The difference between short-circuit and overload protection.

As per subject, I don't understand it. A B16, for example, will trip when the current reaches 16 amps in the circuit, be it a short circuit or too much current draw. So what and why are overload protection used?

Hello. Well, so that you do not overload the wires. Imagine aluminum wires 1.5 square and you connect an induction hob with a power consumption of 7 kW. This is just one example and there are many more.

A short circuit is a very large current in the circuit and the fuse will trip/trip immediately. In the case of overload, i.e. current consumption, e.g. 20 A for a 16 A fuse, the switch-off will occur after some time. What will be the tripping time?, it all depends on the multiplicity of the current flowing through the fuse, but also on the type (characteristics) of the fuse A, B, C, D

Quote "Overload protection - overcurrent protection, protecting installations or devices against undesirable long-term effects of current flow higher than the rated current of the protected devices."

Now practice
One does not exclude the other but, assuming that you have this B16 circuit breaker and you have connected a 1kW electric motor. You don't want the motor to be damaged by overloading, so you use overload protection in its circuit to protect the motor from damage.

joka25 wrote:

Such as B16 will work when the current reaches 16 amps in the circuit

It will not work. It will work only from about 18A, and this is due to the characteristics of the overload element.
Plus, it won't work right away. At, for example, 24A, such protection will only work after about 100s (where it can work within 50-600s).

The overload protection (overload element) is used precisely to "allow" a temporary overload of the circuit, e.g. to enable the start-up of the device (e.g. power supply, cold heater, etc.).

The short-circuit element, on the other hand, operates at a very high current, of the order of 80A, and during this time its task is to switch off the circuit as quickly as possible, usually in the order below 0.1s, where the required time is, for example, 0.4s.

Each of the above elements (short-circuit and overload) is to prevent exceeding a certain temperature in the supply wires, which will damage the insulation. In other words, the protection is to limit the amount of power that will be dissipated on the wires.

A little more on the subject if you're hungry for knowledge: Klajn_Security_and_selectivity[1].pdf

Good to know, I have inductions in the apartment (single-phase) on b16, is there any module that has short-circuit and overload protection? I would replace that. This induction fuse has never popped up for me, but maybe it is within the overload limits and therefore, it would be worth securing it, I don't have much space in the switchgear, so I'd rather replace it with one module than add an additional overload, but if I have to, I'll do it.

How do switch disconnectors relate to all this? Recently, I had a problem with a bending machine at a construction site where there was a 3p B16 protection
I wanted to replace it with C25 but the Lord at Castorama told me to buy a switch disconnector, so I did, everything works and works, but I read a bit that this protection does not protect against short circuit and overload .... so what does it give, it works like FR? I understand that it is dangerous that I only put the switch in the switchboard there?

The Induction Cooker is a different pair of wellingtons. The power supply itself is protected by appropriate fuses. You are only interested in the appropriate cross-section of the power cord, that the cooker and protection of the circuit with a suitable fuse or overcurrent circuit breaker.

joka25 wrote:

on b16, is there any module that has short-circuit and overload protection in it?

After all, an overcurrent circuit breaker consists of a short-circuit and an overload part... The first is a coil and the second is a bimetal.

joka25 wrote:

How do switch disconnectors relate to all this?

This is NO security. This is a camera that does not protect anything, it works on a similar principle as a light switch, it allows you to disconnect the circuit.

stanislaw1954 wrote:

A short circuit is a very large current in the circuit and the fuse will trip/trip immediately. In the case of overload, i.e. current consumption, e.g. 20 A for a 16 A fuse, the switch-off will occur after some time. What will be the tripping time?, it all depends on the multiplicity of the current flowing through the fuse, but also on the type (characteristics) of the fuse A, B, C, D

Then how is it? Does the B16 overcurrent fuse have overload protection in it? Then what is the point of using overload protection alone?

That's what I thought too, so I'll replace it with a C25.

joka25 wrote:

I also thought I'd replace it with a C25.

And IPZ and cable cross-sections allow it?

joka25 wrote:

then what is the point of using overload protection alone?

Security selectivity. Circuit breakers with characteristics B,C,D are not selective with respect to each other. In the event of a short-circuit, if there are several such protections in series, they can trip all at the same time. The aim is to ensure that only the protection closest to the short-circuit site operates.

ok but b20 and b16 are selective to each other?
and c20 relative to b20 no longer?

Neither C20 with B10, nor B10 with B20, D16 and B10 either. And so on.... selectivity in this case can be obtained by the case when the short-circuit loop is sufficiently small, but these devices are not selected on this basis (case).

joka25 wrote:

Good to know, I have inductions in the apartment (single-phase) on b16, is there any module that has short-circuit and overload protection? I would replace that. This induction fuse has never popped up for me, but maybe it is within the overload limits and therefore, it would be worth securing it, I don't have much space in the switchgear, so I'd rather replace it with one module than add an additional overload, but if I have to, I'll do it.

It's best that an amateur colleague does not tinker with the electrical installation at all.

joka25 wrote:

protection 3p B16
I wanted to change to C25 but the Lord in Castorama told me to buy it switch disconnector, that's what I did, everything works And it works

A friend ruined a good installation.
In this condition, the installation is not suitable for operation.
It's best that an amateur colleague does not tinker with the electrical installation at all.
How do you imagine it, friend Joka25?
Electricians are a collection of ignorant people, and an amateur who doesn't know anything will correct them?

Topic to be closed.
Because the purpose of the topic is to spoil the installation by a handyman.