Serial and parallel connection of sockets: a loop and a star
The performance of routine household duties is greatly facilitated by numerous technical devices and equipment. “Tireless workers” illuminate the premises, wash, whisk, bake, wash dishes instead of us. However, just buying them is not enough, the equipment must be correctly connected, agree.
Remember how many negative emotions a triggered machine triggers, which cuts off the line due to overload at an extremely inopportune moment. A very little pleasure is given to a damaged boiler, computer, refrigerator. But the listed troubles can be trivially prevented and generally excluded, which we are happy to help.
To do this, you just need to find out how the parallel and serial connection of outlets for home appliances is made, in which cases the "loop" and "star" circuits are used. This very useful information will be introduced by our article.
The content of the article:
Ways to connect outlets
Today, sockets are connected in two ways: in the first, a separate wiring line is arranged for each point, in the second, several points are connected to one branch at once.
The type of installed sockets is closely related to the type of wiring: whether single-phase sockets equipped with grounding or without it are used, or whether three-phase devices are installed to power devices that operate with a voltage of 380 volts.
The vast majority of technical devices that need to be connected to the power supply are located or confined to the kitchen and bathroom:
Sockets for powerful consumers, for example, electric ovens or boilers, are connected in a separate line. Whenever possible, they use integral pieces of cable during installation, devoid of any connections. Power lines are laid separately from the shield to each point, which somewhat resembles the rays emanating from the star in a pattern.
If it is necessary to connect each such consumer, the powered point must withstand a rated current of 16 - 32A. For a current with the same indicator, it is designed and standing at the input circuit breaker.
A loopback connection is selected if it is necessary to power electrical outlets of the same group. These groups are formed in accordance with the arrangement of household appliances.
The method involves the connection of all elements to a common power supply line.
To reduce the risk of incapacitation of several points at once, the masters recommend that no more than two or three outlets be included in one system. This moment is clearly spelled out in SP 31-110-2003: up to three additional power consumers are allowed to be connected by a loop.
The only condition is that the total current load does not exceed twice the value of the working rated current of the first (main) power receiver.
But, in any situation, the circuit created in this way is designed for a load, the total indicator of which does not exceed 16A. Failure to comply with the operating conditions is likely to create emergency situations.
When connecting outlets, it is not at all necessary to use a clean type of wiring. With a competent approach, they can be combined, for example, bring the power cable to junction box. And after it send one cable in the form of a loop, the other lead separately to the point of supplying powerful equipment in the house.
The number of supply lines laid from the shield depends on how many wiring routes are planned to be laid.
Regardless of the type of method selected, wiring can be performed in one of two options:
- open - involves laying wires on the wall surface;
- closed - involves hollowing out channels for laying power lines in concrete and brick walls, sampling a channel in wood for laying a cable drawn into a corrugated pipe.
The open version is more convenient and simpler regarding not only installation, but also maintenance and control.But regarding the aesthetic aspect, an open wire is not always appropriate. Yes, and besides open installation method “Eats” part of the usable area: it’s impossible to hang a shelf on top of the cable or move furniture close to the wall.
The interior of most cable channels has partitions between which it is convenient to place wires. Monitoring the state of the track is carried out through the upper removable part.
A closed wiring option is convenient in that it eliminates the possibility of accidental damage to the cable, making it invisible to others.
But the "invisibility" of closed wiring can play a trick on trying to "hammer a nail." Therefore, there is an unwritten rule: lay wires relative to outlets strictly vertically or horizontally.
Features of installing a loopback connection
As already noted, the loop method is used to connect outlets in the same group that power low-power devices, such as a computer, audio equipment ...
This type of connection is more economical and technically simpler. Indeed, for its implementation there is no need to lay a lot of cables and use additional protection. But it is worth noting that each additional point of the created chain will make it more vulnerable.
For example, we know that the rated current per outlet should not exceed 16A. If you connect such a load to one point, then nothing bad will happen. But when you turn on such a load at least 2-3 outlets of one line, its total readings will increase, as a result - the power cable may not withstand.
According to the PUE, with a loop connection it is not allowed to break the PE conductor of the protective grounding wire. In any case, its outline must remain inextricable.
The use of one of the technical solutions helps to reduce material costs when connecting a PE conductor to sockets:
This type of connection is chosen if necessary to connect sockets that are located almost close to each other.
With a loop connection, the trunk wire, supplied from the power shield, enters the seat of the multi-seat socket. From it, he feeds the first outlet, from which through his own contacts the power goes to the second outlet, from the second to the third.
When installing a cable, the incoming and outgoing cables are connected directly to the contact part of the device. For this reason, masters recommend using models equipped with a flat spring contact.
In extreme cases, samples whose contacts are made in the form of a plate pressed by a bolt are suitable. Devices in which an ordinary bolt plays the role of a contact are not at all suitable for this purpose.
One of the mandatory operational requirements when connecting sockets with a loop is the need to reduce the transition resistance in the circuit between the contact terminals of the socket and the contacts of the electrical plug.
To achieve the desired effect, the terminals are given shapes that allow you to increase the area of the contacts themselves, as well as the strength of their compression. Today, Scotchlok connectors are often used to install protective zero. This type of clip connector is equipped with mortise contacts.
To use a clip-on connector, you should select products that provide additional space for its placement.
