ᐅ Operation and Control of the Mechanical Ventilation System with Heat Recovery in Single-Family Homes

Hello everyone,

We have installed a Zehnder ComfoAir Q450. After looking into the system a bit more, I realized that the installers probably left it at the default settings.

That means it runs at level 2 with about 230 m³/h (135 cfm). Additionally, I activated the automatic humidity and temperature control, which increases the airflow by a few cubic meters per hour in the evening during summer (around 290 m³/h (170 cfm) in the evening).

I find these airflow rates quite high, which of course also increases electricity consumption. It’s also not completely quiet in the evening at these levels.

House details:
Supply air to living spaces and storage rooms, exhaust air in kitchen / 2 bathrooms / laundry room / technical room
210 m² (2,260 sq ft) living and usable space
615 m³ (22,000 cu ft) air volume in the house
Upper floor: 4 supply air / 2 exhaust air / hallway pressure-equalized
Ground floor: 4 supply air / 2 exhaust air / hallway pressure-equalized
Basement: 2 supply air / 2 exhaust air
4 occupants

After reading up a bit, I would probably set the standard airflow closer to 185 m³/h (110 cfm) (about 30% × 615 m³ = air exchange rate > roughly 4 × 30 m³/h per person for 4 people).

I would appreciate feedback from other controlled residential ventilation owners on what airflow rates they operate at.

There is also an option for time control. Currently, I have it set (for summer) to better regulate humidity and temperature. It seems to help somewhat, but considering the heat capacity of air, I wouldn’t expect it to have a huge effect.

02:00–04:00 increase to level 3 (cold outside air for cooling)
07:30–08:30 increase to level 3 (ventilation after showering)
12:00–18:00 reduce to level 1 (summer heat protection)

Otherwise, normal operation at level 2.

Has anyone had good experience with time-controlled ventilation?

Thanks,
Andreas

Although I have a different system, our current timing schedule is as follows:
7:00 AM to 9:30 PM ventilation level 0
9:30 PM to 7:00 AM ventilation level 2

No heat recovery, as the cross-flow heat exchanger has been removed and a summer bypass cassette installed. Similar to a bypass.

Tentakel schrieb:
I find these airflows quite high, and of course, they also consume electricity. Also, in the evening, it’s not exactly quiet.

Hello Andreas,

Who planned your mechanical ventilation with heat recovery system and developed the ventilation concept? If in doubt, I would ask them.

Ideally, the system should not be noticeable during normal operation if properly designed. Intensive ventilation, yes, but normal or reduced ventilation shouldn’t really be audible.
How much volume flow do you have through each vent? Is it below 25 cubic meters everywhere? Air velocity in the ducts below 2 meters per second (m/s)?

Regarding electricity consumption, I’m a bit surprised. How many watts does it actually use that you’re concerned about the power consumption? No offense, but living in a house larger than 200 square meters (2153 square feet) and worrying about the small amount of electricity used by a mechanical ventilation system? These systems aren’t major electricity consumers and are usually quite efficient. Especially with the plate heat exchanger in your ComfoAir, you actually have an advantage compared to rotary heat exchangers in terms of energy use. So maybe you’re overthinking it?

Hello, thanks for the feedback. Planning with the heating engineer is okay so far, and I have the documentation for it. He just didn’t take the trouble to fine-tune the system precisely, although plus or minus 30 cubic meters per hour doesn’t make a difference.

The main issue is not the power consumption, but rather the moisture intake during humid weather, especially when the system is running at full capacity around midday.

@haydee: Thanks for your settings. I have further reduced mine during the day, and the indoor climate has improved. There is less moisture entering the house.