- Terms of Reference – the starting point for design
- Making a schematic diagram of power supply
- We make working drawings
- We determine the ways of laying cables
- We count the power cable
- We plan a switchboard
- We plan the installation of electrical wiring
The article is intended for the average builder who is puzzled by eternal questions: where to start this complex and incomprehensible electrician, how will this all happen, when you can start, where to look, whom to invite …
The arrangement of electrical communications is the most important stage in the construction of a private house. It is quite obvious that it is impossible to begin the installation of electrical wiring without detailed design, and this statement applies not only to buildings under construction, but also to those that are undergoing reconstruction and major repairs. The quality of planning and performing electrical work depends not only on the functionality of all volatile devices and household appliances, but also on the safety of people. The owner, like no one else, is interested in careful preparation, so it is not worth saving time or money here..
The most optimal solution, of course, would be to order a project from a specialized organization, especially since a well-developed documentation will help to calmly conduct a conversation with Rostekhnadzor and business entities, to launch the facility into operation. The power supply project is the only document according to which electrical installation can be carried out, its main purpose is to ensure the safety and efficiency of wiring already at the development stage. In fact, this is a whole package of documents containing the full amount of necessary information:
- wiring diagrams, characteristics of conductors;
- installation methods and connection types of all elements;
- indication of all equipment, customer specification;
- location and features of wiring accessories;
- load calculations …
Even if the owner of the home has turned to professionals, he must provide the engineers with a technical assignment, which means that he must first sort out many issues on his own. Now we will not try to make an “official” electrical project for a country house on our own, but we will try to outline all the main points, the systematization of which will help you:
- competently answer questions from designers;
- calculate the required capacity, redistribute limited energy resources;
- plan the order of electrical work and synchronize them with general construction;
- predict your expenses;
- competently inspect hired specialists, or get to work yourself.
In general, our task is to completely eliminate the possibility of unpleasant surprises and in any situation to keep everything under our control..
Terms of Reference – the starting point for design
Conventionally, the power supply of a country house is divided into three main parts: wiring in a residential building, organizing communications on the street, connecting outbuildings. Each of these areas should be considered separately and have its own electrical circuit, its own working drawings. To solve this problem, you need to set yourself (or the designers) a technical task. This is the initial plan, which depicts all the power consumers of the house and outbuildings, lighting devices, simplified communication routes. As a rule, the preparation of the terms of reference is the result of the joint work of the designer, the customer and the contractor performing the electrical work..
Drawing up a technical assignment and a project for it will allow:
- take into account all the points of electrical outlets so that every household appliance or unit is powered;
- place sockets and switches in convenient for use, and junction boxes in places accessible for service;
- calculate total power consumption.
We need to first create separate drawings of each floor of the house and each room, where all partitions, door blocks with the direction of opening of the canvas, furniture elements, large stationary appliances (TVs, computer, electric fireplace, refrigerator, internal blocks of split systems, boiler, jacuzzi etc.). A prerequisite is the binding of consumers to the enclosing structures, therefore, you should either finish the construction of internal partitions, or make an accurate and final layout of the layout directly at the facility, determine the level of the finished floor. Only then can we make measurements and make complete plans of the premises, where we will mark all the conclusions, each outlet, switch, lamp.
Special attention is paid to low-current networks – high-frequency TV, Internet, video surveillance, motion and presence sensors, stationary audio systems.
In some cases, local drawings are made for nodes that are especially loaded in the design and electrical plan (concrete walls, multi-level ceilings in separate rooms).
A very important point. For the correct preparation of the technical assignment, it is necessary to have passports of all main consumers, this is the only way to get reliable information about the dimensions of the products, how to connect them, power, etc. For example, it is worth knowing in advance how many switching positions the chandelier will have in the living room (determines the number of veins conductor), or, for example, the specification of the hob (determines the cable cross-section, type and location of the terminal).
At this stage, it is necessary to take care not only of internal communications. We must not forget about: pumping stations; cleaning, air conditioning, ventilation systems; street lighting and outdoor sockets; anti-icing systems for gutters, steps; control and automation systems; standby / autonomous power supply.
When all consumers are known, the total load is calculated by simply adding up the capacities. If the allocated energy resources are not enough, it is necessary to revise the complete set of the house, to choose more economical devices. As a last resort, you can continue to develop the project, and, on its basis, request a larger limit from the electricity supplier.
Based on the terms of reference, you can make a list of the necessary sockets, switches, multi-post frames. We recommend creating a general list of product types, and several small lists for completing each room.
Once again, we note that the technical task cannot be drawn up sitting at the table, more than half of this work is done by the homeowner “in the field” – with a tape measure in his hands, and the whole family on his shoulder.
Making a schematic diagram of power supply
The schematic diagram is a very important and very complex part of the project, which is developed by the specialists of the electrical laboratories. This document is fundamental for planning and carrying out electrical work, when drawing up working drawings.
