Shelly 1 Gen3

At a glance

• In its favour
• Plain fact
• Worth knowing
• Not stated by the maker

• Plain fact: Switches on your monitor’s reading
• In its favour: A true dry contactShelly calls it “potential-free”, for switching lower-voltage devices.
• Worth knowing: Not the Shelly Plus 1PMShelly says the 1PM doesn’t have dry contacts.
• Not stated by the maker: What it does after a power cut wasn’t confirmedShelly’s settings pages couldn’t be opened. Set it to come back off.
• Plain fact: Works locally with Home AssistantNo cloud connection needed.

Setting it for a bedroom

HouseExhale’s setting: switch up at 750 ppm and back at 650, or ramp from 600 to full by 750. Never above 800.

1. Wire its contact to the unit’s low-voltage high-speed input (never line voltage on an input made for a dry contact).
2. Let Home Assistant switch it on above 750 ppm and off below 650.

A Danish study ran a bedroom fan from about 900 ppm and the nights still averaged 835, so a control has to start below the goal. Good home CO₂ sensors are rated within about 55 to 90 ppm at 800, and the night average includes the climb after bedtime, so 750 on and 650 off leaves room for both. A control in the return duct mixes the bedroom with empty rooms, so it needs lower settings still (about 650 on, 550 off), and your monitor in the bedroom has the final word. These are HouseExhale’s numbers: no study has tested a control against an 800 night average yet.

What it works with

Any ventilator with a low-voltage input that holds high speed while two terminals are joined. Ventilator makers don’t name third-party controls: check your unit’s manual and ask your installer first.

How to add CO₂ control to an HRV or ERV · HRV and ERV units

Specs

Contact

Potential-free, 16 A at 240 V AC, 10 A at 30 V DC

Power

110–240 V AC, 24–48 V DC or 12 V DC

Control

Local web page, HTTP, MQTT; Home Assistant

From the maker’s documents, read October 17, 2026. Prices are before tax and shipping and change often.

Smart-home pieces

Use a monitor you already own to switch high speed. Not documented by any ventilator maker: low-voltage inputs only, and check your manual first.

• Home Assistant

  Switches on your monitor’s reading

  Smart-home software that runs at home

• SwitchBot Bot, triggered by the Meter Pro CO₂

  Switches on your monitor’s reading

  A button pusher, no wiring

• Zooz ZEN17 universal relay

  Switches on your monitor’s reading

  Z-Wave relay with dry contacts