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leonb avatar image
leonb asked

Fronius on AC IN or AC OUT

Hello All,

New to AC-Coupled systems and have been reading factor 1 rule etc. Some background..... Client owns a smallish shopping centre drawing around 275kWhrs per day, and does not have any big loads. We are doing a datalogging next week to confirm what inverter sizing etc. My question is as follows:

1. How do you decide to put the fronius on AC in Or AC Out. If on AC out, how does it charge the battery, or is that another clever thing Victron has done?

2. If on AC in, does factor rule 1:1 still apply?

3. If he does not draw very large currents as I expect, do I still need to keep the 1.5 x kWp rule in mind for battery?

Any help will be greatly appreciated.

Regards

Leon





GeneratorAC PV CouplingFronius
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Warwick Bruce Chapman avatar image Warwick Bruce Chapman commented ·

@LeonB where did you get the 1.5 rule from?

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leonb avatar image leonb Warwick Bruce Chapman commented ·

https://www.victronenergy.com/live/ac_coupling:start#minimum_battery_capacity

Here we go

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2 Answers
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @LeonB

The Victron equipment can charge from anywhere in the system (as long as it can see it).

Minimum battery sizing may still apply, it is best to follow the individual and specific recommendations of the battery manufacturer for sizing.

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Janek Plathe avatar image Janek Plathe commented ·

HI Steward, is the expression that the multiplus can charge from anywhere also applicable if i have an Fronius connected to the Multiplus II on AC input and MPPT`s on the DC side of the Multiplus... Would both sources be utilized/combined for charging if available?


greetings

janek

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petajoule avatar image petajoule Janek Plathe commented ·

Yes. The MPPTs are on a "DC bus" and as such are quite decoupled from the AC IN/OUT of the Multi.

The system therefore can utilize power sources on all three AC In and AC out and DC at the same time. The Quattro is very similar in that respect, except it has AC IN1 and AC IN2 and uses a priority scheme (IN1 over IN2) there.

We usually connect a Genset to Quattro AC In1, Grid to AC In2, Fronius to AC-Out1 (leave AC-Out2 alone) and of course MPPTs to DC bus.

And then watch the Quattros juggling. ;-)

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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ petajoule commented ·

Hi @PetaJoule,

I have another design suggestion you may wish to consider.

Putting the loads on ACout2, and only the PV inverter on ACout1.

Then you can disconnect the loads when battery state of charge is low, but still maintain the sinewave from the Multi/Quattro to start up the AC PV automatically when the sun comes out again.

It is an improved effect for the customer (the lights would likely have gone out anyway) if they want to start straight away they can go to the generator, otherwise it might be that they can now do nothing, and the next morning the power works again.

Also MUCH better if the generator is also having issues, because the system will recover normal operation without it.

This is less important if the system also has a DC MPPT connected as well, as that will also start the system from low battery shut down, and is the best and most reliable option.

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petajoule avatar image petajoule Guy Stewart (Victron Community Manager) ♦♦ commented ·

Interessting, I thought AC-Out2 is disconnected as soon as AC-In1 and AC-In2 are missing (no UPS functionality).

What you describe is called in German "schwarzstartfähig" and that's what we have the Victron MPPTs for.

We usually connect a Genset to Quattro AC In1, Grid to AC In2, Fronius to AC-Out1 (leave AC-Out2 alone) and of course MPPTs to DC bus.

I would very much appreciate clarification and guidance here, because right now all AC-Out2 in our installations are void. And if that is an omission, we would like to rectify it.

So the understanding here is, that AC-Out2 is disconnected as soon as Quattro is in Inverter mode, not just when batteries are low. That should be the behavior of AC-Out1.

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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ petajoule commented ·

You are correct, in a default out-of-the-box system, the AC2out is dependant on ACin.

However.... AC2out is just a relay, so it can be programmed to open and close on MANY variables that are set in a VEConfigure assistant. So you can override the default behaviour to instead be state of charge, or battery voltage, or relay dependent (or all three at once).

You are not omitting anything really, and as long as you have DC bus MPPT solar, then your systems will black start and already have the benefit of that.

However, if you ever have an AC Solar only system, then it IS good to know and understand the potential of the Victron systems to make this a more robust and reliable configuration.

I am working on a Victron Professional Online Training course that will run through the most common 'best practice' installation configurations using AC PV. Keep you eyes out (and subscribed to the Victron Professional Newsletter) for it if you want all the details.

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petajoule avatar image
petajoule answered ·

In general, the Fronius can be on IN as well as OUT. It depends on other parameters where you finally decide to put it.


If it's a new installation, AND if you do not want to feed in back to the grid, I would put it on OUT. The "1:1" rule applies (which is actually a N:1 rule if you have several Quattros/Multis).

If you can/want feed back to the grid AND if there are no outages or these aren't critical, AND you would have trouble to satisfy the 1:1 rule, I would put it on IN.

I'm not aware of any 1.5kWp battery rule for the battery. Must be a lead-acid thing. ;-)

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