Who can tell me what happens if you have 2 MultiPlus units (12/3000/120) and a single Digital Multi Control? Does the single DMC somehow get ‘assigned’ to one of the MP’s, or does it control both simultaneously? Does it matter how the MPs are setup (split phase, parallel, independent but networked)? Is there anything in Victron literature about this?
It controls both simultaneously if and when you set the two up to work together.
For this you need a pc, a MK3 interface and the ve.bus system configurator ( or maybe ve.bus quick configure).
The system is explained in the software manuals, all can be downloaded from victronenergy.com
Thanks for the reply. The part that sticks out in your response to me is “when you set the two up to work together.” Could you expand on that? I believe you mean set them up as ‘split phase’ or ‘parallel’?
My case is a bit complicated. The two MPs will each be powering separate 120VAC panels. However, tie-in to grid sources can either be 120VAC single phase, in which case the AC inputs to the two MPs are in phase, or grid supply can also be 240VAC split phase, where each MP is getting 120VAC that is 180° out of phase with the other. My concern is if I set them up as ‘parallel’, and I connect to 240VAC split phase, there will be a problem as the MPs are expecting to be in-phase with each other; likewise, if I set them up as ‘split phase’, and connect them to 120VAC single phase, my concern is that they are attempting to supply split phase power but their AC input is in phase. Perhaps these concerns are unfounded? Perhaps it only matters if Power Assist is enabled? Note that they are each supplying independent panels, and there is only 120VAC single phase devices, so it doesn’t actually matter the phase of one MP relative to the other. I just am imagining that if they are set to parallel and are powered by split phase there could be a problem, and if they are set to split phase and are powered by single phase there could be a problem. I need the flexibility to have the system work regardless of the grid power.
What I’m hoping to achieve is two MPs that don’t care if their AC supply is in or out of phase with the other MP, and both controlled by a single DMC. I’m hoping to be able to utilize Power Assist when connected to 120VAC single phase grid, but if I have to sacrifice this feature it wouldn’t be a major problem.
Are your two panels 120V only, or 120/240 split phase?
Do you have any 240V loads?
Are the two panels in close proximity or separated by a large distance?
Are these panels currently being supplied with split phase 120/240v from the grid?
Two panels are each 120V. The ‘two panels’ are physically one panel, just have two feeds, so yes close in proximity. No 240V loads, and if the two feeds to the two panels were in-phase, 180° out of phase, 36.2° out of phase, etc., it would not matter at all.
Because of that last point I was planning on just having them be independent, but not sure what that would do for system integration e.g. DMC, DVCC, etc.
In general, with Victron you should not do independent systems unless you want to replicate all of the controls, and clearly you do not want that.
So the problem is that you only have split-phase or parallel to choose from.
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If you ever expect split phase grid power to be available, you should configure as split phase. But this means if you don’t have split phase coming in, the system will not run.
However, there is a “switch as group” setting in VE Configure that should allow you to use 120V grid on L1, while L2 uses battery to provide L2 (in split-phase). Someone else here should confirm that is how it works, I have not done this. It may not be what you want.
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I don’t know what happens if you configure parallel instead, and give each inverter split phase as grid input. It may throw an error because it expects both multis to be using the same phase. Or, it may pass though the power just fine. Victron needs to help answer that one. I have not seen this in any documentation.
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Rick, thanks for replying, you captured it 100%. Like you, I’ve never seen anything in the documentation about this scenario. The concerns you raise are the same I have.
Admittedly, it is likely unusual to have the grid supply change from 120VAC single phase to 240VAC split phase from day to day, but that is the situation I’m in. When 240VAC/50A power is available, that is what I connect to, but some docks only have 120VAC/30A power available, so I will take that when it’s the only option. Having that flexibility is very important.
Hopefully someone has tried this and can respond.
I guess worst case is that I set them up as completely independent and unconnected from each other, each with its own DMC. Not sure how I’d deal w/DVCC in that case. I would probably leave 1 MP networked with the rest of the boat, utilizing DVCC, and leave the 2nd off the network and utilize the voltage sense terminals instead of DVCC on that unit. Far from ideal but at least I know this would work.
