I have a MultiPlus II 5000 48 in a small DESS system in our house. Located in the basement, wall-mounted, separated by a door. Under some conditions, and that’s not only high loads, humming of the toroidal transformer is very intensive. That intensive, that you can hear it even one floor above in a solid brick build house.
After a few days observing, I had to take countermeasures to avoid getting in trouble with the rest of the family. It’s just too loud for an inhouse installation, even with no heavy loads in 99% of the time.
What I did to reduce the noise
Decoupled the transformer from the enclosure
Damping mat on the inner side of the housing cover
Damping mat between Inverter and wall
Wall plugs with vibration decoupling
I did not change the fan. Tested a Noctua NF-F12 as alternative. But as soon as the airflow is as high as provided by the original fan, there’s no big improvement
Reduced the surplus feed-in to 1000W in my DC-coupled system since self-consumption is my priority and selling is not a big financial deal anyway. That keeps the inverter in 99% of its time in a low-load mode without fan.
How did it work out
It is still not super quiet
The humming cannot get recognized any longer on other floors
Fan is starting only in very rare cases
What I would love to have on Victron side
A MultiPlus II low-noise version for very common inhouse models like the 3000 or 5000
It can cost a little more if it is improving the overall noise
I would even buy such a new model and sell my current one if it gets available in the future. And yes, I know, Victron might refuse the product warranty after my modification – although I feel somehow forced to do those mods because the product design seemed to ignore the noise topic.
I did exactly the same with mine 3 multiplusses, only difference the multiplus is on rubbermats with rubber plugs (like you did) and on a board that is attached to the wall with rubber plugs
Also decoupled the transformers like you and i decoupled the fans also from the frame with rubber plugs
They are in a separate room in my house next to the bathroom, and can only be heard when there running really hard
Before my mods the noise was crazy in the bathroom
Guess, we are not the only ones @DuivertNL Hello Victron colleagues, we love your products but in that case, a low-noise version might be justified as an option
That’s why my two multis are lying on their backs and the toroid is not screwed down at all. This also generates a lot of resonance on the housing … the house has hardly moved in the last few months.
Including, of course, these anti-vibration mats from the washingmachine …
can hardly be heard or felt …
Hello @Netrange , my MP was also lying on the back when I was testing the mods. You are right, it was already much quieter when not attached to the wall. Removing the screws of the toroid made it even better. So I had the same thoughts - just using it in that horizontal position.
At the end, I guess it was just a kind of tidying obsession and the natural heat flow in an upright position that drove me into that direction.
So, is picture one showing the MPs lying on the back in horizontal position, toroid loose for max decoupling from the housing, without the front cover as you run it today and the second picture shows the vertical mount before? @Netrange
I have reduced some of the noise by using a ratchet strap to compress some inter-battery foam pads against the case. It makes it just about bearable in the room above but it looks ugly.
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Hello @teejay , I used Anti-Vibration Rubber Mats, yes. The challenge is, that you do not have much space between the front-cover and the toroid. At the end, it’s only a workaround. As you can see in Steffens example and like I experienced while experimenting, the MP is rather quite with the front-cover completely removed, lying on its back in horzontal position. The housing itself and the vertical wall-mount position contributes a lot to the overall noise.
Pretty sure, it would be possible to build a low-noise version even with a toroid on Victron side if low noise would be a product design goal.
If it is possible, I would avoid screwing it down completely, because this also goes directly onto the housing AND also make the ‘rubber ring’ underneath as small / narrow as possible. This way, as much mass as possible meets as little material as possible.
The same principle applies to the decoupling of low-frequency loudspeakers. Here, inverted steel cylinders are used which only meet a small point on the bottom. This means that you have a very large weight on a very small surface. This prevents low-frequency cabinet resonance with the floor.
Thank you @B51-technician and @Netrange for your replies. I am really struggling with the noise. The inverter is in the garage, which is directly below our bedroom. I have had to severely reduce the charge rate to get to an acceptable noise level. I have improved things quite a bit with this heath-robinson ratchet strap contraption, which reduces the case vibration but it looks awful:
I once had an idea, which was not pursued here, to simply hang the Multi on 2 springs.
This would achieve complete decoupling from the wall. 2 round eyelets in the wall and the two springs on them. Then also 2 eyelets in the back of the Multi and then hang it on the two springs … Pay attention to the cable connections, of course.
@Netrange , I had the same idea with such a spring mount Would have been my next try in case I still feel the humming is to intense. Guess it would help regarding the wall hum transmission. Would most likely not help for the hum of the MPII enclosure itself.
@teejay , I still use the provided wall mount and did not screw directly through the housing. See the picture attached.
Picture 1, anti-vibration wall plugs with standard mounting rail
Picture 2, damping mat of a washing machine behind the MPII
Yes. I love my Victron system. But in that particular case, I’d highly appreciate the Victron engineers to help us - without kind of forcing us to modify the standard hardware that way with a lot of effort and in some cases with the risk of loosing the product warranty.
@B51-technician Thank you for the extra information. Are you generally happy with the results of your anti vibration actions (transformer and wall isolation) ?
Would have been my next try in case I still feel the humming is to intense. Guess it would help regarding the wall hum transmission. Would most likely not help for the hum of the MPII enclosure itself.
