Resonating plasterboard wall - buzzing plumbing

[readiescards]

Converted a long barn to a holiday cottage, heating system all at one end and two long 28mm (I think) pipes run the half the length of the barn to the UFH manifold.  All works ok and boxed in and hidden now behind plasterboard.  

 

But it is quite loud buzz for what is a nearly continuous noise and in the main living space.

 

Where the two pipes go around a buttress they are forced to do a couple of 90 degree bends. If I put my hand on the plasterboard there I can feel the board buzzing and it also marginally dampens the noise.

 

Are there any tips on how to reduce the plasterboard resonantation?  (I've thought of drilling some holes and squirt some foam through but a quick Google does not indicate if this will work or not)

 

Edited January 21, 2019 by readiescards
grammar

[ProDave]

Change the pump on the UFH manifold.  I had a similar noise, changed the supplied IBO pump for a Wilo and it is near silent.  (still have to do my other manifold to shut that up as well)

[readiescards]

That made me go check and in fact the vibration driving the resonance are coming from the ashp. It is about 3m away on the other side of the wall so I'm most surprised at that.

[Jeremy Harris]

Just now, readiescards said:

That made me go check and in fact the vibration driving the resonance are coming from the ashp. It is about 3m away on the other side of the wall so I'm most surprised at that.

 

I had exactly this problem when I first installed our ASHP.  The problem was that I didn't read the installation manual properly...

 

The manual stipulated that the flow and return pipes from the ASHP had to be at least 1m long large bore, insulated, flexible hoses, run in a loop, to decouple the vibration from the ASHP from the house.  I'd fitted short (around 300mm long) flexible pipes and they were coupling vibration directly into the house.  It was surprisingly noisy, noisy enough that I ordered new pipes, drained the system down and fitted things as per the instructions.  Once I'd done that it was completely silent inside the house, the only way to tell the thing is on is to look at the wall display.

[readiescards]

Thanks @JSHarris we do indeed have ours mounted with approx 1 metre length flexi hoses.  And the concrete plinth it is sat on is not directly connected to the property wall.  So it seems this ASHP vibration is coming through the water - is that possible?

[readiescards]

On 21/01/2019 at 16:31, ProDave said:

Change the pump on the UFH manifold.  I had a similar noise, changed the supplied IBO pump for a Wilo and it is near silent.  (still have to do my other manifold to shut that up as well)

 

Separate to the plasterboard vibration, the noise from the UFH pump is indeed loud and very annoying (to the point the other night it was a relief to have the dish washer running to mask the UFH pump noise).  We have a GRUNDFOS UPM3 AUTO L  running at 3 or 4 out of 5 capacity.    Is the Wilo quieter than a Grundfos?   It is not the pump that is loud but the vibrations it is setting up in the water/wall/mountings I think.

[ProDave]

My pump noise was more of a whine.  I changed the upstairs one first as I already had a spare Wilo pump, that was in the en-suite so proved very annoying.  I have ordered a second Wilo pump to replace the downstairs pump.

 

If any deaf member want's a couple of cheap circulating pumps let me know.

[Jeremy Harris]

Our ASHP hoses run in a loop, rather than straight, as apparently that allows the vibration to be decoupled better.  I think one issue is that the vibration isn't damped well along the axis of a flexible hose, hence the instructions to arrange them in a long loop.

[readiescards]

On 23/01/2019 at 13:52, JSHarris said:

 hence the instructions to arrange them in a long loop.

 

Thanks Jeremy, is that in the manual with the unit as I've not been able to find that instructions - well not in the 4 or 5 page very simple instructions that came with it.  Could you kindly tell me where to look or post relevant bit.  Thanks

[Jeremy Harris]

It's buried somewhere in either the Carrier or Glowworm installation manual I think, where minimising noise transmission by using long hoses is mentioned.  Looping them works perfectly I found, as we can't tell from inside the utility room whether the ASHP on the other side of the wall in running or not.  The only way we can tell is to look at the command unit display.

[Moonshine]

On 23/01/2019 at 13:31, readiescards said:

So it seems this ASHP vibration is coming through the water - is that possible?

 

Yes it is, and can cause noise issues, I was involved with a project where noise from high pressure pumps were causing issues due to pump pressure pulsations propagating along long runs of hydraulic pipe work that ran through noise sensitive areas.

 

Water is a pretty incompressible fluid and energy transfer though this medium is efficient. What the circulating pump is doing, is every time there is a fluid compression from the pump it gets sent down the fluid in the pipe. Say the pump has a operation speed of 1200 RPM (20 Hz) and 6 pumping element (lobes / vanes), it will create a 120 Hz pressure pulsation down the pipe and make the pipe and anything that its fixed to vibrate and create noise.

 

In your ASHP, it seems that the circulating pump and system is creating large pressure pulses.

 

So how to stop it?

• Try another circulating pump that creates a reduced magnitude of pressure pulses, as @ProDave seems to have found.
• Fit a hydraulic noise suppressor / pulsation dampener (though I doubt there there are any specific for ASHP's, as one looked at were in the 3000psi range)
• Make sure that the pipe work is not touching building elements, especially if they are lightweight (e.g. plasterboard).
• Use resilient pipe mounts.
• if sound is still propagating from the pipe, lag with a product such as Soundlag 4525C. 

  

Edited February 5, 2019 by Moonshine