wiring
6.1

General:
6.1.1

Provision for Maximum Load – All conductors, switches andaccessories shall be of such size as to be capable of carrying, without
their respective ratings being exceeded, the maximum current, which
will normally flow through them. Diversity factor shall be considerd.

6.1.2

Estimation of Load Requirements-In estimating the current tobe
carried by any conductor the following ratings shall be taken, unlessthe actual values are known or specified for these elements:
Element
Incandescent lamps
Ceiling fans
Table fansOrdinary socket outlet points
Fluorescent tubes:
Length: 600 mm
1200 mm1500 mmPower socket-outlet

NBC108V2.RV9

Rating in watts
60
60
60
1000
25
50
90
3000

6.1.3

Electrical installation in a new building shall normally begin
immediately on the completion of the main structural building workand before finishing work such as plastering has begun except in thecase of surface wiring which can be carried out after the plaster work.
Usually, no installation work should start until the building isreasonably weatherproof, but where electric wiring is to be concealed
within the structures as may be the case with a reinforced concretebuilding, the necessary conduits and ducts shall be positioned firmly
by tying the conduit to the reinforcement before concerting. When
shutters are removed after concreting, the conduit ends shall be given
suitable anti-corrosive treatment and holes blocked off by putties orcaps to protect conduits from getting blocked.

6.1.4

Selection of Size of Conductors-The size of conductors of circuits shallbe so selected that the drop in voltage from consumer's terminals in a
public supply (or from the bus-bars of the main switchboard

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controlling the various circuits in a private generation plant) to any
point on the installation does not exceed the provision of electricity
rule 2050 at the consumer's terminals (or at two bus-bars as these maybe) when the conductors are carrying the maximum current under thenormal conditions of service.

6.2

6.1.5

Layout & Installation Drawing: The electrical layout should beconsidered after proper locations of all outlets for lamps, fans, andappliances both fixed and transportable, motors, etc. have been
selected and best methods of wiring determined. All runs of wiring andthe exact positions of all points of switch-boxes and other outlets shallbe first marked on the plans of the building and approved by theengineer-in-charge or the owner before actual commencement of thework. The layout of wiring should be designed keeping in view
disposition of the lighting system to meet the illumination levels.
"Power" and 'heating' sub-circuits shall be kept separate and distinct
from 'lighting' and 'fan' sub-circuits. All wirings shall be done on the
distribution system with main and branch distribution boards atconvenient physical and electrical load centres. All types of wiring,whether concealed or unconcealed should be as near the ceiling as
possible. In all types of wirings due consideration shall be given forneatness and good appearance.

6.1.6

Balancing of circuits in three phase - installation shall be arranged
before hand. Conductors shall be so enclosed in earthed metal orincombustible insulating material that it is not possible to have readyaccess to them unless the points between which a voltage exceeding
250 volts may be present are 2 m or more apart, in which case meansof access shall be marked to indicate the voltage present. Where
terminals or other fixed live parts between which a voltage exceeding
250 V exists are housed in separate enclosures or items of apparatus
which, although separated are within reach of each other, a notice shallbe placed in such a position that anyone gaining access to live parts iswarned of the magnitude of the voltage that exists between them.

Non-Metallic surface & recessed conduit wiring:
6.2.1

Type and size of conduitsAll rigid non-metallic conduits used shall conform to accepted
standards IS1653-1972 and shall be used with corresponding
accessories IS 3419-1977; 9537; 9537 (part 1) 1980. All flexible nonmetallic conduits shall conform to accepted standards IS 1653-1972
The conduits shall provide adequate mechanical protection for theenclosed cables. The interior of the conduits shall be free from
obstructions. Flexible non-metallic conduits shall be used only atterminations, wherever specified. The conduits shall be circular incross-section. The conduits shall be designated by their nominal
outside diameter. The conduit wiring system shall be complete in all

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respect including accessories. No non-metallic conduit less than 20
mm in diameter shall be used.
6.2.2

Conduit Acceessories
Rigid conduit accessories shall be normally of grip type. Flexible
conduit accessories shall be of threaded type.

