0W - what has happened?

    Hi there,
    I'm new to the forum and to the shelly's world. I'm using an EM with two 50A clamps, on the "L" wire of my heat pump and main apartment switch. The EM has been working perfectly for a couple of days, readings were coherent with power consumption, and MQTT was working flawlessly. I decided to put some fuses to protect the EM, so I unwired it (only the 220V wires) and reconnected it. AC voltage reading is good but the power on chanell 2 is always 0W. I decided to switch the clamps to see if the issue was on the current sensor or on che EM channel, and I was able to read power for a while. Suddenly channel 1 stopped working, and now it shows 0W.

    I measured AC voltage on the clamps: 13/15 V, which vary accordingly to the load. EM seems to be dead. Do I have to return it?


    Firmware is: Current version: 20220209-094734/v1.11.8-g8c7bb8d

    Thank you in advance.
    best regards.

    13 or 15V AC measured over the current clamps are much too high! Normal values are below 2V AC. Due to the fact, the current clamps are simple coils with a splitted ferrit core, the faulty device must be the Shelly itself.

    „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)

    Thank you for valuable information. I'll repeat the measurement leaving the clamps disconnected from the EM. Actually the reading was far too high even for me... I was wondering if there was any amplifier in the clamp...

    Einmal editiert, zuletzt von 66er (1. August 2022 um 05:18) aus folgendem Grund: fullquote of last thread deleted, please don't do this.

    Despite the time of the day, I managed to take some values from the clamps and shelly em:
    Clamps VAC: 7V and 6V (mains and heat-pump)
    Shelly EM "open circuit": 17V and 14V (AC).

    I think the EM is gone. I'll try to have it replaced from Shelly Italy.

    Thanks for your help!

    Best regards.

    Einmal editiert, zuletzt von 66er (1. August 2022 um 05:18) aus folgendem Grund: same fullquote deleted as above!

    Some additional facts about the current clamps: A resistor in parallel to the clamp is mandatory. These so called „burden resistors“ have 10 to 20 Ω. Hence, voltage measurement at open current clamps gives much higher voltage compared with proper terminated clamps. Clamps for high currents are often damaged if used without burden resistors due to high voltage spikes. Fortunately, this maloperation is harmless with Shelly‘s clamps.

    „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)

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