Wall CO2 controllers with a relayKele

Kele CD-AW

A flush wall CO2 controller with a true dry contact. Ships set to 1,000 ppm, so it has to be set lower.

$288.60 for the CD-AW-LCD at Kele (October 17, 2026)

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At a glance

  • Can be set under 800
  • A dry (unpowered) contactNormally open by default, normally closed by jumper.
  • Ships set to 1,000 ppmSet it to 750. Kele’s datasheet says it adjusts from 0 to 5,000 ppm; its product page says 700 to 1,300.
  • No self-calibration mentionedKele lists a 5-year manual calibration interval.
  • Plan on its own 24 V supplyVentilator makers don’t document powering a sensor from the unit.

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. Change its setting from 1,000 to 750 ppm, with a gap of about 100 ppm.
  2. Wire it to the unit’s input that holds high speed while closed, with its own 24 V supply.

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
Dry contact, 2 A at 24 V AC
Gap
About 40 ppm by default, adjustable 0–200
Power
20–28 V AC or 18–30 V DC
Mounting
Flush on a single-gang box; optional 4-digit LCD

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

Wall CO2 controllers with a relay

A sensor that closes a switch above its setting. Wired to a unit’s high-speed input, it runs the unit on high until CO2 drops. Commercial products; an installer fits them.

Sources