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powersquad asked

2 x Fronius inverter setup with 15kW panels, 10,000VA MultiPlus II and 48V battery on single phase in NZ

Hello folks.

I am looking at setting up solar pv system with off grid capability in extended downtime at our home in New Zealand that is grid tied. We have 2 phases at home but 95% of the load is on single phase currently and I am hoping I can keep the setup on single phase for solar PV as well. I don't care about the remaining 5% load on 2nd phase, and it using grid power when needed. We are currently consuming on average 40kWh per day.


Gear I am looking at purchasing

The plan is to put between 10kW to 11kW of panels on North West to capture afternoon and evening sun as this will generate the most amount of solar energy and put between 4kW to 5kW of panels on South East to capture early morning to late morning sun.


What I want to achieve

  • Ability to power home during extended grid downtime capability where if grid is down for a week for e.g and when the battery storage runs out eventually, the sun continues to provide AC power to home while it's there in the sky or charge the battery and battery continues to provide AC power to running load at same time.
  • Ability to run our 14kW peak power ducted aircon overnight on battery and in event of a grid outage. Aircon usually uses between 5kWh to 7kWH. I will be gradually adding more battery storage every year so I understand that for now 25kWH of battery storage will not last me days or even hours.
  • Ability to export power back to grid while grid is online. I understand power cannot be sent back to grid when it's down for safety reasons.
  • I don't want to setup anything like critical load circuit? I am happy to manually switch off things around the house that we do not need running in the event of grid outage and to conserve battery power.

Is the above hardware I am looking at purchasing through an electrician/pv installer, correct? Is there $ that can be saved? For e.g, Is purchasing 2 x Multiplus II 5VA 48/5000/70-50 better than a single Multiplus II 48/10000/ 140-100 if it can work in my single phase environment and be parallel connected together? Multiplus II 5VA 48/5000/70-50 is $3k each in NZ so $6k total while Multiplus II 48/10000/ 140-100 is $7k for 1 unit. Is Quattro the better solution here? I will never plug a diesel generator as we live in suburbia so due to noise it is out of the equation.

Is it also possible to use the same 15kW PV array that will be connected between the 2 x Fronius AC inverters to bunch of solar chargers/mppt at same time which then connect to the 48V battery directly so I have best of both AC coupled and DC coupled world?


Thanks

Multiplus-IIoffgridgrid
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Rob Duthie avatar image Rob Duthie commented ·

Hi

The Victron Multiplus2 5kW-48v is the only inverter that is partly grid certifed the rest are not grid qualified, or need a grid protect device installed at extra cost $1200 plus.

The Fronius require there own PV system and the MPPT there separate systems.

So what you need is a Micro grid system with black start backup.

2x Multiplus2 @ kW inn parallel is best.

Depending what part of the country you are at , Most lines companies max PV is only now 5 kw it was 10kW but they have reduced it.

I have installed micro grid systems in NZ. as per sample system.

2 phase 180Degree phase shift with 15kw per phase 3x inverters

and 5kw per phase grid tie with 5 kw black start with 40kW battery bank.


20211216-152337.jpg

Regards

Rob D

NZ


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4 Answers
lonesom avatar image
lonesom answered ·

Hi there,

Sounds like a really exciting project!

If you plan on exporting using the Multiplus as well as the Fronius PV inverters:

I recently got a DG installation certified in NZ using a Multiplus II 48/5000/70 in Auckland and discovered during the process that the 8000 + 10000 Multiplus are not certified or listed as compliant to the 4777:2015 or 4777:2020 standards. So if you plan on exporting power to the grid, you can only use the 5000VA model. The 5000VA model is not supported for use in parallel operation however for grid export/feed-in though as per 4777:2015 or 4777:2020.

Some users have reported using an upstream inline grid protection device like the NA003 for parallel 5000VA units:

https://www.tele-online.com/resources/data-sheets/090850_na003_en.pdf

But when I asked Vector about these, they said they weren't compliant, I'm unsure if you'll be able to use one and get it all CoC'd

Also worth noting, I think most NZ grid infrastructure companies have a residential limit of 10kW export, unless you want to jump through a bunch more hoops to go beyond this.

All the best!

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powersquad avatar image
powersquad answered ·

Thanks @Lonesom . I wrongly assumed that the Victron 8VA and 10VA inverters were certified and they are not. Thank you for pointing that out and saving me a lot of grief later if I had pulled the trigger on the 10VA unit. Only up to Victron MultiPlus II 5VA inverter are certified in Australia/NZ. The 8VA and 10VA can only be used in 100% off grid application.

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I only want to export back to the grid via the Fronius PV inverters. Bummer because lines company also verifies the battery inverter as well for approval so I will have to stick with the 5VA model. A single 5VA model will not do the job for me, as it wont charge the 25kWh battery quick enough and not provide enough power to the ducted aircon unit if we want to run it during grid outage.

Can 2 x MultiPlus II 5VA units be connected together in parallel though to provide 10VA of power on single phase purely to serve as a battery inverter only which will be connected to the Fronius ofcourse and a 48V 25kWh battery system?

I take it that your PV system is purely DC coupled 48V connected to a battery if your single MultiPlus II VA is the only inverter in your setup which is allowed to feed back to the grid?


Thanks


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lonesom avatar image
lonesom answered ·

Kia ora,

The 5000VA model is 4777:2015 certified for feed-in/ESS applications in NZ as you mention.

It might be worth checking with your lines company, if it's Vector, Mary at their DG department is very useful and might be able to answer once and for all if you can legitimately install a Tele-NA003 or similar upstream of 2x Parallel Multiplus II 48/5000/70 and still get a DG Cert + COC.

That would be the next move if it were mine.

You're correct, DC coupled indeed for my setup, family of 4 adults, average daily is around 25kWh, and we're pretty much net zero on our power bills. 8kW of PV and a 15kWh battery.

I use my battery for energy arbitrage, charging overnight on cheap rates then selling back to grid excess during the day on solar buyback rates.

All the best


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bipedalprimate avatar image
bipedalprimate answered ·

I am considering a similar system to Powersquad's (albeit only 8.7kw PV on Fronius 6kw) & have come across the same limitations of AS/NZS 4777 & other Victron limitations.

The design I am currently thinking through involves:

  1. Two Multiplus II either 5kw or 3kw connected in Parallel using ESS.
    See ESS design and installation manual

  2. Connect the Fronius to the AC Out of the Multis.
    When grid is down, any PV Inverter will not generate anything as it relies on the grid to provide frequency synchronization - this is to prevent any voltage/current on the distribution network in case any poor line worker gets electrocuted.

    When grid is down and PV Inverter is connected to Multiplus II AC Out, the Multiplus provides a grid signal that the PV Inverter uses - whilst it can still generate one from any battery storage.

    This means if battery bank is too low, Multi will not work. Where extended grid outages are common, the Victron design solution is to also have some DC coupled panels via a Charge Controller to bring the battery bank up to a level where the Multi can start generating AC & then the Fronius connected on the Multi AC out will start.

  3. Also need to consider the AC Coupling 1 to 1 Rule which means that any PV Inverter capacity connected to the AC Out of any Multi cannot be greater than the Multi capacity.
    In Powersquad's case, it might be better to connect the 8kw Fronius with 10.53kw PV (27 panels @ 32% over provision) on the AC-out of the two 5kw Multi's and have the remaining panels on north east roof connected to a DC coupled Charge Controller or split between a smaller Fronius and a DC coupled Charge Controller.

It is worthwhile looking at the Online Courses in Victron Professional to get a good understanding of ESS, Parallel Systems & other design aspects.

So far I have only installed the Fronius & PV - still getting my head around all the other design elements.

Best of luck.

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