jackdaww wrote:Howard wrote:jackdaww wrote:.
re Air Sourced Heat Pumps.
has any one noticed the amount of NOISE from the fans .
if these are adopted in urban areas , i suspect their noise will swamp road traffic noise .
Do you have any evidence for this? I have a modern air sourced heat pump and it's incredibly quiet. Even standing outside listening late at night it's barely audible. Much quieter than the rustle of leaves on trees in our country environment. The same is true for neighbours' units.
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only from some commercial units .
i dont know any domestic installations - maybe they are quiet .
They're not! My friend's newly-installed 5 kw ASHP meets the 46 decibel standard (at one metre distance), but from inside the house it still sounds as though her neighbours have left their car engine running on the drive all night. It's probably quite a good job that she doesn't
have any immediate neighbours.
Our house (5 bed detached) would require a bigger pump, probably 11 or 14 kw, and those things typically kick out 60 decibels at one metre distance - which is somewhere between a washing machine and a vacuum cleaner. A proper look at the noise rules casts a serious question over their suitability.
Basically, you halve the distance between your heat pump and the perimeter of your neighbour's property, and
along that imaginary central line you're required to keep the maximum decibels down to 42. That won't be so bad if it's a 46 db unit, but if you start with 60 db then your neighbours had better be a long way away.
The calc, as I understand it, goes that your received noise at 1 metre drops by 6 decibels during each doubling of the distance. So with at two metres it's heard as 54 decibels, and at four metres it's 48 db, and at eight metres it's finally down to 42 decibels. Now, that's your
midway line, remember. You'd actually have to be 16 metres away from your neighbour's perimeter wall before a 60 decibel ASHP unit met the noise rules!
I'm not an engineer, so do please check my calculations, but it seems perfectly clear (to me
) that this is going to be a problem for many, many homeowners, including just about everybody in a densely-populated urban area. There was a study from Edinburgh Napier university that set all this out a few years ago. And the upshot of its conclusion was that only the smallest ASHPs were capable of meeting the needs of people who lived in close proximity without running foul of the noise regs.
We have a different problem. We live in a conservation zone, and ASHPs can't be installed at all out here without planning permission. They mustn't be on a wall that's visible from any road, and the noise regs are more tightly enforced. In short, not a chance! Not until they get an awful lot quieter. Which, eventually, they will.
BJ