Heat pumps: integrated air to water hot water system. Noise?

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simonm
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Heat pumps: integrated air to water hot water system. Noise?

Post by simonm » Sat Feb 02, 2019 11:06 am

Turning to the font of all wisdom for a heat pump question. :-)

I am looking at getting something like the Toshiba HWS-G1901 installed indoors (in garage) for hot water. This an all-in-one unit as opposed to the more common split unit with an external compressor and an indoor unit so noise is very important. It will most likely be supported by a solar flat collector or tow on the roof. What I am concerned about is noise. Tech spec sheet gives two values: 55 dB(A) according to EN12102 and a noise pressure number of 38.8 dB(A) at two meters.

Anyone got personal experience of such integrated units especially as regarding noise?

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Re: Heat pumps: integrated air to water hot water system. Noise?

Post by a human » Sat Feb 02, 2019 1:17 pm

I can't help you. But when I have this type of question, I spend some time googling the item, looking for customer experiences, complaints, reviews. Sometimes comments by installers and repairmen highlight concerns. You might also explore the noise scale, looking for something like "70 db(a)s is the typical measurement of the noise of a jackhammer"!
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Re: Heat pumps: integrated air to water hot water system. Noise?

Post by lagartija » Sat Feb 02, 2019 2:02 pm

You have to probably look up other things that you know (your refrigerator, washing machine,etc.) with which to compare.

My husband thought that 55dB (A) is relatively quiet.
A whisper is perhaps 35dB, annoyingly loud is 80dB. It is a logarithmic scale, but so is the sensitivity of your ear.

Another issue is the mounting of the unit and if it amplifies the noise because of resonant structures.
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Re: Heat pumps: integrated air to water hot water system. Noise?

Post by simonm » Sat Feb 02, 2019 5:18 pm

Google etc ... been there, done that, haven't bought the T-shirt yet. :-)

I posted here after getting frustrated with those options. Unfortunately not all domestic goods use the same measuring methodology for noise, and the US will have different methods/standards to Europe (EN12102) although the methodology will likely be based on the same set of iso standards.

The local installers seem to do a good enough job with isolating the machines from the structures they are mounted on so I am not worried about that aspect.

Standalone domestic hot water air to water heat pumps are not that common yet so not too much local info here. Most people installing new systems here are putting in combined domestic hot water, (underfloor) heating and air-con systems with an outdoor heat pump but that is about x3 what we want to spend at the moment.

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Re: Heat pumps: integrated air to water hot water system. Noise?

Post by pogmoor » Sat Feb 02, 2019 6:43 pm

There are a couple of free noise meters on the iOS App Store - NIOSH SLM and Decibel X. Doubtless there are similar apps on the Android store. I find these give a good general idea of what different noise levels are like. For example two young grandchildren currently playing noisily in my flat get up to about 80dB and quiet conversation is about 50dB - which accord with lagartija’s comments above. I think I’d find a continuous noise at 50dB annoying; 35dB on the other hand sounds like almost complete silence and would be much more tolerable.
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Re: Heat pumps: integrated air to water hot water system. Noise?

Post by simonm » Sat Feb 02, 2019 9:35 pm

pogmoor wrote:
Sat Feb 02, 2019 6:43 pm
.... I think I’d find a continuous noise at 50dB annoying; 35dB on the other hand sounds like almost complete silence and would be much more tolerable.
Thanks. This is the catch ... The manufacturers give various numbers. Sound power vs Sound pressure. Some say @1m or @2m etc and others give no further info. The UK building performance centre has a paper from 2011 on outdoor units and it suggests that some units are 3 to 4 dB louder than what the manufacturers say while one (which seems to be a newer unit than the rest) is better the stated numbers by 4dB. All sorts of factors play a role in how annoying a noise will be.
The problem with apps and the like is that I will not be able to measure anything until after I get it installed which is then too late. :-)

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Re: Heat pumps: integrated air to water hot water system. Noise?

Post by OldPotter » Sat Feb 02, 2019 10:13 pm

I have never seen one, so don't absolutely know. So my guess it that it will depend on what you want to do with it. If you want to work in the garage and like absolute silence, then it might be a little annoying. The manual I looked at says up to 55dB when its working hardest in a fairly warm room. That is supposed to be similar to a noisy domestic fridge.
If you are not going to be in the room where its working then I doubt you would hear it, though you might notice it when its off.
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Re: Heat pumps: integrated air to water hot water system. Noise?

Post by guitarrista » Sun Feb 03, 2019 2:01 am

simonm wrote:
Sat Feb 02, 2019 11:06 am
What I am concerned about is noise. Tech spec sheet gives two values: 55 dB(A) according to EN12102 and a noise pressure number of 38.8 dB(A) at two meters.
Not a personal experience; just going by the numbers you provided.

EN12102 number of 55 dBA is a sound power level measurement (not sound pressure level). It just means that the unit produces sound power in Watts (Joules per second) which is at the 55 dB level (i.e. 5.5 orders of magnitude greater than the reference sound power of 10^(12) W - so it's about 0.3 microW). That's the sound energy it emits per second in every direction; not the sound pressure you would perceive at a certain point in space and a certain distance. The number for sound power is independent of distance from the unit. It's like saying this light bulb emits 1000 photons per second in all directions.

What we hear as a result of some device emitting sound energy depends on how far from it we are and the geometry and transmission/absorption of the environment around it and between it and us.

The other number: 38.8 dBA at 2m - gives you the sound/noise pressure level when you are 2 metres away from the unit. That's how loud you will perceive the unit at that distance. That number is dBA relative to a reference sound pressure - 20 micro Pascals. So 39dBA is a bit less than 2 orders of magnitude greater than the reference pressure, about 2 milliPascals).

Unless you plan to be right next to it, it seems the noise level is acceptable. Your ear would have to be at a distance of only a foot from the unit for you to perceive a noise at about 55dB sound pressure level (there is a relationship between sound power and sound pressure if you assume various things and for a given distance). BTW, if you are 1 meter from it, that formula gives about 45 dBA sound pressure level.

Just make sure that 39dBA is when it is working at full load.

These sound engineers make everything needlessly confusing :-) 55 dBA sound power level is not 16 dBA larger than 39 dBA sound pressure level - they are completely different beasts since the references are different numbers in different physical units - Watts vs. Pascals).
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