Electric panel and MCB

[mike_mike]

Hello ! I equipped an old electric panel with some new MCB's. I used 25A and 2 poles (2p) on the general, 1 pole and neutral (1p+N) for the rest of the panel: 4x 16A and 4x 10A for electrical outlets circuits and 3x 6A on the light bulbs circuits. All of them C curve.
The earth arrangement is TNC.
The mcb's that I used are Schneider Electric Easy9. I fed the mcb's from the bottom side and at the top side I connected the circuits.
I made the following tests: I used a 4kW consumer at an C10 mcb and the mcb triggered in about a few seconds.
The second test was to make a direct short circuit on the C10 mcb outlet, but instead of triggering only the C10 mcb, it also triggered the C25 mcb (the general 2p mcb).  It is normal to trigger the 25A mcb instead of  triggering only the C10 mcb ?

[rstofer]

For a short circuit, timing is pretty much out the window.  Basically, the instantaneous trip mechanism is a solenoid and it moves pretty fast.

https://img.c3controls.com/image/upload/resources/c3controls-Understanding-Trip-Curves.pdf

[bdunham7]

The second test was to make a direct short circuit on the C10 mcb outlet, but instead of triggering only the C10 mcb, it also triggered the C25 mcb (the general 2p mcb).  It is normal to trigger the 25A mcb instead of  triggering only the C10 mcb ?

With the magnetic trip there are two timings--the time it takes to set the trip mechanism irreversibly in motion and the time it actually takes to disconnect.  The first is very short, the second is the clearing time that you usually see listed and is much longer.  What happens when you short two MCBs in series is that the first one starts the trip process, but that doesn't complete immediately.  During the time between the initialization of the trip and actual disconnect, current is still flowing and the second MCB may start its trip process.  After this point, even if the first one clears (disconnects) the second one will continue its mechanical disconnect process.

[tepalia02]

The second test was to make a direct short circuit on the C10 mcb outlet, but instead of triggering only the C10 mcb, it also triggered the C25 mcb (the general 2p mcb).  It is normal to trigger the 25A mcb instead of  triggering only the C10 mcb ?

With the magnetic trip there are two timings--the time it takes to set the trip mechanism irreversibly in motion and the time it actually takes to disconnect.  The first is very short, the second is the clearing time that you usually see listed and is much longer.  What happens when you short two MCBs in series is that the first one starts the trip process, but that doesn't complete immediately.  During the time between the initialization of the trip and actual disconnect, current is still flowing and the second MCB may start its trip process.  After this point, even if the first one clears (disconnects) the second one will continue its mechanical disconnect process.

Thank you so much for the clarification.