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7hvn avatar image
7hvn asked

Multiplus II 48/5000 GX - Max Export to Grid with Solar PV on ACOut1

I'm in the process of filling in the commissioning paperwork for my DNO with regard the install of my Victron ESS system.

I've fitted the MPII 48/5000 GX (4.4kW) and I have my existing SolarEdge PV Inverter (3.68kW) on ACOut1 such that during LOM I can still charge the battery with Solar. Communication between the two is via the SolarEdge Modbus system. A twisted pair is also fitted between the inverters for the dry contact to set the SolarEdge inverter into Alternative Power Source (APS) mode and enable frequency shifting. This is tested and working.

The DNO sees my configuration, blindly, as 2 generators with total capacity of 4.4 + 3.68 = 8.08kW total. They have permitted me a maximum export of 32A thus ~7.19kW @ 230V.

My first question, assuming the ultimate worst case scenario:

  1. Batteries exporting to grid (4.4kW)
  2. No house loads (un-realistic)
  3. Solar at Max Generation (3.68kW)

Is this even feasibly possible, when the PV is mounted on ACOut1? I.e. Can the MPII 48/5000 allow pass-through from ACOut1 (Solar PV) to ACIn and thus to Grid *as well as providing an additional 4.4kW from the batteries to grid*?

If it's not, is there any documentation that I can send to the DNO as evidence that this max 8.08kW is never achievable for my configuration?

Lets say this can happen, I can limit the grid feed-in to 7.0kW via software which should put me under the 7.19kW limit. That's an administrator task and password protected. Would this be acceptable to a UK DNO to avoid the G100 problems?

This Victron G100 document 'https://midsummerwholesale.co.uk/pdfs/victron-g100-declaration-multi.pdf' doesn't really reflect the more modern Victron systems and especially a MP with GX built in.

Anyone had a similar situation that can offer any advice?

Thanks in Advance,

Multiplus-IIsolaredgedno certification
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4 Answers
patricknl avatar image
patricknl answered ·

I can't talk about the UK regulations and if this will be certified there BUT You should be able to export the maximum of your PV panels to the grid no problem via the Pass-Through. It's rated at a maximum of the 5000VA the MultiPlus can deliver via the AcOut I believe... Also you can put a limit on the ACIn of the MultiPlus that it will not exceed for example the 32A. I can't recall if that's also applied for the feedin to the grid... It should be in the manual...

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7hvn avatar image 7hvn commented ·
Haven't thought about using the current limit on ACIn - Thanks.

Can anyone confirm whether this current limit is bidirectional or not? I.e. Would a 32A limit be applied for both import and export via ACIn?



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daza avatar image
daza answered ·

@7hvn Sorry but you are not correct your array does not determine the power to the grid your inverter does. Please confirm your inverter size ie is it 3kW if so this is what you put. Another person has asked a simular question i will copy my response below.


Oversizing an array is common practise and an array can be 133% larger than its inverter ie if you have a 3kW inverter you can oversize the array to 3.99kW it will still only ever convert 3kW useable energy. Oversizing is a way to make the inverter start its morning cycles early and finish later good for low light conditions. Hope this makes sense. your inverter determines how much you can dump to the grid. PS if one system is AC PV and the other DC not on a hybrid inverter then the two sums of the inverters need to be added to get the overall total of potential power that can go to the grid.

Yes they over compensate building safety margins in, likely hood of you dumping your whole setup into the grid well the stars and the moon would need to align, but over engineering is what we do best in this county and most of the time pays off. Always good to have a buffer margin hope this makes sense?


I have just been though the process of DNO application but its taken a bit longer than some about a month and a half but approved G99 7kW system just because i wanted to build some redundancy into my install for higher load services eventually EV charger so i wanted 100amp supply instead of my 60amp supply. They only approved it after they changed the fuse

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7hvn avatar image 7hvn commented ·

Hi @Daza I've updated the post. I should have written Inverter not Array. FYI Its a 5.4kW array connected to a SolarEdge 3.68kW Inverter.

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daza avatar image daza 7hvn commented ·

7hvn
commented · 4 days ago

Hi @Daza I've updated the post. I should have written Inverter not Array. FYI Its a 5.4kW array connected to a SolarEdge 3.68kW Inverter.


@7hvn ive just read this and your saying it’s a 3.68kW inverter connected to 5kW solar panels? If yes then you could only ever export 3.68kW max

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7hvn avatar image 7hvn daza commented ·
@Daza yes that's correct. 3.68kW export from the AC Solar Inverter. This is wired on ACOut1.
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daza avatar image daza 7hvn commented ·
Sorry ignore me I need another coffee I’m clearly asleep at the mo, are you exporting battery to the grid also? Unfortunately can’t help with the setting as I’ve not got my victron or batteries I may be asking you for setup ESS help. Are you limited on your import and is the Victron running the whole house if so you are already import limited ie the inverter 50amp?
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daza avatar image
daza answered ·

@7hvn Oh right. they would more than likely require you to demonstrate that it does not produce more ie someone might come out to see the system. But yes you are correct you could only ever dump 4.4kW but if the PV was ever wired on the input side then you could dump that potentioal. Not saying you but if someone took over that system it could happen. if that is factored in now by them they never have to worry that extra power not compensated for is being dumped into the grid

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7hvn avatar image 7hvn commented ·
Morning @Daza I ran a test, similar to how I've described below, and set the grid set point at around -6kW. The MultiPlus II passed through 3.68kW Solar (Full on sun :-) ) on ACOut1 and topped this up with Battery power to achieve the export -6kW grid set point.

Ok using Grid Set Point here isn't ideal but its the only easy way of forcing the batteries to discharge for testing (that I have found out of the box). In the future I'll use HomeAssistant to control any forced battery discharge to grid if I so choose.

So it appears the 4.4kW is purely for the inverting of battery juice to load. The flow out of ACIn to grid is not, it appears, restricted to 4.4kW.

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7hvn avatar image
7hvn answered ·

Some updates:

I've looked further into:

  • ESS > Grid Feed-In > AC-coupled PV - feed in excess > Limit system feed-in > Maximum feed-in > 1000W

I cannot get this setup to work - I believe this is for Fronius AC PV Inverters only.

This kind of makes sense as my SolarEdge Inverter can currently only modulate its output in APS mode. The only time it goes into APS mode is on a LOM event where the Victron Aux relay is used to perform the dry contact to set the PV Inverter into APS mode. Thus by default the Victron cannot modulate to reduce the PV generation via frequency shifting if the grid is still live.

Next I looked at 'Grid Current Limit' aka 'Input Current Limit'.

  • VRM Dashboard: 'Grid Current Limit'
  • Remote Console: MulitPlus-II 48/5000/70-50 > Input Current Limit > 50.0

The latter implies that this is an 'Input' current limit only but it appears to be an 'Export' limit also.

For testing I set the 'Grid Current Limit' in the dashboard to 13A (2.99kW @ 230v). I then set the 'Grid setpoint' (ESS > Grid setpoint) to -4000W. The export appears throttled at just under 3000W. Now changing the 'Grid Current Limit' to 16A the export to rise then limits around 3680W.

In theory then if I set the 'Grid Current Limit' at just under 32A I should stay within my export limitation.

I don't really think this is the idea solution though as it limits import too. Is there no way to set an Import Limit and Export limit separately?

Thanks in advance...

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Related Resources

MultiPlus-II Product page 

MultiPlus-II Manual

MultiPlus-II 230V Datasheet 

VE.Bus Error codes

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