Spring-type connecting insulating clamps (PPE caps) are used for safe connection of wires. The main advantage is high-quality insulation. It also takes less time to complete the work and does not require special skills or tools. Clamps are divided into several types depending on the permissible cross-section of the wires.
Many professional electricians most often use PPE caps as temporary insulation repairs. As a repair option, clamps are actively used in the repair of entrances, MOS, in junction boxes, and voltage panels.
To ensure reliable twisting
To ensure maximum contact between the conductors, you need to ensure that they are in close and strong contact with each other. The spring that is built into the clamp enhances this effect. However, it should be taken into account that the metal spring has its own fatigue threshold, and over time the pressure will weaken and contact will gradually begin to be lost. Also, the bare surfaces of conductors are constantly in contact with air, due to which an oxide film and rust inevitably form on them. These factors will decrease conductivity with increasing intensity. Therefore, for greater reliability and durability of the connection, the use of PPE should be combined with other insulation methods; the reverse is prohibited by the PUE.
Advantages
- easy to install, saves a lot of time;
- do not require additional tools and skills;
- The durable cap simultaneously insulates and protects the connected wires;
- does not require a large amount of additional materials;
- the result is a practical and convenient connection; if necessary, the cap can be twisted and the wires disconnected, or the connection can be remade;
- high-quality PPE can withstand temperatures from –40 to +105 degrees Celsius.
Flaws
- you need to ensure that the size of the clamp matches the cross-section of the cable;
- It is not recommended to use for installing a street line;
- It is allowed to connect only copper electrical wires, caps for aluminum cables must be with anti-oxide paste;
- It is not recommended to use the PPE compound in its pure form.
Design
The PPE cap consists of two main parts: the cap (body) and the internal spring.
The body is made of plastic. Moreover, it must be a heat-resistant and non-flammable material. PVC or nylon are most often used. For convenient and quick connection of wires using these devices, the outer surface of the cap is equipped with ribs or grooves that increase the rotation force when screwing.
The inner spring has a cone shape, its main role is to ensure tight contact between the conductors. Typically the spring is made of steel with an anodized coating.
How to choose PPE
PPE caps should be selected according to the cross-section of the wires. To do this, you need to sum up the cross-sections of each wire and compare the resulting result with the table below or with the size table that comes with the clamps. The voltage of the electrical wiring should also be taken into account.
Types of PPE
Installation
In practice, two methods are used for twisting wires using PPE caps. First method: without preliminary twisting. Second method: with preliminary twisting.
Pre-twisted installation
Often in practice, electricians install PPE on a pre-prepared twist of bare wires. To do this, you need to take the stripped wires and press them tightly against each other. The bundle should be fixed using pliers, stepping back a couple of millimeters from the exposed veins. In this case, you need to start twisting the bare ends of the electrical wires pressed against each other clockwise. For twisting, it is best to use another pliers. A small section can be twisted by hand, but if the wires are thick or there are many of them, then use a tool. Once twisting is complete, bite off the remaining exposed wire at a sharp angle.
Note!
Before using connecting clamps, you need to prepare the wires. To do this, they are cleaned using a stipper. If there is no stripper, then you can use a lineman's knife, but in this case, cuts perpendicular to the cable should be avoided.
Installation without twisting
PPE is installed on electric wires and without twisting (more popular practice). To do this, you need to place the bare wires parallel so that the ends point in the same direction, insert the ends into the PPE and start screwing the cap manually (clockwise). Manual screwing must be done until the spring clicks. A click from the spring will indicate that the twist within the cap has been completed. Further, if the length of the bare wire does not extend beyond the clamp, then the work is finished.
Some electricians recommend exposing a longer section of cable to make the twist longer and more secure. In this case, it will extend beyond the cap, and after a spring click, you will need to tighten the connection using pliers or a screwdriver until the entire bundle of wires is twisted to the very insulating coating. After this, the exposed area must be insulated. The best way to do this is with heat shrink tubing and electrical tape.
