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75 views21 pagesWiring 1
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/ 21
im in
rical Installation Estimating and Costing
01 WEATHER
CONDUCTOR INSULATION EATHER PROOe
5. Weather Proof Cables. These cables
Sutdoor wiring and for power
jal supply. These cables
See or PVC insulated or vuleanized rubber
ae eve conductors being suitably taped :
aaeeeace of vulcanized rubber insulated 4.Core Weather Proof Cable
otto) braided and then compounded with Tig, 34
weather resisting material. These cables are
wexlable in 240/415 volt and 650/1,100 volt grade
ara aiain. Weather proof cable is shown in Fig. 3.4.
‘Although TRS cables can be used for outdoor purposes
weather proof cables are generally used for outdoor services.
‘The different sizes of copper and aluminium cables with their current ratings and voltage
drops are given in Tables 3.1, 3.2, 3.3 and 3.4.
%. Flexible Cords and Cables. The flexible cords consist of wires silk/cotton/plastic
covered. Plastie cover is popular as itis available in different pleasing colours. Flexible cords
Hera Gnned copper conductors. Flexibility and strength is obtained by using conductors
having larger number of strands. These wires or cables are used as connecting wires for such
purposes as from ceiling rose to lamp holder, socket outlet to portable apparatus such as
Padiow. fans, lamps, heaters etc. The flexibility of such wires facilitates in handling the
appliances and prevents the wires from breakage. These must not be used in fixed wiring
are used for
supply or industri
It grades. These cables are not affected by heat or
but due to their higher cost,
EFUSIPERE current Ratings of Copper Conductor Single Core Cables (VIR, PVC or Polythene Insulated
including TRS, PVC or Lead Sheathed)
Size of Conductor Two Cables DC or Three or Four Cables
Single Phase AC Balanced Three-Phase AC
Nominal Area| Number and |Current Rating i turrent Rati roximate
rine tame tan| tn ampcce | Length af Ran | in Amperes | Zenath of Bax
in mm For 1V Drop For One Volt
in Metres Drop in Metres |
10 waz 5 49 5 |
25 3/1.06 16 34 13 |
40 710.731 20 aa 15
60 711.06 28 40 25
80 mag 36 49 32
100 7.40 43 55 39
15.0 71.63 52 70 48
20.0 19/1.12 62 16 56
25.0 19/1.40 “ 88 67
35.0 1911.63 7 100 388.
50.0 19/1.80 160 19.4 155 Current Ratings of Alumi
Insulated including TRS,
Wiring Materials and Accessories
inium Conductor Single Core Cables (VIR, PVC or Polythene
PVC or Lead Sheathed)
‘Size of Conductor Two Cables DC or Three or Four Cables Four Cables DC
Single Phase AC Balanced Three Phase or Single Phase AC
Nominal} Number and| Current Rating] Approximate| Current Rating] Approximate| Current] Approximate|
Area, | Diameter | in Amperes | Run For | in Amperes | Run For | Rating | Run for
in mm? | of Wire in One Volt One Volt in | One Volt
aa Drop Drop in |Amperes| Drop in
in Metres ‘Metres ‘Metres
fas | inao 10 23 ° 29 9 25
} 25 11.80 15 25 12 36 34
4 2.24 20 29 17 3.9 41
6 172.80 27 34 24 43 43
10 | 13.55 34 43 31 34 34
16 | 71.70 43 54 38 70 68
25 712.24 59 68 54 85 85
35 | 772.50 69 72 62 98 90
so | me 91 79 82 tor | 69 | 10
| 7 19/2.24 134 9.0 131 95 - | _
95 | 1972.50 153, 98 152 10.0 : =
120 | 3772.06 165 108 161 109 = =
150 | 3772.24 181 14 179 na 7 =
185, 37/2.50 209 12.3 207 1.8 - | -
25 | 7/280 240 135 235 a ale
Current Ratings of Copper Conductor Twin, Three and Four Core Cables (VIR or Polythene
Insulated and Sheathed With Tough Rubber, PVC or Lead)
Size of Conductor
One Twin Core Cable DC
or
Single Phase AC
One Three-Core or Four
Core Cable Balanced Three
Phase AC
Nominal Number and Current Approximate Current Rating | Approximate
Area in Diameter of | Rating in Run For One | in Amperes | Run For One
mm? Wire in mm | Amperes Volt Drop in Volt Drop in
Metres Metres
10 VLIZ 5 46 5 55
15 3/0.737 10 3.0 8 53
25 3/1.06 15 3.0 10 55
40 31 20 34 18 85.
60 7.06 28 40 20 64
80 mz 36 16 25 76
100 7.40 “3 52 30 88
150 71.63 53 64 3t no
200 191.12 62 70 43 ng
25.0 191.40 7 82 82 137
35.0 19/1.63, 97 98 68 15.8
50.0 19/1.80 140 11.3 88 18.3 Internal Wiring
wn ae Estimation
General Rules For Wiring—Determination of Number of Points —Determination of Total
Load—Determination of Number of Sub-Circuits—Determination of Ratings of Main Switch
and Distribution Board—Determination of Size of Conductor—Approximate Current Density
For Determination of Size of Cable For Internal Wiring For Indian Conditions Keeping in
View The Reasonable Voltage Drop—Layout—Estimates—Problems.
GENERAL RULES FOR WIRING
For estimation of internal wiring it is necessary on the part of estimator that he be fully
conversant with the general rules followed for internal wiring. The general rules, which are
to be kept in mind in execution of internal wiring work, are:
1
th teal
_—
Every installation is to be properly protected near the point of entry of supply cables by
a two-pole linked main switch and a fuse unit. In a two-wire installation if one pole is
permanently earthed, no fuse, switch or circuit breaker is to be inserted in this pole. A
3-pole switch and fuse unit is to be used in 3-phase supply.