Victron makes Isolation transformers for boaters.
Look at the auto switch 115/230 V one.
I’m not a boat guy, perhaps someone else will chime in.
Thanks for that. I think you’re correct, an isolation transformer is the best solution for maximum input flexibility. I have considered adding one as there are a lot of upsides. However, I do not want the cost, weight, or complexity that it brings.
Hopefully someone can come along and explain the succinctly worded problem statement you put together:
“I don’t know what happens if you configure parallel instead, and give each inverter split phase as grid input. It may throw an error because it expects both multis to be using the same phase. Or, it may pass though the power just fine. Victron needs to help answer that one. I have not seen this in any documentation.”
Otherwise I think I’m stuck with having them be independent with no common controls.
If you connecting them together you need to set them up as a system.
Not sure if this will work in your setup:
You can only try that.
What will work is:
If you uncheck “switch as a group” you can connect only one phase to one of the units and only that one will use it for pass-through and charging, the other will remain in inverter mode.
If you connect a split-phase to both they will both use it.
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You have moved past this point, i am aware. But it does state so on the product page itself. A control is for one stand alone system.
Two stand alone inverters are not one system.
Nice answer from @ricardocello 
See the DMC one.
Thank you! Seem to be getting somewhere now. Where can I read more about “Split phase 180 (auto detect)”? I don’t see it mentioned anywhere in the MP manual?
I use VE.Bus System Configurator (as opposed to VE.Bus Quick Configure), and I do not see the “Split phase 180(auto detect)” option. I do see options for L2 phase though–L2 fixed, L2 floating, L2 floating with return to original phase. It seems that perhaps L2 floating might be similar to the auto detect in VE.Bus Quick Configure? Should I be using VE.Bus Quick Configure instead of VE.Bus System Configurator?
I asked Grok this question and Grok indicates the “Split phase 180 (auto detect)” is precisely what I need, but would prefer to find this in Victron documentation. Snippet from Grok:
"The key difference is the automatic detection and adaptation capability with “Split Phase 180 (Autodetect).” While “Split Phase 180 Degrees” is a fixed configuration, “autodetect” can adjust based on the input, making it more versatile for varying power conditions but potentially less predictable if the AC input does not match expectations. For example, if an RV or boat uses this setup:
With Split Phase 180 Degrees, you would ensure your setup matches the required phase for proper operation, regardless of the input phase.
With Split Phase 180 (Autodetect), the system would attempt to work with whatever phase relationship the shore power or generator provides, potentially falling back to a different operational mode if the phase isn’t as expected."
Thanks again for your help.
Now you are moving to the three phase and parallel manual (and training) as the set up is now more complex. And you do need some electrical knowlege.
Have you wired your system physically?
It is easier to program with Victron connect which is great sonce you also need to firmware update.
I currently have a single MP installed, won’t bore you with the details of how it is wired currently, but works perfectly. I’m looking to increase capacity of both inverter and charger, so want to add a 2nd MP and maintain my grid input flexibility.
I am an EE and ABYC advanced electrical certified, just have trouble following the Victron documentation breadcrumb trail at times. I believe I’m on the right track now, thanks for those who provided helpful input.
Awesome.
I was really asking trying to gauge where you were in the stream of the plans. But you seem well grounded. And yeah the Victron stuff is a learning curve. But boy does the stuff bring new meaning to backup power and generation.
Not sure this would work for you but just a thought. Instead of 2X 3000 MPs, how about a 230 volt European 5000/12 volt Quattro? Wire one input side with to 240/50 amp shore power. Wire the other input from 120/30 amp shore power and then through an autotransformer. This would take the 120 volt shore and convert it to 240 for the Quattro. The 240 volt AC output goes through another autotransformer to provide 2X120 legs for the panel. I use a similar setup in our motorhome. If I’m correct, you would never have both connected to power at the same time and the Quattro would switch between the active input.
Having only one inverter would simplify the setup and one Quattro with 2 autotransformers is not appreciably heavier or bulkier than 2X Multis.