Question.1. Is Domestic wiring is connected in a series connection, parallel combination, or a combination of both? Justify your answer.
Domestic electric wiring is basically done in parallel connection so that if one appliance stops working due to Some defect, all other appliances keep working normally. In the parallel circuit if R1, R2, and R3 are the resistances of different household electrical appliances and I current enters the circuit then the current passing through three resistances will be I1, I2 and I3 so that total current I = I1 +I2 +I3. Every appliance can draw the required amount of current. So, if one of the appliances gets fused or damaged, other circuits will work.
Question.2. When we connected the appliances in a series combination? Explain with example.
When designing an electric circuit, we should consider whether a series circuit or a parallel circuit is better for the intended use. For example, if we want to connect (or join) a large number of electric bulbs (say, hundreds or thousands of electric bulbs) for decorating buildings and trees as during festivals such as Diwali or marriage functions, then the series circuit is better because all the bulbs connected in series can be controlled with just one switch.
A series circuit is also safer because the current in it is smaller. But there is a problem with this series lighting circuit. This is because if one bulb gets fused (or blows off), then the circuit breaks, and all the bulbs are turned off. An electrician has to spend a lot of time locating the fused bulb from among hundreds of bulbs, so as to replace it and restore the lighting.
Question.3. What are the disadvantages of Series circuits in Domestic wiring?
The arrangement of lights and various other electrical appliances in a series circuit is not used in domestic wiring because of the following disadvantages:
1. In a series circuit, if one electrical appliance stops working due to some defect, then all other appliances also stop working (because the whole circuit is broken). For example, if a number of bulbs are connected in series and just one bulb gets fused (or blows oft), then all other bulbs will also stop glowing.
2. In a series circuit, all the electrical appliances have only one switch due to which they cannot be turned on or off separately. For example, all the bulbs connected in series have only one switch due to which all the bulbs can be switched on or switched off together and not separately.
3. In a series circuit, the appliances do not get the same voltage (220 V) as that of the power supply line because the voltage is shared by all the appliances. The appliances get less voltage and hence do not work properly. For example, all the bulbs connected in series do not get the same voltage of 220 volts of the power supply line. They get less voltage and hence glow less brightly.
4. In the series connection of electrical appliances, the overall resistance of the circuit increases too much due to which the current from the power supply is low. Moreover, the same current flows throughout a series circuit due to which all the appliances of different power ratings cannot draw sufficient current for their proper working.
Question.4. What are the advantages of Parallel connection in Domestic wiring? Verify your answer with an example
Advantages of Parallel Circuits in Domestic Wiring
The arrangement of lights and various other electrical appliances in parallel circuits is used in domestic wiring because of the following advantages
1. In parallel circuits, if one electrical appliance stops working due to some defect, then all other appliances keep working normally. For example, if a number of bulbs are connected in parallel circuits and one bulb gets fused (or blows out), then all the remaining bulbs will keep glowing
2. In parallel circuits, each electrical appliance has its own switch due to which it can be turned on or turned off independently, without affecting other appliances. For example, all the bulbs joined in parallel circuits in a house have separate switches due to which we can switch on or switch off any bulb as required, without affecting other bulbs in the house.
3. In parallel circuits, each electrical appliance gets the same voltage (220 V) as that of the power supply line. Due to this, all the appliances will work properly. For example, all the bulbs connected in parallel circuits get the same voltage of 220 volts of the power supply line and hence glow very brightly.
4. In the parallel connection of electrical appliances, the overall resistance of the household circuit is reduced due to which the current from the power supply is high. Every appliance can, therefore, draw the required amount of current. For example, in parallel circuits, even the high power rating appliances like electric irons, water heaters, and air-conditioners, etc., can draw the high current needed for their proper functioning.
Question.5. Explain the Loop-in method of electrical wiring?
Answer:- This is one of the most widely used methods of wiring within the electrical installation industry. A PVC sheathed cable (phase-neutral and circuit protective conductor) supplies each ceiling outlet point on your lighting circuit. From each point, another cable provides electricity to each control switch. All connections are at the ceiling rose or switch. Electrical looping is loop/loops created between two lights with 1 single wire connected to multiple fittings.
There are many advantages of using the Loop-in method:
- Ease of wiring -all connections are made from one level.
- Easy to fault find – no flooring or inspection traps to lift.
- Can be added too without prior knowledge of where joint boxes are placed.
The only disadvantage is that other trades may accidentally pull out cables during the first-fix period. This is fine if you are the only person around but if there is any danger of this happening, tie or twist your cables together so they provide support for each other.
Question.6. Explain house wiring rule as per ISI Specification
- The wiring should be carried out on distribution systems with main and branch distribution boards to convenient centers and is without isolated fuses.
- All conductors should run as far as possible along walls and ceilings, so as to be easily accessible and capable of being thoroughly inspected.
- In any case, the wiring should not run above the ceiling.
- The circuit on the opposite side of three wires system or on different phases of three phases system is kept as far apart as possible in all cases; the minimum distance should be 7 feet.
- Medium pressure wiring and all associated apparatus should comply with specifications.
- The number of points in light circuits should not exceed 10 or the total load on the circuit should not exceed 800 watts.
Question.7. What should be the maximum load on the power sub-circuit?
Answer:- The load on each power sub-circuit should normally be restricted to 3000 watts. There should not be more than two outlets on each sub-circuit.
Question.8. What should be the maximum load on the sub-circuit?
Lights and fans may be wired on a common circuit. Each sub-circuit should have not more than a total of ten points of lights, fans, and 5 A socket outlets. The load on each sub-circuit shall be restricted to 800 watts. If a separate circuit is installed for fans only, the number of fans in that circuit should not exceed ten.