The conductor used is to be of such a size that it may carry load current safely.
The conductor installed is to be safe in all respects.
Every sub-circuit is to be connected to a distribution fuse board.
Every line (phase or positive) is to be protected by a fuse of suitable rating as per
requirements.
A switch board is to be installed so that its bottom lies 1.25 metres above the floor.
(@ All plugs and socket outlets are to be 3-pin type, the appropriate pin of socket being
connected permanently to the earthing system.
(6) Adequate number of socket outlets are to be provided at suitable places
80 as to avoid use of long lengths of flexible cords.
© Only 3-pin, 5 A socket outlets are to be used in all light and fan sub-circuits and only
3-pin, 15 A socket outlets are to be used in all power sub-circuits. All socket outlets
are to be controlled by individual switches, which are to be located immediately
adjacent to it. For 5 A socket outlets, if installed at a height of 25 cm above the floor
level, the switch may, if desired, be installed at a height 1.30 metres above the floor
level. In situations where a socket outlet is accessible to children, it is recommended
to use shuttered or interlocked socket outlets.
(@) In case an appliance requiring the use of a socket outlet of rating higher than 15 A
is to be used, it is to be connected through a double pole switch of appropriate rating,
In no case a socket outlet of rating higher than 15 A is to be installed.
in all rooms
155
_ —_—e yp
(©) Socket outlets are not to be located centrally behind the appliances with which the,
are used. Socket outlets are to be installed either 25 em or 1.30 m above the fy
level as desired. ,
() No socket outlet is to be provided in the bathroom at a height less than 1.30 metge,
@ Depending on the size of the kitchen, one or two 3-pin 15 A socket outlets are tg,
provided to plug-in hot plates and other appliances. Dining rooms, bedrooms, livin,
rooms, if required, each is to be provided with at least one 3-pin, 15 A socket outiy
(Refer to IS 4648-1968) -
8. @ All incandescent lamps, unless otherwise required, are to be hung at a height of;
metres above the floor level.
©) Unless otherwise specified, all ceiling fans are to be hung 2.75 metres above the foo.
(Refer to IS 4648-1968). an
9. @ Lights and fans may be wired on a common circuit. Each sub-circuit is not to have
more than a total of ten points of lights, fans and socket outlets. The load on each
sub-circuit is to be restricted to 800 watts. If a separate circuit is installed for fan.
only, the number of fans in that circuit is not to exceed ten.
(®) The load on each power sub-circuit is to be normally restricted to 3,000 watts. In no
case more than two socket outlets are to be in one power sub-circuit. (Refer to Is
4648-1968).
10. No fuse or switch is to be provided in earthed conductor.
11. Every circuit or apparatus is to be provided with a separate means of isolation such as
a switch.
12. All apparatus requiring attention are to be provided with means of access to it.
13. In any building, light and fan wiring and power wiring are to be kept separate.
14. In 3-phase, 4-wire installation the load is to be distributed equally on all the phases.
15. No additional load is to be connected to an existing installation unless it has be
ascertained that the installation can safely carry the additional load and that the earthins
arrangements are adequate.
Lamp holders used in bathrooms are to be constructed or shrouded in insulating materi:
and fitted with protective shield and earth continuity conductor is not to be of size le
than 7/0.915 mm.
The metal sheaths or conduits for all wiring and metal coverings of all consumer appa!
or appliances is to be properly earthed in order to avoid danger from electrical shock 4
to leakage or failure of insulation.
Electrical Installation Estimating and Costing
16.
17.
18. Each sub-circuit is to be protected against excessive current (that may occur either de
to overload or due to failure of insulation) by fuse or automatic circuit breaker.
All light conductors are to be insulated or otherwise safeguarded to avoid danger.
. After completion of work the installations are to be tested (the tests are to be carried
as described in chapter 5) before energisation.
8.2, DETERMINATION OF NUMBER OF POINTS (LIGHT, FAN, SOCKET-OUTLETS)
As regards the determination of number of li
details in chapter 7. The number of. points is det
level required (Table 7.1) and the luminous e
edit
ght points, it has already been discussed
termined as per size of the room, illumins"
ficiency of the lamps to be used. Internal Wiring Estimation 37)
‘ Fan size in mm Type Air delivery in m?/minute
900 mm Capacitor ac 140
de 140
1,200 mm Capacitor ac 215
de 215
1,400 mm Capacitor ac 270
de 270
1,500 mm Capacitor ac 300
de 300
The number of fan points is determined as per measure (length, width and height) of the
room and the size of the fans to be used. Ordinarily 3 air- exchanges are expected to take
place per hour in room.
The air delivery for fans of different sizes at test voltage and at full speed is given in
Table 8.1.
As regards the determination of number of socket outlets, recommended schedule of
socket outlets is given below : (Refer to IS 4648 — 1968)
Location Number of 5 A Socket outlets Number of 15 A Socket outlets
Bedroom 2t0 3 1
Living-room 2 to 8 2
Kitchen 1 2
Dining-room 2 1
Garage 1 1
L For refrigerator 1
For air-conditioner 1
Verandah 1 per 10 m* 1
Bathroom 1 1
8.3. DETERMINATION OF TOTAL LOAD
a determination of load of an installation the following rating may be assumed unless the
‘ues are known or specified.
Fluorescent lamps (choke type) 50 W (40 W + 10 W)
) Incandescent lamps, fans and socket outlets — 60 watts
it) Power socket outlets 1,000 watts
(iv) Exhaust fans—as per capacity of exhaust fans. Electrical Installation Estimating and Costing
8.4, DETERMINATION OF NUMBER OF SUB-CIRCUITS _
The number of sub-circuits are decided as per number of points to be wired and total gg
to be connected to the supply systems.
In one light and fan sub-circuit the maximum load that ean be connected is 800 way,
and the maximum number of points, which can be wired is 10.