6.2.3

Wiring Capacity
The maximum number of PVC insulated conductor cable of 250
voltage grade that can be drawn in one conduit of various sizes is given
in following Table .
Size of Conduit (mm)Size of Cable
Nominal CrossSectional Area mm2

Number & Diameter(in mm) of Wires-

1.0
1/1.12 *
1.5
1/1.4
2.5
(1/1.8), (3/1.06*)
4(1/2.24), (7/.85*)
6(1/2.8), (7/1.4*)
10(1/3.55#), (7/1.4*)
16
7/1.7
25
7/2.2435
7/2.2550(7/3#), (19/1.8)* For copper conductors only.
# For aluminum conductors only.

NBC108V2.RV9

Number of cables Max
16
5
4
3
2
-

20
7
6
5
3
2
-

25
13
10
10
6
5
4
2
-

32
20
14
14
10
9
7
4
2
-

40
14
11
9
5
2
2
(2), (2)50
1265(5), (3)6.2.4

Bunching of Cables: For ease of maintenance, cables carrying direct
current or alternating current shall always be bunched so that the outgoing and return cables are drawn into the same conduits.

6.2.5

Conduit Joints: All joints shall be sealed cemented with approved
cement. Damaged conduit pipes fittings shall not be used on the work.
Cut ends of conduit pipes shall have no sharp edges nor any burrs leftto avoid damage to the insulation of conductors while pulling themthrough such pipes.

6.2.6

Protection against Condensation: The layout of conduit should be suchthat any condensation or sweating inside the conduit is drained out.
Suitable precaution shall also be taken to prevent entry of insects
inside the conduit.

6.2.7

Painting: After installation all accessible surfaces of metallicaccessories shall be painted.

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6.2.8

Outlets: The switch box shall be made of either rigid PVC moulding or
mild steel or cast iron on all sides except at the front. PVC boxes shallconform to accepted standards IS 3419-1976; 9537, 9537(part 1) –1980 & 5133(part 2) 1969. These boxes shall be free from burrs, finsand internal roughness. The thickness of the walls and base of PVC
boxes shall be not less than 2 mm. The clear depth of PVC boxes shallnot be less than 50 mm. For METALLIC boxes: The switch or
regulator box shall be made of metal on all sides, except on the front.
In the case of cast boxes, wall thickness shall be at least 3 mm and incase of welded mild steel sheet boxes, the wall thickness shall not beless than 1.18 mm for boxes up to a size of 20 cm X 30 cm and above
this 1.6 mm MS boxes shall be used. Clear depth of the box shall not
be less than 60 mm and this shall be increased suitably toaccommodate mounting of fan regulators in flush pattern. All fittings
shall be filled in flush pattern.

Non-Metallic Recessed Conduit Wiring System shall have following threerequirements also additionally:

7.

a)Fixing of Conduit In Chase: The conduit pipe shall be fixed by meansof staples or by means of non-metallic saddles placed at not more than
80 cm apart or by any other approved means of fixing. Fixing ofstandard bends or elbows shall be avoided as far as practicable and all
curves shall be maintained by sending the conduit pipe itself with along radius, which will permit easy drawing in of conductors. At eitherside of bends, saddles/staples shall be fixed at a distance of 15 cm fromthe centre of bends.

b)

Types of Accessories to be used: All outlets such as switches, wall
sockets, etc, may be either flush mounting type or of surface mounting
type.

c)

Inspection Boxes-Suitable inspection boxes to the nearest minimum
requirements shall be provided to permit periodical inspection and to
faciliate replacement of wires, if necessary. The inspection/junction
boxes shall be mounted flush with the wall or ceiling concrete. Where
necessary deeper boxes of suitable dimensions shall be used. Suitable
ventilating holes shall be provided in the inspection box covers, whererequired.

Earthing
7.1 General – The object of an earthing system is to provide as nearly as possible asystem of conductors at a uniform potential and as nearly zero or absolute earth
potential as possible. The purpose of this is to ensure that in general all parts ofapparatus other than live parts shall be at earth potential as well as to ensure that
persons coming in contact with it shall also be at earth potential at all times.