Please pay attention!
Make sure that the wires do not stick out from under the cap. The documentation for some clamps indicates the required cut length (usually 10–12 millimeters); if there is no information, then preliminary measurements need to be taken. If you made a mistake in calculating the length of the exposed wires and they stick out from under the clamp, then you should additionally insulate them using insulating tape or varnished cloth.
It is also important that the conductors transmit current through the connection and not through the clamp spring. Since the spring is not predisposed to such loads, it will very quickly overheat and fail.
Important!
Immediately after installing PPE, you need to check the quality of the insulation. To do this, apply the maximum possible load to the line and hold it for thirty minutes. Then you need to check the temperature of the clamp. Functional PPE should not heat up; if your test shows otherwise, you should replace it and test it again.
Do not connect cables made of different metals
You also need to know that you cannot twist a combination of copper and aluminum cables together. Since in such cases, special devices (pads) with built-in metal adapters are used.
Choose the appropriate PPE size
If you choose right size caps that will suit the total cross-section of the wires, the twisting will last a long time and the risk of overheating will be minimized.
How to choose quality PPE
There is no uniform quality standard for these devices yet. An important factor when choosing is the total cross-sectional area of the wires. When choosing, you should try screwing the cap onto your bundle of conductors or a similar one with the appropriate dimensions.
In this case, the clamp must ensure the quality of twisting. It should not fly off with a strong jerk, pull, or the like. But when unscrewing it in the opposite direction, after all these manipulations, it should come off normally and be suitable for rewinding. Also check the spring; it should not fail, become severely deformed, or fall off after the first screw onto the connection.
Check the plastic, it should be pleasant to the touch and should also be resistant to squeezing with your fingers. Bad plastic will not shrink, but may break and crack. Good plastic will bend a little when pressed hard and then return to its original position. If you buy clamps made of low-quality plastic, they may not withstand high temperature loads.
Why is it necessary to use PPE and not do simple “Soviet” twists?
Many amateur electricians use regular twists, without installing PPE (when the wires are arranged in parallel and twisted together using pliers). And they believe that such technology has the right to life. Many give examples that simple twists from 30 years ago still do not fail. In fact, the use of twists without connecting insulating clamps is only permissible when installing a temporary connection. Such twists gradually become loose due to the constant heating and cooling of the cable, and contact is lost. 30 years ago, such technology had a right to exist, since the power of technology was much lower and people used fewer devices in everyday life.
The PPE prevents the connection from loosening due to the fixing spring, which expands slightly due to the heating of the wire and presses the conductors together more tightly. However, such a connection does not last forever, although it can last for many years.
Is it legal to use PPE?
The use of PPE is not regulated by the PUE. The document doesn't say anything about connection clamps at all. However, insulating caps comply with the requirements of GOST 50043.1–92. Hence the conclusion is that the use of PPE is completely legal. For the greatest safety and durability, it is recommended to use permanent connections. These include: welding, soldering, pressed sleeves.
Regular twists (without insulating caps) are prohibited by the PUE. Therefore, in some cases, it is possible to screw insulating clamps onto old strands to make connections safer and compliant with the law.
Video on the topic
During assembly electrical diagrams wires need to be connected to each other. At the connection point it is created electrical contact, having a certain electrical resistance.
The task of any installer comes down to ensuring a strong connection of the wiring with minimal transient resistance and reliable electrical insulation.
For these purposes the following are used:
- twists;
- twists with welding;
- rations;
- screw connections;
- assemblies on terminal blocks and screw blocks;
- self-clamping express terminals from WAGO or REXANT;
- insulating caps for twisting.
In this article we will talk about how to connect wires using caps.
Typically, two main methods are used to properly connect two wires: twisting followed by soldering and regular twisting (without soldering).
But it is worth noting that despite the advantages of traditional methods, they are also endowed with some disadvantages: soldering, being a high-quality connection, during disassembly requires complete removal (“biting off” the soldered part of the wires), which is not always possible due to the supply of wire, twisting increases the chance of oxidation and does not provide a guarantee reliable connection.
