Heat pump noise in Switzerland: 45 dBA? - Acoustics

One of the questions asked by potential buyers ofa heat pump installationis about the noise level.

The energy-efficiency renovation of individual homes must take account of this noise parameter if it is to be carried out to the highest standards.

Indeed, the heat pumps don't always have a good reputation when it comes to noise levels.

Particularly if air heat is captured by aerothermy

This is because the outdoor unit contains the compressor, which runs at full speed, especially in extreme cold, and can exceed a certain noise threshold.

If the heating system has an indoor unit, it usually contains only hydraulic accessories and produces no noise.

What are the questions to ask?

Before you read on, if you would like to get a quote from our qualified partner installers, you can follow the steps below:

Which manufacturer's data concerns the noise of the heat pump?

We are talking about aerothermal heat pumps for which the question must really be asked.

Often the manufacturer presents you with two main pieces of information in this regard.

First of all, the sound power in decibels dB or dBA.

This is the absolute noise emitted by the outdoor unit: it's a highly theoretical figure that gives no indication of the noise actually perceived.

Its notation is often Lw.

The heat pump manufacturer also reveals the sound pressure or sound in dB or dBA.

This time, we're talking about the noise actually produced by the monobloc heat pump: it's this pressure in dBA that hits the eardrum!

It is often noted Lp.

It's the one you need to refer to to check whether it's within the norm.

What is the difference between dB and dBA?

The dB is the theoretical, absolute value of the sound pressure

While the dBA is created to evaluate the sound pressure actually felt by the ear.

The ear does not hear all frequencies:

Hence the need to create a scale adapted to this organ which gives us the perception of sound. 

How is the noise assessed to avoid neighbourhood disturbance?

There is a noise formThe website cerclebruit.ch can be downloaded by everyone.

It is this noise circle form that defines the distance regulations between neighbors for the heat pump.

All you have to do is fill it in with the data available to you, and it's quite intuitive.

The municipality or canton refers to him to decide whether the installation is up to standard.

This form is based on :

  • The data of the heat pump
  • Where the heat pump is installed (straight facade, corner facade, etc.)
  • Distance from noise source to nearest neighbor's living space
  • And applies various correction coefficients to take into account the worst case.

Its result defines whether the machine is acceptable.

In residential area, the value not to be exceeded is generally 45dBAto ensure the tranquility of your home.

Depending on the brand of heat pump, and by adjusting the distance between the outdoor unit and the neighbor's window, the threshold can often be met.

How to compare the noise of 2 different machines?

First, you need to retrieve the values for each machine that correspond to the sound pressure at X m.

X being the distance between the planned position of the heat pump and the first window of a neighbor's living space.

If the values are equal, both machines will produce approximately the same noise, to the approximation of each manufacturer.

If the values are different. Then you have to see the difference.

It is a common misconception that a 3dBA difference between two machines means that the noisier machine is twice as loud.

It's not true!

Theory tells us that 3dBA is a very small change in noise.

To really feel a noise difference 2 times higher, it is necessary to count 10dBA !

It's quite rare to have such a difference, but it can happen.

A difference of 3dBA between two machines is not at all a criterion for deciding between two machines.

For those more receptive to theory here is a well detailed article which gives a good basis to understand the why

And know more than most of the salespeople of the big international heat pump leaders.

What element is the source of the noise?

For a outdoor air-water heat pumpThe compressor and the fan at the condenser are the main sources of noise.

But the compressor is the main source with the most annoying frequencies.

For a geothermal heat pumpis mainly the compressor that produces noise.

But these are generally very quiet, and since they're indoors, this isn't a big deal.

Today, almost all heat pumps are equipped with a inverter type compressor which emits very weakly.

Your installer will confirm this.

Which heat pump system makes the most noise?

Of course, compared to the neighbors, it's the outdoor air-to-water heat pump that makes the most noise.

The inconvenience depends on the location.

If the CAP is installed in a corner, the reverberation of the noise will cause more discomfort.

If it is installed in front of the building, much less.

And finally, if the heat pump is installed in an open field, for example in the middle of the garden, the disturbance will be even less. 

High temperature heat pumps: >50°C produce more noise

This is because their compressor must run at higher frequencies to provide the power.

So if you have high-temperature radiators and are keeping them, you are substantially in this situation.

An example of a high-temperature heat pump would be the Daikin Altherma, which provides a water outlet temperature of up to 60°C at -5°C outside air.

Lower quality heat pumps with a thinner panel casing

They let through more noise from the compressor inside, so they're noisier in general.

Many installers play on these values in more or less deceptive ways, to sell more.

The editors suggest Deutsche Qualität, genau!

Yes, Swiss heat pumps don't exist at all!

Labor is far too expensive to achieve a fair manufacturing price.

But some people manage to make it seem so! Real wolves of Wall Street!

However, there is no shortage of Swiss heat pump distributors (distributors).

Are there any anti-noise systems?

Of course, this is a niche market for heat pumps.

Some manufacturers market noise boxes, which fight against noise pollution as sound absorbers.

These solutions are highly effective, but they impact the budget and therefore the return on investment.

On the other hand, their aesthetics sometimes leave much to be desired for standard products.

It is always possible to have a custom-made box made in the desired design.

It is better to call a professional who can find the cheapest solution for you, instead of building a box yourself.

About the author

Juliena mechanical engineering graduate and specialist in climate engineering since 2009, has become a writer specializing in renewable energies, with expertise in heat pumps and photovoltaic solar panels for individual housing.