The Shelly Pro 3EM requires the current transformer on the neutral conductor if it is necessary to measure the current in the neutral conductor, especially in certain configurations or if the entire energy balance of the house is to be monitored.

- This is particularly relevant if you want to measure the total current across all three phases and at the same time take into account the current in the neutral conductor in order to obtain an accurate energy balance.

- The current transformer for the neutral conductor is connected to a specific connection on the device to enable the measurements.