Today there is another solution to such problems - these are connecting ones.
PPE caps for twisting wires
PPE caps- these are connecting insulating clips that are made of non-flammable plastic. Inside these caps there is a conical metal spring.
When they are twisted with a little effort, the spring expands and compresses the wires, and the plastic sheath provides reliable electrical insulation, as well as mechanical and fire protection.
PPE caps are conical parts with metal bushings, which have threads inside. By inserting two wires into this part and turning it a couple of times, the wires will be securely connected. If necessary, this connection can be disassembled without the slightest problem.
Connection caps are produced in different sizes for wires from 0.5 to 1.6 millimeters in diameter.
As a rule, the color of the cap corresponds to the specific diameter and size of the connected wires for which it is intended. Thanks to the use of connecting caps, a reliable connection of wires is achieved without the use of additional tools.
PPE caps characterized by the cross-section of the total twisted wires. This cross-section is expressed by the PPE number from 1 to 5. This figure characterizes the cross-section and number of twisted cores.
| Brand | Number and cross-section of cores, mm² | Color |
| SIZ-1 | 2×1.5 | grey |
| SIZ-2 | 3×1.5 | blue |
| SIZ-3 | 2×2.5 | orange |
| SIZ-4 | 4×2.5 | yellow |
| SIZ-5 | 8×2.5 | red |
Accordingly, the larger the number of the PPE cap, the larger the cross-section and number of wires it is intended for.
All wire connections assembled on self-clamping terminals or insulating caps are highly efficient and are gaining popularity.
Express terminals allow you to quickly create a reliable connection, but have a more complex design and are somewhat more expensive. They are more often used to connect conductors to new measuring, automation and protection devices operating on microprocessor circuits.
For everyday frequent use, they are better suited with a simple device. The connection of the conductors is achieved by screwing their metal ends into a strong spring made in the shape of a cone-shaped spiral.
There is no need to insulate the connection point; the spiral is placed in an insulated cap. The material of its body does not support combustion, is resistant to aggressive environments, and provides good electrical insulating properties.
Twisting of PPE wires
Installing the cap on prepared wires is quick and does not require special tools. The created connection is compact. The caps are convenient to use. However, you need to know the rules for their use and develop the necessary skills. Inept handling can lead to dire consequences.
Insulating caps are suitable for connecting several wires of a certain diameter, which is indicated in the documentation. Manufacturers from different countries use their own designations. Therefore, it is better to be guided by the overall dimensions for connecting the wires, and not by the manufacturer’s markings.
Using PPE caps - practical application
Particular care is required when handling aluminum conductors. Soft metal is easily deformed and quickly loses strength.
At twisted cap aluminum is reliably compressed by a conical spring and works well for a long time. Due to the occurrence of electrochemical processes, aluminum wires cannot be twisted together with copper wires.
It is important to remove the optimal length of the insulating layer from the conductor to ensure maximum contact area between the metal parts. It's easy to define. It is enough to insert one wire inside the cap and visually mark the place where the insulation is cut. Remove the insulation and repeat the test installation of the wire. Exposed metal should not extend beyond the insulating portion of the cap.
When removing insulation, use different ways. Many older installers work with a mechanic's knife with an insulated handle and a short, sharp blade made of durable steel. Wedge or razor sharpening is often used, which removes insulation well, but can cause harm in inexperienced hands.
A knife, especially when directed perpendicular to the conductor, can damage the outer surface of the metal. Any scratch, even a barely noticeable one, will increase in size when twisted, reduce the cross-section of the conductor, and reduce its electrical characteristics. The metal will begin to heat up and burn out, especially under heavy loads. A deep cut in the conductor will cause the wire to break when twisted.
You need to remove the insulation with a knife when its blade is positioned at an obtuse angle to the conductor relative to the direction of the cut, using light movements without damaging the metal.