In one power sub-circuit the maximum load that can be normally connected is 3,054
watts and the number of socket outlets, which can be provided is 2
8.5. DETERMINATION OF RATINGS OF MAIN SWITCH AND DISTRIBUTION BOARD
The current rating of the main switeh is decided as per total current of the circuit ty hy
controlled by it.
The number of ways and current rating of the distribution board is decided as pe, |
number of sub-cireuits to be connected to it and current of the sub-circuit having high.
current rating.
a ee te
8.6. DETERMINATION OF SIZE OF CONDUCTOR
There are three points, which must be taken into account, while determining the size o
conductor for internal wiring for a given circuit.
() Minimum size mainly for mechanical reasons.
(i) Current carrying capacity.
(iii) Voltage drop.
(i) Minimum Size of The Cable. The conductor used in domestic wiring (except
flexible and fitting wires), according to the regulation in our country, must not be of size less
than 1/1.12 mm in copper or 1/1.40 mm (1.5 mm?) in aluminium wire. For flexible cords and
fitting wires, a smaller size is permissible viz. 14/0.193 mm. Lead-in wires to be not less
than one square mm copper or 1.5 square mm aluminium and protected from abrasion.
(i) Current Carrying Capacity. The wire or cable should be of size sufficient to car
the maximum circuit current continuously without overheating. From Table 8.3 the size
wire or cable can be determined corresponding to maximum current of the circuit. The
following points are noteworthy:
(a) The maximum possible currents are not in exact proportion to the sectional areas of
the conductors. The amount of heat developed due to flow of current is proportional to the
resistance of the conductor and consequently in inverse proportion to the sectional area, but
the temperature rise does not only depend on the quantity of heat developed but also on the
rate of dissipation of heat from the surface of conductor. The size of the conductor of the cable
increases, the permissible current density decreases.
(6) Paper insulated or lead covered cables are allowed to carry larger currents than VIR
cables of the same size (except in the smaller size in which the maximum permissible
currents are the same). This is due to the fact that the impregnated paper insulation ca!
withstand higher temperature than VIR cables without injury, PVC cables are, howevel-
predominantly used.
(c) When there are several cables bunched together in the same conduit or more than 0"
conductor in lead covered cable the current carrying capacity for the same x-sectional are
of conductor is less than that of a pair of cables in conduit.
(iii) Voltage Drop. Maximum voltage drop from supply terminals to any point on
installation is not to exceed the prescribed limit viz 2% of the supply voltage plus one V0
for light load wiring and 5 per cent of declared supply voltage for power load wiring.
ali
|
|
| Internal Wiring Estimation
Copper and Equivalent Aluminium Conductor Cables Current Ratings
Copper Conductor
Aluminium Conductor
of eable | Current Rating | Approximate | Size of cable | Current Rating | Approximate
in amperes | ampere-metren in amperes | ampere-metres
per volt drop per volt drop
Nom: | 2-core] 3 or 4 No. and] Nom | 2-core| 4 or
of | inal | cable | core dia of | -inal | cable | 4-core
in| area in cable wire in| area in cable
nor mm | mm*
| 09 | 5 5 55 nao] 16 | 10 9 |
p76] 129 | 10 10 72 wad | 15 | i 9
pois} 193 | 15 13 10 vis0 | 25 n SA ee
0736] 2.90 | 20 15 165 1224] 40 | 2 15 615 |
0.915 452 28 22 260 1/2.80, 6.0 a 21 93
112 6.45 36 29 380 Vi 10.0 A 27 1458
1.32 9.35, 43, 34 ‘545 WLIO 16.0 43, 6 | 238.0
pnes| 1450 | 53 | 42 820 7224 | 250 | 5 | 46 4080
19.35 62 50 1,050 712.50 35.0 oo 55 495.0
25.80 4 59 1,475 7/3.00 50.0 a1 Cy 690.0
38.70 7 78 2,200
ee
1. The Table 8.3 gives the current rating for single, twin or multi-core cable with VIR,
PVC, polythene insulation including TRS, PVC lead or aluminium sheathed, run singly
or in conduit, troughing, casing or in free air. The ratings are based on an ambient
temperature of 30°C.
Use multiplying factor of 1.13 for 25°C, 0.86 for 35°C, 0.69 for 40°C and 0.47 for 45°C.
If more than one cable is used, multiply the given current ratings by a factor of 0.8
for 2 cables, 0.7 for 3 cables and 0.65 for 4 cables.
To determine the size of cable multiply the load current of the circuit by the length of
he circuit cable (lead and return for two-wire circuits and lead only for 3-wire balanced load
it), find the maximum permissible voltage
pere-metres by the maximum voltage drop Peay _ Now look at the voltage drop
le 8.3 and select the next higher size.
|_Voltage drop on ac cables is greater than de due to in
is very small (negligible for small Bigs) and need
the given datas, divide the total Electrical Installation Estimating and Costing
Permissible voltage drop = 52> x 240 + 1 = 5.8V
Ampere-metres per volt of permissible drop
Total ampere ~ metres in the circuit
1,240
Permissible voltage drop 5.8
From Table 8.3 the copper conductor eable having voltage drop of figure next to the figure of ampere
metres per volt drop, determined above, is 19/1.32 mm having current carrying capacity of 74 ampers,
and giving 1 volt drop per 1,475 ampere-metres.
Since the current carrying capacity of the copper conductor cable of size 19/1.32 mm selected ig
74 A, more than circuit maximum current of 60 amperes, and voltage drop caused by this cable wi
7,200
ay
Groner !
Determine the size of cable used for a sub-circuit (light). The supply voltage may be taken as
240 volts ac.
be equal to 4.88 volts, less than permissible voltage drop of 5.8 volts, hence selected
Solution: Maximum load of a sub-circuit (light) =800 watts
Assuming the load as pure light load, the power factor may be taken as unity.
