11th September 2022

Electricity Measurement with Shelly 3EM

This week Peter Kammermeier installed two measurement tools in the switchbox and DC to AC solar converter box. Measurement tool is a Shelly 3EM, "Professional Energy Meter". Shelly is a brand of Allterco, headquarted in Sofia (Bulgary). On their website they say that they have sold over five million devices worldwide.

The package contains:

  1. Shelly computer
  2. Three wire-measurement tools, i.e., Hall effect sensors, labeled "A", "B", and "C".

The Shelly computer is the following:

  1. It has ESP8266 microchip inside with 4 MB flash
  2. Running Mongoose-OS operating system
  3. Running Mongoose web-server
  4. Shelly Script Language: modified mJS
  5. Supports MQTT
  6. Stores data for 365 days power consumption
  7. Power consumption < 1W
  8. Emits its measurements via WiFi 802.11 b/g/n
  9. Max. current 10A
  10. Can power one relay

1. Installation. The cabling is now:

Photo

For the installation Peter used multiple Wago cage clamps.

Before installation, from the breaker there is one cable going to the consumer:

graph TD B(breaker) --> C(consumer)

After installation of the Shelly, the Wago clamp connects three lines:

graph TD B(breaker) --> W[Wago clamp] W --> C(consumer) W --> S(Shelly)

The Shelly 3EM is a 1st generation model, see Shelly Family Overview Generation #1.

2. DC to AC converter. The Shelly 3EM can also be used to measure how much electricity is fed to the power grid. Below images show installation in SMA DC to AC converter.

Photo

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3. Website or Android app. You can either use the Android app, or view the measurements on the web. The results looks similar to below screenshot.

Photo

The website shows a field called PF: This is the Power factor,

$$ \hbox{pf} := \hbox{power factor} = {P\over U_{\hbox{rms}}\cdot I_{\hbox{rms}}} $$

The results of the power measurements can easily be shared by inviting others via e-mail. They in turn can then view the measurements.