Another thread about noise on Vaillant when running on max in posts 56 onwards.

Several good ideas from the Urban Plumber

@judith Thanks for posting these, I have skip read both and intend to read them fully.  They both look to be interesting and have some useful insight.

Posted by: @judith

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Googling noise with ashps and found this technical document https://www.apexacoustics.co.uk/wp-content/uploads/2023/10/NOISE-FROM-ASHPS-WHAT-WE-KNOW.pdf#page5

it identifies several noise related issues 

I have now read this in full.  Very interesting and logical.  One of the better papers I have seen in relation to ASHPs!

@jamespa it's a good find, thank you. Some inaccuracies however, including the assumption that split air source heat pumps have the compressor inside the house. On the contrary, most air to air heat pumps have the compressor externally as part of the air cooled condensing unit, with the DX evaporator fan coil units internally. Some A2W include an internal compressor, but they not very common now that monoblocs are so well established and simple to install.

Posted by: @allyfish

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@jamespa it's a good find, thank you. Some inaccuracies however, including the assumption that split air source heat pumps have the compressor inside the house. On the contrary, most air to air heat pumps have the compressor externally as part of the air cooled condensing unit, with the DX evaporator fan coil units internally. Some A2W include an internal compressor, but they not very common now that monoblocs are so well established and simple to install.

Please thank @judith who posted this initially!

At last caught the ashp on its peak after de-icing. Drawing 3.2kW electrical power (about max seen) for a few minutes, the noise level was  normal, nothing tonal nor particularly loud. I’ve not got calibrated ears but well below normal speech levels.

If anyone has an audio power meter I can share it.

@tallmarc Many would be shocked as it has indeed been touted as a myth. And it is crushing to have a neighbour mention it as an issue (many would be polite and try to live with it - not wanting a "dispute" on file). 

No idea why is is touted as a myth when there is plenty of research to show that it is an issue that needs attention. There are multiple potential issues with sources of noise (and vibration), predominantly low frequency noise which can be a nightmare. Sadly, there have been strong attempts to downplay noise as an issue to date, and to frame the MCS noise test as a nonsense, and even to make a mockery of those who have found noise to be an issue.

As for the 42dB(A) limit, a lack of standardisation of dB(A) measurements from heat pump manufacturers and the absolutely crazy lack of tonal data published by manufacturers means that you can end up with a heat pump that sounds near on twice as loud as advertised [remember 52dB(A) is twice as loud as 42dB(A)], would never pass the environmental health test (BS4142)... but flies through MCS020/PD. Crackers that MCS020 and BS4142 are so poorly aligned (and proposed changes will make them more so).

There are in my opinion some huge red flags here for mass rollout.

I’ve ‘invested’ a whole £3.99 for an audio spectrum analyser app. I’ve not captured all the apps features but this was our 7kW Vaillant running at 3.2kW electrical power.

The microphone is completely uncalibrated and my distance was ~1m. There are tones in the spectrum @200Hz and a broad 50-70Hz. But not of any significant amplitude.

@judith Hi Judith, Those analysers are very good. However, it is significantly warmer today than it was a week or so ago so a reading taken this morning wouldn't be relevant to the issue during the cold snap (it has been 11 degrees warmer today than a week ago in some parts). They also don't account for tonality which can add at least 50% to perceptible noise levels.

Posted by: @tallmarc

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Appreciate this is an old post but I’m experiencing the same thing in the current cold snap. At freezing temperatures, my Arotherm Plus 7KW unit makes a sustained loud buzzing noise. I measured this at about 65db and it’s audible inside the house. The buzzing is not audible during regular operation and is definitely not the unit entering defrost. Annoyingly however it doesn’t do this all the time. It is well above the stated noise levels for the unit so I’m assuming it is a fault…? Anyone else experiencing this? Thank you. 

I've now more or less fixed mine. 

At night I have enabled noise reduction mode.  This does compromise performance when it's at minus temperatures, but you can reduce the severity of nr mide in the installer menu on the control unit from 40% to 30% (the documented lower severity limit is 40% but the actual unit allows 30%), and a bit of nighttime setback isn't a disaster!.  I have also reduced the max compressor current to 13A which is operative 24x7 and doesn't noticeably compromise performance.  I suspect I will be able to undo the nr mode if I fit some sound absorbing mat to one of the pairs of walls which I think is causing a resonance.

Yours sounds as if it may be more serious, I suggest you take a video and ask Vaillant if it's normal (they actually requested me to do that when I told them about mine).  It may be something has worked loose or needs tieing down.

@elton I think "There are in my opinion some huge red flags here for mass rollout." maybe somewhat over stating the issue.  The number of posts on the forum referencing noise problems is tiny relative to the total number of posts and there is little or no indication so far as I can tell from the IoA paper and other reports that complaints about heatpump noise are commonplace.  'Mass roll' out will largely be in cities or large towns, simply because that's where the bulk of housing is.  These are generally much noisier than suburbs and rural areas and IoA are even suggesting a relaxation in the noise requirements in areas where there is more noise, which would include these areas in many cases.

Im not saying that it doesn't have to be managed, but I cant see anything in the IoA report, on this forum or indeed elsewhere that suggests many installations are in fact affected by unexpected noise issues that have material consequence.

That said I do agree that this should be 'run to ground'.  Manufacturers will only measure what they are bound to measure.  Noise requirements can, realistically, be based only on what manufacturers are bound to measure and publish.  If thats not good enough then it needs to change. 

That said its entirely possible that this was known when the standards were devised and a reasoned view was taken by the powers that be along the following lines

"whilst some heat pumps may, in some relatively rare conditions, be louder than the mandated measurements, those conditions are relatively rare and most properties are affected from time to time by extraneous noise that is higher than the general background*.  Thus in the interests of the climate the occasional extra noise is perhaps something we have to accept, just as we accept aircraft noise in the interests of transport and leisure, and lawnmowers in the interests of I know not what.  If it is in fact a nuisance then the nuisance laws protect neighbours notwithstanding that planning permission exists, and its entirely possible for oil and gas boilers, and other domestic things such as MVHR, to be audibly disturbing, yet we don't make heavy impositions on these.

Im not saying that this is the thinking but its entirely plausible that it may be, and it does have some merit.

*For example I am affected severely in summer by lawnmowers and pressure washers during the daytime, and throughout the year by airplanes

Posted by: @elton

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@judith Hi Judith, Those analysers are very good. However, it is significantly warmer today than it was a week or so ago so a reading taken this morning wouldn't be relevant to the issue during the cold snap (it has been 11 degrees warmer today than a week ago in some parts). They also don't account for tonality which can add at least 50% to perceptible noise levels.

nevertheless it had just finished a de-icing cycle and was in the following 3.2kW power draw peak, which is the same amplitude that it generated a few days ago. It was ~3C OAT this morning here. The difference is a few days ago in the early hours it was more frequent. 

I will try and get more readings when the conditions are appropriate.

@tallmarc it's exactly the same with the mitsubishi ecodan. i actually got their engineer out who just stated the figures in the brochure were lab and not real world and that nothing was wrong. the only way to fix it as i see is to have sufficiency oversized heat pump its never maxed out..... which then has other issues. 

i have to say, 9 months into my heat pump journey, im not to impressed with the technology. i'd swap back to my boiler given 1/2 a chance. i do feel a bit conned and missled.