Just try searching for “soundproofing wall plugs” … whatever they’re called in English. At the moment, that’s the only thing that actually works to reduce the transmission of low-frequency sound.
The 15,000 one is in a different league from a 3,000 or 5,000 one, though … and brick walls vary from country to country, too …
I’m afraid you probably won’t be able to silence the “monster” on the wall completely.
I’d definitely build a freestanding wall in front of it and acoustically isolate it from the floor … Put some dense insulation wool in the cavity, and under no circumstances attach it to the brick wall.
I’d definitely mount the MP 2 decoupled, though I don’t have a specific idea in mind right now (I’m not facing that challenge at the moment ).
As for the screws: they’re suitable for a wall plug in a concrete wall. Otherwise, of course, you’ll need to choose a fixing system that suits the substrate. Decoupling is the next level of expertise.
Do you have the details for those dampers, and did you mount them flat (load bearing) or against the wall? They look interesting and better built than most I’ve seen.
I’ve looked at lots of different ideas for doing this and none look great for an 80KG inverter . Even mounting it directly to the wall without absorption needs careful consideration so I can sleep at night.
In theory, it shouldn’t, but from what I have read it can depend on the load. Candidates for noise would be anything using half wave rectification, or PWM power control. I have read about cheap dishwashers using half wave rectification on the heating cycle causing buzzing/humming
Apart from the dual-fan design and airflow noise, I’ve found the MultiPlus-II 15000 to be significantly quieter than the MultiPlus-II 5000, particularly in terms of transformer hum and electrical buzzing.
The MultiPlus-II 5000 also produces a distinct, high-pitched fan whistle, even though mine is the latest 2025 version.
Would you go as far as just screwing it to the wall and not worrying about the hum? Or could I trouble you for a video or audio clip of the noise either side if that’s feasible?
As already mentioned, this also depends on the actual wall.
One of my MP-II 5000 is directly bolted to a concrete wall and all the buzzing is 100% not transferred into the house. Though, the fan whistle can be heard in a calm night.
Another MP-II 5000 is mounted on a plastered solid log-wood wall/cabin and is able to resonate through all small house, on farthest point is heard only in the quietest nights.
Here is an unedited audio recording of MP-II 15000 but without a sound reference might not be really helpful, the beginning buzz is the phone haptic feedback.
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The recording is 40cm away from the MP while all 3 are pulling 200-250A from battery, no fan at all at this point. This is 3-phase system mounted in a concrete basement.
Wow, so that’s 3 x MP 15K units at 40cm and they are drawing 200A+ each. That doesn’t seem too loud to be honest, that is really helpful.
My main question then is: if you are in any other room, can you hear the hum, and if so how much? This is excluding via directly hearing it through open doors etc.
Secondly, what fixings did you use? There are 14 x 6.8mm holes in the mounting plate. These are fairly small holes so would only allow 6mm anchors?
Complete system is installed in the basement. The adiacent rooms, one beside without sharing installing wall and one room above, do not suffer by any noise, except fans when doors are open.
Mounting is custom, using the original mounting plate, bolted to a rack made from flat iron 8x80mm. MP’s are practically suspended, hanging by 4 M14 rods drilled in the top concrete beam and another 4 M16 rods, drilled in the wall for the lower part of the rack.
It is definitely overkill but being an very old building, did not want surprises.
In the picture, on top you can see the concrete beam, every mounting point also have a corresponding vertical flat iron, two horizontal flat irons complete the rack.
That is a substantial installation! I like the idea with rear plates and that is something I was considering rather than just mounting directly on the wall.
My plan was to use some unistrut for the top mount as per the images below but with vibration pads between the top and bottom pieces of unistrut. The middle two being bolted together. Is use some M12 bolts in the top/bottom unistrut to fix it to the wall.
The bottom of the inverter would just have a narrower piece of unistrut with some vibration pads as standoffs seen as the bottom isn’t load bearing.
I may not bother with pads though if hum isn’t that much of an issue because it just adds a point of failure and I’d need to arrange a secondary restraint incase they failed.
Looks solid enough. You might want to consider adding a layer of rubber matting (like the anti-vibration mats used under washing machines) between the Unistrut channels and the wall.
I used chemical anchors (e.g., Sika or Den Braven) to secure the threaded rods into the wall or beam. The result is extremely solid, and chemical anchors are suitable for both solid and hollow bricks, provided the appropriate installation method is used.
There is very little clearance between the mounting plate and the back of the inverter. I had to enlarge four of the mounting holes to accommodate M8 roundhead screws.
They are from www.sd-dresden.de .
If you ask support, they will calculate best model based on weight , frequency and amount of mounting points and mounting angel.
For what it’s worth, I have the classic Quattro 15K. That should be louder than the Multi II 15k.
I have the Quattro mounted directly on a solid brick wall. My bedroom is a room away. My Quattro usually runs low loads - about 2000w. I have grid connected to AC in but that is programmatically controlled. One thing to note is that the Quattro is in a climate controlled environment via an AC unit.
I don’t hear the Quattro at all in my bedroom on a quiet night. However, I hear the fans (not too loudly) when the grid occasionally kicks in.
In your situation, I would isolate the mounting just to be on the safe side but I wouldn’t go overboard.
I fitted my single MultiPlus II using 100mm long 7mm self tapping concrete screws for the back plate into the 9 newton concrete blocks of my garage that is built into the hillside opposite my house across the driveway. The outer wall is subterranean 500mm re-enforced concrete and there is a concrete beam and block floor above it with 100mm of kings pan insulation and a 50mm+ screed with underfloor wet heating in it and an 18mm bamboo floor on top of that. This was my office but has been taken over by my eldest son as a five metre square bedsit with a corner kitchen and a shower room toilet.
The noise is loud enough to keep him awake and I packed a square of 1" thick closed cell foam between the back of the Victron and the wall in an attempt to reduce the resonance of the back panel, which seemed to amplify it. It has helped a little but it is still very audible. Luckily my son has got used to it.
The problem with trying to remount it is the weight and cable connections otherwise I would have tried something more elaborate.
At the moment, that’s the only thing that actually works to reduce the transmission of low-frequency sound.
).
. Even mounting it directly to the wall without absorption needs careful consideration so I can sleep at night.