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7.2 Earthing associated with current-carrying conductor is normally essential for the
security of the system and is generally known as system earthing, while earthingof non-current carrying metal work and conductor is essential for the safety ofhuman life, of animals and of property and it is generally known as equipment
earthing.
7.3 Earth Electrodes: Earth electrode either in the form of pipe electrode or plateelectrode should be provided at all premises for providing an earth system. Detailsof typical pipe and plate earth electrodes are given in relevent standard figures.
7.4 As far as possible, all earth connections shall be visible for inspection and shall becarefully made; if they are poorly made or inadequate for the purpose for which
they are intended, loss of life and property or serious personal injury may result.
7.5 The earthing of electrical installations for non-industrial buildings shall be done inaccordance with good practice IS 3043-1966.

8.

Inspection and Testing of Installation:
8.1 General: Before the completed installation, or an addition to the existing
installation, is put into service, inspection and testing shall be carried out inaccordance with the Electricity Rules. 2050. In the event of defects being found,these shall be rectified, as soon as practicable and the installation retested.
Periodic inspection and testing shall be carried out in order to maintain the
installation in a sound condition after putting into service. Where an addition is
to be made to the fixed wiring of an existing installation, the latter shall be
examined for compliance with the recommendations of the Code.
8.2 Completion Drawings-On completion of the electric work, initial wiring diagram
shall be verified at actual basis of works and submitted to the engineer-in-chargeor the owner's representative. All wiring diagrams shall indicate clearly, the main
switchboard, the runs of various mains and sub mains and the position of all
points and their controls. All circuits shall be clearly indicated and numbered in
the wiring diagram and all points shall be given the same number as the circuit inwhich they are electrically connected. Also the location and number of earth
points and the run of each load should be clearly shown in the completiondrawings.
8.3 On completion of wiring a general inspection shall be carried out by competentElectrical Engineer in order to verify that the provisions of this Code and that ofElectricity Rules, 2050 have been complied with. This, among other things, shall
include checking whether all equipments, fittings, accessories, wire/cables, usedin the installation are of adequate rating and quality to meet the requirement of
the load. General workmanship of the electrical wiring with regard to the lay out
and finish shall be examined for neatness that would facilitate easy identificationof circuits of the system, adequacy of clearances, soundness, contact pressure
and contact area. A complete check shall also be made of all the protective
devices, with respect to their ratings, range of settings and co-ordination between
the various protective devices.

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8.4 Testing of Installation – After inspection, the following tests shall be carried out,
before an installation or an addition to the existing instillation is put into service.
Any testing of the electrical installation in an already existing installation shallcommence after obtaining permit to work from the enginner-incharge and after
ensuring the safety provisions.
8.4.1 Switchboards
All earth connections shall be checked for continuity. The operation of the
breakers, switches and fueses shall be tested from all control stations.
Indication signaling lamps shall be checked for proper working. Contact
resistance of main and isolator contacts, cable's contact etc. shall bemeasured. All high and low voltage switchboards shall be tested for
dielectric test as per IS 8623 (part 1) 1977.
8.4.2 Cables
It shall be ensured that the cables conform to the relevant. Standards. Tests
shall also be done in accordance with good practice IS 1255-1967. The
insulation resistance before and after the tests shall be checked. The
insulation resistance between each conductor and against earth shall bemeasured. The insulation resistance varies with the type of insulation used
and with the length of cable.
8.4.3 Wiring Installation

NBC108V2.RV9a)The insulation resistance shall be measured by applying between earth
and the whole system of conductor or any section thereof with all fuses
in place and all switches closed, and except in earthed concentric
wiring, all lamps in position or both poles of installation otherwise
electrically connected together, a dc voltage of not less than twice theworking voltage, provided that it does not exceed 500 volts for
medium voltage circuits. Where the supply is derived from three-wire(ac or dc) or a poly-phase system, the neutral pole of which isconnected to earth either direct or through added resistance theworking voltage shall be deemed to be that which is maintained
between the outer or phase conductor and the neutral.

b)

The insulation resistance in megaohms of an installation measured asin (a) shall be not less than 50 divided by the number of points on thecircuit, provided that the whole installation need not be required tohave an insulation resistance greater than one megaohm.

c)Control rheostats, heating and power appliances and electric signs,
may, if desired, be disconnected from the circuit during the test, but inthat event the insulation resistance between the case or framework, andall live parts of each rheostat, appliance and sign shall be not less thanthat specified in the relevant Standard specification or where there isno such specification, shall be not less than half a megaohm.

