The Shelly Pro 3EM is the reference three-phase meter of the range: up to 120 A per phase, DIN rail mounting, and the only meter in the family compatible with Matter.
Fitting it has more edges than a single-phase meter, and nearly all of them gather at one point: which clamp goes on which phase.
Before opening the board
Switch off at the main breaker and verify the absence of voltage with a multimeter — all three phases separately. On three-phase, checking one is not enough. If you are not electrically trained, this installation is not for you.
Measure the space before buying, and not just for the module: the three 120 A clamps are bulky. If the board is tight, the Pro 3EM-3CT63 solves the same problem in less room.
Voltages, and the detail that leaves the device dead
Four line terminals: A, B, C and N. Each phase to its terminal, neutral to N.
And here is the detail worth knowing beforehand rather than afterwards: phase C is also what powers the device. Without C, the meter does not start. If one day it turns up dead while the other two phases have voltage, you know where to look before writing anything off as faulty.
Range 100 to 260 V, drawing under 3 W. Protect with a type B or C breaker of 16 A maximum, with a breaking capacity of at least 6 kA.
The four clamps
Four inputs: IA, IB and IC for the three phases, and IN for neutral. The neutral one is optional and not included.
Each clamp must go on its corresponding phase. If the IA clamp ends up on phase B, the phase shift between voltage and current on that channel is not the real one, and that phase will report absurd power, negative power, or both depending on the moment.
It is the number one mistake on three-phase installations, and a treacherous one because the device starts, connects and appears to work. Only the numbers give the crossover away. Respect the arrow direction too, grid towards load.
There is no relay
Unlike the Pro EM-50, the Pro 3EM has no built-in relay. To drive a contactor you need the switch add-on, which connects to the serial interface on the side.
That interface is at high voltage while the device is powered. The add-on is always connected with the device unpowered, no exceptions.
Bear it in mind when quoting: if the project includes switching loads, that is two part numbers, not one.
Network
Wi-Fi, Ethernet and Bluetooth, each independently switchable. As across the Pro range, the network cable goes in with the device switched off.
Give it a static IP if it is going to feed any integration. A three-phase meter is usually the data source for something — load management, a vehicle charger, a monitoring system — and having it change address after a router restart breaks everything hanging off it.
If the board holds several devices, provisioning them as a batch with the SIT-IoT app puts them all on the network with their static addresses in a single pass.
Three functions worth switching on
The Pro 3EM ships with three professional-grade features that many people never touch:
- Phase sequence detection. It watches that the order is A → B → C and reports an error if it finds A → C → B. It is your safety net against cross-wiring, so enable it and act on the warning.
- Channel-by-channel calibration. It evens out the response of all three. It needs at least 500 W of load per channel to run, so do not try to calibrate on an empty installation.
- Minimum load threshold. Below 30 VA per channel it shows power but does not accumulate energy. That is deliberate: it stops background noise polluting the statistics with consumption that does not exist.
Commissioning
- Restore the supply. The power LED turns red.
- Hold the button for 5 seconds to enable the access point.
- Configure it from the app or by joining the network it broadcasts.
- Check all three phases before closing up. Voltages coherent with each other, and no negative power you were not expecting. If one phase sits outside the pattern, you have a crossed clamp.
What data you get
Four-quadrant measurement per phase: active and apparent power, energy, power factor, and fundamental active and reactive energy. Accuracy of 1% between 2 and 120 A, 2% from 1 to 2 A and 5% below 1 A.
It stores at least 45 days at one-minute resolution, exportable to CSV and JSON. That is the shortest history in the range — the Pro EM-50 keeps 60 days. If you need long series to justify a bill or analyse a season, plan on exporting the data regularly.
What to watch afterwards
On three-phase there is something that does not show on fitting day and does show after a few weeks: imbalance between phases. An installation can be wired perfectly and still, as loads get added, end up with one phase carrying twice what the others do.
That is not caught in a site visit, it is caught by watching the trend. In the console, telemetry lets you follow that drift without going back to the board, and last seen tells you whether the meter is still reporting or has been silent for days — which, on a device feeding load management, is a fault with consequences rather than an inconvenience.
The recurring mistakes
- Clamps crossed between phases: the number one cause of odd three-phase readings.
- Forgetting that phase C powers the device: without C, it does not start.
- Expecting it to switch loads without the add-on: it has no relay.
- Not measuring the space for the clamps: discovered with the board already open.
If the readings do not add up, the general causes are in why a meter reads higher than expected.
The app and the console work with Gen2, Gen3 and Gen4. The app is on Google Play: SIT-IoT Smart Installer Tool.