Current in the sub-circuit = 520 = 3.33 amperes
Computing the voltage drop and seeing that the same is within permissible limits of 2% of
declared supply voltage plus 1 volt the most suitable cables are
Copper conductor cable of size 1/1.12 mm (the least permissible size).
Aluminium conductor cable of size 1/1.40 mm (the least permissible size) Ans.
oe)
Determine the size of cable required to carry the maximum current of 50 amperes. It is giver
that length of cable is 500 metres and allowable voltage drop is 5% of declared supply voltage.
Declared voltage is (i) 400 volts de and (ii) 400 volts ac.
Solution: Maximum current to be carried, I,,,, =50 A
Length of cable, 1 =500 metres
‘Total ampere-metres in the circuit =500 x 50 = 25,000 ampere-metres
Declared voltage, V =400 volts
The permissible voltage drop, v =400 x % 20 volts
Ampere-metres per volt of permissible volt drop = Total ampere~ metres in the circuit
Permissible voltage drop
25,000
20
(i) When supply voltage is de, copper conductor cable of 19/1.32 mm (from Table 8.3) of curre®!
carrying capacity of 59 amperes and causing 1 volt drop per 1,475 ampere-metres will be ™°*
suitable.
Voltage drop with the cable of size 19/1.32 mm
25,000
“Tiig = 17-0 volts, less than permissible voltage drop of 20 volts
1,250 Internal Wiring Estimation m1)
(ji) When supply voltage is ac copper conductor cable of 19/1.32 mm (from Table 8.3) of current
carrying capacity of 59 amperes and causing 1 volt drop per 1,327 (0.9 x 1475) ampere-metres (taking
‘account inductance and capacitance of the cable) will be most suitable.
Voltage drop with the cable of size 19/1.32 mm
= 25,000 _
1,397 = 18.0 volts less than the permissible voltage drop
into
87. APPROXIMATE CURRENT DENSITY FOR DETERMINATION OF SIZE OF CABLE
FOR INTERNAL WIRING FOR INDIAN CONDITIONS KEEPING IN VIEW THE
REASONABLE VOLTAGE DROP
coTCarEnee!’w—jw—_
‘The size of the conductor depends upon the current, it is required to carry.
The current rating of standard size of cable is given in Table 8.3 and so the cable of
suitable size can be determined as per current to be carried by it. A rough and ready guide
which is convenient to remember for determination of size of cable is given below :
Current density of For x-section of conductor of
5 amperes/mm” less than 5.00 mm?
4 amperes/mm? 5.00 mm? to 10.00 mm*
2.5 amperes/mm? 10.00 mm* to 20 mm?
2.0 amperes/mm* 20.00 mm? to 40 mm?
The maximum permissible currents in different sizes of conductors are as follows.
Size Cross-section in mm? As per above rule IEE Ratings
14/0.193 0.387 1.9 2
23/0.193 0.645 3.220 4
40/0.193 1.097 5.485 7
7010.193 1.936 9.680 13
110/0.193 3.097 15.485 18
162/0.193 4.516 22.580 23
waz 0.96 48 5
310.736 1.29 6.45 10
310.915 1.93 9.65 13
710.736 2.90 14.5 15
10.915 4.52 22.6 22
WAZ 6.45 25.80 29
Contd... ating and Costing
1162 Electrical Installation Estim:
a 2 | Ax per above rule
Cross-section in mim*
374
36.25
7/1.626 of 868
a 48.4
19/1.12 = |
19/1.32 26.80 51.6
19/1.62 38.70 114 -
fe determined from above rules has a safer margin ove,
It will be noticed that the cable
the IEE rule and is easier to remember.
8.8, LAYOUT
Position of Main Board. The supplier meter board consisting of energy meter and main
fuse is placed as near the point of entry of the service cable as practicable. The consumers
main board consisting of main switch and fuse is placed as near the supplier board as
possible. Meter board, meter, and fuse is supplied, fixed and sealed by the supplier and two
leads (one phase and one neutral) are taken out from the meter to be connected to the
consumer's main board, this point is the starting point for internal wiring. Supplier main
board and consumer main board are fixed at a height of about 1.5 metres.
Position of Switches and Socket Outlets. The position and height of the switches and
ocket outlets should not be selected in a haphazard way. It is to be ensured that all the
ches are fixed at the same height unless there is a definite reason to the contrary. The
most usual heights are 1.25 metres, 1.35 metres and 1.4 metres above the floor. In nurseries
and children’s hospitals a much higher standard height is desirable, say, 1.6 metres to L$
metres. In schools 1.8 metres is a good standard height. While fixing the position of socket
outlets the position or character of the apparatus to be connected to them must be kept in
view. Switches or switchboards should be fitted by the side of usual place of entry.
Height and Size of Lamps. The correct height, at which the lamps must be hung depends
upon the size and shape of the room and the class of shades used, and in large rooms and
spaces 2.25 metres or 2.5 metres is a good average height for ordinary pendants or brackets
to give a general illumination in the room.
In a medium sized dwelling house 10 watts per square metre of floor area gives enough
guide for the size of filament lamps, if the decoration of the rooms is of light finish and the
lamps are only obscured by shades with a light finish, In bedrooms a lower average wattage
per square metre is sufficient. In case use of fluorescent tubes is made, a considerably lowet
aggregate wattage will suffice. ’ ”
Dining-Room. In a small and average sized dining-room, the right place for the light sour?
is over the centre of the dining table. In large dining-rooms an additional point is requ
for the service table in the form of either a pendant or bracket. One or two 5 ampere socket
outlet and one 15 A socket outlet points should be provided for portable lamps and other
appliances,
Drawing-Room. For a drawing-room no hard and fast rule can be mentioned, as uc
depends on the disposition and style of the furniture and decoration, In a small or medit™
sized drawing-room sufficient illumination will be obtained from a central light, but it # Internal Wiring Estimation m 163
Jarger rooms brackets are required and also soc!
standards.
