Zehnder ComfoAir Q350 HRV

At a glance

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

• In its favour: HVI-certified (HVI 2505023)Its airflow and efficiency were tested to the Home Ventilating Institute’s standard.
• Plain fact: 195 cfm at 0.4 in., 195 cfm at 0.5 in. of duct pressureCertified fresh air delivered, at HVI’s headline rating point and at the higher pressure many real ducts run at.
• In its favour: Zehnder’s own CO₂ sensor works through its Option BoxAirflow rises gradually as CO₂ rises. Set it to 700 ppm (3.5 V in sensor mode), not the 1,000 Zehnder suggests.
• In its favour: Humidity control documented
• Plain fact: How it handles frost in very cold weatherAutomatic frost protection. An optional adaptive electric pre-heater (9656-00) warms incoming outdoor air to keep the core from freezing, and Zehnder recommends it for cold climates. Frost protection can also cut supply airflow, which leaves the house slightly out of balance unless the fireplace setting is on. No source gives the temperature at which it starts.

Certifications

• HVI certified

  HVI 2505023

  The Home Ventilating Institute tested its airflow and heat recovery. The certified numbers on this page come from its directory. Find HVI 2505023 in HVI’s directory

• ENERGY STAR (Canada)

  Not on the list

  Not on Natural Resources Canada’s ENERGY STAR list when we checked. ENERGY STAR certifies HRVs and ERVs only in Canada, so a unit sold in the U.S. may never have been submitted; that isn’t a sign it’s less efficient. Its HVI numbers show its heat recovery and fan power. NRCan’s ENERGY STAR list (checked October 19, 2026)

• Passive House

  Component 0956vs03

  The Passive House Institute certified it as a ventilation component for very airtight homes. Its Passive House listing

Would it cover your home?

Tell it who sleeps in each bedroom. It’s checked against the 800 ppm goal the same way the app checks a unit an installer quotes.

Certified airflow

How much fresh air it delivers as the ducts push back. More duct pressure, less air: that’s why the installer’s duct design matters as much as the unit.

Lowest steady airflow (maker)

41 cfm

Highest airflow (maker)

195 cfm

Heat recovery

Sensible recovery (SRE) is the share of heat kept in winter, after the fan’s own heat is taken out. Higher is warmer incoming air for the same airflow.

• Plain fact: Keeps 86–92% of the heat at 32°FAcross the airflows HVI tested.
• Not stated by the maker: No very-cold (−13°F) test in the HVI directory

HRV or ERV: which fits your home?

Turning up on CO₂

A CO₂ control can switch it to a higher speed when the bedroom needs air, then back. HouseExhale’s setting: up at 750 ppm, back at 650, never above 800.

• In its favour: Zehnder’s own CO₂ sensor works through its Option BoxAirflow rises gradually as CO₂ rises. Set it to 700 ppm (3.5 V in sensor mode), not the 1,000 Zehnder suggests.

Documented control setups for this unit

• Zehnder CO2 Sensor 0-10V67 + Zehnder Option BoxWorks directly with this system

  Airflow rises as CO₂ rises. Each bedroom sensor sends a proportional request through an independently configured Option Box input. The Q350 compares requests and responds to the highest demand within the commissioned airflow limits.

  Set it to 700 ppm.

  About the Zehnder CO₂ sensor

• Greystone Energy Systems CD2RMC + Zehnder Option BoxProfessional setup option

  Airflow rises as CO₂ rises. The third-party sensor's 0-10 V output can feed the Option Box, which documents support for sensors within that input range.

  Set it to 700 ppm, if it can be set that low: its maker doesn’t publish its range.

  About the Greystone CD2RMC · About the Zehnder CO₂ sensor

• Aranet Aranet4 HOME + Open Home Foundation Home Assistant + Zehnder ComfoConnect LAN CDIY smart-home option

  Automation changes fan speed. Home Assistant reads Aranet over Bluetooth and writes a Q350 ventilation preset through the community ComfoConnect integration.

  Set it to 750 ppm.

  About the Home Assistant

What Zehnder (ComfoAir) documents

• In its favour: Its own CO₂ sensor, through the Option Box (ComfoAir Q)Airflow rises gradually as CO₂ rises. Up to four sensors; the highest reading decides.
• Worth knowing: Set it to 700, in sensor modeIt works to hold the room at its setting, so aim under 800. Zehnder suggests 1,000, and the sensor’s own controller mode holds 1,050; in sensor mode, 3.5 volts on the Option Box is 700.
• Worth knowing: The sensor’s light stays green up to 1,200 ppmGo by your monitor’s number, not the light.
• Plain fact: The Q unit has no boost terminals of its ownIts switch and sensor inputs are on the Option Box.

Four ways to make it turn up by itself

• Its maker’s CO₂ controlMade for it

  Zehnder’s 0–10 V CO₂ sensor and Option Box, in sensor mode with the setting at 700 ppm (3.5 V).

• A night scheduleAsk your installer

  Ask whether its control or the ComfoControl app can run a higher speed at night.

• A CO₂ control on its high-speed inputAsk your maker first

  A third-party sensor on the Option Box’s 0–10 V input isn’t documented by Zehnder.

• Your monitor and a smart-home relayAsk your maker first

  Home Assistant’s ComfoConnect integration is unofficial and marked legacy.

How to add CO₂ control to an HRV or ERV · CO₂ controls

Installing it

The maker’s facts an installer plans around. Your installer confirms them for your home.

