Heat pumps are different to boilers and one of the major differences is noise. There are two main sources of noise in an heat pump; the compressors and the evaporator fans. Every heat pump uses compressors and there are many different types including reciprocating, scroll and screw amongst others. Compressor noise can be dealt with easily using acoustic insulation in the housing, thicker insulation equals less noise.
Air source heat pumps have a particular issue with noise. It is necessary to draw the ambient air through a heat exchanger (evaporator) which causes noise. It is generally this noise source that causes problems especially at night in residential areas.
Clade heat pumps are generally lower noise than our competition but here are our insights on reducing the impact of ASHP noise.
How To Mitigate For Air Source Heat Pump Noise
The first thing to do is to consider noise in the design phase. The location and proximity to residential buildings should be thought about carefully – there are usually local planning rules and engineering standards that define acceptable limits. Once the location has been fixed there are several further noise attenuation measures that can be considered to reach the right noise level:
- Time heat generation for non-sensitive times. With a thermal store sized properly this is a cheap and easily implemented measure.
Add additional evaporator fans to slow the air speed down. This is reasonably cost effective and doesn’t affect the performance of the heat pump.
- Acoustic fencing. This is a good option where a security fence would be necessary anyway, available at various heights and with a range of finishes. This is an intermediate cost option.
- Full acoustic enclosure. This is the nuclear option, 100% effective and any noise level can be designed for. Unfortunately it is also the most expensive.
Noise is a difficult subject to understand and apply in a practical way, for example measuring noise is highly sensitive to the environment – which makes manufacturers’ data tricky to apply.
There are two main values used to evaluate acoustic impact:
Sound power is the acoustic energy emitted by the heat pump, this is a fixed value. However, on a large heat pump which is several meters long the concept of sound power is less relevant than sound pressure.
Sound pressure is the level produced by the sound power at a set distance. Whilst this can be calculated, other factors such as reverberant surfaces also have an effect and these are specific to each installation.
Acoustic engineering is a specific discipline, there are experts available to help and advise for challenging installations. Otherwise the Clade Engineering team are happy to provide advice.