Electrical Wiring for the Lighting Circuit - Assignment Example

1. Brow a line diagram for a one way lighting circuit 2. Brow an electrical wiring diagram for the one way lighting circuit Note: Earth wires have not been shown in the diagrams for clarity, but must be put in at all earth terminals. 3. Explain how this circuit functions 1-way or 2-way indicates the number of switches controlling a light. A one way light circuit is a circuit where only one switch operates a lamp. In live wire, the voltage changes all the time but in neutral the voltage remains the same. Both switches have a live wire and a switched live wire. As soon as the switch is put on, the connection is made between live and switched live wire. Thus this makes the circuit complete and the current flows through the circuit. The bulb glows up. A fuse is used in the active line of a circuit, to protect the circuit from possibility of current surge. 4. What rating of fuse would you use and why? Fuses can work up to a limited flow of current. So they are rated according to the amperage. The rating of fuses depends on: 1) Voltage across the circuit 2) Current under normal operation Each electrical instrument is marked with its power and voltage. So, to calculate the amperage of the fuse to be used in a circuit following formula can be used: (Power in watts/ Volts) = Amperage After calculation, a fuse which has nearest rating just above the required amperage is chosen. In general we use a 5amp fuse for lighting circuits and a 15amp or 13 amps fuse for power sockets. 5. Brow a line diagram for a two way lighting circuit 6. Brow an electrical wiring diagram for the two way lighting circuit Note: Earth wires have not been shown in the diagrams for clarity, but must be put in at all earth terminals. 7. Explain how this circuit functions Two way light circuit is a circuit where two switches are used independently to operate a lamp. When it is necessary to control the lamp from more that one positions e.g. a bathrooms where lamps need to be operated both from inside and outside. In these situations we use two way circuits. The basic functioning remains the same as it is in 1 way switch. There is a common terminal between two switches and apart from it there are two other connections also. This common connection facilitates independent functioning of the switches. 8. What rating of fuse would you use and why? Fuses can work up to a limited flow of current. So they are rated according to the amperage. The rating of fuses depends on: 1. Voltage across the circuit 2. Current under normal operation Each electrical instrument is marked with its power and voltage. So, to calculate the amperage of the fuse to be used in a circuit following formula can be used: (Power in watts/ Volts) = Amperage After calculation, a fuse which has nearest rating just above the required amperage is chosen. In general we use a 5amp fuse for lighting circuits and a 15amp or 13 amps fuse for power sockets. 9. Explain in each case what size of cable you would use, with calculations The size of the cable is specified referring to cable diameter and cable’s rating is given in terms of the current it can carry under operation. The size of the cable which is used in any circuit depends upon the electrical equipments which are used like, Heater, lightings, etc. Any electrical appliance has the information regarding the voltage, wattage and frequency of its operation. In order to calculate the size of cable, the value of voltage and wattage is required. When wattage is given in range, we take the higher value for the calculations. Now we need to apply the formula: (Power in Watts/ Volts) = Amperage Dividing the wattage by the voltage (Standard 230v for domestic circuits), one will get the amperage. Now one needs to know the one way length of the cable to be fitted. As per Ohm’s law, there will be some voltage drop along the cable due to resistance of the cable wire. Empirically voltage drop of 5% is considered for single phase circuit. If wire length is then it won’t really matter much. Now the formula for wire size is: Wire diameter = ((conductor resistivity) 2 X Amperage X One way cable length)/Voltage drop Conductor resistivity can be taken for copper or aluminium which are generally used in cables. In general the cable used for lighting circuits is of diameter 1 mm, 11 amps and 3 cores. 10. Explain what a ring and radial circuits are There are two different types of configurations for power outlet circuits. First one is ring circuit and second one is radial circuit. In the radial configuration, the outlets from a point make a chain which run continuously from the supply point to the final point. The figure below depicts a radial circuit. Unlike radial circuit, in ring configuration, the final outlet is connected back to the supply. In ring configuration, every outlet has two diverging paths to the starting supply. Looking at a ring circuit it can be said that ring circuit is like a radial circuit with final outlet connected back to the supply. Figure below depicts a ring circuit. 11. Braw a line diagram for a mains power circuit 12. Brow a wiring diagram for the mains power circuit 13. Explain how this circuit functions. From the diagram of mains power supply for domestic purpose given above, it is clear that it has different branched circuits. Here it has two circuits. One circuit supplies electricity at 230 volts and 5 amperes for lighting purpose. Another one supplies electricity at 230 volts and 13 amperes for sockets which is also called power point circuit. The live wire from the outside mains supply carries the current at high voltage (230V). It enters the house through main switch box after passing from the electrical meter. Each branched circuit has to be further protected by their own fuse. Current, at a lower voltage returns to the outside power supply through the neutral wire. If there is any live current short circuit, then this surge in current is taken safely away through the Earth wire. The function of important component of any mains supply is as follows: 1. Live: To Carry supply current at maximum voltage 2. Neutral: To returns current at lower voltage 3. Fuse: To breaks the circuit in case of current surge by melting 4. Earth: To returns excess current safely to earth in case of short circuit 14. What rating of fuse would you use and why? Generally rating of fuse which is used in domestic mains supply is as follows: 1) Lighting connections: 5 Amps 2) Socket connections: 13 amps Each and every circuit in any domestic supply has to be protected with correct rating of fuse. The fuse protects the circuit from the danger of possible current surge which can even be fatal. The current surge ahs got a heating effect and the circuit can melt. High current surge can also cause electrical fire. Protection against this is provided by the fuse. The fuse breaks the circuit by melting under the influence of heat because of the current surge. This stops a dangerous current surge passing to the rest of the circuit. 15. Braw a radial circuit for a shower unit & 16. Brow the electrical diagram for the shower unit The above diagram depicts a radial electrical circuit for shower. 17. Calculate the size of protection device to be used? To calculate the size of fuse i.e. the protection device, the total power requirement of the shower system must be known. There are two different radial circuits in shower unit. First one is for lighting having a lamp of say 60 watt power. Second circuit is for electric water heater. The quickness, in which water is heated, needs to have a powerful heater say 12 KW. Now voltage is same in both the circuits say 240 Volts. Now applying the formula: (Power in Watts/ Volts) = Amps Calculations: 1) For Lighting circuit: 60/240 = 0.25 Amps Fuse rating should be near this value. 2) For Electric Water circuit: 12,000/240 = 50 Amps Thus the rating of fuse should be high enough. 18. What size of cable would you use in both cases explaining why? Shower unit has two radial circuit arrangements. Different size of cable for both lighting and heater circuits can be used as requirements are different. 1) For Water heater circuit: From calculations above, current rating is quite high. We can use 3 cores 10 mm diameter cable which can carry up to 56 amperes of current. 2) For Lighting circuit: A flexible dual core 0.5 mm diameter cable can be used which can carry up to 3 amperes of current. Read More