Ultra-detailed explanation of the electrical construction drawing process

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An extremely detailed explanation of the process for electrical construction drawings: The contents covered in electrical construction drawings vary depending on the different functions of a building. These mainly include building power supply and distribution, power and lighting systems, lightning protection and grounding, as well as building low-voltage electrical systems, all of which are used to represent the various aspects of electrical design. I. Characteristics of electrical construction drawings (1) Most building electrical engineering drawings are created using unified graphic symbols along with textual annotations. (2) Electrical circuits must all form a closed loop. (3) All the various devices and components in the circuit are connected together as a whole through wires. (4) When reading architectural electrical engineering drawings, it is necessary to consult the corresponding civil engineering drawings and other installation engineering drawings in order to understand the interrelationships between them. (5) Building electrical engineering drawings often fail to fully reflect the installation methods for equipment, quality requirements, as well as technical requirements for operation and maintenance. Therefore, when reading such drawings, it is necessary to refer to relevant atlases and specifications regarding installation methods and technical requirements. II. Composition of Electrical Construction Drawings (1) Drawing Catalog and Design Specifications Include information on the contents of the drawings, their quantity, an overview of the project, the basis for the design, as well as various other matters that are not clearly expressed in the drawings. Such as the source of the power supply, power supply method, voltage level, wiring method, lightning protection and grounding, installation height and method of equipment, main technical data of the project, construction precautions, etc. http://img.civilcn.com/d/file/dianqi/dqlw/2019-08-28/f8c38477b15126963acfdfaf3dd2fa99.png (2) List of main materials and equipment: This includes the names, models, specifications, quantities, etc., of various devices and materials used in the project; it serves as one of the important bases for preparing plans for purchasing such equipment and materials. http://img.civilcn.com/d/file/dianqi/dqlw/2019-08-28/44e6c93d2158b28acd4019a5af0938d5.png (3) The system diagram serves as a complement to the floor plan; it works together with the floor plan and is an important element for guiding construction. http://img.civilcn.com/d/file/dianqi/dqlw/2019-08-28/8be761ac5e8743eae58e81eaae50dfbb.png http://img.civilcn.com/d/file/dianqi/dqlw/2019-08-28/c83da42a7f87c3c07658e9945a94957b.png Such as the power supply and distribution system diagrams for power transformation and distribution projects, the lighting system diagrams for lighting projects, and the cable TV system diagrams, etc. The system diagram shows the basic components of the system, the main electrical equipment, the connections between the components, as well as their specifications, models, and parameters. http://img.civilcn.com/d/file/dianqi/dqlw/2019-08-28/3a15bbb0d66b44dc02be003f77174c65.png Lighting system diagram
http://img.civilcn.com/d/file/dianqi/dqlw/2019-08-28/8193e5f83e9a4203fce78bdf1402d9b0.png Fire protection system diagram
http://img.civilcn.com/d/file/dianqi/dqlw/2019-08-28/55ac6ba88525a589d981d7a803e0b8e4.png Power system diagram
The system diagrams mainly consist of power supply voltage, main switches, branch switches, wire specifications, conduit specifications, installation methods, circuit numbers, and circuit capacities. http://img.civilcn.com/d/file/dianqi/dqlw/2019-08-28/d30b00b42789154cdff71022897b3a99.png Composition of the system diagram (4) The layout plan is a supplement to the system diagram; it corresponds one-to-one with the system diagram and serves as an important guide for construction. http://img.civilcn.com/d/file/dianqi/dqlw/2019-08-28/8233d5f972c0f4b51173084cff9c1f3c.png The layout plan is one of the important drawings in electrical construction drawings; it includes plans for the installation of electrical equipment in substations and distribution stations, lighting plans, lightning protection and grounding plans, etc. Such plans indicate the numbers, names, models of electrical equipment, as well as their installation locations. They also show the starting points of electrical circuits, the areas where they are laid, the methods of laying them, as well as the types, specifications, number of wires used, and the diameter of the conduits. After understanding the basic components of the system by reading the system diagram, it is possible to prepare an engineering budget and a construction plan based on the floor plan, and then organize the construction. Floor plans are usually divided into: the lighting plan, the power plan, the fire protection plan, the low-voltage electrical plan, the lightning protection plan, and the grounding plan. http://img.civilcn.com/d/file/dianqi/dqlw/2019-08-28/26d5a1bb77039a576034589a69367fd0.png – Lighting layout
http://img.civilcn.com/d/file/dianqi/dqlw/2019-08-28/275f6c0100a06175cb5d9e8a7528eacc.png – Power supply layout
http://img.civilcn.com/d/file/dianqi/dqlw/2019-08-28/111ad752f07c8e02f53c2a5b7d6c8ee4.png – Fire protection layout
http://img.civilcn.com/d/file/dianqi/dqlw/2019-08-28/a2661f5fe5c29a07c6d6cb28c4bc7966.png – Lightning protection layout
http://img.civilcn.com/d/file/dianqi/dqlw/2019-08-28/f9744651b0c9bb8e9b14e7c9d1dc46ed.png – Grounding layout
The layout diagrams consist mainly of equipment, distribution boxes, wires connecting the equipment, and circuit numbers.
