Smart-home piecesZooz

Zooz ZEN17 universal relay

A Z-Wave relay with two dry contacts and a timer that can switch it back off on its own.

$35.95 at ameriDroid (ZEN17 800LR), October 17, 2026

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At a glance

  • Switches on your monitor’s reading
  • Dry contacts, normally open and normally closedZooz lists HVAC equipment among its uses.
  • After a power cut it goes back to its last stateA blip during a boost can bring it back on. Its settings can force it off after an outage instead. (From the 700-series manual; the price below is for the newer 800LR.)
  • An auto-off timer can act as a safetyOff by default. Set it, and a stuck relay opens unless Home Assistant turns it on again.
  • Needs a Z-Wave controller for Home Assistant

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. Set it to stay off after a power cut, and set its auto-off timer.
  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

Contacts
Normally open 20 A, normally closed 10 A
Power
12–24 V AC/DC or USB-C
Control
Z-Wave (Home Assistant’s Z-Wave JS)

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.

Sources