Are air source heat pumps really that noisy?
Introduction to heat pump noise
There is quite some concern over heat pump noise, but we believe this is largely based around older units that weren’t as heavy regulated, and didn’t have the luxury of updated sound reducing technology.
That is why we offer a range of high-quality and cost-effective heat pumps designed to help households reduce their CO2 emissions and save money on their energy bills. We are committed to providing our customers with the best possible service and support, and we are determined to help them make the switch to renewable energy as easy and seamless as possible.
KNOWLEDGE HUB ARTICLE | Heat pump Noise
1. Heat pump noise new regulations
From 1 April 2021, heat pumps with an outdoor unit will be subject to a new requirement for maximum noise during night time hours. Heat pumps installed from that date onwards will be allowed to produce a maximum noise of 40 decibels in the evening and at night between 7pm and 7am. This is calculated at the property boundary with neighbours or at an open window on the same plot. During the day, the noise may be slightly higher. This may then be a maximum of 45 decibels.
The new legal standards for noise in regards to space heaters now follows (EU) No. 813/2013. This norm applies strict regulation on sound pressure as follows:
Sound pressure level at property boundary:
Daytime (07:00 to 19:00) maximum 45 db(A).
Nighttime (19:00 to 07:00) maximum 40 db(A).
In addition to EU/UK government regulation. The MCS certification process, which ensures your £5,000 Boiler Upgrade Scheme (BUS) grant, requires a Sound Power Level test as part of the design and commissioning process to ensure the heat pump meets additional sound level requirements.
MCS020 takes into account the following factors:
- The assessment position
- The sound levels must be measured from a location which represents a natural location from which the homeowners will come in proximity to the heat pump.
- The sound power level (dB) of the heat pump
- The sound pressure level (dB) of the heat pump
- Distance from the heat pump to the assessment position (meters)
- dB Distance Reduction calculation (a calculation based on the above factors)
- Barriers between the pump and the assessment position
- This is an important factor as reflective surfaces increase sound pressure
- Calculated sound pressure level at the assessment position
- Background noise levels at the assessment position
2. What causes maximum heat pump noise
First of all, it is good to know exactly where heat pump noise comes from. The main heat pump sits outside your house. Inside this outdoor unit is a fan that rotates and this fan creates noise. When a heat pump is running at full speed, this can result in audible noise.
This occurs when:
- It gets colder outside, such as in autumn and winter. Often, the most noise is produced when it is +/- 0°C outside. Once it is below +/- 0°C degrees, the immersion heater in your buffer tank takes on a proportion of your heating requirements, eliminating the high noise.
- You turn the thermostat up a few degrees because you want your home warmer. In this situation the heat pump will work harder to get you up to your desired temperature. Once it reaches this temperature it will return to Eco mode.
- Initial start-up. As above, when the heat pump is first turned on, it will work harder to get the water temperature up to the desired level.
Good to know is that, on average, a heat pump with an outdoor unit makes around 40 to 50 decibels of noise. See below to understand what this noise level is comparable to.
Adlår heat pumps are installed with extra capacity built in, and in combination with temperature sensors and pre-programmed environmental heating curves, we can account for the worst case scenarios which could cause the heat pump to need to work at a higher noise and output level.
Our extra capacity includes:
- 3kW Immersion heater, within a 60 or 90 litre buffer tank
- 1.5kW domestic hot water (DHW) cylinder air source heat pump (ASHP)
The buffer tank smooths out demand, having heating hot water available to distribute to your heating system. The 3kW immersion heater can be activated if the heat pump’s capacity is close to maximum and the temperature settings aren’t being met by the heat pump alone.
The 1.5kW DHW ASHP cylinder works independently from the heating, to supply only for your domestic hot water. As DHW takes priority over room heating in most systems, by splitting the system as we do, we avoid the heat pump being in over capacity and prevents heating capacity for hot water from ever being diverted to the DHW.
3. Adlår Castra heat pump noise levels
The noise of the Aurora II is between 22 and 50 decibels. Of course, this does depend on various factors such as how loud it is running (see above for main factors affecting maximum noise), how far it is from the property boundary, living spaces, and how it is set. Our goal is to install a whisper-quiet heat pump in your home so that, using our patented technology, the decibel level is only 22 decibels at 5 metres away!
All of Adlår Castra’s heat pumps are lab tested by TUV, a world leading testing and certification organisation.
TUV’s test labs follow UKCA and EU test regulation to accurately test the pumps. This is a core requirement in the heat pump testing.
The maximum sound pressure levels:
1m: 42dB(A)
2m: 36 dB(A)
The maximum sound pressure levels:
1m: 43dB(A)
2m: 37 dB(A)
The maximum sound pressure levels:
1m: 47dB(A)
2m: 41 dB(A)
We have designed our own packages depending on where the heat pump is installed.
If the heat pump is installed on the ground floor outdoor space, we place the heat pump on specially designed feet which dampen noise. We also ensure others things such as water runaway and heat pump balacing.
If the heat pump is installed on a roof or wall mount, we also install the heat pump with anti-vibration shock absorbers, specially weighted for the heat pump. This removes vibration, and prevents any vibration moving through the floor or wall into the house.
4. Comparing heat pump noise
For a comparison these Combi Boilers (which are rated as the quietest combi boilers by Energy Guide) have the following rated noise (as they are situated inside your house the noise is much more significant than an outdoor unit:
- Viessmann Vitodens 200 – 36 dB
- Worcester Bosch Greenstar 200 – 43 dB
- Ideal Logic Max C35 – 44 dB
- Vaillant EcoTec Plus 838 or 938 – 45 dB
Quietest Combi Boilers – Which is the Quietest Boiler in the UK in 2023? (energyguide.org.uk)
dB may be a foreign concept to you, and it is difficult to understand what 40dB in noise actually is.
Here you can see an infographic to give you a rough idea of what items make what noise.
You can also see this by typing dB noise pressure chart into a search engine to get more comparisons.
5. Tips for reducing heat pump noise
- First of all: get good advice from an installer when choosing a heat pump. This is because the perfect heat pump for you depends on several factors.
- Pay attention to the sound power rating on the energy label so you know what the power rating is.
- Choose a heat pump with that has a function for a night mode. That way, you can set it to automatically make less noise at night.
- Insulate your home as best you can so that the warm temperature stays indoors for as long as possible. Because (as described above) a heat pump is going to produce more noise if the temperature is turned up a few degrees.
- Place the outdoor unit as far away from your house and your neighbours’ houses as possible to reduce noise pollution, without affecting the heat pump’s efficiency.
- Avoid sound reflection by not placing the outdoor unit in niches with walls on three sides.
- Do not place the outdoor unit too close to your home’s bedroom windows.
- Do you have a garden with lots of plants or forestation? Perfect! The more greenery, the less reflection of sound. The only thing to note is not to cover the fan entrance with plants that can influence air flow.
- Avoid, where possible, installing the heat pump’s outdoor unit against the walls of living areas you reside a lot.
- Would you prefer it on the roof? That’s also possible, just keep in mind good vibration damping. See above for Adlår’s base design and how we account for this on our installs.
Adlår Castra
Our mission is to accelerate the transition to renewable energy by making it affordable for households in Western Europe. We understand that the transition to renewable energy is crucial for the future of our planet and we believe that everyone should have access to affordable and sustainable energy solutions.
That is why we offer a range of high-quality and cost-effective heat pumps designed to help households reduce their CO2 emissions and save money on their energy bills. We are committed to providing our customers with the best possible service and support, and we are determined to help them make the switch to renewable energy as easy and seamless as possible.
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