Electrical Installation Planning For Residential Building
Table of Contents
Introduction to Electrical Installation Planning
Electrical Planning means planning something or scheduling or forecasting something. Before the beginning of any project or task, the acquisition of complete information or knowledge and adopting a comprehensive strategy based on that information for the completion of the proposed task is called planning. From the electrical engineering point of view, planning means electrical installation (e.g., electrical wiring, earthing, service lines, and installation of different electrical appliances on the substations, etc.) in the corresponding places according to the electrical rules and electrical design in a proper arrangement is called planning. Several points are kept in mind for the successful planning of any electricity-related project. For example, at the time of planning electrical wiring, selection of wiring system according to the conditions and requirements, correct selection of cable and its size, selection of the proper electrical appliances proposed to be installed, the number of lamps and ceiling fans, distribution of the circuit according to load, and earthing system, etc., are important points, which tend to be a part of planning. Moreover, it is also evaluated at the time of planning how much cost is going to be incurred on this project. Besides weighing the costs of a project, the actual object of planning is to commence a project correctly and also to overcome or solve hardships being expected during the accomplishment of the initiating project. Planning occupies an important place for the successful implementation of any project. Because without correct planning, implementation of any electrical project seems almost impossible.
Planning and Designing of Electrical Installations
Acquisition of complete and accurate information about different stages of any project through proper planning, so that installation of electrical wiring and electrical appliances etc., can be done according to set electrical rules apart from keeping in view requirements, right from the point of initiating an electrical project to its completion, and based on a clear set of information and vivid planning, designing a plan in such a way that a minimum cost incurs on the project apart from its shortest possible completion period, is called designing and planning of the electrical installations. The importance of planning can be understood from the point, that no electrical project can be accomplished within the desired period and in an accurate manner at the lowest possible costs without proper planning. Through correct and comprehensive planning, designing becomes easy and through proper designing, any project can successfully be completed along with all its merits. Thus, in order to perform various stages of any electrical project in a proper arrangement, the designing and planning of this project are inordinately essential. As all factors concerning a project are kept in mind at the time of planning or designing it, e.g., selection of a wiring system before the wiring, requirements of outlets and light points, distribution of electrical circuits into different parts, assessment of load, selection of cable, selection of circuit breaker and fuses, safety, durability and reliability, precise and accurate sketches and electrical drawing, etc. As such, planning and designing have a similar capacity in an electrical system that a backbone has in a human body.
After planning, top-quality designing can be carried out in any building or outdoor spot for the purpose of electrical installation according to the electrical rules and codes. The designing for electrical installations means the installation of electrical appliances along with their wires and cables in such a manner that the current flowing through the appliances and wires, can safely be supplied to all the instruments. As the design of every electrical installation or electrical system is prepared as a result of an electrical plan or electrical planning, therefore details about the complete wiring diagram of an electrical system, its single diagram, etc., and important sketches and layouts like the front side and top, accessories and drawing, etc., should be available in the design. So that a clear picture transpires in the mind of a person who has to carry out the installation. It must also be inculcated in mind that changes in set planning or designing owing to any prospective technical difficulties or issues, are also a part of planning, however, it depends on the needs and changing demands of the owners of the residential and commercial buildings.
The detail of all important steps being undertaken for the successful planning of some electrical installation are as follows;
Necessary Steps for Planning Residential Building
The detail of all steps necessary to be kept in mind for successful planning of an electrical installation in any residential building is as follows; In other words, the steps which must be kept in mind before planning an electrical installation in any residential building, are as follows; Remember that these steps or stages, also prove helpful in the designing of an electrical system apart from its planning.
Selection of Wiring System
There are different methods or systems of wiring and every method has its own benefits. However, there is no such single system, which can be suitable or effective for all types of installations. Therefore, the selection of a wiring system first at the time of planning an electrical system for a building is very important. The wiring system is selected according to the nature of a building, nature of work going to be done in it, weather conditions, load and requirements and costs of the owner, etc. if the building is simple or of an ordinary type, batten wiring can be done in it instead of a conduit wiring, however, if the building is the attractive type and expensive one, its beautification may tarnish as a result of batten wiring. Therefore, PVC concealed conduit wiring will be more appropriate according to the need of the owner in such a type of building. The objective behind the selection of a wiring system tends to be the transmission of electrical power up to the desired place in a safe, proper, and efficient manner according to the needs of the owner and the nature of the building. Remember that if the building is of a commercial type or a factory etc., instead of a residential one, in such a situation wiring system is always selected on the basis of the nature of work proposed to be done in the building. For example, batten wiring cannot be done in a molding or mintage factory due to the fear of damage to the wire insulation as a result of the existence of extreme heat in the building.
