Test: Estimation & Costing - Electrical Engineering (EE) MCQ

Each option listed is indeed a method of wiring:

• A. Joint box: Used for connecting multiple wires or cables together, often in electrical installations to manage and protect connections.

• B. Tee system: A type of wiring system where branches of wires are connected to a main wire, forming a "T" shape. It is commonly used in both residential and commercial wiring.

• C. Loop in system: A wiring method where the electrical loop is formed by connecting multiple points in a circuit, allowing for flexibility and multiple outlets or switches in a single circuit.

All these methods are used in various wiring configurations and installations.

Electrical wire is made of materials like copper, aluminium and silver. As silver is expensive, mostly copper and aluminium are used in wiring.

Copper:

• It is a good conductor of electricity.
• It is used in wiring materials in cables.
• Is has low resistance and is used for conduction of electricity at high, medium and low voltage.

Aluminium:

• It is light weight and cheaper in comparison to copper. Therefore, this type of conducting material is mostly used in electrical wiring
• It is silvery–white in colour and it has a soft texture. It is often used in wiring and making cable.

0.914 m distance should be provided as the working space around the main switchboard according to IE rule 51.

• Batten wiring is not suitable for outdoor wiring where the wiring is exposed to sun and rain
• It has a high risk of fires.
• They are not safe from external wear & tear and weather effects because the wires are openly visible to heat, dust, steam, and smoke.
• Heavy wires are not recommended for this wiring scheme.
• Only suitable for below 250 V.

Batten wiring: In this, insulated wires are run through the straight teak wooden battens The wooden battens are fixed on the ceilings or walls by plugs and screws The cables are fitted onto the battens by using tinned brass link clips These clips are fixed to the battens with rust-resistant nails CTS or TRS or PVC sheathed wiring, lead sheathed or metal sheathed wiring are types of batten wiring This wiring installation is simple and cheap as compared to other electrical wiring systems also takes less time to install These are mainly used for indoor installations.

• An electrical conduit is a tube used to protect and route electrical wiring in a building or structure. Electrical conduit may be made of metal, plastic, fiber, or fired clay.
• Most conduits are rigid, but flexible conduit is used for some purposes. Conduit is generally installed by electricians at the site of installation of electrical equipment.
• An elbow is an engineering term and they are classified as 90 deg or 45 deg, short or long radius.
• Elbows have industrial standards and have limitations to size, bend radius and angle. The angles are usually 45 deg or 90 degrees.
• As elbows are pre fabricated, cast or butt welded, they can be sharp like right angles and return elbows which are 180 degrees.
• Conduit elbows are usually located at sharp ends.

Factors to be Considered During Preparation Of A Detailed Estimate Quantity of materials: For a large construction, a large quantity of materials is required and this can be purchased at a rate cheaper than the rate of materials required for minor work. Therefore, rate of works should be framed considering the volume of work.

• Availability of materials: Estimated cost of a particular item is higher than the scheduled rate if there is no assurance that the materials will be available as and when required, and it is detrimental to the progress of the work if the workers and maintenance staff remain idle for paucity of materials.
• Transportation of Materials: If smaller quantity of materials is required to be transported to a considerable distance, the proportionate cost of transportation becomes higher in comparison with the cost of a large quantity transported at a time.
• Location of site: If the site of work is located at an odd place for which loading, unloading, stacking and restacking of materials are necessary, several times, due to different kinds of journey, the point of damage or loss in transit should be considered carefully.
• Local labour charges: Skill and daily wages of local labourer should be considered before preparation of a detailed estimate.

Cleat wiring system:

• This system of wiring comprise of ordinary VIR or PVC insulated wires (occasionally, sheathed and weather proof cable) braided and compounded held on walls or ceilings by means of porcelain cleats, Plastic or wood.
• Cleat wiring system is a temporary wiring system therefore it is not suitable for domestic premises.
• Cleat wiring systems are not used nowadays.

Advantages of Cleat Wiring:

• It is simple and cheap wiring system
• Most suitable for temporary use i.e. under construction building or army camping
• As the cables and wires of cleat wiring system is in open air, Therefore fault in cables can be seen and repair easily.
• Cleat wiring system installation is easy and simple.
• Customization can be easily done in this wiring system e.g. alteration and addition.
• Inspection is easy and simple.

