Which Shelly device does the CT 120A clamp work with?

It works with the Shelly Pro 3EM energy meter, to which it connects via the 2-pin MX3.0-2x1Y connector. It is a measuring accessory and does not work on its own.

Do I have to cut the cable to fit the clamp?

No. The split-core opens on a clip, is placed around the phase conductor and snapped shut again, without cutting or disconnecting the existing cable.

How thick a cable fits through the clamp?

The conductor aperture is Ø15 mm. Thicker conductors on large service entries may not fit, so check the cross-section before ordering.

How many clamps do I need for a three-phase installation?

One per phase, so three CT 120A clamps for a three-phase system, connected to the three channels of the Shelly Pro 3EM.

Can I install the clamp in the panel myself?

Installation should be done by a licensed electrician, since the work is inside a live distribution board. CasaSmart advises free of charge; a site visit and design are paid services.

What are the main technical specs of the CT 120A?

Maximum primary current 120 A, 3000/1 ratio, ferrite core, 3000 VAC/60 s strength, Ø15 mm aperture, 650 mm cable, 75 g weight, -10 to 50 °C temperature.

Shelly CT 120A current clamp Pro 3EM

Name: Shelly CT 120A split-core current transformer for Pro 3EM
Brand: Shelly
SKU: SHELLY-CT-120A

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

About this product

The Shelly CT 120A current transformer is a measuring accessory rather than a standalone device: it operates only together with the Shelly Pro 3EM energy meter. Its split-core opens and closes on a clip, so the clamp fits around the phase conductor without cutting or disconnecting the existing cable.<br><br>Maximum primary current is 120 A at a 3000/1 ratio, the core is ferrite, and dielectric strength reaches 3000 VAC for 60 seconds. The conductor aperture is Ø15 mm, and the 650 mm cable ends in a 2-pin MX3.0-2x1Y connector that plugs straight into the Pro 3EM input.<br><br>A three-phase setup needs one clamp per phase. Installation should be carried out by a licensed electrician, since the work takes place inside a live distribution board.

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

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Where it works

Use cases

A single-phase apartment in Chisinau where the owner tracks monthly cost in the app.

One CT 120A clamp on the apartment phase lets the Pro 3EM meter show energy use in real time.

A house with a three-phase supply where load balance across phases is monitored.

Three CT 120A clamps, one per phase, feed the three Pro 3EM channels for a full balance.

A household with solar panels that wants to see the exported surplus.

The clamp measures cable flow and shows when the panel exports energy back to the grid.

For the installer

Technical specifications

full spec · wiring · datasheet

Power

Rated max. primary current: 120 A
Current ratio (primary/secondary): 3000/1
Electrical strength: 3000 VAC, 60 s

Physical

Core material: Ferrite
Conductor aperture: 15 mm
Cable length: 650 mm
Dimensions (HxWxD): 45x40x36 mm
Weight (with cable): 75 g
Mounting: Split-core, snap-on

Connectivity

Output connector: 2-pin MX3.0-2x1Y
Compatible meter: Shelly Pro 3EM

Environment

Ambient temperature: -10 to 50 °C

Full device datasheet

Support

Frequently asked questions

Which Shelly device does the CT 120A clamp work with?
It works with the Shelly Pro 3EM energy meter, to which it connects via the 2-pin MX3.0-2x1Y connector. It is a measuring accessory and does not work on its own.
Do I have to cut the cable to fit the clamp?
No. The split-core opens on a clip, is placed around the phase conductor and snapped shut again, without cutting or disconnecting the existing cable.
How thick a cable fits through the clamp?
The conductor aperture is Ø15 mm. Thicker conductors on large service entries may not fit, so check the cross-section before ordering.
How many clamps do I need for a three-phase installation?
One per phase, so three CT 120A clamps for a three-phase system, connected to the three channels of the Shelly Pro 3EM.
Can I install the clamp in the panel myself?
Installation should be done by a licensed electrician, since the work is inside a live distribution board. CasaSmart advises free of charge; a site visit and design are paid services.
What are the main technical specs of the CT 120A?
Maximum primary current 120 A, 3000/1 ratio, ferrite core, 3000 VAC/60 s strength, Ø15 mm aperture, 650 mm cable, 75 g weight, -10 to 50 °C temperature.

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Questions about this product?

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+373 60 944 922

Updated: 18 June 2026· reviewed by CasaSmart Expert Team