ASHP acoustic cover

[Tony K]

3 minutes ago, Moonshine said:

 

Decibels are a logarithmic value, reduction of half the pressure is a 3 dB reduction (= 10 x log10(1/2)) 

 

There's only one thing I don't understand about what you just said @Moonshine, and thats all of it! ?

 

If I buy one will it halve the noise levels?

Edited August 5, 2021 by Tony K

[Ralph]

30 minutes ago, Tony K said:

Regarding noise reduction, this is interesting, though I am not sure I understand the claim to have reduced the noise from an ASHP 'by half', when the graph shows a 3db reduction?

I spotted one of these for about £900. I wonder what effect it would have on the sound in the house as it's open at the back?
Mine has not been fully installed yet but I might consider this just because it could easily be sprayed to blend in with the cladding, never mind reducing noise. 

[puntloos]

Interesting part for me is that most Daikins are split units, so you'd care at least as much about indoor noise too.

 

[Tony K]

1 hour ago, puntloos said:

Interesting part for me is that most Daikins are split units, so you'd care at least as much about indoor noise too.

 

 

Split units meaning that part of the ASHP lives indoors? 

 

My thinking was to use one of their sound enclosures (or one like it) over a NIBE external ASHP, if the enclosure serves purpose, but as per my earlier post I don't really understand the extent of the claimed noise reduction made in the video. 

[puntloos]

1 hour ago, Tony K said:

 

Split units meaning that part of the ASHP lives indoors? 

 

My thinking was to use one of their sound enclosures (or one like it) over a NIBE external ASHP, if the enclosure serves purpose, but as per my earlier post I don't really understand the extent of the claimed noise reduction made in the video. 

 

Correct, split means there's a meaningful part indoors. I'm not 100% clear if there's a compressor indoors, but it's not silent. As far as I can tell from the specs the indoor part is more silent than ext though.

[joth]

20 hours ago, Marvin said:

23 hours ago, Tony K said:

haven't read the MCS standards, but I presume that is where you are getting the 10m distance from? 

Yes.

https://www.planningportal.co.uk/info/200130/common_projects/27/heat_pumps/2

 

More distance between ASHP and item to be heated/cooled equals more inefficient.

 

PD just requires compliance to MCS020 (or equivalent) not a full MCS install.

I don't see anything in this doc that limits the distance from outside to inside unit? Only distance to the nearest neighbour door or window.

https://mcscertified.com/wp-content/uploads/2019/07/MCS-020.pdf

[Tony K]

Something of possible interest to those concerned with noise from ASHPs:

 

I received this from a local authority Environmental Health officer that I know:

 

I don't really know much about these pumps and how they work.  It is always difficult to be confident about these matters without knowing background noise levels and exact distances to nearest windows, etc but a robustly constructed timber enclosure with no gaps and good density of timber with something like 50mm rock wool insulation to absorb reflections should give a good 10dBA reduction, although attention may be needed for ventilation.  It's always a compromise.

 

Night time noise levels of 30dBA at residential windows is fine for the vast majority of neighbours, even perhaps 35dBA.  For distance attenuation assume 6dB for every doubling of distance.  So, if the plant is 45dB at 1m, it will be 39 at 2m, 33dB at 4m.  This will be the maximum attenuation - likely to be slightly less due to reflections in the built environment.

 

[joth]

11 minutes ago, Tony K said:

Something of possible interest to those concerned with noise from ASHPs:

 

I received this from a local authority Environmental Health officer that I know:

 

I don't really know much about these pumps and how they work.  It is always difficult to be confident about these matters without knowing background noise levels and exact distances to nearest windows, etc but a robustly constructed timber enclosure with no gaps and good density of timber with something like 50mm rock wool insulation to absorb reflections should give a good 10dBA reduction, although attention may be needed for ventilation.  It's always a compromise.

 

Night time noise levels of 30dBA at residential windows is fine for the vast majority of neighbours, even perhaps 35dBA.  For distance attenuation assume 6dB for every doubling of distance.  So, if the plant is 45dB at 1m, it will be 39 at 2m, 33dB at 4m.  This will be the maximum attenuation - likely to be slightly less due to reflections in the built environment.