A certain part of electricians use pliers or wire cutters to remove insulation; they deform the metal at the point where the conductor is crimped, which is not acceptable. Insulation can be removed efficiently using special pliers produced for such work.
The method of twisting wires with pliers and then putting on the cap does not ensure reliable contact and its insulation. The caps just fall out over time. But some installers don't understand this.
Taking advantage insulating caps, force must be applied when twisting. It will ensure tight contact between the metals of the conductors and the spring.
To evaluate the effectiveness of using caps before their mass use, it is necessary to connect wires with them and pass a rated current through it with a load device for about half an hour. Analyze the heating of the connection. Then exceed the current and identify problem areas.
Such electrical tests help professionals recognize the weak points of the electrical circuits they create, improve their skills, and perform quality work.
From the point of view of the current rules, wire twists can be roughly divided into two types:
- correct
- not correct
Correct twists include those that are fixed in some way. The following can act as a retainer:
Wires that are simply twisted without fixation are considered an incorrect connection element. It doesn’t matter how many turns you made, how beautifully you connected the wires - all this is outside the rules and prohibited. 
Soldered and welded conductors are considered the best connection, but for most they are simply not suitable due to the banal lack of necessary tools or skills. 
If you decide to repair the wiring yourself, assemble the junction box and at the same time save on installation, without violating the current rules, then PPE caps are an ideal option.
Firstly, you don't need to buy any special tools. For example, expensive welding machines or press pliers. 
PPE caps - 8 types
PPE stands for connecting insulating clamp. This type of caps came to us from the West. In America, this connection and method of insulating wires is considered the most common.
Moreover, foreign consumers have a much richer choice than we have.
Our manufacturers actually produce only two types of PPE:
In the West, as they say, you can choose one for all occasions. It is not clear why the Chinese have not yet jumped in and started producing the same thing for our market.
Here are the main 8 types of PPE caps that can be found there (taken from here).
This is a classic and reinforced (with wings) PPE that we are all familiar with: 
PPE with an improved cap shape, providing more comfortable operation when screwing on: 
PPE cap with low profile design for work in limited space or small junction boxes: 
Low profile wing design for enhanced torque: 
The next cap is a very controversial decision in my opinion, but it is also being released. PPE for connecting aluminum conductors to copper. The cap is filled with a special antioxidant that prevents oxidation: 
Moisture-proof clamps that can be installed on wires in electrical cabinets on the facade of the house, or in wet rooms, and even directly in the ground in the garden: 
They contain 100% silicone sealant, which protects against moisture and corrosion. 
There is no need for heat shrinkage or hermetically sealed insulation of joints. 
PPE with a hole in the top of the cap. 
This is not a defect at all, as it might seem at first glance, but a clamp specially designed for twisting grounding conductors. One of them is brought out through a hole and connected to the body of the panel or equipment. 
There are also similar clamps where the wire is pressed not by a spring, but by a screw connection. 
There is also a device - a connector filled with silicone. 
Any PPE cap with wires can be placed inside it. 
After this, this twist can easily be considered waterproof and placed underground - in the garden, near watering cans, when entering the house, etc. 
Sizes and selection of PPE caps
Domestic and Chinese manufacturers produce PPE caps in 5 sizes from PPE-1 to PPE-5. The largest of them is designed for a total wire cross-section of up to 32mm2.
By the way, be more careful when choosing caps based on cross-sections. Some Chinese PPE may confuse you. On the cap itself it may be written that it is designed for up to 20mm2. 
And on the packaging it is only up to 15mm2. It’s not clear what to believe. 
Quality can be checked even by touch. Low-quality PPE is characterized by poor plastic that can burst during operation. You can distinguish it by simply squeezing it with your fingers. 
More expensive and normal clamps, with difficulty, but are compressed under the force of two fingers. Low-quality options are rougher and much more difficult to compress.
Some people use pliers to help themselves when tightening the PPE. Again, with cheap Chinese caps, when doing this, a break may occur, or the spring may simply fall out. 