Distribution of Electrical System in Different Circuits
At the time of planning an electrical system for a building, an electrical system is distributed into different circuits according to the load requirements, and all these circuits are drawn according to the load of the electrical installations and appliances. The object of doing so tends to be an equal distribution of the load among all the circuits, so that repeated tripping does not occur as a result of an overload of any particular circuit. And, the entire electrical system continues working effectively through successful planning.
Estimation of Load
For the purpose of carrying out better planning of any building, it is necessary to have an idea about the estimation of the load going to be installed on it. For this purpose, to determine the required rating of the main cable, sub-main cable, fuse and circuit breakers, etc., an entire load of lamps, sockets, outlets, and fixed appliances or items is summed up. In this way, an overall load can be assessed, wherein 10 to 20 percent load is added as a precaution needs or keeping in view the extra needs that may arise in the future. Normally, a load above 75% is not used at a time, however, occasionally a full load may also be used at a time. However, it happens very rarely. As a household consumer does not use all lights, fans, iron, electric heater, tv, fridge, AC, etc., simultaneously, therefore it is necessary to keep the diversity factor in mind while estimating the load.
The diversity factor is represented in percent and its definition is as follows;
Diversity factor = Total connected load/ Actual maximum load
Selection of Size of Cable
As a load of every circuit of an electrical installation and wiring may be different, therefore selection of the correct size of the main cable and sub-main cables according to the load, also tends to be a part of successful planning. For this purpose, the following points or factors are essential to be kept in mind;
(i). Selection of Different Sizes Cables for Different Circuits
An important point during the selection of a cable tends to be the selection of cables of different sizes or ratings for various circuits (e.g., sub-circuit or final sub-circuit, etc.). For example, load situation on different parts of wiring from the energy meter to the final sub-circuit always tends to be different. From the service box to the energy meter, the energy meter to the main switch, and from the main switch to the distribution board, a current flows according to a total load of all the circuits. Whereas, in the sub-circuit, the total current of the final sub-circuit passes.
Therefore, the selection of an appropriate cable is done according to the current or load of every part (or sub-circuit and final sub-circuit) of wiring.
(ii). No. of Cores
At the time of selection of a cable, it is also necessary to keep in mind the number of cores in a cable according to the system of wiring. For example, a cable consisting of two or more cores is used on the main and sub-main circuits, whereas a single-core cable is generally used for the wiring of the final sub-circuit.
(iii). Voltage Drop
We know that every cable has some sort of resistance. When current passes through a cable, a voltage drop occurs on it due to its resistance. If the size or diameter of the conductor on a cable is large (i.e., if the conductor is thick), its resistance will be low, resultantly the voltage drops taking place on this cable will also be lower. On the contrary, as the resistance of a thin wire tends to be high, therefore its voltage drop will also be high. Moreover, voltage drops also tend to be high due to an increase in the length of a conductor. According to the Para B-32 of the Institute of Electrical Engineering (IEE), voltage drop up to any point between the power supply terminal and installation must not exceed 2.5 percent of the total provided supply voltage. Therefore, such a size of the cable must be selected, through which the desired voltage can be received on any appliance or load point.
(iv). Minimum Permissible Cable Size
According to electric rules, an under-gauged wire must never be used on any circuit on electrical and mechanical grounds (a wire which cannot sustain the required load, is called an under-gauged wire). Therefore, the minimum cable size for a household power circuit must never be less than 7/0.29”, whereas, for a lighting circuit, a minimum 3/.29” wire should be used.
Selection of Switch Gears Size
The ratings or sizes of the switch gears are selected according to the maximum total current of all loads mounted on any installation (electrical instruments which are used to control any circuit or used as an ON or OFF switch, are called switching gears, e.g., circuit breakers, switches, and relays, etc.). As a further increase in a load of larger buildings can be expected in the future, therefore such a selection of switchgear is made keeping in mind this expected addition, the rating of which is 1.2 times the overall load. Its advantage is that in the case of momentary overloading, switchgear remains protected and there is no need to change it in the event of an expected over-loading. Thus, through better planning, the selection of low-rated switch gears should not be made compared to the overall load requirements.
