A high-quality connection of conductors is the foundation for the safe and durable operation of any electrical circuit, be it wiring in a car, a switchboard in a home, or complex industrial equipment. Incorrect connection often causes overheating of contacts, melting of insulation and even fire, so the skill of competently sealing cores must be honed to the point of automaticity. Many craftsmen neglect to use special tips, simply twisting the wires, which is a serious mistake, especially under conditions of vibration and temperature changes.
During the installation process, it is important to understand that copper and aluminum cores have different physical and mechanical properties, requiring an individual approach to preparation. If you plan to do the job professionally, you will need not only a basic set of tools, but also an understanding of how different types of contact groups work. For multi-core wires, the use of lugs is a mandatory requirement of the PUE, since without crimping, thin wires quickly fluff up and contact is lost.
Next, we will analyze all the stages of preparation, selection of consumables and the actual connection process in order to eliminate the risk of oxidation or weakening of the contact in the future.
Necessary tools and materials for high-quality installation
Before starting any work with electricity, it is necessary to prepare a specialized tool that will ensure a reliable connection. The basic element is crimping pliers (crimper), which allow you to create pressure sufficient to deform the metal of the tip and core, turning them into a monolithic whole. The use of pliers or a hammer is unacceptable, as they cannot guarantee uniform crimping on all sides, which will lead to voids and heating.
You will also need strippers for careful stripping of insulation without damaging the conductor. Working with a knife takes longer and is more dangerous, since there is a high risk of making a notch on the copper, which will become a breaking point during vibration. To clean oxidized surfaces and give the wire the desired shape, a needle file or fine sandpaper is often used.
- 🛠️ Crimper - the main tool for creating a permanent connection, selected for the type of tip.
- ✂️ stripper — allows you to quickly and accurately remove insulation without damaging the metal.
- 🔥 Heat shrink tube — necessary to insulate the joint and protect it from moisture.
- 🧴 Contact lubricant — prevents oxidation of copper or aluminum during operation.
Don't forget about personal protective equipment. Dielectric gloves and glasses will protect you from accidental sparks or metal particles when cleaning. Remember that tool must be in good working order: the jaws of the pliers must not have any play, and the cutting edges must be sharp.
Choosing the right terminals and lugs
The electrical engineering market offers a huge variety of connecting elements, and the choice depends on the type of wire, current strength and operating conditions. Terminals can be screw, spring or knife, each of which has its own installation features. For automotive wiring, ring or fork lugs are most often used, which provide maximum contact area.
When choosing tips, it is important to pay attention to the material of manufacture. Brass products are cheaper, but conduct current less well and are more susceptible to corrosion compared to tinned copper. For power circuits where the currents are high, it is recommended to use only tinned copper lugs, often marked with the abbreviation NSHVI (for bushings) or NKI (ring insulated).
The size of the tip must strictly correspond to the cross-section of the wire. If you try to insert a thin wire into a wide sleeve, the contact will be weak even after crimping. Conversely, pushing a thick strand into a narrow shank will result in damaged insulation or an inability to connect.
| Tip type | Marking | Application | Material |
|---|---|---|---|
| Bushing insulated | NSHVI | Connection to machines, terminal blocks | Tinned copper |
| Ring isolated | NKI | Bolted connections, weight | Copper |
| Fork insulated | NVI | Screw terminals (easy access) | Copper |
| Shtyrevoy | NSHPI | Butt or socket connection | Brass/Copper |
Preparing the wire for connection
The quality of wire stripping directly affects the reliability of the contact. When using a knife, there is a high risk of damaging several of the outer strands of the stranded wire, which will reduce the effective cross-section of the conductor. Therefore use stripper is the most preferred option. The length of the area to be stripped must exactly correspond to the depth of the contact sleeve of the tip.
If the insulation is stripped too short, some of the cores will remain exposed, which may result in a short circuit or poor contact. If it is too long, the loose part of the wire will dangle, creating a risk of shorting to adjacent elements. After stripping, it is recommended to lightly twist the strands with your fingers to give them a tight cylindrical shape before inserting into the sleeve.
When stripping stranded wire, always twist the strands slightly clockwise - this will prevent them from fraying as they enter the ferrule and ensure a tighter contact.
For aluminum wires, preparation has its own nuances. Aluminum instantly oxidizes in air, forming a film with high resistance. Therefore, it is necessary to clean the aluminum core immediately before installation and be sure to lubricate it quartz-vaseline paste or special conductive lubricant.