 

 

Looks like they were reading from the PDF I linked immediately above

Page 21 "Note 4 DB distance reduction" and "Note 5 Barrier between heatpump and assessment position" show exactly the -6dB and -10dB factors

https://mcscertified.com/wp-content/uploads/2019/07/MCS-020.pdf

 

[Moonshine]

14 minutes ago, joth said:

show exactly the -6dB ... factors

 

That's because the -6 dB is how the maths / physics works out for spherical spreading (assuming not other loses such as ground or air absorption or barriers, or other contributions from reflections), Its called the inverse square law.

 

The surface of a hemisphere at 2m is 25.1m2, at 4m its 100.5m.

 

So the loss in pressure over the area of the hemisphere from 2 -> 4m is 10*log10(25.1/100.5) -> -6 dB

[Tony K]

3 hours ago, Moonshine said:

 

That's because the -6 dB is how the maths / physics works out for spherical spreading (assuming not other loses such as ground or air absorption or barriers, or other contributions from reflections), Its called the inverse square law.

 

The surface of a hemisphere at 2m is 25.1m2, at 4m its 100.5m.

 

So the loss in pressure over the area of the hemisphere from 2 -> 4m is 10*log10(25.1/100.5) -> -6 dB

 

4 hours ago, joth said:

 

Looks like they were reading from the PDF I linked immediately above

Page 21 "Note 4 DB distance reduction" and "Note 5 Barrier between heatpump and assessment position" show exactly the -6dB and -10dB factors

https://mcscertified.com/wp-content/uploads/2019/07/MCS-020.pdf

 

•  

 

The question though @Moonshine and @joth is: Does it work?

 

I am keen on using an ASHP, and after considering some of the more concerned comments on here about efficiency, extent of slab insulation etc remain content to proceed but am concerned that noise might be a deal breaker.

 

If I can be relatively confident that, should the ASHP sound prove more invasive than anticipated I do at least have the option to construct an acoustic enclosure which will be effective, that will be enough for me. 

[joe90]

As someone with an ASHP that does not find noise an issue why not just instal it then decide if soundproofing is required, a fairly solid timber enclosure with sound absorbing foam inside will (IMO) make a big difference. I used this kind of foam on the inside of my sewerage treatment plant and it made a big difference.

[Marvin]

8 hours ago, joth said:

 

PD just requires compliance to MCS020 (or equivalent) not a full MCS install.

I don't see anything in this doc that limits the distance from outside to inside unit? Only distance to the nearest neighbour door or window.

https://mcscertified.com/wp-content/uploads/2019/07/MCS-020.pdf

May be mistaken. Will have another look.

[Dan F]

 

1 hour ago, Tony K said:

5 hours ago, joth said:

 

Looks like they were reading from the PDF I linked immediately above

Page 21 "Note 4 DB distance reduction" and "Note 5 Barrier between heatpump and assessment position" show exactly the -6dB and -10dB factors

https://mcscertified.com/wp-content/uploads/2019/07/MCS-020.pdf

 

•  

 

The question though @Moonshine and @joth is: Does it work?

 

There is a calculator available that takes into account distance, reflective surfaces and barriers and outputs a value and pass/fail.

 

https://mcscertified.com/wp-content/uploads/2019/09/MCS-Heat-Pump-Calculator.xlsm.  Look for the tab named "MCS020".

 

 

 

[Tony K]

1 hour ago, Dan F said:

 

 

There is a calculator available that takes into account distance, reflective surfaces and barriers and outputs a value and pass/fail.

 

https://mcscertified.com/wp-content/uploads/2019/09/MCS-Heat-Pump-Calculator.xlsm.  Look for the tab named "MCS020".

 

 

 

 

Thanks for this @Dan F

 

1 hour ago, joe90 said:

As someone with an ASHP that does not find noise an issue why not just instal it then decide if soundproofing is required, a fairly solid timber enclosure with sound absorbing foam inside will (IMO) make a big difference. I used this kind of foam on the inside of my sewerage treatment plant and it made a big difference.