Through the contact of the first outlet, the phase wire of the supply cable and the PE conductor of the loop, coming further to the second outlet, are fed. On the second contact are the neutral wires of the power cable and a loop to the second outlet. By the same principle, they connect to the third and subsequent outlet, if its presence provided for a power wiring diagram.
According to the PUE p. 1.7.144 for connecting the open conductive part of the device to the neutral or grounding conductor, it is necessary to branch in the cavity of the wiring of the wiring accessories intended for this purpose. These include sockets.
The main task when connecting outlets equipped with grounding is to ensure reliable connection elements throughout the line. After all, if the ground contact for any reason burns out in the head power outlet, all other participants in the circuit will lose the protective zero. And therefore, if necessary, branches of the grounding conductor use the most reliable type of connection - crimping.
The method involves, in addition to the usual twisting of wires, additional insulation and crimping of their ends with a sleeve. This ensures uninterrupted contact of the circuit elements and its high mechanical strength.
Installation of an additional junction box
This method involves the installation of a junction box connected to the shield of a branch box or a connecting block next to the loop of sockets. In this case, the cable branches in the junction box on the site until it is brought to the socket.
Connections within the branch box leading to each outlet are most often made by welding. The insulated ends of all conductors are recommended to be laid in junction boxes so that they do not intersect and do not touch each other.
In both cases, when a phase and zero are connected to the sockets of the wires, a loop is formed, and a branch from the PE conductor. Therefore, when looping outlets, it is important to observe the polarity of the contacts: remove the zero from the terminal with a zero conductor. Do the same with the phase wire.
Given the number of working electrical appliances, the number of sockets in the room can reach 10 pieces. Using tees and extension cords is not always convenient, and it’s also dangerous. In this case, they solve the problem by installing outlet blocks instead of a single outlet.
The design of the outlet block, including up to four separate elements, is connected in the same way as a single outlet.
When connecting the blocks, the conductors are connected by any of the methods described. The exposed areas are insulated with a heat-shrinkable tube or wrapped with insulating tape.
Parallel Connection Specifics
A feature of the parallel socket connection scheme, otherwise called the “star”, is a separate connection to the shield of each socket.
The third well-founded name is “unmanned”, because suggests the possibility of rejection of the junction box.The method is actively practiced in European countries, and we use it to provide powerful consumers with a separate line, most often in combination with loop technology.
One of the options for a parallel circuit shows a selection of photos:
Plus “stars” in ensuring the maximum degree of security. A significant advantage is the creation of the ability to individually manage large energy consumers, which is a priority for power wiring for “Smart home”, eg. The minus of the circuit lies in the impressive labor costs of the electrician and in almost three times the cable consumption.
A parallel circuit is also used to connect three-phase power sockets that will power powerful electrical appliances. At the same time, the cross section of the cores supplying such consumers should be at least 2.5 square meters. mm
For greater reliability, they should have a small current margin. This will make it possible to compensate for the actual deviation from the diameter indicated by the manufacturer from their nominal value, which often “sin” products on the market today. In addition, this solution will provide the ability to operate equipment in overload mode.
This installation method is advantageous in that the operability of each individual point does not affect the functioning of the other participants in the circuit. For household appliances, such a scheme is considered the most stable and safe.
Connecting a three-phase outlet, equipped with grounding, is performed using a separate four-wire wiring. The cable, which includes three phases, grounding and zero, goes directly from the shield.
The purpose of the wire is most easily determined by the color of the insulation:
- "Phase" - wires with a white tint;
- “Zero” - the insulation is colored blue;
- "Grounding" is a yellow-green braid.
Grounding is essentially a protective zero. In order for it to remain such, it is necessary to ensure its reliable and constant connection throughout the line.
To connect the wires and connect to the outlet, the first thing to do is shorten their ends. The use of side cutters will allow the most accurate work. The end of each wire is stripped 15-20 mm from the outer insulation with a sharp knife.
The wire connection is performed in the following sequence:
- Remove the plastic protective cover from the outlet.
- The clamping screws are loosened by 5-6 mm.The same manipulations are done with the screw and on the ground terminal.
- The stripped ends of the wires are alternately inserted into the box, taking into account the position of the input terminals, and laid in the appropriate sockets.
- The jacks with laid wires are tightened with screws.
- A socket with connected wires is inserted into a wall niche and fixed with side clamps.
To obtain a more reliable assembly, some masters twist the bare ends of the cores in the form of a loop or ring so that their diameter matches the size of the legs of the screws.
After that, each screw is unscrewed in turn, its base is wrapped with a wire ring and tightened tightly.
At connecting outlet blocks all the advantages of the circuit are preserved. The only thing is that the connection process takes a little more time and effort.
Increased costs are not an argument for those for whom safety is a priority. If you look at the situation more globally, it is sometimes better to immediately invest more money and effort by equipping an autonomous power line for the outlet. Then every time you don’t have to think about whether it is possible to use a point to connect a particular appliance.
Conclusions and useful video on the topic
Video # 1. Guidelines for the application of the loop method:
Video # 2. Detailed familiarization with one of the safe options for connecting outlets:
Provided that the amount of energy spent on household needs is increasing every year, and therefore the requirements for the reliability of outlets will certainly increase, preferring to still follow a parallel wiring diagram. Especially when it comes to serious energy consumers.
To power luminaires, electric alarms and similar devices, the option of connecting with a cable is suitable.
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