Selection of Fuse Wire
It must be kept in mind while selecting any wire for the fuse that the capacity of a fuse to pass a wire current must be less than the current capacity of a minimum current conductor installed on the circuit (i.e., fuse wire must be selected according to the current rating of the lowest size cable used on the circuit). It has often been seen that a 10-ampere fuse is installed for providing protection to a circuit with a 5-ampere current rating. It is absolutely wrong according to electric rules, because doing so may not only inflict a loss to the electrical equipment installed on a circuit, it may also damage the circuit itself.
Availability of Accessories
The continuous availability of accessories in the market, related to wiring must also be kept in mind while planning an electrical installation, so that work does not suffer due to the non-availability or paucity of accessories in the market.
Present Load Capacity and Future Load Capacity
The design of an electrical installation must have at least such an accommodation that it can not only withstand the present load, but it does also have a capacity to fulfill the extra load expected in the future. The type of planning, under which expected addition in the future load through some necessary modification in the installation is not possible, is considered unsuitable from a technical point of view.
Standard Voltage and Frequency
It is essential to have know-how about the appliances and equipment proposed to be used in an electrical installation, what is the standard value of voltage and frequency required for an installation, and at what ratio the supply company provides voltage and frequency. A better planning is considered as one, wherein the voltage and frequency of appliances going to be used on installation tend to be compatible with the voltage and frequency of the supplier’s company. As such, switch gears and other electrical appliances planned to be installed, must always be according to the declared standard voltage and frequency of the supplier company.
Safety Precautions
Safety is an important factor in every installation. At the time of installation, apart from the safety of electrical appliances, personal safety, and safety of other’s lives, the safety of related electrical installation as well as precautionary measures is also kept in mind. From the perspective of safety, wiring must be completely leakproof. Wires must always be selected according to load and quality. Therefore, the national electrical security code must always be kept in mind at the time of doing wiring, and precautionary measures must also be previewed while planning their installation so that no loss occurs to the installation and the appliances and people related to it. For this purpose, safety-related literature is provided by the manufacturer of the appliances and instruments, which is necessary to be carefully implemented before the installation. Remember that these safety measures can be different for each electric appliance or instrument.
Flexibility
From the technical point of view, flexibility means a prospective variation or accommodation in any design or devised planning, under which an easy addition or deletion in this planning could be possible. As such, every installation must be designed in such a manner that an easy change within its design or planning can be possible without any sort of damage or loss. For example, if appliances e.g., boards, circuit breakers, motors, etc., installed on any installation (e.g., electrical wiring) are required to be shifted from one place to another suitable place, then the design or its prepared planning must have the accommodation or capacity to accommodate such changes. Moreover, that installation may also accommodate and withstand the load of the electrical appliances or accessories shifted to the new place.
Accessibility
The design of an electrical installation must be comprehensive and its planning so clear that easy access to every installed appliance can be possible. And, it can easily be repaired or controlled whenever required. Furthermore, no difficulty should be observed in making any sort of addition or changes and it’s looking after.
Reliability and Durability
The prepared design and planning of an electrical installation should be such that it should be reliable and reliable apart from being technically correct and comprehensive. In other words, such type of an installation design should be prepared which, apart from internal and external dangers and calamities, can also support all types of internal and external effects, and unavoidable situations, e.g., may also work effectively under rains, severe storms, earthquakes, intense heat, moisture, poisonous smoke, and chemical reactions, etc. As the design of an installation depends on the nature of work, its reliability, and durability, therefore the life of an installation may also be assessed at the time of planning any electrical installation.
Complete Installation Design
Keeping in view all the above-mentioned factors, such a complete and detailed data should be prepared for an installation, which contains a piece of comprehensive information e.g., measurement of the structure of the corresponding building, places to install electrical appliances and their nature as well as configuration, sizes of wires, number of wires and places for their passing, earth points, main supply line, supply boards, distribution boards, place of switchgear, size and rating, security instruments and necessary precautions being adopted during the work. Separate circuits for light wiring and power wiring should be available. The wiring technician should be provided a layout in the shape of a blueprint of the whole wiring, which consists of a complete wiring diagram, single line diagram, standard electrical diagram, tables, schedules, a complete description of appliances, and other necessary layouts, etc.
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