Bedroom Lights. In a bedroom one light is necessary, a few centimetres in front of the
ing table, hanging at a height of about 2 met
a im eae u tres from the floor between the dressing
table and the person using it. If only one light is to be provided in bedroom, then two way
pitching is essential, one near the door
and the other by the bed. A second light is usually
required over the bed for reading, which should be fairly close to the wall, In the bedrooms
which are fitted with basins, a third light is required over the basin. The
for bedroom lighting has already been given in Art, 6.5. In bedrooms 2 to 3
and one 15A socket outlet should be provided.
‘ket outlet points for portable floor or table
reuit diagram
5A socket outlets
Kitchen and Scullery Lights, In kitchens light should be provided as hanging down close
in front of the cooking burner. A second light, however, may be provided where light is
required and not necessarily in centre of the room.
In sculleries the light should be provided over the sink.
In kitchens two 15 ampere socket outlet points and one 5 ampere socket outlet should
be provided.
Bathroom Lights. Special precautions must be taken in selecting the position and character
of points and switches to avoid danger. The light should be a well glass fitting or an
equivalent totally enclosed fitting fixed directly on the ceiling and out of reach of a person
standing on the edge of the bath. The switch should be either outside the door or in case it
is to be provided inside, it must be out of reach of a person standing in the bath. Flush type,
preferably, switch should be used in bath room.
Staircase Lights. In lighting the staircase it should be remembered that some light at any
rate should always fall directly on the bottom of each flight of stairs so that the rises are
not in shadow. The staircase light point is controlled from two points, one near the bottom
and other near the top of the staircase. The wiring diagram for staircasing lighting has
already been given in Art. 6.4.
ne
Draw @ neat diagram showing the position of the switchboards, distribution board and accessories
With necessary connections in looping-in system for a hall of 15 m x 6 m x 4.5m height. The
hall is to be fitted with fan and light points, Make your own assumptions for the number of light
and fan points and other missing datas.
Solution : Floor area of hall = 15 x 6 = 90 m? |
Taking 10 watts/m? of surface area as illumination requirement we will require 10 x 90 = 900
Watts i.e, 10 lamps of 100 watts each will be fitted and 4 ceiling fans of 60 watts each will be fitted.
Positions of lamps and fans are shown in Fig. 8.1
Connected load = 10 x 100 + 4 x 60 = 1,240 watts.
Assuming supply voltage of 240 volts
1,240
Line current = “ya
So 3/ 0.736 mm, twin core, 650 V grade, copper conductor PVC cable having current carrying
“*acity of 10 amperes will be used between meter board and main distribution board
coy 5866 the maximum number of points in a circuit must not exceed 10 and maximum load which
“0 be connected in one cireuit through loop-in system, is 800 watts, we will have two circuits. Eac!
‘hem feeding 7 points and a load of 620 watts.
5.2. amperes ql Electrical Installation Estimating and Costing
é
oo
Fa
bs ba
y
f é
£ lls él] gq f
= a= = = = S fe fe
‘sm 30m ts yf
Sm tem 30m tom 5A] ||cam led
& 2m i Hey
| 35m
st
| . | =
-—————— 1m
Layout of Wiring
Fig. 8.1
Full-load current in each circuit = 2 = 2.6 amperes —_
So 1/112 mm, single core, 650 V grade, copper conductor
PVC cable will be used for circuit wiring.
Other datas assumed are :
(® The height at which meter board, main switchboard are
to be fitted = 1.5 metres from ground level.
(ii) The height at which casing-capping will be run = 3.5
metres from ground level.
DISTRIBUTION BOARD
(iii) The meter board is to be fixed on entrance wall at a
distance of 2 metres from the left hand side wall.
Gea SBNo# SBNo3_ SBNo2 SBNot
Draw the electric circuit and estimate the quantity of material
and total cost for PVC wiring system used in a hall of
15 m x 6 mx 4 + m height. The hall is to be fitted with fan switck
BOARD No!
points and light points. Make your own assumptions for the
number of fan and light points and other missing data:
Solution : Floor area of the hall = 15 x 6 = 90 m? Hor ko
Taking 10 watts/m? of surf ce area as illumination Single Line Diagram
requirements we will require 10 x 90 = 900 watts i.e. 10 lamps Fig. 8.2
of 100 watts each will suffice, 4 ceiling fans of 60 watts each, will be fitted. Position of lamps a™4
fans is shown in Fig. 8.3
Connected load = 10 x 100 + 4 x 60 = 1,240 watts.
Assuming supply voltage’ of 240 V Internal Wiring Estimation g 165
uy & ly le
° ° Oo oO oO
mf few fw Bn ot
be u Lb bo Lio
° oO oO oO O°
15h — 3M—#}+ — 3M —+}>— 3M ele — 3M» is+
M
15M
Fig. 8.3
Line current = 4240
240
So 1/1.80 mm, single core, 650 V grade, aluminium conductor PV C cable having current carrying
capacity of 15 amperes will be used between meter board and main distribution board
Since the maximum number of points in a circuit, must not exceed 10 and maximum load which
can be connected in one circuit is 800 watts, we will have two circuits, each of them having 7 points
and a load of 620 watts.
Since maximum load current is 5.2 amperes and there are two circuits, 240 V, 16 A, DPIC switch
fuse of any make approved by IS will be used as main switch.
2way, 240 V, 16 A/way, IC double pole distribution board of any make approved by IS will be
used as main distribution board.
2A
620
240
1/1.40 mm, aluminium conductor, single core, 650 volt grade, PVC cable having current carrying
capacity of 10 amperes will be used as phase and neutral wires beyond the main distribution board
Other datas assumed are :
Since full load current in each circuit 26A
(i) The height at which meter board, main switchboard are to be fitted = 1.5 metres from ground
level.
(ii) The height at which conduit will be run = 3.5 metres from ground level.
(iii) The meter board is to be fixed on entrance wall at a distance of 2 metres from the left hand
side wall.
Layout of wiring is shown in Fig. 8.1.
Length of PVC Conduit
Cireuit No 1. From meter board to main board = 0.2 m
Vertical run above main board 2.0 m
Horizontal run along the wall above the main entrance = 2.2 m
Horizontal run along the left hand wall up to L; 15-15 = 135m
Vertical drop along the left hand side wall up to switch boards SB, and SB,
=2+2=40m
Vertical run up to ceiling and run along the ceiling up to points Ly, Ly, Ly, Ly and L;
= 56x (1+15)= 125m
Vertical run up to ceiling and run along the ceiling up to points F, and
Creu = 2x (+3)
itNo 2. ‘The horizontal run along the entrance wall = 3.8 m
Horizontal run along the right hand side wall up to Ly = 15 ~ 1.5 = 13.6 m
8.0m J Electrical Installation Estimating and Costing
Vertical dr ng the right hand side wall up to switch boards SB, and SB
ht hand si 1 5 7
along the rigl
Vertical run up to ceiling and run along the ceiling up to points Lg, Ly, Ly, Ly and L,,
= 5x (1 +15) = 125m
a long ceiling up to points F, and F,
Vertical run up to ceiling and run along 6 up to Poi ne Fs an a som
Total length of PVC conduit run = 0.2 + 2.04 2.2+ 13.5 + 404195,
8.0 + 3.8 + 13.5 + 4.04 12.5 +95
= 84.2 metres
Wastage and length used in joints 15% = 12.63 metres
‘Total length of PVC conduit required = 84.2 + 12.63
96.83 metres = 100 metres (say)
Length of 1/1.80 mm, single core, 650 V grade, aluminium conductor PVC cable from meter boar
to main board = 0.50 metre (including wastage)
Length of 1/1.40 mm, aluminium conductor, single core, 650 V grade PVC (phase wire) cable
Circuit No 1. From main distribution board to switchboard SB,
=2+22415+20=7.7m
From switchboard SB, toL, =2+1415= 4.5 m
From SB, to F, =2+15+14+3=7.5m
From SB, toL, =2+341415= 7.5m
From SB, toL, =2+6+1415=10.5m
From $B, to SB, = 2+9+2=13.0m
From SB, toL, =2+1+15= 4.5m
From SB, toF, =2+15+14+3.0=75m
From SB, toL; =2+3+14+15=7.5m
Circuit No 2. From main distribution board to SB, = 2+ 3.8 + 1.5 +2
From SB, to Ly =2+14+15=45m
From SB, toL;=2+3+14+15=75m
From SB, to F,
From SB, to Ly =2+6 +1 +1.
From SB, to SB, = 2+ 9 + 2= 13.0 m
From SB, to Ly = 2414 1.5
From SB, to Fy =2+1.5 + 1.0 +3
From SB, to ly =2+ 341+ 15 .
y Total length of phase wire = 7.7 + 4.5 + 7.5 + 7.5 + 10.5+130+4.5+7.5+7.5+93+4°
+ 7.5 + 10.5 + 10.5 + 13.0 + 4.5 + 7.5 + 7.5 = 145.0 m
For wastage and connections = 20 per cent of 145.0 m = 29.0 m
Total length = 145 + 29 = 174.0 m
2Q+45+14+3=1
Length of Neutral Wire
Circuit No 1. From main distribution board to L, = 2 + 2.2 + 1.5 + 1.0 + 1.5
From L, to F, =1.5+1415+1+3=80m Internal Wiring Estimation
Fy
TO CIRCUIT No. 2
111.40 mm
ALUMINIUM
CONDUCTOR
CABLE
2.WAY 16AWAY
eT 240 v, 1c
240 V, 164
L- DPIC SWITCH
111.80 mm
ALUMINIUM
CONDUCTOR CABLE
— PHASE WIRE
NEUTRAL WIRE ia
HALF WIRE —— Frou meter
— EARTH WIRE BOARD
Circuit Diagram of Lamps and Fan in Circuit No. 1
Fig. 8.4
From F, toLy =3+1+1.5+1+15=80m
From L, to Ly =15+14+8+1+15=80m
From L, to Fy =15+1+15+10+3.0=80m
From F, toL,=3+1+15+14+15=80m
From L, toL, =15+14+3+1+15=80m
Cireuit No 2. From MDB to L, =2+38+15+1+15=98m
From L, toL; =15+1+3+1+15=80m
From L, toF, =15+1+15+14+3=80m
From F, tol, =3+1+15+1+15=80m
From Ly toby =15+1+8+1+15=80m
From Ly to F, =16+1+15+1+3=80m
"
From F, to Ly =3+14+15+1415=80m
Total length of neutral wire = 114.0 m
Wastage and used in connections, 10% = 11.4 m
Total = 125.4 m
Total length of 1/1.40 mm wire = 174 + 125.4 = 299.4 = 300 m (say)
The method used for determining the length of phase and neutral wire is very laborious one.
A: general rule the length of phase wire, may be taken approximately two times and that of neutral
ire approximately equal to the length of the route (conduit) i.e. total length of cable required may
‘aken as three times of the route (conduit length).
imei lh® length of cable required from approximate formulae (mentioned above) = 3 x 100 = 300
es, the same as determined from the method adopted formerly.
Length of ire. Ei ire is required for socket outlets and main switch. Since no
weet outlet is hee. tod earth wire of 14'SWG (GI) of 0.26 m length will be sufficient for
'ng the main switch and main distribution board. a
Electrical Installation Estimating and Costing
B BASIS OF ITEM WISE RATES
ESTIMATE ON 1
[S.No] Description of Material With Quantity Rate
Full Specifications Required
Quantity | Unit] @ | PT Per
1, | 240 V grade, 16 A, DPIC switch fuse 1 no | 300 }00 | each
unit
2. | 2.way, 240 V, 16 Alway MCB type
‘ le distribution board
ce een Board] 1 do | 300 }00| do | 900 {00 | DB wien
mcp} 2 do | 300/00! do | 600] 00 | mew,
3. | Teak wood boards double
() | 30 em x 25 em 1 do 900} do | 00 | For main
board
(i) | 25 em x 20em 4 do | 65}00] do | 260/00 | For swine
board
4. | PVC conduit pipe, 25 m diameter 100 m 22/50] m | 2,250 |00
5. | 1/1.80 mm, single core 650 V grade
aluminium conductor PVC eable 05 | do | 10/00] m 0
6 | 1/1.40 mm, single core 650 V grade
aluminium conductor PVC cable 300 do 3/00) m 900 | 00
7. | Piano switches; one-way, 5A
surface type 14 | nos | 12}00| each | 168 |o0
Round wooden blocks 10cm x 4m M4 | do} 16/50] do | 231/00
9. | Ceiling rose two-plate PVC type 4 do 12/00} do 168 | 00
10. | Pendant holders (PVC) type 10 do 18/00} do 180 | 00
11. | Flexible wire 23/0, 193 mm 25 m 8/00) m 200 | 00
12. | Earth wire 14 SWG GI wire 0.25 m 10/00} m 2/50/1 metre
weighs 30
gms app
18, | Earthing thimbles with bolts and nuts | 4 nos | 15 00] each] 6000
14. | Wooden screws |
51 mm for fusing boards 50, do 45/00} 100 22 | 50
19mm for fusing switches 100 do 30/00 | 100 30 | 00 |
15. | PVC sheets for mounting switches |
ceiling rose, associated sizes 38 do] 22 [50] each! 855/00 |
16. | Cement, sand, paint, varnish ete 300 {00 | Lump sum
provision
Total | 6,923 00
Labour cost @ 60 per point | {080 |p 2 Points for
Total | 8,003 ]00 | MBD and
} Contingencies 6% | 400 [0 | 2 Points for
Grand Total {8,403 [oo | DB
Say % 8,420.00 Internal Wiring Estimation ae
ESTIMATE ON THE BASIS OF SU
LY/FIXING RATES
— ya
Description of Material With "
5 No Full Specifications Rranticy Rate | Amount | Remarks
fo | Quantity | Unit} & | Pl per |e | P
1-7, | Supply and fixing of 16 A, 240 V grade ~ | ~ —
| DPIC rewirable type switch fuseuniton | ho
poard complete is all respects
Supply 425 |00 | each | 425 |00
Fixing 50/00] do | 50 |oo
2, | Supply and fixing of flush mounted
2away distribution board without MCBs 1 é
complete in all respects |
Supply 650 }00] do | 650 | 00
Fixing 65 |00| do 65 | 00)
3, | Supply and fixing of MCBs 5 A, 9kA in |
item no. 2 above 4 do
Supply 200 |00| do | 800 |00 |
| Fixing 15 }00| do | 60 | 00
4, | Wiring of points for light with 1.6 mm?
insulated single core wire in PVC con-
duit pipe concealed in wall complete in 10 | do
all respects |
Supply 250 |00 | do | 2.500 |00 |
| Fixing 90 |00| do | 900 |00 | |
| |
5. | As above but for fan points 4 do
Supply 340 |00 | do
Fixing 90 |00| do
Total
Contingencies 5 %
Grand Total
Say
Note: Cost of the work comes out’to be more with rates on the basis of items as the items are to be
Purchased in small quantities and the labour charges are also higher because the work is small
Ea
Draw the electrical eireui i }
electrical circuit and estimate
quantity of materials and their cost Pe eatesad
feduired for PVC casing-capping used ENTRANC
; D
Seis amerncity ofeaia = fay
te metres and one plug point is to oa 7
ovided in each room. + poo t
cc wis s688thn fameasm wi
No. of light points = 6
No, of fan points = 1 2. +2
No. of plug points = 2 je 84 meres al
wee, Per recommendation of ISI the
(ou, of cach light, fan and plug socket
than power sockets) may be taken as
=
Fig. 8.5 |
60 watts for the purpose of load estimation. FO
i) Electrical Installation Estimating and Costing
x 60 = 480 watts ozmT] LiMo
8 x 60 = 480 wa o2m | Awe
ed is
Connected loa
Since number of points to be connect
8 (less than 10) and load is 480 watts (less
than 800 watts), one circuit is used and
distribution board is not required.
480 _ 9
240 w
Full-load current. I =
Hence 240V, 16A, DPIC switch fuse of eae
any standard make may be used as a main be
switch and 1/1.40 mm, aluminium conductor, Obs
single core, 650V grade, PVC cable having RRS ED
current carrying capacity of 10 amperes may a
be used for phase and neutral connections.
Assumptions :
Assume the height of main board and switchboard = 1.5 metres
Height of casing-capping run = 3.0 metres
Height of bracket light points = 2.4 metres
The distance of meter board (MB) from the front wall (in hall) = 0.2 metre
The wiring plan is shown in Fig. 8.6.
