Shelly 3EM negative power draw at low power

[wigster]

The problem

I've just installed 2022.10.5 with the patch for Shelly EM reporting a negative power factor https://github.com/home-assistant/core/pull/80348#issue-1409651470

This has fixed the power factor being reported by one of my Shelly em3 circuits, but it has not fixed the negative power draw being reported by that circuit. To be concrete, this circuit:

• When drawing a large current (when the device is on), reports a positive power factor and power draw
• When drawing a small current (standby mode, 2W power draw), in HA reported both a negative power factor and power draw. After this 2022.10.5 patch, the power factor is now positive, but the power draw is still negative.
• In the Shelly web interface, both the power factor and power draw are negative at low currents.

I believe the negative power draw here is the same problem as the negative power factor that got fixed.

What version of Home Assistant Core has the issue?

2022.10.5

What was the last working version of Home Assistant Core?

none

What type of installation are you running?

Home Assistant OS

Integration causing the issue

Shelly

Link to integration documentation on our website

https://www.home-assistant.io/integrations/shelly/

Diagnostics information

config_entry-shelly-42d51c806c98e27e5c4c3c8924c2c489.json.txt

Example YAML snippet

No response

Anything in the logs that might be useful for us?

No response

Additional information

No response

[home-assistant[bot]]

Hey there @balloob, @bieniu, @thecode, @chemelli74, mind taking a look at this issue as it has been labeled with an integration (shelly) you are listed as a code owner for? Thanks! _{^{(message by CodeOwnersMention)}}

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shelly documentation shelly source _{^{(message by IssueLinks)}}

[bieniu]

• In the Shelly web interface, both the power factor and power draw are negative at low currents.

As you can see the problem is related to the Shelly firmware. Have you asked the Shelly support about it?

[wigster]

I asked on the Shelly forums that since this is at low powers, it's a result of interference really and they don't worry about it. It may well be that this 2 W result is in any case fake. The only reason I have put this issue here is because the power factor got a workaround in HA and I thought this might be appropriate. I have created an absolute value filter for myself, just as in the patch, so I can live with this.

[G6EJD]

As far as I’m concerned the Power Factors reported by the Shelly EM are correct, the recent change to the Shelly EM integration in 2022.10.5 now returns the absolute value so -0.8 becomes 0.8, that is wrong.

The issue seems to be that most users of the integration don’t understand Power Factors and that they do swing from + to - depending on the load type, or if their property has solar for example then when there is an export PF will be negative.

what was a correctly operating integration has been ruined by making changes based on the PF must always be positive - that’s wrong.

When loads are low it is not unusual for then dominant house loads like LED lighting to send the PF negative!

[thecode]

Closing this issue, regardless if this is related to a device problem or not, we are not going to change values reported by the device. If you believe the value should not be negative (in this case it is not correct anyhow) please contact Shelly to fix it in the device.