question

zeron avatar image
zeron asked

Multiplus-II critical AC-out and overload risks?

Hey Victron users,

I'm having some trouble decide how I need to organize my electrical network before starting to install everything.

I have a Multiplus-II 48/5000 with a 5kW Fronius AC inverter (and the required amount of panels/batteries)

I want to be able to power the whole house (not at once ofc) with solar power in the event of power going down. To get that done I need to have the whole electrical network on the critical AC output, right?

Thus, I'm at the risk of overloading the Multiplus if I'm not being careful (or don't notice the grid going down) . What happens if I try to load 9kW from the Multiplus 5000 ? Will it just shut off and let me manually restart it after turning off what caused the overload?

Bonus question : is there any way to be able to power some appliances while off-grid from solar only but not from batteries? (I assume I can't, but I'd rather ask while it's a good time)

Multiplus-IIESS
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3 Answers
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @Zeron ,

When overloading the Multi will first try to run the loads, with a 5 kW PV supply from the AC PV, and the 5 kVA from the Multi, you might actually be able to run some 9 kW for a while (sunshine permitting), but if it becomes too much, the Multi will overload and shut down.

After 30 seconds, it will restart itself, and try again. If it overloads again it will shut down again and will try this cycle 3 times, if the overload persists after 3 retries, then it will remain shut down until you manually turn it off and on again.


There are two AC outputs on the MultiPlus. The AC out 1 is live as long as the Multi is On. The AC out 2 is programmable, by default, it is only live when there is a connection to AC-in 1 (the grid, or a generator). Further programmability of this relay is possible though.


For more information on these behaviours, I would suggest to watch these videos;

What is a Victron ESS?- https://vimeo.com/407782757

MultiPlus Assistant Programming - https://vimeo.com/407782757

Victron and Fronius - https://vimeo.com/603741393

Introduction to MultiPlus - https://vimeo.com/400828936

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maha avatar image
maha answered ·

@Zeron

I have a Multiplus-II 48/5000 with a 5kW Fronius AC inverter


The inverter must be a 1-phase inverter. In germany it is not allowed to use a 5 kW single-phase.

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zeron avatar image
zeron answered ·

Thanks Guy, I'll look into how the AC-Out-2 can be programmed, this might very well solve all the small issues I'm thinking about !

maha I believe the maximum grid-injection allowed per phase in France is 6kW (and energy supplier has no issues supplying me with up to 12kW in a single phase so replacing part of that with the Fronius shouldn't change anything) so I should be fine on that part (Multiplus is able to limit what's being re-injeted I believe even if I don't think I'll let back much between batteries, water heaters and a fully electrical house)

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