update on “The engineer did apply a known Vaillant dampening “fix” onto one of the panels, which was simply a sheet of stick backed plastic”
I had my second service a few weeks back and used Vaillant.
The engineer advised that the sheet was actually a rain fix, where it had been reported that water was getting into the back panel. NOT a noise dampening, as i posted. Apologies.
A permanent fix is applied to newer models apparently.
That’s really good feedback. Nice to see a potential solution. Did you fit the 1 1/4 in option?
I did some work myself to isolate my primary pipework where it passed through walls and joists, which helped a bit.
But then, between last winter and this, I’d say 70% of the remaining noise just went by itself. I’ve no idea why.
These ones are actually DN25s (1”), as they’re downstream of some steel braided flexible hose (initially attached by the installer) which apparently downsized the 1.25” connections exposed at the back of the heat pump. Other setups may differ.
Does anyone know if this same issue occurs with the 10kw version?
I have the 7kw but I’m currently upgrading for other reasons
If not 100%, could you give a rough sense of how big an impact it had? 99.999%?
Good question.
I don’t yet have the means to measure the impact, so my answer for now will be subjective and imprecise. To answer your question unscientifically therefore, I would summarise the overall improvement as ~75%. I’ll try to explain:
Before the bellows were installed I would hear an uncomfortable resonance in different parts of the house, at varying compressor levels. I would also feel a slight vibration in the plasterboard on the inside of the wall where the pipes run up the outside of the house, especially at higher compressor modulations. I no longer experience either of those things. Win!
However, at lower compressor modulations I am still hearing a faint buzz and feeling some very slight vibrations closer to the heat pump, so it’s like the lower frequency vibrations are still having an impact. So, still a work in progress.
I have a few hypotheses that I plan to test over the coming days and weeks (since I want this issue as-close-to-eliminated as possible):
None of my proposals at the moment include moving the heat pump off the wall, since I don’t think the vibrations are transferring through the mount. Instead I think they are travelling through and emanating from the pipework.
Before I try any of the above however, I want to find a way to accurately measure the remaining vibrations in the pipes. Does anyone have any recommendations on how to do this?
Looks good. I’m going to give it a go. Have you insulated them?
Great, let us know how you get on!
Re insulation, I haven’t insulated them yet as I’m still tinkering with positioning, sequencing etc, however Google’s AI assist suggests that insulating rubber bellows might not be a good idea, citing reduced lifespan of the bellows. I’m a little sceptical of this summary and it’s relevance to lower flow temp domestic applications, so I plan to give FlexEJ (the suppliers of the bellows I use) a call when they open tomorrow. I’ll let you know what they say.
Not sure where you’re planning to position the bellows in your setup @Jason (in my opinion right on the back of the heat pump is probably optimal), but just a reminder that those anti-freeze valves will need to remain at the lowest point in your system. When a Vaillant engineer came out to us, prior to our bellows being installed, that was something he flagged.
I’ll be interested to hear what they say. I was thinking that we might use some extra large pipe insulation (like Primary Pro), but I didn’t want vibration to pass along the insulation, so I thought we’d split it into two sections and allow a small gap in the middle between them.
I called FlexiJ - always very helpful, and they advised not to put any thermal insulation around the rubber of the bellows. The reasons they gave were:
I also learned that under normal operating conditions (which includes the temperature range that a domestic heat pump will be operating at) the bellows should last 5-10 years. The chap I spoke to suggested considering just replacing them at the 5 year mark.
Thanks for that information. You’d think that pipes that are always carrying warm(-ish) water would never get condensation.
Yesterday my installer, Darren Russell our local Heat Geek, installed a pair of the Flex EJ rubber bellows fittings on the pipework behind our heat pump. It’s early days but it seems to have worked brilliantly! I can’t hear a vibration anymore. 
I’ve made a little YouTube video about it… https://youtu.be/m4YxHzXisGs
Thanks to @pippyscottins for finding those joints and Flex EJ for making a great product.
That’s brilliant news @Jason! I’m really glad they seem to be having a positive effect, and kudos for such a comprehensive video.
The reduction in hum you’ve experienced matches / validates the results we’ve observed.
I, like you, remain cautious however, as winter operations will really tell us whether or not further improvements are still required. Not only will the heat pump have to do more heating, but the air will be denser which in turn could impact the vibrations generated by the compressor (even though theoretically denser air means the compressor doesn’t have to work as hard). Time will tell!
In the meantime a couple of minor observations from your videos (all of which may or may not be helpful / necessary for you):
As I say, your vibrations may already have dropped to a satisfactory level, in which case the above can be disregarded. Also I’ve come to the conclusion that a lot of the tweaking I’m doing is a dark art, and depends on many factors, like the design of the house, building materials etc etc.
In any case, please keep us posted! I’m sure we’ll be in touch again by November 
Hi @pippyscottins, thanks for getting back to me. Yes, the Flex EJ fittings have worked very well. I really appreciate you finding them and giving us the inspiration to try them for ourselves.
Aside from placing some PrimaryPro insulation over them in the autumn, I’ll probably just leave them alone for now. It seems to me that the vibration we heard was coming in through the pipework and not through the walls. The clamps Darren used have rubber dampers where that grasp the insulation, and I couldn’t feel any vibration in their metalwork even when I could definitely feel it in the insulation itself.
Anyway, things are much improved here, so thanks again for the advice.
Cheers
Jason.
Use an android app that has an an acceleration spectrum graph (like phyphox) Don’t try to capture such noise with a microphone, it won’t work.
Just put your phone on any surface and capture the problem frequency and it’s resonances. You’ll then be able to see it easily and do so repeatably in an arbitrary magnitude (FFT) which you can compare.
Totally valid and yes that’s the same.
I was just wondering why people were posting saying it’s hard to quantify.
Microphones in phones and RTA gear will have low pass filters that are unavoidable so any dB(A) measurement almost useless to track these down unless it’s unbelievably loud.
But will show up easily on an acceleration FFT.
What App is that from?
That’s an app I have on Android called Spectroid.