Our task is to create a simplified power supply scheme that will help us see the overall picture of the power supply at home. In fact, it can be a visual drawing, a drawing with symbols, which will resemble a tree with a root in the form of a main distribution board and branches ending in separate outlets or lamps. The trunk is the highway, where the branches are separated – these will be additional shields or junction (junction) boxes. Cables leading from the board to the device directly can be knocked out of the general canvas. You can include circuit breakers and residual current devices in the circuit, then it will look something like this:
If the electrical at home is very complicated, then it makes sense to make a power circuit diagram and your own circuit for lighting, since they are always bred separately in the house.
If the cottage is powered by three phases, then we make three different schemes. At the same time, in order to achieve a power balance, on the basis of the technical assignment (consumer capacities), the load should be evenly distributed on each of the phases – to proportionally group devices and units.
We make working drawings
The working drawing is a document according to which the electrician on the site performs the cabling. If the project is more focused on justifying the choice and agreeing on certain technical solutions, then the working documents are intended for the implementation of this project. This is a hybrid of technical specifications drawings and a schematic diagram. A working drawing is developed on the basis of a technical design and with strict observance of the requirements of the PUE.
Here you need maximum detail for each room, sometimes they create their own working drawing for a specific wall. Separately, it is necessary to depict the working floor plan, which shows the highways and entrances to specific rooms.
What should be indicated in the drawing:
- Lead points with reference to walls, floor, ceiling; single and multi-point sockets; switches, lamps.
- The lines indicate which lighting groups a particular switch key is responsible for..
- Locations of distribution boxes and trunk points, group shields.
- Paths of wires.
- Brand and cross-section of conductors.
- Connecting a group to a particular phase.
- Arrangement of low-current circuits.
Example of a lighting layout
An example of a layout of outlets
Do not forget to give the exact name of the room or unit for which the plan was made.
When making a working drawing, apply color highlighting, label groups and individual consumers with numbers, make notes and explanations. The lines of the networks are drawn on the plan with thicker lines than for drawing elements of the building and stationary equipment. The number of conductors in one line is indicated by short oblique serif strokes directly on it. There is a generally accepted set of conventions, as well as established requirements for numbers and inscriptions used in electrical drawings. They are shown in GOST 21.614–88.
We determine the ways of laying cables
Depending on the structure of the building and the types of finishes, it is necessary to determine the methods of laying the cables. For a private house, there are two main options:
- by gender
- on the ceiling
Wiring in the floor is possible if the screed has not yet been poured. The method has a number of advantages, among which a more economical consumption of cables can be noted. Ceiling mounting is possible if suspended structures are used. This wiring option allows safe floor drilling during future general construction works, makes it possible to perform installation regardless of the type and condition of the floor. For wooden houses, open wiring is often used in channels or on insulators, including along walls.
Attention! Low-current communications are recommended to be kept separately from power.
To select the route to follow for each line, you must:
- conduct a thorough examination of the structure and technical condition of the building;
- plan ways to avoid / cross obstacles and technical communications;
- develop ways to go to different rooms / floors / outside.
It is important to remember here that all electrical communications, without exception, must turn at right angles with a moderate bending radius. The descent of the wire from the ceiling or its wiring from the floor to the wall must be carried out strictly vertically. For more information on the types of installation and the rules for performing cable work, see the article “How to securely and safely lay electrical wires”.
We count the power cable
Now that we have the exact location and specificity of the power points, the routes of communications have been determined, a decision has been made on the method of laying, there is a schematic diagram and a working drawing on hand (which means that we know where the junction boxes will be and which consumers are powered from them) – we can accurately calculate the required amount of each type of cable.
In a private house, there must be grounding – therefore, a three-core wire with a soft copper conductor in double insulation must be used. For sockets, wires with a conductor cross section of 2.5 mm are suitable2, 1.5 squares are used for lighting, for powerful consumers (with connection to terminals) and powering intermediate boards (storey, for individual buildings), 4 mm cables are often used2 or even 6 mm2. Note that the following consumers are traditionally connected directly to the shields, bypassing the boxes:
- engineering units and systems (pumping stations, air conditioners, heated floors, cleaning and anti-icing systems);
- powerful household appliances (oven, hob, boiler, washing machine, dishwasher, electric boilers and heaters).
Using a tape measure, we measure the length of each conductor:
- from the shield to the terminal box;
- from the board to the consumer (with direct connection);
- from the box to the power consumer, to the switch, to the lighting device.
It is necessary to take into account the supply of wires for output from the walls and junction boxes – from 15 to 25 cm, and the supply of wires near the electrical panel – up to 1 meter (with a large number of wires, some of them have to be run into the box from below, and some from above).