A good PPE clamp can easily withstand the operating temperature range from -40 to +105 degrees.
Here are the markings and types of PPE caps with all the characteristics produced by the domestic manufacturer KVT: 
The company also produces a reinforced version of the cap with ears or wings: 
Caps with ears are of course much more convenient than simple ones, but here you need to proceed from the free space in the junction box. Since such ears can take up up to 20% of the space of the total area of the cap.
PPE, as well as sleeve and fork tips, can be distinguished by color. Each color corresponds to a specific wire section.
Using PPE, you can connect 4,5,6 wires, the main thing is that the total cross-section of the twist corresponds to the calculated purpose of the PPE.
In this case, you can easily twist wires of different sections. When crimping wires with sleeves, this causes real problems and difficulties.
You can select and order sets of PPE caps for yourself.
How to properly twist PPE caps
Let's consider the twisting process itself when using PPE. First of all, you need to accurately select the desired clamp according to the cross-section of the wires. The quality of the connection will depend on this.
To do this, add up the total cross-section of the conductors that will be twisted inside the cap.
Let's say these are 3 wires of 1.5 mm2 each. This means the total twist cross-section is 4.5 mm2. Use the table to find the required cap. 
In this case, you do not need to focus on extreme values so that there is no twisting, which is called end-to-end. In this case, the clamp simply will not work, or will work poorly, and the wires will get hot.
For our version of 4.5 mm2, it is better to choose SIZ-3, designed for twisting from 1.5 to 6 mm2. PPE-2 in this case will not be the best choice.
1 way to twist PPE
First, combine the wires. There is no need to pre-twist them or stack them on top of each other. Place them in a PPE cap. 
Then you begin to press it inside the PPE and turn the cap itself clockwise until the spring releases. As soon as the spring has captured the wires, you can begin the process of twisting the wires.
If there is not enough manual effort, and the cap does not have “ears,” you can use pliers or even a screwdriver. The process will speed up significantly.
There is even a specially designed screwdriver attachment for quickly twisting wires using PPE. With this method, the cap remains completely undamaged. 
You can, of course, adapt an ordinary “Shurik” for twisting without any adapters, but the outer insulating layer of the cap will be scratched. 
2nd method of twisting PPE
The second method involves preliminary twisting of the stripped cores with pliers or again with a screwdriver. 
Then you trim the ends for evenness, and only then screw the clamp onto the twisted wires. 
Which method to choose depends on the cross-section of the conductors being connected.
Just try twisting together 4 GOST wires with a cross-section of at least 2.5 mm2 with your hands and a cap. The load on the cap and the spiral will be such that if you move it incorrectly, you can break it.
But twisting two 0.5mm2 wires into PPE is not very difficult.
Twist length
What should the twist length be? According to the manufacturers' recommendations, the twist should be equal to or slightly less than the length of the cap itself (10-12mm).
IEK technical passport for PPE caps -
Navigator data sheet for PPE caps -
If you make it 3-4cm long, at first glance this should not affect the quality of the connection and its resistance. However, there is one caveat here. Namely, the dependence on the number of twisted wires.
The more there are, the more desirable it is to increase the twist length.
If you twist five wires at the same time, to a depth of the PPE cap of only 1.5 cm, then you will never be able to create the same area of contact of these wires, which is obtained with a twist length twice as long.
So be thoughtful about your approach. The main thing after this is to reliably insulate the remaining exposed part of the wire. 
True, in this case it is no longer correct to call the connection PPE, since the cap itself no longer insulates the entire exposed core.
In any case and at any length, this twist is quite reliable and, thanks to the fixation with an insulated cap, the wires will not come loose during operation.
After which it can again be safely used on other equipment or object.
Another common use of PPE is the legalization of twists in old junction boxes following regulations from fire inspectors. 
The caps themselves are made from PVC plastic, which does not propagate combustion. And this is one of the conditions for fire safety requirements for electrical equipment.
