Which Shelly device does this current transformer work with?

The CT 120A is designed solely for the Shelly Pro 3EM three-phase energy meter. It connects to the meter input via a 2-pin MX3.0-2x1Y connector and does not work as a standalone device.

Does it have Wi-Fi or Bluetooth?

No. The clamp is a passive accessory with no radio. Measurement, power calculation and the connection to the Shelly app are handled by the Pro 3EM meter it plugs into.

How many sensors are needed for three-phase metering?

Full three-phase metering needs three CT 120A units on one Pro 3EM — one each on phases L1, L2 and L3. A single sensor measures only one phase.

What maximum current can it measure and what cable diameter does it accept?

The transformer measures load current up to 120 A per channel at a 3000/1 ratio. The conductor opening has a 15 mm diameter.

Does the power line need to be cut to install it?

No. Thanks to the split-core design the housing opens and clamps onto the conductor without cutting the cable. Installation inside a live panel should be done by a qualified electrician.

How long is the cable and where can the sensor be placed?

The cable is 650 mm and ends in an MX3.0-2x1Y connector. The sensor operates at -10...50 °C and up to 80 % humidity, so it is placed inside a panel sheltered from direct rain.

Shelly 120A Current Transformer Pro 3EM

Name: Shelly 120A Current Transformer for Pro 3EM
Brand: Shelly
SKU: SHELLY-CT-120A-PRO-3EM

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What it is, who it's for, what it does

About this product

The Shelly 120A Current Transformer is a split-core current transformer used together with the Shelly Pro 3EM three-phase energy meter. The clamp itself has neither Wi-Fi nor Bluetooth: measurement and data transmission are handled by the Pro 3EM meter it connects to.<br><br>The snap-on housing opens, fits over a phase conductor up to 15 mm in diameter and locks in place without screws and without cutting the cable. A 3000/1 transformation ratio and a ferrite core allow load current of up to 120 A per channel to be measured.<br><br>The 650 mm cable ends in a 2-pin MX3.0-2x1Y connector that plugs into the matching input on the Pro 3EM meter. For three-phase metering, three of these sensors are fitted to one meter — one per phase.

Delivery
Free from 1500 MDL
Returns
30 days to return
Warranty
24 months

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Where it works

Use cases

In a house near Chisinau the owner sees real L1, L2 and L3 consumption and spots phase imbalance

Three CT 120A on a Pro 3EM measure current on each incoming phase

A small shop checks that total load stays within the contracted capacity

A sensor on the incoming conductor tracks peak power

A workshop tracks kilowatt-hours on each equipment phase through the Shelly app

Monthly per-phase metering for cost allocation

For the installer

Technical specifications

full spec · wiring · datasheet

Power

Rated primary current: 120 A
Transformation ratio: 3000/1
Electrical strength: 3000 VAC / 60 s

Physical

Core type: Split-core ferrite
Conductor aperture: 15 mm
Dimensions: 45x40x36 mm
Weight with cable: 75 g

Connectivity

Cable length: 650 mm
Connector: MX3.0-2x1Y 2-pin
Compatible meter: Shelly Pro 3EM

Environment

Operating temperature: -10...50 °C
Humidity: 0...80 % RH
Max altitude: 2000 m

Full device datasheet

Support

Frequently asked questions

Which Shelly device does this current transformer work with?
The CT 120A is designed solely for the Shelly Pro 3EM three-phase energy meter. It connects to the meter input via a 2-pin MX3.0-2x1Y connector and does not work as a standalone device.
Does it have Wi-Fi or Bluetooth?
No. The clamp is a passive accessory with no radio. Measurement, power calculation and the connection to the Shelly app are handled by the Pro 3EM meter it plugs into.
How many sensors are needed for three-phase metering?
Full three-phase metering needs three CT 120A units on one Pro 3EM — one each on phases L1, L2 and L3. A single sensor measures only one phase.
What maximum current can it measure and what cable diameter does it accept?
The transformer measures load current up to 120 A per channel at a 3000/1 ratio. The conductor opening has a 15 mm diameter.
Does the power line need to be cut to install it?
No. Thanks to the split-core design the housing opens and clamps onto the conductor without cutting the cable. Installation inside a live panel should be done by a qualified electrician.
How long is the cable and where can the sensor be placed?
The cable is 650 mm and ends in an MX3.0-2x1Y connector. The sensor operates at -10...50 °C and up to 80 % humidity, so it is placed inside a panel sheltered from direct rain.

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Questions about this product?

A CasaSmart manager calls you within 1–2 working hours and answers anything — compatibility, install, alternatives.

+373 60 944 922

Updated: 18 June 2026· reviewed by CasaSmart Expert Team