I'm trying to get confirmation from Victron that the AC-In connection cannot send power back out to whatever is connected to it i.e. Generator, AC shore power, etc.
asked
Confirm that MultiPlus AC-In is "one way" only and cannot send power out
In it's default factory configuration it does not allow backfeed. If AC is present at the input then this energy will be used to supply loads and / or charge the battery.
A conscious decision needs to be made, in VE.Configure software, to apply a grid code to the unit which would then enable backfeed if an ESS assistant is loaded for example.
No grid code means that the unit cannot run "grid parallel" no backfeed is possible and the unit acts like an appliance.
Section 2.4 (page 3) of the manual states:
Here is a link to the manual:
https://www.victronenergy.com/upload/documents/Manual-MultiPlus-II-12V-24V-48V-3k,-5k,-8k,-10k-230V-EN-NL-FR-DE-FI-SV.pdf
I've had a look at the manual thanks but the statement above doesn't explicitly call out the "AC-IN" connection? I can image that there are use cases where you connect AC-Out to the Grid (to power the house, boat, van) and it might find it's way back out onto the wider power network but find it hard to understand why the same would be true of the AC-IN
AC-out must never see the grid.
Damage to the Multiplus may occur, if this will happen.
Grid is only connected to AC-in in all cases.
BR
Surely, AC-Out is what you connect your loads to and, in a domestic environment, that means it will be connected to the Consumer Unit and in turn the Grid?
Have a close look at this block diagram of a Multiplus2.
The 2 relays towards AC-in will only close, if the inverter is in sync to the grid. Otherwise, if not in sync, bad things may happen.
In default configuration, invertering is completely disabled (except power assist) and the MP only charges the battery from Ac-in, when Ac-in relays are closed.
Understood but what I want to confirm is that if I have AC-IN connected to the "Grid" (in my case the domestic power supply) to charge the batteries over night, that power can never be sent from the Inverter out towards the Grid?
Looking at a diagram I created below, the "Grid" is connected to AC-IN for the sole purpose of charging the battery during the night:
I need to be sure that power can never come from the Inverter back to the Grid to comply with local laws.
A competent person would never connect AC-OUT to the network or a generator.
AC-IN is where the network connection is made.
A series of relays prevent connection to the network when the inverter is running.
When in the "On" position with network power available at AC-IN, the relays close and inverter is disabled, only battery charging and pass through to AC-OUT is possible.
If the network is not present at AC-IN or "Inverter Only" is selected or "Ignore AC" is requested, then the backfeed relays will open and the Inverter is allowed to operate.
If you want to power the house without rewiring then you need to have permission to apply a grid code and install and configure ESS. In this configuration the backfeed relays will stay closed with the inverter running synchronous to the network. Your house will be supplied by reverse energy from AC-IN.
Otherwise you need to rewire your distribution board / have another board fitted whose circuits will be powered by AC-OUT and will also inherit UPS function.
We seem to be going round in circles here, to be 100% clear:
1) I want to power a dedicated circuit (utility Room) that won't be connected to the Consumer Unit/Grid but will be connected to AC-Out.
2) During the night I want to be able to top-up the battery from AC-In but only if I can be 100% sure that no power will ever go back out that route
Hope that helps to clarify :-)
OK, my apologies. Let my try and put it a different way.
In the default configuration DC to AC-IN is not allowed.
DC energy can only go from battery to AC-OUT.
If network is present on AC-IN then it can only go one direction from the network to the battery or the load on AC-OUT.
Like Markus also said, leave the default configuration as is, feeding from DC to grid is not allowed.
I have a quattro with ac coupled pv. On sunny days when the load is high the quattro will call for the generator to run. If the load suddenly switches off the ac coupled pv will momentarily push power out the ac input to the genset until the frequency shift has time to ramp the pv back. If your gamed to try it you can see it all happen on vrm.
I meat to say the frequency shift can't ramp the pv back. (Gen is running seting frequancy)
I'm not planning on using AC coupled PV but will use an MPPT Charge Controller connected to the Battery and Inverter, so hopefully this mitigates the problem you mentioned Andrew?
