How to install the Shelly Pro 3EM three-phase step by step

The Shelly Pro 3EM (model SPEM-003CEBEU) is the range's reference three-phase meter. It measures up to 120 A per phase, mounts on DIN rail and is the only Shelly meter compatible with Matter.

This guide covers the step-by-step installation according to Shelly's official documentation.

Before you start

Cut the supply at the main switch and verify the absence of voltage with a multimeter. In a three-phase installation this is especially important: check the three phases separately.

The unit takes up 94×19×69 mm on the rail, but also factor in the space for the three 120 A clamps, which are bulky. If your panel is tight, consider the Pro 3EM-3CT63.

Wiring diagram

Three-phase Shelly Pro 3EM DIN-rail installation diagram with its four clamp inputs

1. Power supply and voltages

The unit has four line terminals: A, B, C and N. Connect each phase to its terminal and the neutral to N. One important detail: phase C is also the one that powers the unit.

Range of 100 to 260 V, consumption below 3 W. Protect with a type B or C breaker of 16 A maximum, with a minimum breaking capacity of 6 kA.

2. The four current transformers

There are four clamp inputs: IA, IB, IC for the three phases and IN for the neutral. The neutral clamp is optional and not included.

Here's the most expensive mistake of this installation: each clamp must go on its corresponding phase. If you put the IA clamp on phase B, the phase shift between voltage and current will be incorrect and that phase will give absurd or negative powers.

Also respect the direction of the arrow (K towards L, from the grid towards the load).

3. Load control

The Pro 3EM has no relay. To drive a contactor you need to add the Shelly Pro 3EM Switch Add-on, which connects to the proprietary serial interface on the side.

Be careful: that interface is at high voltage when the unit is powered. Always connect the add-on with the unit powered off.

4. Network

Wi-Fi, Ethernet and Bluetooth, which can be enabled or disabled independently. As with the whole Pro range, connect the network cable only with the unit powered off.

Features worth enabling

The Pro 3EM includes three professional features worth configuring:

Phase-sequence error detection. It checks that the order of zero crossings is A → B → C. If it detects A → C → B, it reports a phase_sequence error. Very useful for detecting crossed wiring.
Channel-by-channel calibration. It equalizes the response of the three channels. It needs at least 500 W of load per channel to run.
Minimum-load threshold. Below 30 VA per channel, the unit shows the power but doesn't accumulate energy, to prevent noise from cluttering the statistics.

Start-up

Restore the supply. The power LED turns red.
Press and hold the button for 5 seconds to enable the access point.
Connect to ShellyPro3EM-XXXXXX or add it from the Shelly app.
Check that the three phases show consistent voltages and that none gives unexpected negative power.
If you want Matter, enable it from the unit's settings.

Data you'll get

4-quadrant measurement per phase: active and apparent power, active and apparent energy, power factor, and fundamental active and reactive energy. Accuracy of 1% between 2 and 120 A (2% from 1 to 2 A, 5% below 1 A).

It stores at least 45 days at one-minute resolution, exportable to CSV and JSON. It's the shortest history in the range, something to bear in mind if you need long series.

Common mistakes

Clamps crossed between phases: the number-one cause of odd readings in three-phase.
Forgetting that phase C powers the unit: without C, the meter won't start.
Expecting it to cut loads without the add-on: it has no built-in relay.
Insufficient space for the three clamps: measure it before buying.

How to install the Shelly Pro 3EM step by step

Before you start