Shelly EM negative power factor, but postive power

There are 5 replies in this Thread which has previously been viewed 930 times. The latest Post (December 18, 2023 at 4:05 PM) was by johnpsom.

  • Hi,

    I just installed a Shelly EM with 2x 50A clamps and it is updated to the latest firmware from the web UI.

    I installed a clamp over the wires to my heatpump and the other clamp is attached to the indoor unit with the waterpumps and backup heating element.

    The clamp attached to the heatpump is reading positive power, but a negative powerfactor which I don't think is right?

    The clamp attached to the indoor unit is reading positive power and a positve powerfactor which looks good.

    If I flip the clamp attached to the heatpump, I'm getting negative power, but a positive power factor.

    If I attach the clamp to my solar panel wires for example, both values are negative. So I'm not sure if there is something with the Shelly (firmware) or my installation.

    I hope someone can assist here. Thanks in advance.

    Screenshot 2023-08-01 at 09.25.25.png

  • Welcome to the forum!

    To your issue: A very small negative power factor with a positive consumption is absolutely consistent if the load has some capacitor in its guts to prevent radio interference. Hence, you’ll need no further intervention…

    „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)

  • Yes. Cause a power factor of 1 was expected. Only -0,01 is the difference - small enough, in my humble opinion…

    The scale is as following: -0,8 … -0,9 … - 0,99 … 1 … 0,99 … 0,9 … 0,8

    „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)

  • Thanks I didn't know that.

    But now I have another strange issue... I connect the Shelly EM to my heatpump because there is already a MID meter connected to it and wanted to compare how accurate it was. It was pretty accurate and only 2-3W off.

    Today I picked up my Tesla Model 3 and I don't have a loadstation yet. For the time being I wanted to use a normal 16A socket with the mobile charger and use the Shelly EM to meassure the power into the car to I can make an expense note for the charging costs at home.

    I was charging the car at 9A and I saw my housemeter go up to around 2400W. 370W was the powerdraw of the house so I was around 2100W for the car. But the Shelly EM reports 1150W. I tried it an hour later at 3000W and the Shelly was reporting around 1750W. It seems like the Shelly is only reporting about 60% of the real power draw. Does anyone has an idea why that could be? I moved the clamp around a little bit, but that made no difference.

    EDIT: fixed the problem. The Shelly EM was connected to a different phase and seems to mess up the reading. I'm not sure if that was stated in the manual, but Googling helped me.

    Edited 2 times, last by broodro0ster (August 3, 2023 at 3:23 PM).

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