I think under the circumstances with dc coupling you would be fine. I am sure i have read in victron documentation that under certain circumstances limited backfeed can occur on the ac in and I can tell you that with the ac coupled set up you can absolutely demonstrate (and I have done) this. I think that with the dc coupled set up this would probably not occur as you don't have the slow responding pv generators on the ac out. With my set up when large amounts of power are required the quattro has no choice but to start the generator. When the house load suddenly drops and there is then more energy available from pv on ac out and from generator on ac in this energy has to go somewhere. You see the battery voltage suddenly rise and power go out (export) on the ac in. I don't think you can take it for granted that just because you are using ac in that it will never see ac going in the other direction. This may well be why certain grid operators will not allow multis, quattros even in off grid set ups using the grid as their effective back up generator for their installations.
Image Caption
Note the negative input power.
That is with AC-Coupled PV right? Then that behaviour would be expected if the generator is running (backfeed relay closed) and the system is suddenly unloaded. That reverse energy would be coming from the PV Inverter and not the MultiPlus. The control loop would respond to this change and then the MultiPlus can load up to charge if the battery is not full.
If you have AC-Coupled PV then you either have permission from the network operator or you are off-grid in which case the network operator is not involved.
The OP is talking about a DC-Coupled system. They have no interest in any AC-Coupling at all.
We're also seeing current apparently being sent to the grid, in our case from a MultiPlus 48V/3000/35A in a narrowboat. We have no ESS and no solar panels. We are connected to a shore line from October to March, with current limit set to 6A on our Multi Control GX Panel due to limited capacity of the shore line. We leave the boat ring main (AC out) on when we are away but nothing plugged in. Returning after 5 months we plugged in the fridge but nothing else. That night we noticed that the MultiPlus fan was running loudly; the mains light was on steady and the inverter light was flashing, indicating that PowerAssist is active; and our main battery bank (400 Ah) was running down unusually fast. If we switch the MultiPlus off and on it returns to normal operation and bulk charging. If we leave it running, it stops PowerAssist after about half an hour, with the battery at about 95%, and resumes bulk charging. While PowerAssist was running, the VRM display from our Venus GX showed current going out to the grid (AC In was set to 'Grid' in set up; we have now changed it to 'Shore' as that seems more appropriate). We left the boat for a further 2 weeks with fridge off and the system operated normally, with no PowerAssist events. We returned and switched the fridge on, and the same things happened as before, 3 nights running. Trying to understand what is happening, I switched on our immersion heater and a hair dryer and sure enough the same things happened. However, this time I was watching the VRM and saw that current continued to flow IN from the grid while the immersion and hair dryer was on: presumably this is the intended behaviour. However, when I switched the hair dryer off, PowerAssist continued to operate although probably no longer needed and less current was being drawn from the shore line. And when I switched the immersion off as well, PowerAssist still continued but now current was flowing OUT to the grid, and continued to do so until I switched the MultiPlus off and on. So it seems that there is a substantial delay in the unit reacting to the reduced AC load, and during this time, the surplus current produced by PowerAssist is going to the grid, or at least that's what the Venus GX and VRM are showing. This seems very similar to what was described in the preceding posts. The fridge does not normally pull much current, so presumably the events it causes are due to short-term spikes in load when the fridge motor starts up. Our questions are: 1) is our MultiPlus really sending current out through AC-In and if so, why, 2) is our MultiPlus or Venus GX faulty and in need of repair? 3) if we go away and leave the boat on shore line and fridge on, might it damage our battery bank or will it always resume charging before too much is lost? Any advice will be very welcome.
Attached are screenshots from the VRM:
1. Immersion on, hair dryer off.
2: Immersion + hair dryer.
3: Immersion only, hair dryer switched off.
4: Immersion off - current going to grid.
5: After switching MultiPlus off and on: charging resumed.
Presumably your Multiplus grid code is set to "None". I have a narrowboat but luckily 16A shorepower so never had power assist working. I do not think that the "Grid" or "Shore" option actually affects anything, but I likewise changed to "Shore"
Thanks for response. Where do I see/set grid code? Cannot find it in VRM portal.
You need a MK3 interface and VE configure software. You also need the correct grid code
So is it possible that the behaviour I'm seeing is due to incorrect grid code? What grid code would be correct? Should it be set to 'none' - and would this stop current going to grid?
Okay can now confirm our grid code is set to 'None'. Does this mean it should not send current to grid? Why does VRM show it doing so?
