Any thoughts as to why this would impact the 7kw and not the 5kw Vaillant?
Speculation of component differences across units, but no defined references.
It still feels like compressor speed related resonance, but hard to construct a replicable test so far.
Hello,
Iāve been following this thread as my 5kw unit seems to be making a similar noise. A constant humming. Currently -1 degrees outside, so working hard. Flow rate is 37 degrees and pulling about 1350w. Today is the first time Iāve heard this since having the system installed in October 2025. Noise levels currently 65db from 3m away.
Apologies for the video, it was taken at night.
Edit: added video below.
Welcome, Ryan.
Have another try, Iāve promoted you. We much prefer such things to be posted here - that way they donāt disappear and remain available and meaningful.
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I think mines probably around the same power level point as when itās flat out it seems quiet. Keep us updated on the pipe clip mod as this was an excuse Vaillant tech support gave for my noise when I called. Iād like to know if it states noise reducing mounts in there manual as when I pushed them for a part no. I got nothing specific.
How far does your primary pipework run inside the house?
Adam, my run of pipework is just under 10m under the floor each for flow and return between heat pump and tank cupboard. Only a couple of meters run external which have no fixings at all between ashp and popping through the wall. Thinking I might add some support here.
I will post here the results. Iām not too optimistic of eliminating the inside noise completely but I do think I notice a slight improvement with half the clips changed so far.
Have you seen the post in the Vaillant fb group from Mike Mike? He seems to think his fix might help. Your pipe runs are very long. Mine are about 5m to the tank then 5m back to the pump. Have you got flexis on the external pipes?
Yes I did see the post. Certainly worth a look although I think we are still dealing with a symptom and not the cause. Also, yes, I do have flexi pipes fitted at the heat pump but there is still vibration on the pipes even in the cupboard at the other end of the run.
Yep sounds like the same issue as mine. Trouble is to get to the pipes Iād have to start ripping up the floors upstairs. it would be easier to run new pipes in primary pro down the side of the house.
You can effectively defeat resonant noise by adding mass on top of whatever is vibrating, look up what weight can safely go on top of the unit and see if it makes a difference. Basically making a mass dampener.
Even a slight change, like a brick; can solve the issue.
Please also note that an RTA or anything measuring dbA may not be helpful if its not airborne noise, its likely your microphone has a low-cut filter. Use an accelerometer or your phone with phyphox to measure it.
Hold on! Basic physics hereā¦
Adding mass will not damp resonance. It will however lower the resonant frequency. Increasing stiffness will raise the resonant frequency. Damping requires something that absorbs energy from the resonant system.
I too have an Arotherm 7K. In our case, we can only hear any resonant vibration in one room, our bedroom. The primary pipe runs up the outside of our bedroom wall. Certain very specific compressor speeds can cause a noticeable hum at 40Hz, or a quieter hum at about 100Hz.
I wonder if it would be possible to produce pipe lagging such as Primary-Pro, but made from a visco-elastic foam (memory foam) that would also add damping?
Could one perhaps use some large magnets positioned next to the copper pipes to add some eddy-currant damping?
Or, one could potentially add additional stiffness to the pipe mounting to increase the resonant frequencies to above the problem range.
Itās not a simple problem!
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Another thought has crossed my mind about how to minimise resonance in pipe runs ā¦
Make sure that the pipe supports are unevenly spaced!
The location of, and spacing between, the supports will have a significant effect on any transverse vibrational modes in that pipe run (think of guitar strings and harmonics). A long pipe run with equally spaced supports will promote a vibrational mode at a very specific frequency. If you make the supports randomly spaced, this will prevent these kinds of vibrations from being excited, or at least will damp them significantly.
Am I right?
I think this sort of thinking is overlooked by most (all?) HP installers, who will space their supports evenly, prioritising visual neatness over vibrational dynamics.
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I have zero idea whether this would work but I love it! 
Youāll even get better efficiency due to the eddy current heatingā¦
I like your thinking.
If my HP can play Stairway to Heaven at differing compressor speeds, iāll stop complaining about the noise. 
Iām actually quite happy not having to participate in threads where people argue about which song gives the best COPā¦
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That would surely be a song by the Police.. 
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In addition to the usual fairly buzzy outdoor unit at high compressor speeds, and indoor hum from the primary pipework, Iāve also found this January and the previous January that after a prolonged cold spell, the outdoor unit starts to develop some really nasty resonant vibration in the case, which brings it from āa bit louder than hopedā to āoutrageously noisyā, like hole in a carās exhaust, wake up the neighbourhood noisy, even in noise reduction mode. If I poke around at different parts of it I can usually muffle the extra rattle temporarily. I wonder if this is something to do with cold temperatures stiffening the vibration dampers?
Anyway, do we need to form a petition group to get Vaillant to do something about this? Iāve seen scattered discussions on a few different platforms where the 7kW issue comes up, so it seems like there are a lot of us tolerating it. Judging from how often you see the 7kW pictured in news articles about HPs, I think there are a lot of them out there!
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problem is some seem to have struck gold somehow and have a quiet unit. mines quiet outside it just inside it cant stop humming especially when its cold.