It is advisable to provide at least two lighting sub-circuits in each house so that in case of a fault in one sub-circuit the whole house is not plunged into darkness.
Question.9. Explain Wood casing wiring?
(iv) Casing and Capping Wiring Material Used: The various materials used in casing wiring are VIR or PVC insulated wires, casing enclosure (made of wood or plastic), capping (made of wood or plastic) and casing, and capping joints.
In this type of wiring, cables are run inside a wooden casing having grooves. This is then covered with wooden capping. The casing and capping should be of well-seasoned wood free from knots and defects. The live and neutral wire in case of single-phase wiring installation and the different lines in three-phase wiring installation, should not be bunched together in one groove. Wires of the same phase may be bunched in one groove.
Question.10. Which type of wiring is used for temporary installation?
Cleat wiring is suitable for temporary installations where cost is the main criteria but not the appearance.
Cleat Wiring In this type of wiring, insulated conductors (usually VIR, Vulcanised Indian Rubber) is supported on porcelain or wooden cleats. The cleats have two halves: one base and the other cap. The cables are placed in the grooves provided in the base and then the cap is placed. Both are fixed securely on the walls by 40 mm long screws. The cleats are easy to erect and are fixed 4.5-15 cms apart.
Question.11. Explain the Lead Sheathed method of electric wiring?
Answer:- This type of wiring system is also adopted for low voltage installations. This system is more or less similar to the CTS wiring system except that the cable used is different in this wiring system. In this system, conductors used are insulated with vulcanized Indian rubber and then covered with an outer sheath of the lead-aluminum alloy containing about 95 percent lead and 5 percent aluminum. The metal sheath is provided over the insulated conductor in order to protect the wiring system from mechanical injury, dampness, and atmospheric action.
Protection against mechanical injury, dampness, and atmospheric conditions is much better in this system compared to all the other systems of wiring. As such, this system of wiring can be used in damp places or in places exposed to sun and rain. However, due to the higher cost of the cable, the overall cost of the wiring system is much more compared to CTS wiring.
Question.12.What is the function of the distribution board in electrical wiring?
Answer:- Ater the main switch, the supply should be brought to the distribution boards for light and power circuits separately. Branch distribution boards should be provided with a fuse on the live conductor of each circuit while the neutral conductors of each circuit should be connected to a common link capable of being disconnected individually for testing purposes. One spare circuit of adequate capacity should be provided on each branch of the distribution board.
Question.13. What is the minimum height of the energy meter installed in the domestic circuit or wiring?
The energy meter should be at a height not less than one meter above ground level.
Energy meters should be installed in such a place that is easily accessible. This should be located at a height from where it is convenient to note down meter reading. The energy meter should be provided with a protective covering. enclosing it completely except the glass window through which the readings are to be noted.
Question.14. Why the neutral conductor of each circuit should be connected to a common link?
Branch distribution boards should be provided with a fuse on the live conductor of each circuit while the neutral conductor of each circuit should be connected to a common link capable of being disconnected individually for testing purposes.
After the main switch, the supply should be brought to the distribution boards for light and power circuits separately. One spare circuit of adequate capacity should be provided on each branch of the distribution board.
Question.15. What is the premises voltage drop level at the consumer end?
Voltage drop in consumer’s premises from the point of entry to the farthest point should not exceed 3%. In the case of power wiring. voltage drop should not exceed 5%. These limits, however, are much on the higher side and normally the voltage drop should be between 1 and 2% in the case of light circuits and 2 and 3% in the case of power circuits to ensure better efficiency and performance of electrical appliances.
Question.16. Explain the polarity test method of electrical wiring?
A polarity test is carried out to ensure that switches are controlling the phase wires and not the neutral wire. One terminal of the megger is connected to the phase and main switch and the other to the terminal of the control switch. The megger in this condition should read zero, otherwise, it indicates that the switches are controlling the neutral wire.
Question.17. What is the function of Three pin socket outlet?
Answer:- Three-pin sockets are available in 5 A and 15 A capacities. They are provided in the switchboards to tap power to appliances like electric irons, TVs, refrigerators, water heaters, air conditioners, table fans, etc. The right side pin carries the supply line. the left side pin gives a neutral connection and the top pin, which is larger in diameter than the other two pins, gives a ground connection to the appliances in order to protect the user against any electrical leakage.
Question.18. Explain the batten wiring method?
Answer:- In batten wiring, insulated wires are run on wooden battens. PVC wires are run on well seasoned straight teak wood battens. The battens are fixed on the walls or ceilings by plug and screws. The cables are held on the batten by means of tinned brass link clips. The clips are fixed on the battens with rust-resistant nails. Batten wiring is widely used for indoor installations. Batten wiring is cheap and takes comparatively less time to install.
Question.19. What is conduit wiring? Explain its type?
Answer:- Conduit wiring consists of PVC wires taken through either steel conduit pipes or through PVC conduit pipes. Conduits are run over the surface of walls and ceiling or are concealed under masonry work. When conduits are run over the surface of walls, the wiring is called surface conduit wiring. When the conduits are run inside the walls, the wiring is called concealed conduit wiring. Surface conduit wiring s used in factories for the installation of heavy motors and other electrical equipment. The system is waterproof and replacement of defective wires is easy.
Question.20. What are the disadvantages of the conduit wiring method?
- Conduit wiring is an expensive wiring system (Due to PVC and Metallic pipes, Additional earthing for metallic pipes Tee(s) and elbows, etc.
- It’s very hard to find the defects and faults in the wiring.
- Installation is not easy and simple.
- Risk of Electric shock (In case of metallic pipes without proper earthing system)
- Very complicated to manage additional connections in the future.
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