Clarification on negative power factor

There are 8 replies in this Thread which has previously been viewed 293 times. The latest Post (December 18, 2023 at 11:08 PM) was by thgoebel.

  • Hi,

    I have a EM that open/close as well as measuring the power of the solar water heater those days that there is no sun.

    The power measured is for example 3700watts, however the power factor is -1 as well as the VAR is negative.

    Obviously the EM switch and the solar water heater are on the same phase.

    When checking the 3EM, the phase C where the solar water heater belongs, is showing correctly power factor 1.

    In the system there are no solar panels or anything that producing energy.

    Attached the 2 screenshots of EM and 3EM when solar water heater is on.


    Any idea why this is happening?

  • Please check firmware version of Shelly EM! If a new version gives no remedy, you should turn the current clamp of Shelly EM by 180°.

    „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)

    „I can be smart when it‘s important, but most men don‘t like it.“ (N. J. Baker, 1926-1962)

  • You’ll never know if you don’t check it…

    „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)

    „I can be smart when it‘s important, but most men don‘t like it.“ (N. J. Baker, 1926-1962)

  • Is this an answer to my question?

    AC is not for playing around! so since EM is measuring also both ways, turning around the clamp, it will show it as generative power which is not correct!
    So if you do not know the why, it is preferably to give no answer or say i do not know. it is not a bad think!

    by the way, here is the screenshot, showing exactly what i told you. Consumption showed with a -.

    VAR however remains negative, so that is why now the power factor is positive but the power is negative.

    Any ideas anyone?

    Thank you in advance.

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