Shelly Pro 3EM Switch Add-On

Description

The Shelly Pro 3EM Switch Add-On is a specialized expansion module for the Shelly Pro 3EM energy meter.

By default, the Pro 3EM is purely a meter—it monitors three phases of electricity but cannot physically turn them on or off. This add-on “snaps” onto the side of the meter to give it switching capabilities.

How it Works

The Add-On connects to the side of the Shelly Pro 3EM via a proprietary header (no separate power supply is needed; it draws power from the main unit). Once attached, it provides a galvanically isolated dry contact relay.

Because the relay is only rated for 2A, it is not meant to power a water heater or motor directly. Instead, it is designed to act as a trigger for a contactor.

• The Chain: Shelly Pro 3EM (Brain) → Switch Add-On (Trigger) → Heavy Duty Contactor (Muscle) → High Power Appliance.

Key Features

• Dry Contacts: Since the switch is potential-free, you can use it to switch any voltage (up to 240V AC or 30V DC).
• DIN-Rail Mountable: It matches the form factor of the Pro series, sitting neatly next to the energy meter in your breaker box.
• Automatic Integration: Once plugged in, the Shelly app recognizes it as a new “output” for the Pro 3EM.

Technical Specifications

Why would you need it?

This is the “logic-to-action” bridge. The most common use cases include:

• • Solar Self-Consumption: Set a rule that says: “If my solar panels are producing more than 3kW of excess power, close the relay.” This triggers a contactor to turn on your electric water heater or pool pump, using “free” energy.
  • Load Shedding: If your total house draw exceeds a certain limit (e.g., 10kW), the Shelly can automatically open the relay to drop a non-essential load and prevent your main breaker from tripping.

• Weather-Based Automation: Using the Gen3/Pro scripting capabilities, you can tell the relay to turn off your exterior lighting or heating if the weather forecast predicts specific conditions.