The Shelly Pro 3EM-3CT63 (model SPEM-003CEBEU63) shares chassis and electronics with the Pro 3EM, but completely changes the way it measures. Instead of three split-core clamps it uses the 3CT63: a single piece that integrates the three phases and mounts directly over the circuit breaker.
It's the solution for panels with little space.
Check this before buying
The 3CT63 has a conductor opening of 9 mm. It's the unit's most important limitation and it's worth measuring before ordering anything: if your phase cables don't fit through that diameter, this model is no good for you.
The second limitation is the current: 63 A maximum. If your service exceeds that figure, you need the 120 A Pro 3EM.
As always: cut the supply at the main switch and verify the absence of voltage on the three phases before touching anything.
Wiring diagram
1. Power supply and voltages
Four line terminals: A, B, C and N. Range of 100 to 260 V at 50/60 Hz, consumption below 3 W. Protection with a type B or C breaker of 16 A maximum.
It supports both three-phase and single-phase installation, which makes it more versatile than its name suggests.
2. The 3CT63 clamp
Here's the big difference. The 3CT63 is a single 14×54×26 mm piece that sits directly over the phase cables, fitting over the circuit breaker, with no rail fixing.
It connects to the meter via three 2-pin MX3.0 connectors. Respect the current direction marked as K → L: if you get negative readings where you expected positive ones, the clamp is fitted the wrong way round.
Pay attention to the wire color code (red and black) when connecting each phase to its corresponding input.
3. Load control
Like the Pro 3EM, this unit has no relay. To drive a contactor you need the Shelly Pro 3EM Switch Add-on. The add-on interface is at high voltage while the unit is powered: always connect it with the power off.
4. Network and protocols
Wi-Fi, Ethernet and Bluetooth 4.2. It supports Modbus TCP over port 502 in addition to MQTT and RPC, like the rest of the Pro range meters, which makes it easier to integrate into building management systems and industrial installations.
Features to configure
- Phase-sequence detection: reports an error if the order of zero crossings isn't A → B → C.
- Channel-by-channel calibration: requires at least 500 W per channel.
- Minimum-load threshold: below 30 VA per channel it shows power but doesn't accumulate energy.
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
ShellyPro3EM3CT63-XXXXXXXXor add it from the app. - Check the three phases and confirm that none gives unexpected negative values.
Data you'll get
4-quadrant measurement: active and apparent power, active and apparent energy, power factor and fundamental active and reactive energy. Accuracy of 1% between 2 and 63 A (2% from 1 to 2 A, 5% below 1 A).
It stores up to 60 days at one-minute resolution, exportable to CSV and JSON. The internal clock keeps the time even if the connection goes down.
Where it fits best
Shelly's documentation aims it at panels with limited space: commercial buildings, motor control centers, data centers, substations and panel refurbishments where conventional clamps don't fit.
In residential installations it makes sense when the panel is full and there's no room for three 120 A clamps.
Common mistakes
- Cables that don't fit through the 9 mm: check the diameter before buying.
- K → L direction reversed: gives negative readings.
- Mixing up phases when connecting the three connectors: check the color code.
- Expecting it to cut loads without the add-on: it has no built-in relay.
Related products and guides
- Shelly Pro 3EM-3CT63: the three-phase meter with the 63 A combined clamp.
- Shelly Pro 3EM 120A: if you exceed 63 A or 9 mm of cable.
- Pro 3EM-3CT63 frequently asked questions.
- Pro range comparison: the four DIN-rail meters.
Not sure if your cables fit through the opening? Send us a photo of your panel and we'll confirm it. Technical support in English and shipping from Spain.
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