Air source heat pumps: Volume & immission guide values

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Viessmann Vitocal 100

The heat generation of a heat pump is based on the compression principle, in which the evaporated refrigerant is compressed and its temperature is raised to the required level. This can produce noises that, above a certain level, may be perceived as annoying by some people.

Technical instructions for protection against noise as a basis for design

With air source heat pumps, there is also active heat recovery through fans, a process which also causes noise. Since the perception of noise is very subjective, it requires a basis for design. This is provided by the technical instructions for protection against noise (TA Lärm), which in turn is regulated as an administrative regulation by the German Immissions Act (BImSchG).

Accordingly, there are several areas in which different levels must be maintained. If a system is used in an industrial area, for example, the noise level can be up to 70 decibels (A). However, if the same system is intended for operation in a hospital or nursing home, then a limit of 45 decibels (A) during the day and 35 decibels (A) at night must not be permanently exceeded.

Immission guide values

The following table shows the guideline values for immission locations outside buildings according to the Technical Instructions on Noise Abatement (TA Lärm).

TownTimeLimit in dB(A)
Industrial estateall day70
Trading estatesDay
Urban areasDuring the day63
Urban areas, villages and mixed areasDay
General residential areas and small housing estatesDay
Purely residential areasDay
Spa areas, hospitals and care homesDay

Individual short-term noise peaks must not exceed the immission guideline values by more than 30 dB(A) during the day and by more than 20 dB(A) during the night.

The immission values for immission location inside buildings or rooms requiring protection as defined by DIN 4109 are considerably lower and are 35 decibels (A) during the day and 25 decibels (A) at night. Rooms requiring protection include:

  • Living rooms and bedrooms
  • Child's bedroom
  • Work rooms/offices
  • Teaching rooms/seminar rooms

An eat-in kitchen, which is where the residents live, should also be regarded as a room requiring protection within the sense of No. A.1.3 TA Läärm (in conjunction with DIN 4109, November 1989 edition).

Low-frequency sounds are considered annoying

In addition to compliance with the legally prescribed noise level, the reduction of low-frequency sounds is an important focus. Many people find these annoying, even though the sound level, i.e. the volume, is below the legal limit. Low-frequency sound is the term used to describe the portion of noise that has a frequency of less than 90 Hz. People start to perceive sounds in a range of around 20 Hz.

The reason why low-frequency sounds are nevertheless perceived as irritating is partly because these sounds are only perceptible at higher volumes. In addition, people cannot differentiate sound in this range, which is why low-frequency sounds are commonly referred to as a "hum".

Due to the division into outdoor and indoor units, the sound is hardly perceptible with air source heat pumps. (Vitocal-111-S)

Reducing noise levels through the design of the Viessmann heat pump alone

As sound concerns are becoming increasingly important, Viessmann has, since 2009, introduced numerous design measures to minimise the sound emissions or volume of heat pumps. In the development of our heat pumps, sound specialists and cooling circuit developers work hand in hand to develop highly efficient and quiet heat pumps. In addition to the 3D sound concept, this has also resulted in the AAD system (Advanced Acoustic Design), which probably makes Viessmann heat pumps the quietest heat pumps on the market.

Air source heat pumps from Viessmann are among the quietest appliances on the market

Air source heat pumps from Viessmann are among the quietest appliances on the market. You can find out what else makes them special in the section on benefits of the air source heat pump. How high the noise level of individual heat pump units is depends, among other things, on the coefficient of performance and the distance to adjacent buildings.

The sound calculator of the German Heat Pump Association can provide you with a guide. With its help, homeowners can determine the possible noise emissions of listed air source heat pumps with a heating output of 35 kilowatts or less. In addition to the emission data, the sound calculator also calculates the distance required to adjacent rooms requiring protection. The results are no substitute for an individual noise assessment, but nevertheless provide a very helpful basis for planning.