MVHR drone

[JohnMo]

I've had good service from duct store 

[Nick Laslett]

1 hour ago, JohnMo said:

I've had good service from duct store 

 @S2D2, I bought all my spiral ducting form the Duct Store, like @JohnMo.

 

https://www.ductstore.co.uk/acatalog/Attenuators.html
 

They have attenuators. 
 

I used the Lindab Safe Click system, which has rubber gaskets. I bought all these components direct from Lindab. Just find the nearest sales office to you. 
 

https://www.lindab.co.uk/Products/ventilation/Sound-attenuation/?sort=popularity&display=16&page=1

 

They have a huge choice of attenuators. 
 

If you want to be confident that you are going to cut most of the MVHR unit sounds before they hit the manifold, you need an attenuator that is 1000mm long. If you look at the spec sheet for the Lindab Attenuator, the difference between 500mm and 1000mm is significant. 
 

A semi-flexible radial system will also help mitigate the noise. Also, you don’t want your individual ducts going to a supply outlet being too short. 

 

Here is a photo from one of @Nickfromwales installs showing 500mm attenuators, foam insulated ducts and a Ubbink manifold. 
 

Edited October 7 by Nick Laslett

[Nickfromwales]

2 hours ago, Nick Laslett said:

 @S2D2, I bought all my spiral ducting form the Duct Store, like @JohnMo.

 

https://www.ductstore.co.uk/acatalog/Attenuators.html
 

They have attenuators. 
 

I used the Lindab Safe Click system, which has rubber gaskets. I bought all these components direct from Lindab. Just find the nearest sales office to you. 
 

https://www.lindab.co.uk/Products/ventilation/Sound-attenuation/?sort=popularity&display=16&page=1

 

They have a huge choice of attenuators. 
 

If you want to be confident that you are going to cut most of the MVHR unit sounds before they hit the manifold, you need an attenuator that is 1000mm long. If you look at the spec sheet for the Lindab Attenuator, the difference between 500mm and 1000mm is significant. 
 

A semi-flexible radial system will also help mitigate the noise. Also, you don’t want your individual ducts going to a supply outlet being too short. 

 

Here is a photo from one of @Nickfromwales installs showing 500mm attenuators, foam insulated ducts and a Ubbink manifold. 
 

I added a 3rd attenuator to that job, as the client wanted “graveyard in Gravenhill” levels of shhhhh! at night.

 

Then foam duct defo helps out, but I’m now being ‘directed’ towards spiral galv rigid ducting against my will…..

 

I’ll do one and see if it passes muster, if not I’ll be reverting back to foam. 

[Jolo]

I also experienced a droning noise, but after buying a rectangular attenuator from Lindab (thanks to your photos and advice here @Nick Laslett and @Nickfromwales!) which didn't stop it, I determined that it wasn't coming from the main unit, but was being generated within the green ribbed Ubbink Air Excellent ducting.

 

So for the bedroom I added a 1m flexible attenuator at the end, just before the vent, and it works great. To avoid adding too much more static pressure I went for one with a 100mm internal diameter (larger than the 75mm internal diameter of the ducting). It works really well, even on boost it's barely audible and at night we don't have it that high anyway, so it's totally silent.

 

I since added another to one of the living room vents, and it's worked great there too.

 

While this does work, is there anything I'm missing? Is there a reason I've never seen this recommended anywhere? 

[Mike]

8 hours ago, Jolo said:

Is there a reason I've never seen this recommended anywhere? 

Because it's cheaper to centralize the attenuators, rather than installing them per-room. And noise generated within the duct would normally be due to excess air velocity, which shouldn't happen - but you seem to have found an exception :)

[JohnMo]

8 hours ago, Jolo said:

at night we don't have it that high anyway

If at night you can turn down the MVHR aren't you actually running too high in general. There should be zero reason to change base rate at different times of the day.

 

Get a simple co2 monitor and move about at different times of the day. And actually look at what is occurring and tune the flow based on actual needs.

 

I am using Ubbink duct, no noise. You have either under installed ducts based on your flow rates or you are flowing to high a rate.