Vaillant Arotherm: excessive noise from compressor

Hardware Heatpump
161

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.

162

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.

163

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.

164

Does anyone know if this same issue occurs with the 10kw version?

I have the 7kw but I’m currently upgrading for other reasons

165

If not 100%, could you give a rough sense of how big an impact it had? 99.999%?

166

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):

  1. I suspect the flexible hosing that is immediately upstream of the bellows (see photo) may perform better if it were downstream of the bellows. The vibrations I feel on the connector at the end of the hosing furthest from the heat pump are arguably worse than those right on the back of the heat pump; it’s as if the the flexible hose exacerbates the low frequency vibrations. I may try to switch them round.
  2. I suspect that the cheap lagging used on the pipework that runs up the side of the house isn’t providing any acoustic insulation, and the noise of the pipes is transferring into the house. I may try wrapping the pipework in something like this instead.
  3. I suspect that the cheap clips that attach the copper pipes to trusses and joists as the pipework enters our house may be acting as an acoustic bridge into the building. I may try something like these instead.
  4. given the positive impact the initial set of bellows had, I may try a second pair in a vertical orientation in case they help to eliminate residual vibrations on a different axis.

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?

167

Looks good. I’m going to give it a go. Have you insulated them?

168

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.

169

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.

170

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.

171

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:

  1. Insulation could inhibit the movement of the rubber and thereby degrade performance.
  2. Insulation could cause condensation to build up on the outside of the rubber, which reduces the lifespan of the product.

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.

172

Thanks for that information. You’d think that pipes that are always carrying warm(-ish) water would never get condensation.