Electrical wiring has long been the same mandatory engineering system for residential real estate as water supply, heating and sewerage. Taking into account the relative simplicity of its construction, it is formed directly on the object. In the process of its implementation, a lot of cables are laid, some of which serve several loads, i.e. works in group mode.
When implementing such a structure, individual cable segments must be connected to each other at the points of branching and making branches. There are several technologies for the formation of these elements, among which the version based on spring terminals has been rapidly gaining in recent years.
Among the spring connectors, which have a number of well-known advantages, the most popular are the products of the WAGO company, Figure 1. It is known that there are no ideal technical solutions and any of them always has both advantages and disadvantages. Knowing the deficiencies is useful in that it helps to minimize the risks of their manifestation.
What limits the load capacity of the WAGO terminal?
A simple formula for calculating electrical power is known from the school physics course: P = R * I ~ 2 (squared). From this simple relation it directly follows that this parameter for an electrical connector is inversely proportional to its contact resistance R.
Disadvantages of a technical solution quite often become a direct continuation of its merits. With regard to WAGO terminals, this rule is manifested in the fact that a high speed of connecting wires with this component is achieved through the use of spring clamp, Figure 2, which in the working position is not able to guarantee a high interaction area with the connected wires.
The contact resistance R of the splice is directly proportional to the area of interaction between the wire and the contact.
It immediately follows from this that:
- WAGO terminal blocks can only be used when forming circuits with relatively low currents;
- the installation of terminal blocks requires careful adherence to technology;
- even small movements of the wires relative to the terminal block have a strong negative effect on the quality of the formed splice.
The latter is determined by the fact that after exposure to even a small load, the contact surface area slightly increases due to the effect of welding the spring clip and the wire. Such welding has low mechanical strength and is easily destroyed even with a slight change in the spatial position of the wire relative to the clamp.
How to minimize the risks of exceeding contact resistance
The thermal power released at the increased resistance leads to the heating of the contact area, which in severe cases leads to the terminal block melting and destruction, Figure 3.
Therefore, during installation and operation, it is important not to allow a significant increase in this power.
To do this, it is enough to follow a few simple rules:
- control the maximum current in the formed circuit;
- observe installation technology;
- do not allow movement of the terminal strip.
If these conditions are met, the terminal block will function normally throughout that considerable warranty period, which is set by the manufacturer.