Noise levels: 10kVA MP2 vs 2 x 5kVA MP2


I’ve currently got a 5kVA Multiplus II, but micromanaging loads during loadshedding is becoming tiresome. I would therefore like to double capacity by either replacing the current unit with the 10kVA model (as soon as it is allowed by CoCT), or by adding another 5kVA unit in parallel.

Adding another unit would require me to do extensive rewiring and rearranging of everything on the wall - not a small job. I’m therefore very tempted to just replace the current unit with a 10kVA model, but I’m concerned about noise. The installation is in the scullery and I would describe the current noise levels as “bearable” when sitting in the lounge around the corner. Much louder and it would start to enter “not ok” territory.

I’ve read some horror stories about the noise levels of the fans in the 8kVA and 10kVA units. How bad is it really compared to the 5kVA models? Anyone with first-hand experience?


I consider adding a 3.6K Solis PV inverter downstream of the Multi.
As it is AC-coupled it can be installed in another location and uses natural cooling AFAIK.
The wiring mods( Note) should be far easier and COCT-approved and cheaper.
You would still be limited to the Multi’s capacity at night but will have basically double the power during the day.
The Solis may even stop the existing Multi from getting as hot.

Note: A CT may be required to limit exports


I already have a Fronius Primo 5.0 on the output side of the Multi. It doesn’t help with the problem I am trying to solve, which is that I only have 4kW of reliable power available.

It’s not only due to the fact that a cloud can block the sun at any moment, but when loadshedding starts and ends the Fronius often drops out for a minute or so.

At the moment, for example, when the washing machine and dishwasher enter their water heating cycles at the same time I am in trouble if the grid happens to be down. Training the occupants of this household to only switch on one big appliance at a time when loadshedding is in progress or imminent is harder than herding cats.

I have a Sonoff on mine… They cannot be used at the same time - no power to the dishwasher solved all evils :wink: I also don’t allow washing machine hot washes… cold if fine!


On this topic… lately I’ve had a few switch-offs because of overheating the Multi. The dishwasher on heating cycle along with my other loads pushes the 3kVA to around 2.8kW. It will hold that for several minutes, and then eventually flash the temperature LED, and if I don’t respond, it will switch off for about a minute. On the other end of that coin, it seems to run 3.2kW also for many minutes, as long as it does not overheat.

That means I too am wondering if perhaps it is time to upsize. But I also want to look into a Multi RS in the future, so I’m delaying this a bit.

The Multi RS Solar seems like fantastic value compared to a similar Multiplus II + MPPT setup. What’s the catch? (I assume there has to be a catch.)

Looking at the datasheet all I see that jumps out at me is the 30A AC current limit, which I assume to mean no 50A passthrough like with the MP2?

Also, what are the practical downsides to being a HF design with tiny transformer? Flickering lights when large loads are switched on and off?

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A lot of things don’t quite work yet. In the first iterations, 1) no ESS support, 2) no generator support, 3) no 3-phase support, 4) no parallel support.

But it already has a kind of ESS (just no grid codes, yet), which doesn’t even need a GX device to work. Generator support is currently in testing. And flexible 3-phase support is coming.

I have no idea what the capacity of the transfer switch is, but the 30A is for the inverter itself, and it can peak at 50A for 3 seconds, so I assume the transfer switch should be at least capable of the same.

Anyway, that’s why I said I want to look into this product in the future, it still needs to bake a little.


Andy, had an interesting solution:

Just a note on this (I have not watched the whole thing)… if you put two inverters in series, and the second one runs ESS… it will not work. When running ESS and therefore grid-coupled, it has to stop feeding energy into the grid whenever there are signs of a possible outage… including frequency variation. And from experience I can tell you that feeding a Multi with ESS from another Multi… causes the second one to constantly stop feeding in because of frequency variation.

If you however run it like a normal inverter (which is what he is doing), with PowerAssist, yes then it works.

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jip, the enzymes in modern washing powders work very well in 20-30c, gone are the days of boiling stuff, except if you have to do ICU bed linen :rofl:

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Personally don’t appreciate the noise from MPII 8/10kVA. MUCH more than compared to 5kVA MPII and not recommended for those mentioned mounting scenarios.

Even with under 2kW loads, the fans kick in early at medium speed = noise. Granted the unit works well but better located in garage or separate building.

Not sure about CT allowed list but think there is a 10kVA Quattro with special low noise spec/fans.

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