From grid-tie to microgrid / hybrid backup

Hi everyone

I’m inheriting a Fronius Primo 5.0-1 with 19x ??? 405w panels installed at our new house. (The current owner has promised to look for invoices to determine exact panels.) They face almost exactly north & east, leaning sliiiiightly east.

The installation is fairly minimal in terms of safety equipment, but it does seem like the two strings are fused on both + & -.

(This is under the blue roof on the left of the top image.)

I think I’d like to add a Victron Multiplus II 48/5000/70-50 with ESS on lithium batteries to help with self-consumption and obviously load-shedding, Fronius on the output.

At this point I’m not sure of the power requirements yet, but there are a couple of aircons and a heat pump for the swimming pool, so splitting the DB will absolutely be required. Our normal use at our current house would be well served by a MP 3000.

What other things do you think I should be considering? We’ve only moving in Jan, so there’s still some planning time.

FWIW, I still have 12x SolarWorld 260W panels in my garage which could look quite good on that right-hand-side roof after the defunct pool tubes have been removed, possibly on a BlueSolar MPPT directly to the batteries. Pity the old 150/70 next to them is no longer supported.


What a lucky packet! This should keep you busy for a couple of weekends…

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The Fronius work well with the Multi II. Their rating need to match or the Multi II need to be larger, so you will not be able to go smaller than the Multi II 5k.

You might not need anymore panels that what is there currently already. Best would be to move in and use it for a few months while keeping an eye on the meter, and then decide if you need more panels.

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Yes, I’m only thinking about more panels since I have them already.

Pity the 8KVA MP isn’t on the CoCT list (yet).,%20notices,%20tariffs%20and%20lists/Approved%20Photovoltaic%20(PV)%20Inverter%20List.pdf

The house actually seems to be fairly inefficient, so I may get greater gains from a heatpump geyser and so on.

Is there an 8kVA multiplus?
I see there are no Quatros on the list…

unfortunately not, largest is the 5 kVa Multiplus II

There’s an 8KVA & 10KVA Multiplus II on Victron’s site, and I’ve seen it offered online, e.g. Victron Multiplus-II 48V Inverter Charger 48/8000/110-100 | High Quality Solar and UPS System Components for Hybrid Off-grid and On-Grid

However, the datasheet on Victron’s site says the 8 & 10s cannot be parallelled, but the PDF manual doesn’t make that distinction. Unsure if it’s the newness, software, or design.

And it’s not on the CoCT list, so it might as well not exist for me.

Quattros and the original Multiplus will never be on that list since they don’t have all the hardware required by the relevant regulation. The Ziehl anti-islanding relay (on the list) “fixes” that problem for you, since it sits between the grid and the inverter where it provides the required checking and relays. But it is expensive.

I’m not 100% sure if Ziehl-ing an otherwise noncompliant inverter will paper over all problems, but the Victrons were damn close to compliance.

I forgot to mention that my wife and I both work from home and you couldn’t pry her three monitors out of her cold, dead hands, so load-shedding backup is essential. Hence planning starting now.

Hmm, those do look like Half-cell type modules, so I would guestimate at least 400W per module? (Unless its the 122Cell ones, then 300W).

I think you will not go wrong with the MP2-5000 and throw in those extra modules as you have them. With the correct set up you will be very happy.

I think trying to configure any other inverter to the Fronius might give more headaches that they are worth! (Apparently Sunsynk can, but Fronius and Victron has come a long way!).

As noted by the guys, while you can buy the Victron now and have it installed with the DB board changes, best would be to measure and find out what exactly you need.

Also note, that “change of ownership” also requires you to re-register that system with the City of Cape Town, so best is to do all in one and get it done!

It’s not just that it is expensive. It’s that depending on who you listen to, it might not actually “fix” the problem. The thing is, it has to be TESTED in combination to get it approved. The Ziehl+Quattro combo was tested for VDE-AR-N-4105 (the German grid code), but it wasn’t tested for NRS097. So while the Ziehl on its own is on the list, you may well find that the application is rejected because the Quattro isn’t.

The Ziehl on its own isn’t enough, because that only implements passive anti-islanding measures. NRS097 requires at least one active anti-islanding measure. This is implemented in all Victron inverters (known as LOM, loss of mains detection), but again, regulators can be quite stubborn about requiring that it be tested in that configuration.

I’m told that you can use a Ziehl anti-islanding relay together with Hoymiles micro-inverters. I can only assume it was tested as a combo…

Also, adding a Quattro to that setup may not require any additional paperwork. Counterintuitive perhaps, but here is how I understand it.

The inverter isn’t the embedded generator. The PV modules are. The inverter is the conversion device between the embedded generator (the PV modules) and the grid. In this case, the conversion device is the Fronius PV-inverter. And that has NRS097 certification. The Quattro is just a UPS, and the regulators don’t care about it. They should… if they were consistent… but they don’t.

Makes sense re the Ziehl – it’s only a small part of a complex system.

By the Quattro reasoning a 8KVA MP2 should be similar, assuming it is actually available. Would adding DC-coupled solar change that? Since it would only actually charge the battery.

I like that idea, but it seems dangerous to apply too much logic to what is essentially a tick-box exercise. You can easily lose. :expressionless:

But that would be my ideal, since it should handle almost everything, just not all at once. Then runtime calcs can be done for battery size. The eTower expandability and current rating looks really good, especially since it seems like FreedomWon have implemented the voltage-control. Hopefully the batcompat page magically updates soon.

I suppose I can always get things installed with the Fronius on the MP input with no DC coupling, since that is extremely simple compliance-wise to get going. Re-doing the applications for a Fronius on the output + DC MPPT would be tedious, but things would at least be working at that point.

Do we have a feeling for how difficult CoCT actually is in practise?

Yeah, for the 5KVA I think this makes the most sense.

Reason I’m really considering the extra panels is due to the pool heatpump: my gut tells me I’ll want to use it more in winter than summer (right? :stuck_out_tongue:), but that’s when my array might be insufficient. Probably worth waiting a season before buying too many things though.

what about two Multiplus II’s in parallel

Yeah, but feels wrong :slight_smile:

It would probably make the most sense to add 1x 5KVA as UPS, then give it until spring before adding #2 and the panels. Will just have to plan spacing and so-on properly. Have seen too many very nice installs ruin their aesthetic by chucking a second MP in a cramped corner!

The 8 and 10kva multi plus 11 is freely available currently. The bigger ones not so common.

I meant on the CoCT list

Should be listed shortly. Victron I busy vir the certification.

yes learn from our mistakes :laughing:

I still think two multis is better than one big one, always have a backup if one dies. Plus you can always add more. If I’m not mistaken the 8 & 10kVA units can’t be paralled with another of the same size.

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I was reading your updates specifically and just shouted “Noooo!” at my computer screen a while back… Wife came running to see what’s wrong. :slight_smile:

Is your fuse still hanging in the air? :expressionless: