Electrical and Electronic Control: Garden Lighting Wiring Design

This assignment presents a detailed electrical wiring design for a garden lighting system. It begins with the calculation of pole placement, considering the dimensions of the garden and the desired illumination. The assignment determines the number of poles and bulbs required, as well as the total power consumption. It then proceeds to calculate the appropriate circuit breaker size and the cable length needed for the wiring. The assignment provides a comprehensive breakdown of the cable sizes, including the length from the switch to the circuit breaker, along the sides and width of the garden, and from the poles to the bulbs. It also factors in termination allowances for connections. The solution includes a circuit diagram illustrating the wiring layout. The reference used is Murray, R. T., 2011. Commercial Electrical Wiring. 2nd ed. hull: Craftsman Book Company.

ELECTRICAL AND ELECTRONIC CONTROL 1
ELECTRICAL AND ELECTRONIC CONTROL
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ELECTRICAL AND ELECTRONIC CONTROL 2
Calculation of the poles
Taking interval of 9 meters along the length of the garden and 7 meters along the width of the garden.
Poles along the length = Total length
9 −1
Poles along the length = 63
9 −1= 6 poles (on the length)
Poles along the width = Total width
7 −1
Poles along the length = 21
7 −1= 2 poles (on the width)
This gives a maximum of 12 poles used for the design and installation.
The poles are of height 4 meters from ground and extends 7 meters into the garden at the top, and it
looks like the one below
Figure 1: Showing type of pole used in installation (Murray, 2011)
There is additional 2 poles which are (sp) supporting poles where wires will be supported from the
switch to pole P1 and pole P12.
Total pole number will then be 14

ELECTRICAL AND ELECTRONIC CONTROL 3
Calculation of number of bulbs
In the design one pole was to support one bulb, and putting the bulbs at an interval of 7 meters in the
width gave a maximum illumination and equal distribution of light in the garden.
Calculation of power
Assuming that each bulb is rated 20 watts
The total power = Total number of buble× bulbrating
The total power = 20 ×12
Total power = 240 watts.
Selection of circuit breaker
Total power = VI
Where V is voltage = 240
I is total current
240=VI
I =¿240/240
I=1A, therefore any value above 1A could be used successfully,
Therefore we would use a circuit breaker of 2A
Calculation of cable length and size
The cable size used for lighting is 1.5mm2
Type of cable used is here is twin and earth
Cable length
Assuming that the circuit breaker is situated just one meter from the switch,
Length of the cable from switch to circuit breaker
1000mm
Cables running along the two sides of the garden
63000×2=126000 mm
Cable running on the width (where switch is)

ELECTRICAL AND ELECTRONIC CONTROL 4
21000 mm
Cable running from poles to bulbs
There is 7 m from the pole to the bulb, therefore the total cables running is obtained by
Total cable length = 7000 ×12
Total cable length= 84000mm
Cable supporting pole from height of the switch to top of the supporting pole
The switch is situated at 1500mm from ground, which means it we will have to use a wire of length 2500
to reach the top of the supporting pole.
Length will be 2500×2=5000 mm
Calculation of termination allowance of cables
For every connection there must be an allowance of 100 mm,
There are 12 bulbs + 1 switch+ 1 circuit breaker
Total terminations are = 14
Total length of cables at this point = 14 × 100
Total length of cables at this point = 14 00mm
Total length of the cable
126000 mm+ 21000 mm + 84000mm + 5000 mm + 1400mm
Total length of the cable = 237,400 mm (237.4m)

ELECTRICAL AND ELECTRONIC CONTROL 5
The circuit diagram for the garden
SP= supporting pole
L = Live
N= neutral
P = pole
L= light ( bulb)

ELECTRICAL AND ELECTRONIC CONTROL 6
Reference
Murray, R. T., 2011. Commercial Electrical Wiring. 2nd ed. hull: Craftsman Book Company.