What is the accuracy of Shelly EM and 3EM for small wattages (5-50W)?

  • I know, the handbook states the accuracy of the EM is 1%. Whatever that means.

    Given the maximum current is 50A or 120A, the maximum wattage is 220V x 50A = 11.0kW, or x 120A = 26.4kW.

    But what does this mean for small wattages?

    Do I always have an absolute precision of 11kW x 1% = 110W, for the 50A solution? X/

    What about measuring small values like 10-50W? How precise is the Shelly EM then?

    Did somebody compare Shelly EM with Shelly 1 or 1PM, for such small values?

    Thank you! :thumbup:

  • Hi ploneric, I have the same question, but for both shelly EM and 3EM. I have asked official support and my questions and the answer are bellow:

    Dear Shelly team,

    Thank you for your support. Just few more questions I have :) :

    -is Shelly 3EM working with 50 A clamps?

    -what is the minimum current when Shelly 3 EM starts to measure accurately?

    -what is the minimum current when Shelly EM starts to measure accurately?

    -is minimum current and accuracy dependable of which clamp is used, 50 or 120 A?

    -----------------------------------------------------------------------

    Shelly 3EM cannot work with 50A.

    24.57kW is the max limit , which device can measure per phase and total.

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    If you find some more information please share it with me.

    Best regards.


  • 24.57kW is the max limit , which device can measure per phase and total.

    This answer is really thrilling: If I have maximum consumption (24,57kW) on one phase, the other phases should have zero consumption. Otherwise my energy metering will be not correct! What a shame…

    „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)

  • Hi,

    any findings on this topic?

    I just got a shelly-EM and was testing it using a wall plug before installing it in the main circuit but the measurement always comes as 0W, given that I am measuring shelly EM self consumption I guess it falls under the precision...

  • Welcome to the forum, scerio !

    Would you please give us some hints how you‘ve installed your Shelly EM to test it? And what consumer did you connect? A little sketch or a photo would be sufficient…

    „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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