2360 Electrical Installation Work Course C

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  • Topic: The Circuit, Circuit, Jalal Merhi
  • Pages : 5 (1076 words )
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  • Published : February 23, 2013
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QUESTION 1a
Block L will be powered by a single phase 100A distribution board. Power
One ring circuit will provide power for the generator/switch room and substation room and will be protected by a 32A type C BS EN 60898 RCBO. An RCBO will be used because equipment could be plugged in and taken outside and it will be type C because inductive loads could be plugged in. The other ring circuit will provide power for the workshop and restroom and will also be protected by a 32A type C BS EN 60898 RCBO. An RCBO will be used because equipment could be plugged in and taken outside and it will be type C because inductive loads could be plugged in inside the workshop as well as equipment being used inside the restroom. The roller shutter door will be wired on its own radial circuit because if it faults due to rain or strain it won’t trip out a ring circuit. It will also be protected by a 16A type C MCB to allow for start-up of the motor. Outside Lighting

Lighting in block L will be provided by fittings using high frequency control gear to combat the stroboscopic effect around the generator. Calculations for the five 150W high pressure sodium fitting outside lights – 150W x 5 = 750W 750W x 1.8 = 1350W

I = P = 1350W = 5.87A load current
V 230V
The outside lighting radial circuit will be protected by a 10A type C BS EN 60898 RCBO, this will be required because 5.87A is too close to a 6A breaker and will be running hot. A 10A type C will be used to allow for the inductance in the discharge lighting and the 10A capacity allows for more lights to be added in the future.

Inside Lighting
The inside lighting will be protected by either a 6A or 10A type B MCB depending on the circuit. The fittings are twin 6ft fluorescent luminaires with each tube rated at 70W. The calculation to work out the maximum number of luminaires on each circuit is shown below: current per fitting = P x 1.8 (discharge lighting factor) V

current per fitting = (2 x 70W) x 1.8
230V

current per fitting = 1.1A

number of fittings = __MCB rating___
current per fitting

number of fittings = _6A_ = 5.45
1.1A

number of fittings = 10A = 9.09
1.1A

So that the breaker doesn’t run hot –
6A MCB – 5 fittings
10A MCB – 8 fittings

Identification
The circuits are divided as per the drawing 2360-023-07-08-1/1, each with its own colour and identified in the following way: Function – Circuit Number – Fitting Number
For example, the third socket outlet on the circuit 2 ring main in the workshop/restroom would be: P – 2 – 3

Calculations for Design Current
In order to create a board schedule for the lighting and power distribution board, every circuits design and diversified current has to be calculated. The maximum diversified current cannot exceed the board’s 100A maximum demand.

Circuit 1
Final ring circuit (workshop/restroom) – 32A
Diversity Factor from OSG 17th edition – 1
32A x 1 = 32A

Circuit 2
Final ring circuit (generator/substation/switchroom) – 32A Diversity Factor from OSG 17th edition – 0.5
32A x 0.5 = 16A

Circuit 3
3kW roller shutter door
I = P = 3000W = 13.04A
V 230V
Diversity Factor from OSG 17th edition – 1
13.04A x 1 = 13.04A

Circuit 4
Lighting – Outside
150 x 5 = 750W 750W x 1.8 = 1350W I = P = 1350W = 5.87A V 230V Diversity Factor from OSG 17th edition – 0.9

5.67A x 0.9 = 5.28A

Circuit 5
Lighting – Switchroom (eight 70W double flourescent fittings) I = P = (70 x 2 x 8 x 1.8) = 8.77A
V 230V
Diversity Factor from OSG 17th edition – 0.9
8.77A x 0.9A = 7.89A

Circuit 6
Lighting – Switchroom (six double fluorescent fittings)
I = P = (70 x 2 x 6 x 1.8) =...
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