Protect Shelly Dimmer 2 from light short circuit

  • Hi,

    I would like to protect my Shelly Dimmer 2 from overload due to faulty led light bulbs.

    Here is the setup: I have had a very pleasant 100% working setup with a Shelly Dimmer 2 controlling a string of 30 dimmable LED light bulbs for more than a year. Each bulb is 6 watts.

    A few month ago, while it operates as usual for about 20 minutes, it stops, and I hear a "Pshffhop" sound from the Shelly box. I removed the Shelly from the setup and tested the light string alone, triggering the corresponding house breaker.

    I then tested one bulb at a time and found that bulb #29 was the faulty one. I replaced that bulb and tested the light string again without any problems.

    The next step was to buy a new Shelly Dimmer 2 and replace the fried one. For good measure, I added a 1-amp glass tube fuse between the Shelly and the light string (30x6w=180w / 230v = 0.78 amp).

    I hooked everything up tightly and cleanly, switching on/off and dimming up/down; everything worked as intended—awesome! I'm a happy geek.

    Weeks passed, and the last "OK Google, turn light string on at 20%" resulted in a "Pshffhop" and infinite darkness. The glass tube fuse fried, as well as the Shelly Dimmer 2.

    I followed the same procedure as before, finding, removing, and replacing the faulty light bulb.

    Now, I am trying to protect the Shelly Dimmer from the next light bulb failure more effectively.

    Light bulbs are no-name Amazon light bulbs, and I won't consider changing the whole set as I still have a few spare ones. Therefore, I'm looking for a system to prevent the Shelly Dimmer 2 from failing when it happens.

    I was thinking of replacing the glass tube fuse between the Shelly and the light string with a differential breaker.

    Any advice or considerations will be highly appreciated.

    Have a great one.

  • Welcome to the forum!

    Prevention of semiconductor devices from dead by overload isn’t simple: Very often, the semiconductor protects the fuse…

    In fact, you would need a very fast fuse (semiconductor grade). Unfortunately, these fuses are not cheap - and moreover not very reliable in its protection function.

    What do you mean exactly with the term ‘differential breaker’?

    „Habt Geduld. Alle Dinge sind schwierig, bevor sie einfach werden!“ (aus Frankreich)

    „Nothing in life is to be feared, it is only to be understood.“ (Marie Curie, 1867-1934)

    „Es reicht nicht“, rief Schiller, „Gedankenfreiheit zu fordern, man muß auch denken können, sonst fordert man Gedankenlosigkeitsfreiheit und die ist die Freiheit zur Dummheit, welche wiederum die schlimmste Unfreiheit überhaupt ist!“
    (Aus „Besuch aus Weimar“ von Gert Heidenreich, Schriftsteller, *1944 in Eberswalde)

  • Thanks for the link! I do understand that you want to install a residual current device (RCD), which does not help with your issue. Because the Shelly does not break due to residual current, but caused by an overload condition due to the lamp failure.

    „Habt Geduld. Alle Dinge sind schwierig, bevor sie einfach werden!“ (aus Frankreich)

    „Nothing in life is to be feared, it is only to be understood.“ (Marie Curie, 1867-1934)

    „Es reicht nicht“, rief Schiller, „Gedankenfreiheit zu fordern, man muß auch denken können, sonst fordert man Gedankenlosigkeitsfreiheit und die ist die Freiheit zur Dummheit, welche wiederum die schlimmste Unfreiheit überhaupt ist!“
    (Aus „Besuch aus Weimar“ von Gert Heidenreich, Schriftsteller, *1944 in Eberswalde)