The connection of electrical circuits in a modern car requires high reliability, especially when it comes to power lines or signal lines subject to vibration. Usage NShVI tips (insulated pin bushings) has become the quality standard for connecting dissimilar conductors. Often a situation arises when it is necessary to combine two wires into one connection point, for example, when parallelizing power or combining signals.
Simply twisting two wires together and inserting them into a terminal is a blunder that can lead to heat, oxidation, and even fire. Correct Application double tips NSHVI or the clever use of single versions for paired cores ensures mechanical strength and perfect electrical contact. In this article we will analyze all the nuances of selecting standard sizes and installation technology.
The main problem when working with two wires is that their total diameter may not match standard tip gauges. If you try to stuff two cables into single NSHVI, intended for one, you will damage the insulation or will not be able to fix the wires. On the contrary, using a tip that is too large will leave voids, leading to sparking.
What is NShVI and why are they needed in auto electrics?
Abbreviation NSHVI stands for Insulated Pin Sleeve End. This is a metal sleeve, usually tinned (coated with tin), with a plastic cuff on one side. The cuff serves two purposes: it prevents electric shock when touched and prevents the wire from slipping out when clamped, since it has a larger diameter than the inlet hole of the terminal block.
In automotive wiring, where there is constant shaking and temperature changes, the soft copper core tends to “flow” under the pressure of the screw. Over time, the contact weakens, resistance increases, and the connection begins to heat up. Pressure testing of NShVI turns a bundle of soft wires into a monolithic solid rod that is perfectly clamped in the terminal and does not deform over time.
⚠️ Warning: Using bare ends in a vehicle without additional heat shrink or insulation is dangerous. Vibration can cause a short circuit between adjacent contacts if the metal part of the sleeve moves beyond the clamp.
There are various modifications including NSHVI-2 (double), which structurally have an elongated metal part to receive two wires. However, it is not always the double standard size that is at hand, and the electrician has to improvise with single ones, which requires an accurate calculation of the cross-section.
Always use tips with a colored plastic collar that matches the section. This allows you to visually control the correct selection of tools and eliminates confusion when repairing complex harnesses.
Standard sizes: how to choose NShVI for two cores
The most difficult aspect of working with paired wires is the mathematics of cross-sections. Standard single tips are marked with two numbers, e.g. 1,5-8 or 2,5-10. The first number indicates the cross-section of the wire in square millimeters, and the second number indicates the length of the metal part in millimeters.
When you take two wires, their cross-sections are added together. If you connect two 1.5 mm² wires, the total cross-section will be 3 mm². Standard single tip NSHVI 1.5 will be small and NSHVI 2.5 may be large if the wires have thick insulation or the flexibility class of the core is high. Ideally, a special size has been created for two 1.5 mm² wires NSHVI 2x1.5, but it is not always possible to find it on sale.
To select the correct size, you can use the following correspondence table, which will help you navigate when combining wires:
| Wire cross-section 1 (mm²) | Wire cross-section 2 (mm²) | Total cross-section (mm²) | Recommended NSHVI | Cuff color |
|---|---|---|---|---|
| 0,75 | 0,75 | 1,5 | NSHVI 1.5-8 | Black |
| 1,5 | 1,5 | 3,0 | NShVI 2x1.5 or 4.0-10 | Blue/Red |
| 2,5 | 2,5 | 5,0 | NSHVI 6.0-12 | Yellow |
| 1,5 | 2,5 | 4,0 | NSHVI 4.0-10 | Red |
| 4,0 | 4,0 | 8,0 | NSHVI 10.0-14 | Red |
It is important to understand that the actual wire cross-section may differ from that declared by the manufacturer, especially when it comes to budget brands. Therefore, before mass crimping, always do test installation. The tip should be applied with slight force, but should not require the use of a hammer.
Tool for high-quality crimping
The quality of the connection directly depends on the tool. To work with NSHVI Ordinary pliers or side cutters are absolutely not suitable. They cannot ensure uniform compression of the liner on all sides, leaving gaps into which air and moisture then enter, starting the corrosion process.
A professional approach involves the use of specialized pliers - crimpers. They have profile jaws that, when compressed, form the correct geometric shape of the tip (usually hexagonal or square, depending on the model). For double wires or paired single wires, there are clamps with double matrix, allowing you to clamp two wires simultaneously into one sleeve.