Open the box, remove the electrical tape from the old twist and screw a new cap over the cores. True, you may come across twists made counterclockwise, so be careful.
The disadvantages of insulated PPE caps include the fact that they are not suitable for multi-core wires and are only applicable for mono-core wires. 
Manufacturers also do not recommend twisting aluminum wires with them, pointing out that this is primarily a clamp for copper.
Some companies, as mentioned above, produce universal PPE clamps designed for aluminum too. However, for the most part, their use for this particular metal is prohibited. 
And sometimes it can lead to the following consequences: 
Domestic PPE also does not provide a hermetically sealed connection. In a damp room, moisture can accumulate inside the cap, which gradually leads to rust and disruption of the compressive force of the spring.
To avoid this, you can insulate both the wires and the PPE cap itself with electrical tape. 
Another inconvenience of such clamps is their dimensions. If there are a lot of wires in the junction box, then the PPE will take up a lot of free space inside. Sometimes this may even force you to replace the box with another, larger one. 
In general, the choice in favor of insulated PPE caps is made primarily because of their cost-effectiveness and ease of installation. If you need a more reliable and durable connection, then invite professional electricians with all the necessary equipment.
Here is an interesting test of a PPE cap for mechanical load. The guy collected the wires in PPE and hung a punching bag from it, thereby checking how mechanically reliable this contact can be:
To assemble electrical circuits, there is always a need for strong wires and cables between each other.
The following methods of connecting cables are distinguished:
- regular twist;
- twisting using insulating tape;
- twisting using welding;
- connection using a blowtorch;
- connection using self-clamping terminals;
- screw connection;
- twisting using terminal blocks and screw blocks;
- insulating caps for twisting wires.
Connecting wires using caps
The most popular of these methods are conventional twisting and soldering of cables. However, they have their drawbacks. Regular twisting does not allow the wires to be securely fixed and increases the chances of their oxidation. It is impossible to solder cables without removing a certain part of the cable, which is not always convenient. There is also such a thing as PUE (electrical installation rules). These rules clearly indicate the ban on the use of simple twisting; wires must be welded or soldered together, and the use welding machine or a blowtorch can take quite a long time.
One of the best alternatives for connecting cables today is PPE caps.
PPE stands for connecting insulating clips. The outer part of such caps is made of insulated heat-resistant cone-shaped plastic, which can withstand both high temperatures(for example, when the cable overheats) and low (very convenient when installing electrical wiring in severe frost conditions). Inside the cap there is a metal spring-clamp. When the wires are inserted inside, the spring expands slightly and wraps around the cable, thus securely fixing it inside the cap. The outer part reliably protects the twist from moisture and any mechanical impact.
Inside the caps there is a spiral that compresses the connected wires
Usage
To make a connection using PPE, you must perform the following procedure:
- strip the ends of both wires. Here it is necessary to remove the optimal length of the protective (insulating) layer. It’s easy to find out this length - you just need to insert one wire into the cap and mark the cut location. You can remove the insulation from the wire with a regular knife at an obtuse angle. This must be done very carefully, since the slightest scratch will reduce electrical conductivity, and a large cut can even lead to failure of the entire wiring. Removing insulation using wire cutters or pliers is highly not recommended, as they deform the wire;
- pre-twist the ends in a screw pattern;
- insert the wires into the insulating cap;
- turn the cap a couple of times clockwise.
The cap must be screwed clockwise
Thus, the wires will be firmly and securely fixed inside the cap.
It is strongly recommended to test the caps before using them for operational use. To do this, you need to connect two cables using PPE and test them using a load device for about half an hour at rated current. After this, you need to analyze the heating level of the contact, then increase the current level and identify possible problem areas.
It must be remembered that twisting aluminum wires must be carried out very carefully and carefully, since the metal itself has a fairly low melting point, so it can deform very easily.
Do not connect aluminum and copper wires together - aluminum wire will quickly oxidize and thus the formed galvanic couple will destroy the connection.
