Dimension central ventilation system

Thank you for your answers. I cannot say which air exchange rate is targeted. For me, it is about fresh, good air without having to open the windows and without having too much humidity in the house. If possible, I also don’t want to hear the system, so it shouldn’t have to run at full strength. But well, the statement is that the 350 should be sufficient. The 600 is probably oversized. I will have a look at the price difference between 350 and 450 and then decide.

we have the comfoair 350 for a 125sqm house. the ventilation normally runs on level 2 of 3, which for us corresponds to about 40-50% of the power. for a 170sqm house, the system is probably a bit too small. the system should rather run in the lower range, because at nominal power it consumes significantly more electricity! the bigger devices apparently also have a larger impeller wheel
basically, the size doesn't really matter, as underdimensioning is not a big deal. the air is still exchanged, just a bit less. on the other hand, the bigger version does not cost much more, so better to go one size up right away and that's that.

The surcharge is about 20-25%, respectively a few hundred euros, compared to the model Q450. In this respect, it is definitely worth designing the system accordingly.

Hi,

The surcharge is about 20-25%, respectively a few hundred euros, compared to the Q450 model.

A few hundred would even be worth it to me, currently the difference is about €650.
€2070 for the 350er
€2720 for the 450er.

That's a whopping 30% surcharge. And that's for the fact that the bigger one makes 1 dBA less noise? Power consumption is also almost identical.

If anyone sees it cheaper, please send me a PM, because I would also have to order soon...

Best regards,

Andreas

I just looked up our apartment ventilation calculation (it was handed over to us).

All values are only approximate and just as a reference:
parameters: normal location, usage unit 0-15m above ground level, high thermal insulation (new building), wind zone windy (30-40km to the North Sea)

volume to be ventilated: 315m³ (126 floor area x 2.5)
air volume flow for moisture protection 45m³/h (unfortunately it does not say here how this value was calculated)

and from this the sizing of the ventilation system is determined:
ventilation moisture protection (absent) 55m³/h
nominal ventilation (level 2/3) 185m³/h
intensive ventilation 240m³/h

from this you can see that you need about 0.6 of the enclosed volume per hour as nominal output (at least for the house size). For a 170sqm house multiplied by 2.5 (450sqm * 0.6 = 270m³/h required nominal performance) this results in stage 6 out of 8 on the comfoair and a power consumption of 105 watts. That’s quite substantial... the comfoair 550 only needs 69 watts at 265m³/h. That makes a difference of 35 watts/hour. At 8760 hours per year, that rounds down to 300 kWh savings. At an electricity price of almost 30 cents, that rounds up to almost 90 euros per year.

And this is exactly where the advantage of the larger systems lies. They simply run more efficiently at these air volumes.

Oh yes: if you want KFW with the ventilation system, it must be set up by someone anyway (or you need a volume measuring device and also a plan for how much air should come from which opening). Otherwise, more air comes out of the pipes with the shortest route to the ventilation system than from the line with the longest route. And if this is not properly adjusted, there will be a refusal from the KFW consultant at the end of construction.

Hope I could help a bit

Thank you very much for the information. Definitely helps.