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phatjoe avatar image
phatjoe asked

Multiplus II 48/3000 + Fronius 3000 on AC-Out (Essentials) - Max power to Non-Essential?

Hey Everyone, hoping you can help me out....

Currently have a Multiplus II 48/3000 hooked up to a 150/45 Victron MPPT attached to a 2360w Solar Array. I'm wanting to expand the system by adding another 3kw solar array and am thinking to do so by means of an AC Coupled Fronius as the intension is for this array to be predominantly for direct use. Being that I live in South Africa where their is frequent load shedding I intend to put the Fronius on the AC Out side of the Multiplus so I don't loose the benefit of it when the Grid is down.

Question I have is... With the fronius on the AC-Out (Essential loads) side of the Victron, what will the max PV power that will be able to be fed back to AC-In (non Essential Loads) when the Grid is up? The Fronius will have the ability to provide 3kw and the MPPT around 2.4kw but considering the Multiplus is only a 48/3000 will I be limited to only passing 2.4kw back to non-essentials or will I be able to feed back the full 5.4kw as a result of the Fronius provided PV already being AC (so Victron doesnt have to invert it)?

Or would the full benefit of the Fronius PV yield only be possibly if I put it grid side of the Victron (ie on the non-essentials circuit)?

Multiplus-IIMPPT ControllersESSFroniussystem design
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4 Answers
marekp avatar image
marekp answered ·

@phatjoe

I think the only limit is the max current your MP-II can pass through (32A for 230V model).

In my system I have 6 MP-II units so I will never see the max possible since I have Fronius 10kW on AC-out and 6kW in MPPT chargers. The max feed in I have seen was 13kW.

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phatjoe avatar image phatjoe commented ·
Thanks @MarekP, I assumed this was the case whilst still hoping it wouldn't be.
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marekp avatar image
marekp answered ·

@phatjoe

Fronius connected at AC-out of MP-II will not be supplying power to the AC-in side when grid is gone.


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phatjoe avatar image phatjoe commented ·

Thanks @MarekP, this is understood. The question rather is when the grid is up, what will the total PV yield (across MPPT and Fronius PV arrays) will be possible to be passed to AC-in. Considering I have a multiplus 3000 (2400w) and that the combined potential PV yeild across both MPPT and Fronius will exceed 2400w I'm curious as to if the cap of power that will be possible to send back to AC-in will be 2400w or the total potential yeild of 5.4kw?

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marekp avatar image
marekp answered ·

@phatjoe

I think, if your setup permits the grid feeding from your PV sources, the loads connected to AC-in will benefit from PV production.

screen-shot-2022-02-10-at-122143-pm.png

You will need a power meter (EM24 or ET340 for 3phase or ET112 for 1phase system) to be able to limit the feed in to grid if you need to do it.

In my case the limit is 9500W.


screen-shot-2022-02-10-at-122143-pm.png (24.2 KiB)
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phatjoe avatar image phatjoe commented ·

Thanks @marekp, so you believe there is no limitation to the total wattage of PV yield which can be passed back over AC-in even though my system is a 3000/48? You believe the total of MPPT + Fronius yeild of 5.4kw (in my case) could be fed back over AC-In?

Could I ask what Inverter you have and if you have seen it exceed it's rating when feeding back to non-essentials (ie if you have a Mutigrid II 3000 have you seen it feed more then 2400w of PV back to non-essentials?).

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marekp avatar image
marekp answered ·

@phatjoe

Different take on your problem.

If most of your load is nonessential, why not adding Fronius on the AC-in side.

When grid is gone your essentials are powered by MPPT, but if grid is gone longer you can flip a transfer switch that moves your Fronius to AC-out side (small change in GX setup is needed to).

I was usunig this method when I had PV inverter (before I got Fronius) that was not communicating with Victron properly.

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phatjoe avatar image phatjoe commented ·
This is a great suggestion, thanks @marekp! Might just follow through as described.
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