http://img.civilcn.com/d/file/dianqi/dqlw/2019-08-28/1c63c95b6ccb95b753538ca7ce70381c.png
(5) Control schematic diagrams: These show the electrical control principles of various electrical devices in the system, and are used to guide the installation of these devices as well as the debugging of the control system. (6) The installation wiring diagram, which includes the layout and wiring of electrical equipment, should be read in conjunction with the control schematic diagram to carry out system wiring and calibration. (7) Installation detail drawings These are drawings that show in detail the methods for installing electrical equipment; they include specific illustrations and precise dimensions for various parts of the installation components, and serve as an important reference for carrying out the installation work and preparing plans for the engineering materials needed. http://img.civilcn.com/d/file/dianqi/dqlw/2019-08-28/f66d95cc97f07a226c05857bf446ba81.png Detail drawing 3. Methods for reading electrical construction drawings (1) Become familiar with the electrical diagram symbols and understand what they represent. Common electrical engineering legends and textual symbols can be found in the **issued ‘Standard for Electrical Graphic Symbols’.** (2) For a set of electrical construction drawings, they should generally be read in the following order, after which specific sections can be examined in more detail. ① Check the title bar and the drawing index to find out the name of the project, its scope, the design date, as well as the content and quantity of the drawings. ② Read the design specifications to understand the general overview of the project, the basis for the design, and other relevant details that are not clearly expressed in the drawings. ③ Check the equipment and material list to find out the models, specifications, and quantities of the equipment and materials used in the project. ④ By examining the system diagram, one can understand the basic components of the system, the connection relationships between the main electrical equipment and components, as well as their specifications, models, and parameters, thereby gaining an overall understanding of the system’s structure. ⑤ Look at the layout plans, such as the lighting layout plan and the lightning protection and grounding layout plan. Understand the specifications, models, quantities of electrical equipment, as well as the starting point of the circuits, the locations where they are laid, the methods of laying them, and the number of wires. Reading a floor plan can be carried out in the following order: power supply inlet, main distribution box, branch circuits, distribution boxes, and electrical equipment. ⑥ By examining the control schematic diagram, one can understand the electrical automatic control principles of the electrical equipment in the system, which serves to guide the installation and debugging of the equipment. ⑦ Consult the installation wiring diagram to understand the layout and wiring of electrical equipment. ⑧ Check the installation detail drawings to understand the specific methods of installing electrical equipment, as well as the exact dimensions of the installation components. (3) Focus on the key points of electrical construction drawings when reading them. When examining such drawings, it is necessary to concentrate on the essential aspects, such as: ① Based on determining the load class, understand the source of the power supply, the method of connection, and the number of circuits ； ② Find out how the power supply enters the building: through low-voltage overhead lines from the outside or via buried cables ； ③ Clarify the phase sequence, path, pipeline installation location, installation method for each power distribution circuit, as well as the type and number of wires ； ④ Specify the planar installation positions of electrical equipment and components. (4) Read in conjunction with the civil engineering construction drawings. Electrical construction is closely integrated with civil engineering construction, and coordination among different types of workers is often required during the construction process. The electrical installation plan only shows the layout of electrical equipment in a plan view; by combining it with the civil engineering drawings, it is possible to understand the three-dimensional arrangement of such equipment as well. (5) Be familiar with the construction sequence to facilitate the reading of electrical construction drawings. When reading electrical distribution system diagrams and lighting and socket layout plans, it is necessary to first understand the construction sequence of indoor wiring. ① Determine the equipment installation location, wire routing method, routing path, and the locations where wires pass through walls or floors based on the electrical construction drawings ； ② In conjunction with civil construction, embed various embedded parts, conduit pipes, junction boxes, and protective pipes ； ③ Install insulating supports, clamps, etc., and lay the wires ； ④ Install lighting fixtures, switches, sockets, and electrical equipment ； ⑤ Conduct wire insulation testing, inspection, and power-on testing ； ⑥ Project acceptance. (6) When reading, the various drawings in the construction plans should be considered together. For a specific project, a power distribution system diagram is necessary to illustrate the power distribution relationships ； A floor plan is required to indicate the specific installation locations of electrical equipment and components ； To explain how the equipment works, a control schematic is required ； An installation wiring diagram is required to indicate the connection relationships between components ； To describe the characteristics and parameters of equipment and materials, tables of equipment and materials are required. These drawings serve different purposes, but they are interconnected and coordinated with one another. When reading the drawings, it is necessary to combine them as required in order to gain a comprehensive understanding of the entire project or its individual components. IV. Introduction to Common Electrical Construction Drawings Design Notes: The design notes are generally the first sheet in a set of electrical construction drawings, and they mainly include: (1) Project overview; (2) Design basis; (3) Scope of design; (4) Power supply and distribution design; (5) Lighting design; (6) Wiring installation; (7) Equipment installation; (8) Lightning protection and grounding; (9) Low-voltage systems; (10) Construction