We make a list of all wires for each room, give the name of the group or device in numbers, designate them in accordance with the markings indicated in the working draft. The work seems unnecessary and tedious, but it still has to be done at the stage of preparation and cabling..
Summing up the indicators, we get the need for cable and wire products of various types. The same figures show how much you will need to buy protective corrugation, insulation pipes or cable ducts..
We plan a switchboard
As we have already said, in a private house there may be several shields, this is the main input-distribution device, as well as simplified shields for floors and auxiliary buildings. Each of them is assembled approximately according to the same principle, contains a similar set of elements.
The number of installation products here can be very diverse, but it is always worth giving preference to boxes with several spare “places”.
For a high-quality arrangement of shields, their design should be carefully worked out. For this, a special wiring diagram is created for each input-distribution device. The procedure is as follows:
- Making a list of all incoming wires.
- We indicate the load and the maximum current for each of them.
- We select the appropriate circuit breaker for all list items.
- For several groups of consumers we select residual current devices, but a fire-fighting RCD is installed on the entire system.
- We make a working drawing.
- Making a list of required protection devices and accessories.
Examples of electrical panel diagrams:
1 – introductory machine; 2 – counter; 3 – zero bus; 4 – grounding bus; 5-9 – differential automata; 10 – lighting machine
1 – introductory machine; 2 – counter; 3 – fire-prevention RCD; 4 – common zero bus; 5, 6, 12 – lighting machines; 7 – RCD for consumers 2, 3, 4; 8, 9, 10 – machines for consumers 2, 3, 4; 11 – additional zero bus; 13 – differential machine; 14 – RCD for circuits 5, 6, 7; 15, 16, 17 – machines for consumers 5, 6, 7; 18 – additional zero bus; 19 – grounding bus (conductors from lighting can also come here)
Attention! Switching of low-current networks cannot be performed in power panels, for them separate boxes must be used.
We plan the installation of electrical wiring
The main task of this stage is to coordinate the arrangement of power supply with other construction works. The second point is to logically organize the activities of the installer; optimize the processes of supplying materials, using special tools and devices; properly prepare the workplace.
Electrical work begins at the stage of production of rough general construction operations, as a rule, in parallel with them. For example, the cabling on the floor is carried out before the screeds are installed, but on the walls that are plastered, it will be more rational to finish the rough finish, cut the grooves – after that, wire the wires and fix the socket boxes. When cladding walls and ceilings using frames, the cables are passed before the installation of the cladding and remain in the cavity, and then holes for the installation boxes are cut out and the ends are pulled out. Open wiring is done over the finishes. The mechanisms of wiring accessories are mounted after the main painting and facing works; frames of sockets and switches, lighting fixtures are installed after finishing.
Electrical work is the least mechanized in construction, but some aspects can be optimized. For example, you can order a complete input-distribution device manufactured at the factory, perform a number of preparatory work in advance (marking, cutting and marking the cable, pulling conductors into a protective corrugation, making strobes, installing line fasteners in place, installing installation boxes, stripping and crimping the ends). Many of these jobs can be outsourced to less qualified personnel..
In capital construction, measured pieces of wires from one box are commutated on a special preparation line, and then they are dragged to the installation boxes (nodal method). The second option is “ray”, when an electrical installation product is connected to the prepared wire (cut, stripped and crimped) at the stand, and then the cable is dragged to the junction box. In low-rise individual construction, due to the relatively small volume of work, these operations are not subject to industrialization, however, all of them must be carried out in accordance with the current regulatory documents, such as PUE or SNiP 3.05.06–85 “Electrical devices”.
In a private house, manipulations to organize the input will be mandatory. The developer has a lot of questions about the arrangement of grounding. We list the stages of installation of the “internal” in chronological order (some operations can be performed simultaneously), for auxiliary buildings and street consumers the order of their implementation does not change:
- Marking the locations of the installation products and the paths of the lines.
- Cutting grooves and niches for installation and distribution boxes, preparation of channels.
- Making passages to various rooms.
- Installation of boxes, socket boxes, boxes for ASP.
- Preparing cables for installation.
- Routing and fixing power wires along their routes, marking conductors.
- Installation of lighting circuits.
- Layout of low-current networks.
- Preparation, switching of conductors in junction boxes.
- Assembly of switchboards, switching.
- System health check.
- Installation of wiring mechanisms.
- Second check, commissioning.
- Installation of facades for sockets and switches.
- Installation and connection of lighting devices, household appliances.
- Connection of various power units, autonomous power supply devices and ATS.
- Connection of low-current consumers (antennas, fire and security sensors, routers and modems, elements of audio systems).
This is how we saw the planning of work on the design and installation of electrical networks of a country house. Of course, we were not able to cover all the nuances, but we hope that you were able to gather some useful information. In subsequent publications, we will continue the “electrical” topic.