Classification
PPE caps have the following classification:
- SIZ-1 - designed for two wires with a cross-section of 1.5 mm, gray color;
- SIZ-2 - designed for three wires with a cross-section of 1.5 mm, color blue;
- SIZ-3 - designed for two cores with a cross-section of 2.5 mm, orange color;
- SIZ-4 - designed for four wires with a cross-section of 2.5 mm, color yellow;
- SIZ-5 - designed for eight cores with a cross-section of 2.5 mm, red color.
However, it is necessary to remember that there are also PPE European production. Such caps are also marked by numbers, but their diameter is much smaller. Therefore, it is necessary to pay attention to the cross-section and number of wires indicated on the packaging.
If you use a twisting cap of the wrong size and diameter, there is a high probability that it simply will not fit on the wires, and if you use PPE that is too large, the cap may fly off and the entire electrical wiring may fail.
Comparison with analogues
The main analogue of PPE caps are screw terminal blocks. In this case, the two wires are connected together using a screw. However, this method has several disadvantages:
- The connecting screw must be tightened periodically, since it becomes loose over time and the contact between the cables weakens. This is especially inconvenient if the terminal block is used on an industrial scale or is located in a hard-to-reach place;
- There are a large number of terminal blocks made in China made of polyethylene shell on the market, which can cause a fire when used.
In contact with
We have already reviewed the article: how to twist wires, but only old methods were considered there, which cannot be called safe and simple. For efficient and high-quality connection of wires, it is necessary to use PPE caps. In this article we will look at how to use PPE clips, consider the types, sizes and key benefits use.
Design of PPE clamps
The design of the caps for connecting wires is considered very simple; it includes two components:
- The cap, it is made of plastic and shows electrical insulating properties. Plastic is not afraid of temperature changes and can even withstand a voltage of 600 V.
- Spring. As a rule, the spring has a conical shape, due to which the wires are clamped. The spring is made of steel, but other materials may be used in some situations. Additionally, the spring is treated with an electrochemical solution.
This is what the PPE cap looks like in the photo. 
How to use
We will look at two methods of twisting wires using PPE:
- Without preliminary twisting of the cores.
- With pre-twisting.
If necessary, connect two wires, they can be inserted into the spring with little effort. Then you need to twist them using clockwise rotational movements. 
If you need to connect several wires, then initially they must be twisted together using old methods; for this you can use ordinary pliers. After twisting, the wires must be inserted into the PPE, see photo.
Remember! The wires must be twisted until they are fully connected to ensure reliability. We perform twisting only clockwise; during this process, use force, this is what will ensure a reliable connection for a long time.
Also remember that if the connection is correct, you will not need to additionally insulate the wires, since the caps do an excellent job of this task. However, here it is extremely important to choose the correct size cap so that the wire fits perfectly into it.
You can see how to use PPE clearly in the next video.
Connector classification
Our subscribers often ask the question: how to choose a cap? In fact, you should be careful here, but there is nothing complicated about it.
It’s worth highlighting right away that all PPE connectors are divided into two types:
- Domestic.
- European.
Their markings are the same, the only difference is the quality of execution.
The marking of PPE caps is as follows: 
If we talk about such a parameter as color, then there is no particular point in paying attention to it. Only professional electricians are guided by color, who can determine the cross-section of wires at a glance. And remember that some manufacturers do not adhere to color coding.
Is it worth using: pros and cons
Initially, we will highlight several reasons why it is worth using modern connectors:
- Quite low price.
- Twisting wires with them is a pleasure.
- On their body you can leave designations, for example: where is the phase or zero.
- Safety is created and the likelihood of spontaneous combustion is minimal. Since the plastic of the connectors does not support combustion.
However, there are several disadvantages:
- In many situations, it is not possible to firmly secure the wires.
- Copper and aluminum wires cannot be connected to each other in the caps.
So we looked at what PPE connecting clips are. Finally, we recommend watching a few more videos on this topic.
One more thing, but notice there are a few errors here.