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d)

The insulation resistance shall also be measured between all conductor
connected to one pole or phase conductor of the supply and all the
conductors connected to the middle wire or to the neutral or to theother pole of phase conductors of the supply. Such a test shall be madeafter removing all metallic connections between the two poles of theinstallation and in these circumstances the insulation resistance
between conductors of the installation shall be not less than thatspecified in (b)8.4.4 Efficiency of Earthing:
The earth resistance of each electrode shall be measured. Earth resistanceof earthing grid shall be measured. All electrodes shall be connected to thegrid and the earth resistance of the entire earthing system shall bemeasured. These tests shall preferably be done during the summer months.
8.5 Completion Certificate-On completion of an electrical installation (or an extension
to an installation) a certificate shall be furnished by the contractor, counter-signedby the certified electricla engineer under whose direct supervision the installation
was carried out. This certificate shall be in a prescribed form

9.

Lightning Protection of Buildings.
While every structure, theoretically, has a chance of being struck by lightning, thedegree of this chance varies depending on a number of associated factors, such as
lightning incidences, surroundings and types of terrain. For a certain group ofoccupancies, which form a source of danger, such as those housing explosive factories
of stores or flammable materials, complete protection against lightning shall be
provided. In other cases, it may be necessary to decide whether this protection iscalled for, under a given set of circumstances. There are a number of factors, affecting
the risk of the structure being struck by lightning and consequential effects of a
stroke, which are capable of assessment. There would be other factors, which are notcapable of such assessment in relative terms. Yet these may over-ride all otherconsiderations; for example, a requirement that there should be no avoidable risk tolife, or the overwhelming importance or value of the structure. In such cases lighting
protection shall always be provided. In other cases, however, it may be desirable to
make a decision on an assessment in terms of the chances of the structure being
struck. For this purpose, various factors denoting chances of the structure being struckby lightning and the total effect of these factors shall be assessed.

10.

Telecommunication and other services:
Layout arrangements, EPABX, methods for internal block wiring and otherrequirements regarding provisions of space, etc, may be decided depending as thenumber of phone outlets and other details in consultation with Engineer/Architect
and user.

References : National building code of India 1983
Electricity Act. 2049
Electricity Rule 2050
Regulations relating to electrical wiring installations in buildings(CTEVT) 1997.
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FORM OF COMPLETION CERTIFICATE(CLAUSE 8.5)
I/ We certify that the installation detailed below has been installed by me/us and tested andthat to the best of my/our knowledge and belief, it complies with Electricity Rules 2050.
Electrical Installationt at ………………………………………………………………………
Voltage and system of supply ………………………………………………………………….
Particulars of Works:a) Internal Electrical Installation.
No.

Total load

Description

hp/kW

Type or system of wiringi) Light point.
ii) Fan point.
iii) Plug point.
3-pin 5 A.
3-pin 15 A.
b) Others.

Type of starting.

1) Motors:
i)
ii)
iii)
2) Other plants:c) If the work invloves installations of over head line and/or underground cable.
1)i) Type and descriptionof overheadline.
ii) Total length and No. of spans.
iii) No. of street lights and its description.

2)i) Total length of underground cable and its size.
ii) No. of joints:
End joint:
Tee joint:
Straight through joint:

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Earthing.
i) Description of earthing electrodeii) No. of earth electrodesiii) Size of main earth lead
Test Results:a) Insulation Resistancei) Insulation resistance of the whole system of conductors to earth……………..Megohms.
ii) Insulation resistance between the phase conductor and neutral.
Between phase R and neutral………………..Megohms.
Between phase Y and neutral ………………..Megohms.
Between phase B and neutral…………………Megohms.
iii) Insulation resistance between the phase conductors in case of polyphase supply.
Between phase R and phase Y………………..Megohms.
Between phase Y and phase B………………..Megohms.
Between phase B and phase R………………..Megohms.
b) Polarity test:
Polarity of non-linked single pole branch switchesC) Earth continuity test:
Maximum resistance between any point in the earth continuity conductor including metal
conduits and main earthing lead………………..Ohms.
d) Earth electrode resistance:
Resistance of each earth electrode.
i)………………………Ohms.
ii)………………………Ohms.
iii)………………………Ohms.
iv)………………………Ohms.

Signature Of Electrical Engineer

Singature Of Contractor

Name and Address

Name and Address

NBC108V2.RV9

7 December 1993