MVHR drone

[Mattg4321]

On 25/10/2025 at 22:52, Mike said:

Zehnder aren't cheap, but that looks like list price. It should be possible to knock at least 30% off that.

 

The supplier I used (in Germany but delivery to France, not sure if they'll deliver to the UK post-Brexit) are currently offering the main body at a 43% discount (€205 including VAT).

 

You also only need  one unit to silence 10 terminals.

Looked into this more thoroughly. I had thought you needed to be buy the manifold and also the attenuator, as well as both end plates (1x160 and 10x75). It appears I’d only need the attenuator and the end plates, which makes the cost slightly more palatable. 
 

Looking at the data and particularly at the low frequencies, what I find hard to get my head round is how 2x attenuators stacked, performs worse than only 1x at the low frequencies. Whats also slightly concerning is no 32Hz as part of their test. Would be frustrating to spend 300 odd quid and a few hours and not get a satisfactory result!

Edited Sunday at 21:16 by Mattg4321

[Mike]

8 minutes ago, Mattg4321 said:

I had thought you needed to be buy the manifold and also the attenuator

The main box is an attenuated manifold - item 990323502. Plus you need one end plate with a 150mm connection to suit your 150mm duct (item 990323568, by the look of it), and one end plate with 10 pipe connections (75 or 90mm - 990323614 / 990323615 depending on what you have). So yes, 3 items in total. Check those codes though!

 

13 minutes ago, Mattg4321 said:

what I find hard to get my head round is how 2x attenuators stacked, performs worse than only 1x at the low frequencies.

Yes, something counter-intuitive happening there - something to do with the extended dimension -v- the wavelength, I suppose.

 

However I note that the figures on the last line - with the 10 x 75/90mm end plate - are different to those in the French brochure. Either the English or the French figures have to be wrong (though whichever is correct still gives good attenuation). I just went looking for the German version, but the one I found doesn't quote any figures at all...

 

Looking again at the French figures, they give them for two connected boxes (160mm end plate + manifold core + manifold core + 10 x 75/90mm end plate) as well as for the single arrangement; the result is more intuitive:

 

 

 

48 minutes ago, Mattg4321 said:

Whats also slightly concerning is no 32Hz as part of their test.

32Hz is really low - I guess it's not normally a concern. I don't think you actually mentioned which MVHR unit you have, BTW?

 

 

[Mattg4321]

8 hours ago, Mike said:

The main box is an attenuated manifold - item 990323502. Plus you need one end plate with a 150mm connection to suit your 150mm duct (item 990323568, by the look of it), and one end plate with 10 pipe connections (75 or 90mm - 990323614 / 990323615 depending on what you have). So yes, 3 items in total. Check those codes though!

 

Yes, something counter-intuitive happening there - something to do with the extended dimension -v- the wavelength, I suppose.

 

However I note that the figures on the last line - with the 10 x 75/90mm end plate - are different to those in the French brochure. Either the English or the French figures have to be wrong (though whichever is correct still gives good attenuation). I just went looking for the German version, but the one I found doesn't quote any figures at all...

 

Looking again at the French figures, they give them for two connected boxes (160mm end plate + manifold core + manifold core + 10 x 75/90mm end plate) as well as for the single arrangement; the result is more intuitive:

 

 

 

32Hz is really low - I guess it's not normally a concern. I don't think you actually mentioned which MVHR unit you have, BTW?

 

 

It’s the Vent Axia Sentinel FH. I’m starting to wish I’d gone for the Zehnder Comfoair though, which was also a contender. Size and cost swayed me towards the Vent Axia, which many on here seem to be happy with. 
 

Thanks for your help @Mike and everyone else. Looking at the figures, these comfowell manifold attenuators seem to perform significantly better than almost any pipework silencer than I can find, and it should be a relatively straightforward job to swap it out, so that’s what I’ll be doing asap when I’m back. 
 

Will update in due course. 

[Jolo]

On 24/10/2025 at 22:36, Mattg4321 said:

Which flexible attenuator did you use on the ductwork to bedroom? How did you adapt it onto the semi rigid ducting? I have a double run to the bedroom

 

It's a DEC International flexible silencer non-woven, Ø 100mm, 1m long. (Pretty cheap, about 25 quid?)

 

I used Ubbink Air Excellent distribution box adaptors to connect the semi-flex ducting to the silencer, as I have several spares of these (I'd accidentally over-ordered when ordering the parts for the distribution boxes!). https://www.ubbink.com/int/products/ventilation/air-excellent-ventilation-ductwork/duct-adaptors/air-excellent-ae48c-dbox-adaptor/

 

The ducting clicks into it as designed, and I've used aluminium tape to attach the silencer onto the adaptor. I guess a cable-tie might also be a good idea, I might add one before I put the cupboard ceiling back on. The outer diameter of the adaptor matches the inner diameter of the silencer fairly well, so it fits together pretty neatly.

 

At the vent end of the silencer I did the same thing in reverse, though this was only necessary because I have a Vent-Axia UniflexPlus wall vent in the bedroom, and the design of the ducting connector means it needs the semi-flex duct to be air-tight. If I'd used another brand of ducting at the bedroom (such as the Ubbink Air Excellent ones) then the end of the silencer would just slip over the vent adaptor and be taped on, as the air-tight design on those would allow that simpler connection.

Edited yesterday at 09:25 by Jolo
Added guide price of silencer, added link to item

[JamesP]

In 2017, BPC supplied a metal silencer, ASM 150600 with my kit.

I fitted it between the Vent Axia unit and supply manifold only.

Unit fixed down well?

It might help temporarily, disconnecting one of the supply from the manifold to the bedroom as

you have a double.