Dimensioning of the silencer (Helios Controlled Residential Ventilation EC 370)

How critical is the length of the silencer in the ventilation system?

Helios sells flexible duct silencers with a length of 1000 mm and recommends using them uncut. In practice, however, the silencers are often shortened because the required installation space is not available. Helios says that it is common to make compromises here but does not specify minimum lengths for reasonable sound attenuation.

How do you assess the lengths of the silencers?

How long is your silencer? Are you satisfied with the sound attenuation?

We have a Helios controlled residential ventilation EC 370. Our silencer is shortened to 420 mm and we are dissatisfied with the noise level.

Hi,

420 mm seems very short to me. Here, silencers with 1000 mm are installed, additionally silencers are placed in front of the outlets in all bedrooms.

That’s okay. At full power, however, the system is already slightly audible.

In der Praxis werden die Schalldämpfer aber oft gekürzt, da der nötige Bauraum nicht zur Verfügung steht.

Then the planner slept on it and planned the system incorrectly. Then he should have created the required installation space.

Best regards,

Andreas

For silencers, the sound attenuation is proportional to the length. Assuming the silencer has an insertion loss of 10 dB in the unshortened state, it is only 4.2 dB at the length you specified.

This is now very simplified physically, but basically practically applicable. Your system is 6 dB louder than necessary and thus has the same "loudness" as 4 systems with the large silencer (logarithm - doubling the sound power corresponds to +3 dB).

Hi! Our silencer is 80 cm long and we find the sound attenuation acceptable. We only hear the ventilation system at the outlets when it is set to "party mode." Otherwise, you can hear the device when standing in the technical room.

I have connected 1m each to the supply air and exhaust air, and then another one behind in series, but only for the upper floor, in the exhaust air another 50cm, so it is quiet enough...

I have connected 1m each of supply air and exhaust air and then added another one behind them, meaning in series, but only for the upper floor; in the exhaust air, there is another 50cm, making it quiet enough...

And where is the second silencer located? How far is it from there to the outlets?