precautions. To read a set of electrical construction drawings, one should first carefully read the design specifications. By doing so, it is possible to understand the general overview of the project, the aspects involved in the construction, the basis for the design, the precautions during construction, as well as any matters that are not clearly expressed in the drawings. The example below is the electrical design specification for an apartment, which provides a preliminary understanding of the design notes in electrical construction drawings. Design Instructions I. Design Basis 1. \"Code for Electrical Design of Civil Buildings\" (JGJ/T 16—92) ； 2. Code for Design of Lightning Protection of Buildings (GB 50057—94, 2000 edition) ； 3. \"Technical Specifications for Cable Television Systems\" (GB 50200—94) ； 4. Other current regulations, codes, and standards related to ** and the local area. II. Design Content The electrical design for this project includes a 380V/220V power supply and distribution system, a lighting system, a lightning protection and grounding system, and a television and telephone system. III. Power Supply System 1. Power Supply Method: This project plans to draw 380V/220V three-phase four-wire power from the community’s low-voltage distribution network, leading it to the main distribution box on the first floor of the residences, from where it will be distributed to various electrical outlets ； The grounding system is of the TN-C-S type; the neutral wire at the point of entry must be grounded again, and a dedicated PE wire shall be provided, with the grounding resistance not exceeding 4Ω ； This project adopts a radial power supply method. 2. Cable laying: For low-voltage distribution main lines, copper-core cross-linked polyethylene insulated cables (YJV) are used, which are laid underground in steel pipes or along walls ； For main and branch lines, as well as branch circuits, copper-core wires (BV) are used and installed concealed along the building walls, floors, and ceilings within steel pipes. IV. Lighting Section 1. For this project, the lighting system is designed in accordance with standard residential requirements. 2. All fluorescent lamps are equipped with electronic ballasts. 3. The sockets in the bathroom are waterproof and splash-proof types ； All sockets indoors that are below 1.8m in height are safety-type sockets. 4. The installation heights of various lighting fixtures are detailed in the main equipment and materials list. V. Lightning Protection and Grounding System 1. This project adopts lightning protection measures in accordance with the requirements for Class III civil buildings; the metal structures of the building are used as lightning protection and grounding elements. Artificial lightning conductors are installed on the parapets, while the two diagonal main rebar bars within the frame columns serve as lightning downconductors. The rebar in the structural foundation functions as a natural grounding element. All lightning protection rebar bars are welded together. All metal components and equipment on the roof should be welded to the lightning conductors using 10-mm galvanized round steel, ensuring that the grounding resistance remains below 4Ω. If the actual value is higher than this, additional grounding electrodes must be installed until the required standard is met ； For specific procedures, please refer to the relevant drawings. 2. This project is equipped with a general equipotential bonding system. The PE main conductors of the building, the grounding main conductors of the electrical equipment’s grounding electrodes, metal pipes such as water pipes, and metal components of the building—such as conductors—should be equipotentially connected. The practice of equipotential bonding is in accordance with the national standard 02D501—2 \"Installation of Equipotential Bonding\". 3. All bathrooms equipped with bathing facilities shall be connected to an equipotential system; for specific methods, refer to 98ZD501—51, 52. 4. Overvoltage protection: A first-level surge protector (SPD) is installed in the main power distribution cabinet. 5. The grounding system for this project adopts the TNCS system; the power supply is re-grounded at the point of entry, and the same grounding electrodes are used for both power grounding and lightning protection grounding. VI. Telephone and broadband systems 1. Telephone cables are introduced from outside through pipes buried in the ground to the telephone distribution box on the first floor, and then routed to various user locations ； 2. The conduits and outlet boxes of the telephone system are installed concealed; the specifications of the conduits are shown in the system diagram. VII. Common antenna television system 1. The television cable is introduced from the outdoors through pipes buried in the ground to the television headend box on the first floor, from where it is distributed to various user networks ； 2. The pipes and outlet boxes in the television system are installed concealed; the specifications of the pipes are shown in the system diagram. VIII. Installation method IX. Other matters: During construction, close cooperation with the civil engineering team is necessary to ensure proper pre-arrangements and embedded components are in place. Construction must be carried out in strict accordance with relevant specifications and standards. Any unresolved issues shall be addressed during the drawing review phase and during construction; any changes must be approved by the design unit. A lighting distribution system diagram is an electrical engineering drawing created using graphic and textual symbols to represent the power supply method, the distribution of distribution circuits, and their interconnections in a building’s lighting system. It provides a comprehensive overview of aspects such as the installed capacity, calculated capacity, calculated current of the lighting system, the distribution method, the type, specifications, quantity of wires or cables, the method of installation, as well as the diameter of the conduits used, along with the specifications of switches and fuses. Through the lighting system diagram, one can obtain an overview of the electrical lighting distribution system inside a building; it is also one of the main drawings used for electrical installation and commissioning. For example: The image at http://img.civilcn.com/d/file/dianqi/dqlw/2019-08-28/68638f1bc205695d17beea1dc3bde993.png shows the lighting distribution system diagram for the electrical panels on a certain shopping mall floor