Disadvantages of Cleat Wiring:

• Appearance is not so good.
• Cleat wiring can not be use for permanent use, because sag may be occur after sometime of the usage.
• In this wiring system, the cables and wiring is in open air, therefore, oil, Steam, humidity, smoke, rain, chemical and acidic effect may damage the cables and wires.
• it is not lasting wire system because of the weather effect , risk of fire and wear & tear.
• it can be only used on 250/440 Volts on low temperature.
• There is always a risk of fire and electric shock.
• it can’t be used in important and sensitive location and places.
• It is not lasting, reliable and sustainable wiring system.

The safety factor used for the current rating in a power installation is 2. For an AC motor with known output power, in addition to its efficiency, it is also necessary to know its power factor.

• The cross-sectional area of conductor for house wiring is usually expressed in mm².
• Frequency is expressed in Hertz or Hz.
• Length is expressed in mm or cm or meter.

• When one circuit or cables are passing through another circuit or cables in the cleat wiring system then insulators are used on lower cables for safety purposes.
• At the turning points in cleat wiring, special types of cleats are used. Normally, the distance between two cleats is kept approximately 0.5 m or 18 inch or 45 cm and it can be a maximum of 0.6 m
• The distance cables and the wall is approximately 1.5 cm
• The distance between the two cables is 4 to 7 cm according to their current rating.
• The distance between the earth and cables is approximately 2.5 to 3 cm

• Rigid metal conduit (RMC) is a thick-walled threaded tubing, usually made of coated steel, stainless steel or aluminum.
• Galvanized rigid conduit (GRC) is galvanized steel tubing, with a tubing wall that is thick enough to allow it to be threaded. Its common applications are in commercial and industrial construction
• Electrical metallic tubing (EMT) is commonly used instead of galvanized rigid conduit (GRC), as it is less costly and lighter than GRC. EMT is more common in commercial and industrial buildings than in residential applications.
• PVC conduit pipe suitable for embedded use in concrete, and heavier grades suitable for direct burial and exposed work.

Salt and coal are filled to maintain the moisture which reduces the resistance of the earth.

When one circuit or cables are passing through another circuit or cables in the cleat wiring system then insulators are used on lower cables for safety purpose. At the turning points in cleat wiring, special types of cleats are used.

• Normally, the distance between two cleats is kept approximately 0.5 m or 18 inch or 45 cm and it can be a maximum of 0.6 m
• The distance cables and the wall is approximately 1.5 cm
• The distance between the two cables is 4 to 7 cm according to their current rating.
• The distance between the earth and cables is approximately 2.5 to 3 cm

Electrical wiring is the electrical power distribution through the wires in a perfect manner for economic use of wiring conductors inside a room or building with better load control.

Methods of internal wiring usually used are:

• Cleat wiring system
• Wood casing wiring
• CTS or TRS or PVC sheathed wiring
• Lead sheathed or Metal sheathed wiring
• Conduit wiring

A guard wire or earth wire is the top most conductors in high voltage transmission lines. It is used mainly to protect lines from lightning. If in case lightning struck then it carries the excessive current inrush to ground.

The minimum cross-sections of conductors that are used for power wiring are given below.

If the conductor is made up of aluminium, the cross-section is 2.5 mm².

If the conductor is made up of copper, the cross-section is 1.25 mm²

In concealed wiring replacement of wiring is not easy because PVC conduit pipes are placed inside the chiselled brick/block wall before plaster.

• Batten Holder: This type of lamp holder is fitted directly on the wooden board, which itself is fixed on the wall. The lamp is then supported in the batten holder.
• Pendant Holder: When the bulb is to be suspended from the ceiling rose, this type of holder has to be used for holding the lamp.
• Angle Holder: Angle holders are used when the light of the lamp is needed at a certain angle. These are directly fixed to the walls.
• Bracket Holders: These are used where direct light is needed in the room. These are also used on table lamps. Brackets used with such type of holders are made of brass material.
• WaterTight Bracket Holder: These are provided with tubular glasses with watertight covers. These are mainly used for street lighting. They are also used for supporting bulbs outside the house premises.