- 🛠️ NSHVI pliers with ratchet: They automatically regulate the force and do not allow the jaws to open until the crimping is completed completely.
- 🛠️ Clamps with a set of dies: Provide maximum force for thick wires, but require more setup time.
- 🛠️ Electromechanical presses: Used in production environments for large volumes of work, guaranteeing perfect repeatability.
If you are using a multi-tool, make sure the jaw size matches the diameter of the cuff. An incorrectly selected jaw can crush the plastic insulation or, conversely, not reach the metal.
⚠️ Attention: Never use the method of “tinning” (soldering) the ends of the wires before inserting them into the NSHVI. Solder is a soft metal, it will “float” under the pressure of the terminal screw, the contact will loosen, and the connection will burn.
Installation technology: step-by-step instructions
The process of connecting two wires using NSHVI requires accuracy and adherence to sequence of actions. A violation of technology even at one stage can negate all efforts to ensure reliability.
First you need to strip the insulation. The stripping length must exactly match the length of the metal part of the tip. If you strip too little, the insulation will get caught under the clamp and there will be no contact. If there is too much, bare copper will remain outside, which can lead to a short circuit.
☑️ Algorithm for crimping two wires
After stripping, fold the two wires parallel to each other. Don't twist them too much, just a slight twist is enough to keep them together. Insert the wires into the sleeve NSHVI all the way. You should feel the copper reach the bottom of the case.
Insert the tip into the corresponding groove of the crimper. Make sure that the jaws of the tool are encircling the metal part and not the plastic collar. Close the handles until the mechanism makes a characteristic click or until it is completely closed. After this, check the connection: the wire should not be pulled out of the sleeve by hand.
What to do if you don’t have a double NSHVI at hand?
If there is no special double tip, you can use a single tip with a larger cross-section, but there is a risk of poor contact. It is best to buy a universal NShVI with a reserve diameter or use a GML sleeve (tinned copper) without insulation, selecting it to match the total diameter, and then insulate it with heat shrink.
Common mistakes and how to avoid them
Even experienced craftsmen sometimes make mistakes that appear after a while. One of the most common is the use aluminum wires with copper tips. NShVI are intended only for copper. The contact of copper and aluminum causes a galvanic reaction, leading to the rapid destruction of the connection. For aluminum you need special tips with quartz-vaseline lubricant.
Another mistake is “double crimping”. Some people try to crimp the same tip twice in different places. This leads to deformation of the sleeve and disruption of the internal structure of the metal, which reduces conductivity. The crimping must be single and full.
- ❌ Stripping too long: The exposed wire sticks out from under the cuff, creating a risk of short circuit.
- ❌ Using insulation as a stop: The wire rests against the plastic, and not against the metal of the sleeve, there is no contact.
- ❌ Padding: Excessive force can break the wires inside the sleeve, especially if the wire is stranded and thin.
Also worth mentioning is the color selection error. Although the color of the cuff is just a marking, in professional assembly of harnesses it is customary to follow a color code (red, blue, yellow) for quick visual diagnosis of wire cross-section without tools.
FAQ: Frequently asked questions
Is it possible to crimp two different wires into one NShVI?
Technically it is possible if their total cross-section falls within the range of the tip. However, electrical standards recommend avoiding connecting dissimilar cores (for example, with different classes of flexibility or from different metals) at one point without special adapters, since their coefficient of thermal expansion is different.
What is the difference between NShVI and NShV?
NShVI is an insulated tip (with a plastic cuff), and NShV is a non-insulated tip (just a tinned tube). It is always better to use NShVI for a car, since the cuff provides additional protection against vibration and accidental touches.
Do I need to lubricate the contacts inside the NShVI?
In automotive electrical systems exposed to moisture, it is recommended to use a contact lubricant (for example, lithium-based or a special conductive lubricant), but only after crimping, applying it to the point where the wire enters the terminal block to displace moisture.
Which tool is better: automatic or manual?
For one-time work, high-quality hand pliers with a ratchet are suitable. Automatic (pneumatic or electric) tools only make sense when assembling hundreds of connections per day, since they eliminate the human factor, but require adjustment for a specific type of tip.