Technology of crimping and insertion into the terminal
The joining process begins with selecting the correct die in the jaws. The crimper jaws are usually marked with cross-sections (for example, 1.5, 2.5, 4.0 mm²), which should match the cross-section of your wire and the size of the tip. Insert the wire into the lug sleeve as far as it will go, making sure that the wire insulation extends slightly inside the metal part (for insulated lugs) or is flush against the end (for non-insulated lugs).
Position the tip in the plier nest so that the sleeve seam (if visible) is in the middle of the die jaws. Squeeze the handles sharply and confidently until you hear a characteristic click or the jaws completely close. For bushings NSHVI a trapezoidal matrix is often used, which compresses the sleeve on four sides, providing maximum contact area.
☑️ Procedure for crimping
After crimping, be sure to check the connection. Try to slightly pull the wire and the tip in different directions - they should not move relative to each other. If the tip rotates or falls off, it means that the crimping was performed poorly, and the procedure must be repeated with a new consumable.
⚠️ Attention: Never use the tin-plating method before inserting a stranded wire into a screw terminal or spring terminal. Under the pressure of a screw or spring, the soft solder will “flow” over time, the contact will weaken, which will lead to sparking and fire.
Features of connection to screw and spring terminal blocks
When using classic screw terminal blocks (for example, barrier or in junction boxes), it is important to observe the tightening torque. Overtightening the screw can cause the wires inside the tip to break, especially if soft copper is used. An under-tightened screw will leave a gap in which sparking will occur.
Spring terminals such as popular WAGO, greatly simplify installation. To connect wire with lug type NSHVI It is enough to insert it into the hole until it stops. The spring mechanism will automatically fix the wire. However, it is worth remembering that not all spring terminals are designed to work with lugs - some models are designed only for solid solid wires.
Why can't copper and aluminum be connected directly?
Direct contact between copper and aluminum results in galvanic corrosion. In the presence of moisture, an electrochemical reaction occurs between these metals, which quickly breaks the contact, increasing resistance and causing heating. Use bimetal strips or tinning for these connections.
If you are connecting the wire to the battery or starter terminal, use ring lugs. They provide better contact compared to fork ones, since the contact area is larger, and eliminate accidental slipping when the vehicle vibrates. Be sure to use washers and locking screws to prevent the nut from unscrewing itself.
Isolation and final system check
After successfully connecting all wires, it is necessary to ensure reliable insulation of the connection points. The best way is to use heat shrink tube. Select a tube of the appropriate diameter, put it on the joint and heat it with a hair dryer or carefully with a lighter (being careful). The tube will tightly wrap around the connection, creating an airtight cocoon.
The final stage is checking the assembled circuit. Visually inspect all connections for protruding wires or damaged insulation. If possible, measure the circuit resistance with a multimeter - it should be minimal and correspond to the calculated values. Under load (turning on the consumer), check the temperature of the terminals: they should not heat up above 50-60 degrees.
- 👀 Visual inspection - no gaps, protruding wires or damage.
- 🌡️ Temperature test — checking heating under load after 15-20 minutes of operation.
- 🔌 Mechanical check — slight twitching of the wires for secure fixation.
High-quality heat-shrink insulation protects not only from short circuits, but also prevents the entry of moisture and oxygen, stopping the oxidation of the metal for many years.
Regular maintenance of electrical connections, especially in a car, involves periodically tightening the screw contacts, since metal tends to “flow” under load and vibration. Compliance with installation technology ensures that the system will last its entire service life without failures.
⚠️ Attention: Before starting any wiring work, be sure to turn off the power source (remove the terminal from the battery or turn off the machine). Working under voltage is fatal and can short-circuit equipment.
Frequently asked questions (FAQ)
Is it possible to crimp the tip with ordinary pliers?
Theoretically it is possible, but the quality of such a connection will be extremely low. The pliers do not apply even pressure on all sides, leaving voids inside the case. This results in high contact resistance and heating. Use a specialized crimper.
Do I need to tin the wire before inserting it into the terminal?
No, you cannot tin the wire before inserting it into screw or spring terminals. Solder is softer than copper, and under the pressure of the screw it will begin to deform (flow), the contact will weaken, and the connection will begin to heat up. Use mechanical crimping only.
What to do if the wire is aluminum and the terminal is copper?
Direct connection of copper and aluminum is prohibited due to galvanic corrosion. Use special bimetallic tips (copper-aluminum), lubricate the contact with quartz-vaseline paste, or use an intermediate steel washer (although this is a less reliable method).
How to choose the size of heat shrink?
The diameter of the heat shrink before shrinking should be approximately 10-20% larger than the diameter of the widest joint (usually where the wire enters the ferrule). After shrinking, it should shrink at least 2 times, tightly fitting the surface.