 

That's precisely what I will do @joe90 but before I take the plunge I'd like to understand whether I can realistically make any meaningful change to noise level if the worst comes to the worst and I find the noise uncomfortable once the ASHP is up and running. 

[SteamyTea]

2 hours ago, Tony K said:

worst comes to the worst and I find the noise uncomfortable once the ASHP is up and running

What sort of noise do you think they make?

[Tony K]

15 minutes ago, SteamyTea said:

What sort of noise do you think they make?

 

Volume or type? 

 

The specs tell me they emit something around 50bd, and as part of my research I've been to see (or more to the point, listen to) ASHP systems installed by one of the firms quoting for my business. I would describe the sound as noticeable. 

Edited August 6, 2021 by Tony K

[SteamyTea]

2 minutes ago, Tony K said:

type

 

[Tony K]

Mechanical. Whirring. Distinctive. 

[SteamyTea]

7 hours ago, Tony K said:

Mechanical. Whirring. Distinctive. 

It is hard to describe, but the ones I have stood by is more of a hum and the occasional whoosh.

Though I did hear one that was rattling, but then it was battered to hell (had secondary use as a bike stand).

 

There is an estate in St. Agnes where every house has an ASHP, never heard anyone mention the noise, lack of performance or high running costs.

There is a global map, the World Hum Map, where people log when they hear a hum (if they can be bothered).  I notice that St. Agnes is devoid of 'hearings'.

https://thehum.info/newhummap/html_docs/

Edited August 7, 2021 by SteamyTea

[Marvin]

My understanding is that if you baffle the sound you would lose some of the efficency of the ASHP due to a rise in static pressure.

Is this right or am I talking b again?

 

 

[joe90]

Depends on what you use, When I briefly thought about a cover fir mine, I planned slightly down sloped louvres (30’ to keep the weather out) but big gaps. Nothing at the back (all noise comes out the front due to the fan pushing the air out the front). If the air is not very restricted I guess the airflow (this efficiency) would be ok.?

[SteamyTea]

10 minutes ago, Marvin said:

My understanding is that if you baffle the sound you would lose some of the efficency of the ASHP due to a rise in static pressure.

Is this right or am I talking b again?

 

 

There may be a slight difference, but hardly noticeable, as long as you are not reducing the overall area of the intake and outlet from the radiator.

Imagine it is like leaving a door open a bit, or a lot.

Don't overthink it.

[Marvin]

For what it's worth I have had no sound issues so far.

[Dan F]

 

13 hours ago, Tony K said:

The specs tell me they emit something around 50bd,

 

Don't forget that:
- ASHP won't be running at a fan speed that produces 50dB all of the time, it will modulate down.

- Most ASHP's have a configurable quiet period where fan speed will be limited.

 

Ours for example (7kW) has sound power of 55dB and sound pessure of 49dB@1m.  But, with quiet mode enabled the sound pressure is limited to 42dB@1m.  In practice is anyone going to be 1m away from ASHP when it is running anyway?

 

[Tony K]

Useful advice as ever on here, thanks. Regarding noise alone, my conclusion is to install the ASHP, see how it goes especially when it is configured and programmed to best effect, and then go for a cover if needs be. 

 

I've recently looked again at the advice I received from the heating engineer who quoted for a system that includes the nibe pump, UFH and water tanks. I'm reminded that he raised the idea that my water tanks could be housed in an external timber lean-to if I preferred, so as to free up space in the utility room, so long as the lean to was properly insulated. As part of this scheme I would place my ASHP on the far side of my (small) garden, and run a 160mm round diameter connector with 2 x 32mm poly pipes installed inside it, all 1.2 metres below ground level.

 

In the end I felt I could fit the tanks in my utility room (just), so I didn't pursue the idea. Looking at it now it also occurs to me that placing the ASHP on the far side of the garden means facing it towards my property, which appears a bad idea if, as I think I now understand, they operate a bit like speakers with most sound projecting from the front. 

Edited August 7, 2021 by Tony K