Power

240 V, 60 Hz. 208 V also works but gives about 7% less maximum airflow. Maximum draw is 180 W / 1.42 A without the pre-heater and 1,850 W / 10 A with it. It needs a dedicated 240 V / 60 Hz / 15 A circuit, and the rough-in guide gives the receptacle as NEMA 6-15. The installer manual lists a 2.5 m power cord in the box.Scope: circuit and receptacle from the Electrical rough-in requirements guide (https://zehnderamerica.com/wp-content/uploads/2024/08/Electrical-Rough-In-Requirements.pdf); cord from the installer manual

Duct connections

Four round duct connections of 160 mm (6.3 in), which turn freely and sit on the top or the side. The installer manual gives 160 mm inside and 190 mm outside.Scope: same for the Q350 HRV and ERV

Size

Height 32 in (809 mm), 34 in (850 mm) with connectors; width 29 in (725 mm), 31 in (790 mm) overall; depth 22 in (570 mm), 22.8 in / 23.4 in (580 mm / 595 mm) total.Scope: same for the Q350 HRV and ERV

Weight

110 lb (50 kg)Scope: same for the Q350 HRV and ERV

Mounting

Wall-mounted on the supplied bracket, on a wall of at least 200 kg/m². Floor-mounted on the optional Zehnder base or frame, which is also for lighter walls. The connections come set up for the right side and can be changed to the left. Ceiling hanging is not mentioned.Scope: same for the Q350 HRV and ERV

Drain line

Yes, it needs a drain line for condensation. There are two bayonet drain connections: one is capped, and the other goes to a dry siphon (no U-bend) rated for at least 500 Pa of suction. The drain fits 32 mm tube or a 1¼ in thread (DN 32 external thread on the spec sheet). Pour a cup of water into the seal every six months to keep sewer smells out.Scope: six-month refill from the user manual p. 27; DN 32 from the spec sheet

Cold weather

Automatic frost protection. An optional adaptive electric pre-heater (9656-00) warms incoming outdoor air to keep the core from freezing, and Zehnder recommends it for cold climates. Frost protection can also cut supply airflow, which leaves the house slightly out of balance unless the fireplace setting is on. No source gives the temperature at which it starts.

Balancing the airflow

Constant-flow/pressure monitoring and guided commissioning

Service space

1 m front

Ducts

Dedicated Zehnder distribution preferred; engineered integration required

In the box

Unit, mounting bracket, condensation drain set, power cord, documentation and dust cover. No wall control is included.

Controls

Humidity control

Documented

Bathroom boost

Documented

Works without the internet

Documented

CO₂ inputs

0–10 V input, dry-contact input

Owning it

Equipment price

Not stated in the sources we found

Rebates

Federal tax credits ended for work after 2025. Some states and utilities still pay toward an HRV or ERV: rebates by state.

Filters

• Type: Two panel filters: one on the outdoor (fresh) air side and one on the indoor (extract) air side
• MERV: Outdoor air F7 (MERV 13); extract air G4 (MERV 7-8)
• Part: Filter set G4/F7 9672-00 (2 filters); G4 9671-00; F7 9670-00
• How often: At least every six months (user manual). The display warns 'EXPECT FILTER CHANGE SOON', then 'CHANGE FILTERS NOW'.

Scope: change interval from the ComfoAir Q user manual, p. 28

Warranty

• Parts: 24 months after fitting, up to 30 months after manufacture (user manual). Zehnder America's FAQ: all its products sold in North America carry a two-year limited warranty.
• Labor: Not covered: the customer pays to remove and reinstall the unit, including labor and return shipping (FAQ). On-site assembly and disassembly are not covered (user manual).
• Conditions: Claims go by certified mail with proof of purchase date. The warranty is void after improper installation, wiring, maintenance or voltage, or misuse. The user manual adds running without filters, non-Zehnder parts and unauthorized changes.

Scope: FAQ terms from https://www.zehnderamerica.com/?p=7677 (2017-08-17), which covers all Zehnder America products

Sound

Sound from the unit's casing into the room where it is installed (sound power, ISO 3741): 33.8 dB(A) at 88 cfm up to 52.0 dB(A) at 206 cfm. The reference guide states the same range as 34 dB(A) at 150 m³/h and 25 Pa up to 52 dB(A) at 350 m³/h and 200 Pa. Sound power into the ducts: extract side 35.0 to 51.0 dB(A), supply side 46.0 to 66.0 dB(A). These are sound power ratings, not the loudness heard at a set distance.

Availability

Active: the HRV version (article 9648-01) is on Zehnder America's current Q350 spec sheet and ComfoAir Q page

Zehnder’s page for the CAQ350 HRV (opens in a new tab)

Not known yet

What we couldn’t confirm from the maker or HVI. Ask the installer, and get it in writing with the quote.

• A current equipment price to compare
• What it costs installed where you live
• How much fresh air it delivers while defrosting
• A current equipment price

Where the maker’s own documents disagree

• The part-number conflicts listed under zehnder-caq350-erv (CO₂ sensor 9260-01 / 9767-00, ComfoSwitch, LAN C, floor stand, filter set) apply to this model too.
• The voltage conflict (230 V ±10% 50-60 Hz in the 2021 NA installer manual, 240 V 60 Hz on the spec sheet) and the dimension-line conflict within the spec sheet also apply.

Other sizes and similar units

Other Zehnder ComfoAir Q350 sizes

• 

  Zehnder ComfoAir Q350 ERV

  ERV · HVI 2005163

  201 cfm at 0.5 in.

Other HRVs with similar airflow

• 

  Fantech HERO 200H

  HRV · HVI 2505147

  195 cfm at 0.5 in.

• Broan AI Series B230H75RS

  HRV · HVI 2505229

  220 cfm at 0.5 in.

• Lifebreath 205MAX

  HRV · HVI 2505460

  159 cfm at 0.5 in.

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