Shelly EM reporting 'only' 4W consumption

Third party integrations
1

Hi all,

I’ve started using the Shelly EM’s to monitor Power and Energy of some circuits, but also for my EV Charging.

For the last purpose, I was able to get the Shelly EM into the app and it is also visible in the Shelly Integration. We are talking about a Shelly EM, with a 120A clamp.

I put it on a 230V powersupply and the clamp on the wire towards my power charger. After rebooting the Shelly EM, I have following readings for my power charger:

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This is not what I was expecting, unless these graphs show the reality. Continuous consumption of 4W is really interesting for charging vehicles :slight_smile:

The total Energy consumption is also, not displayed… :-/

I’m not able to get the ‘real’ readings from the power line towards my charger. What I’ve tried sofar was to enable unicast (set the IP to IP of homeassistant with the unicast port), but that didn’t solve the issue.

Do you think that it is possible that I should enable MQTT ? Is it probably because the power cable is too lose in the clamp ? should I recheck the physical connections of the clamp into the shelly ?

Any other suggestions ?

Looking forward to your suggestions !

Kr,

Bart

2

Few points, which may be completely invalid, but more a sanity check:

  • Do you power Shelly from the same phase as your charger? You should, do have correct V * I calculations for power.
  • Are you sure you did not connect to DC side and did it on AC side? CT clamps work for AC normally.
  • Any other wiring problems with the clamp?
  • Are you sure you only clamped the L and not both? If you udo both, the values will negate itself.

My Shelly EM shows much more entities as yours.

I have this one:

Shelly EM (SHEM)
Firmware: 20231107-164916/v1.14.1-rc1-g0617c15
Hardware: gen1
3

Hi tilz0r,

Good points :slight_smile:

I power the shelly with a power supply, so not directly from the circuitbreaker of the charger.
What do you mean ? On the shelly itself ?
There are no wiring problems with the clamp for so far I know
I think the last mention might be the problem. For my circuitbreaker, there is one big line going to the charger. Didn’t think of it that the L, 0 and N are in that same line

Where did you get the details about your hardware so I can copy in the same format ?

Kr,

Bart

4

Shelly EM (not EM PRO) is a single phase measurement device, as such you have to make sure that power of Shelly EM and power of your measured device, are on the same phase. Sure you can have the circuit breaker between Shelly L and consumer device L, but it is important they are “in phase” - same sine curve.

To calculate the power, it:

  • Measures the current with CT clamp
  • Measures to voltage on the power supply side.

The power is the P[W] = U[V] * I[A]. If you use different phase for voltage and for current measurement, you need to consider the cosine between them, so P = U * I * cos(angle). You want the angle to be 0, which can only happen if you use the same phase for powering the Shelly and measuring the consumer device.

Here is an example of my Shelly setup from dashboard. You see the data in the top-left corner:

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5

THanks a lot for the info !

My Device info is just the picture I sent earlier, nothing more unfortunately

I will try out your suggestions

Kr,

Bart

6

Please make sure you have latest firmware on the Shelly. Open the shelly website (connect to local IP) and check if any firmware available.

Here is the wiring diagram you should have:

  • L is the Phase input. There is a MCB that protects the charging part. When MCB is turned ON, L on charger is the same L as on the shelly. This is what you want
  • N is common for charger and Shelly
  • CT clamp is connected only to L part, after MCB

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7

BTW You are using an old, unmaintained, custom ShellyForHass integration.

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It is recommended to migrate to the Shelly core integration.