Length of PVC Casing-Capping
From meter board to main board
From meter board to switch board SB, = 1.5 +2+1.5= 5m
Vertical run to ceiling in hall (above SB,) = 3.6 - 3.0 = 0.6m
Run along ceiling in hall = 2.4 + 2.4 + 2.4 = 7.2 metres
Drop from ceiling to L, = 3.6 — 2.4 = 1.2 metres
Drop from ceiling to Ly = 3.6-2.4 = 1.2 metres
From switchboard SB, to Ly = 1.5 +0.3+18+0.6=42m
Vertical run to ceiling in room = 0.6 metre
2m
Run along ceiling in room = 2.7 metres
Drop from ceiling to lamp Ly = 3.6 — 2.4 = 1.2 metres
Total length of casing-capping
+ 2.7 + 1.2 = 24.1 metres
.6 metres (say)
= 27.7m = 28m (say)
Wastage and length used in joints (15%)
Total
Length of Conduit of 19 mm Size
2+ 5 FOG FT2+LZ+1LV+AD+>OGE
Connections are taken from SB, to SB, and from light point L, to L, through 19 mm conduit
Hence length of conduit required = 0.25 + 0.25 = 0.5 metre
Length of Phase Wire [1.5 mm* aluminium conductor, single core, 650 V grade PVC cable]
From meter board to main board = 0.2 metre
From main board to switchboard SB, = 1.5 + 2 + 1.5 = 5 metres
From SB, to fan point = 2.1 + 2.4 = 4.5 metres
From SB, to light point L, = 2,1 + 2.4+2.4+1.2=81m
From SB, to light point 214+244+24+12=81m
From SB, to SB, = 0.25 m
From SB, to light point L, = 1.5 + 0.3 + 1.8 + 0.6 = 4.2m
From SB, to light point L,
From SB, to light point L,
1.5 + 0.3 + 1.8 + 0.6 + 0.25 = 445m
=15 + 0.3 + 18 + 0.6 + 2.7 + 1.2 = Interal Wiring Estimation
Total length = 0.2 +5 +4.5+8.148.1+0.25+4.2+4.
= 42.9 metres
wastage and extra wire at distribution boards 8.6 metres
Total length
1.5 metres
45mm?
NEUTRAL WIRE +7) sLuMINIUM
HALF WIRE ‘CoNDUCTOR
14 swt cone
WIRE
MAIN BOARO
| 200V
DPIC SWITCH
88,
-N
CIRCUIT DIAGRAM % row
2 BonRO
Fig. 8.7
Length of Neutral Wire [1.5 mm?, aluminium conductor, single core 650 V grade PVC cable]
From meter board to main board = 0.2m
From main board to fan point F = 1.5 +2+06+24= 6.5m
From fan point F to light point L, = 2.4 + 1.2 = 3.6m
From light point L, to light point Ly = 1.2 + 4.8 + 1.2= 7.2m
From light point L, to switchboard SB, = 1.2 + 24+ 24 +2.1= 81m
From SB, to SB, = 0.25 m
From SB, to light point L, = 1.5 + 0.3 + 1.8 + 06
From light point L, to L, = 0.25 m
From light point L, to Ly 0.25 +124 2.7 +12 = 535m
Total length of neutral wire = 0.2 + 6.5 +3.6+7.2 +8.1 + 0.25 + 4.2 + 0.25 + 5.35
.65 metres
w
42m
Wastage and length used in connections (10%)= 3.6 m
39.25 metres
Total length of neutral wire required
neural Henge of aluminium conductor single core PVC cable of size 1.5 mm”
= 51.5 + 39.25 = 90.75 metres = 90 metres (say)
length of Earth Wire required (14 SWG GI wire)
d = 0.2 metre
15+2+15=5m
required (Phase +
From meter board to main boar’
Pam From main board to switchboard SB, i
Switch board SB, to switchboard SB, = 0.25m
Total length required including wastage = 6m = 0.2 ke (say) ue] Electrical Installation Estimating and Costing
ESTIMATE ON THE BASIS OF ITEM WISE RATES
IS. No. Description of Material With Quantity Rate ee
Full Specifications Required : marks
Quantity | Unit z P| Per @ P
1. | 240 V grade, 16A, DPIC switch with 1 no 300: ]00 | each | 300 | 00 ——~
fase and neutral link
2. | PVC casing-eapping 76 mm x 25 mm 28 m | 9000] m | #40 |o0
. | 14 SWG GI wire (earth wire) 02 kg | 270 ]00} kg 54 |00
4, | Earthing thimbles with nuts and bolts. 3 nos | 15 ]00 each | 45 | 00 | For earth,
Jeonnectiens
from meter
board to ain
board and
from main
board to
° switchboard
5. | 1.5 mm® single core 650 V grade 90 m 3/00/ m 270 |00
aluminium conductor PVC cable
6. | Piano switches, one-way 5A surface 8 nos 12 | 00 | each 96 |00
type
7. | Ceiling rose, two plate PVC type 1 no 12/00] do 12 | 00 | For fan
8. | Brass brackets with holders 4 nos 52 |50| do 210 | 00 | For light
points L,.L,
L, and L,
9. | Watertight bracket with holder and 1 no 75 {00} do 75 | 00 | For light
globe point Ly
10. | Plug sockets 3 pin 5A 2 nos 22 do 45 |00
11, | Teak wood boards (double)
(@) 25cm x 20cm 2 do 65/00] ds 130 | 00 | For MB
and SB,
(ii) 20cm x 15cm 1 do 52/50] do 52 |50 | For SB,
12. | Round wooden blocks do 16 |50| do 99 | 00
10cm x 40m
13. | Teak wood gutties 100 do 75 |00 | 100 75 | 00
14, | Wooden screws |
(@) 51 mm for boards 18 nos 75 {00 | 100 13 |50
(ii) 32 mm for casing 45 do 60/00] do 27 {00
(iii) 13 mm for capping 180 do 30 {00} do 54 |00
(iv) 19 mm for switches 32, do 30/00] do 9 | 60
15, | Cement, sand, paint, |
varnish ete 500 |00 | Lump-su
provisi_J
‘Total | 2,907 | 60
Labour cost @ 60 per point | 600 |00 te ints
plus 2
3,507 | 60 |for MB
Contingencies 5% | 175 | 3
Grand Total [3,682 |98
Say &. 8,700.00
a" | =