50a 5th wheel with dual Multiplus configuration help

rv_solar

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May 15, 2022
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Hello all-

I am a new member to the forum and was directed here by a friend who suggested this community may be able to help with sorting out some diagnostics and setup issues I am having with my DUAL Victron Multiplus 12/3000/50 120v installation.

My system was installed a year ago by a licensed electrician familiar with solar and larger off grid systems, but who had never worked with RV's or Victron equipment & the mix of (relatively) small-scale 12V DC and 120V AC. As such, the initial configuration and details of Parallel vs Split-Phase wiring and setup were never fully understood by or explained to me, and within a short time issues started to appear. After learning some basics myself, it appears that my system was wired to be used as a split-phase setup (see PDF single line drawing attached as provided to me by the installer), but the two Multiplus inverters were never connected via an RJ45/Ethernet communication cable, and so have basically been operating as two separate standalone units, each serving one side of my RV's AC breaker panel. As I have learned, this will lead to some issues since the Neutral wire is shared between the units, but they have no way of knowing what the other unit is doing.

The two problems I have been experiencing are:

1) The biggest issue is this: When connected to a 240v 50a shore power receptacle, if I set the input AC current on either inverter to MORE than 20a, I start running into major issues when any significant load is applied (Air Con, Electric FP, etc) - the inverter will give me overload errors, will bounce between Pass-Thru, Assisting, Inverting modes, and will sometimes actually show a NEGATIVE AC input, as though it is trying to back-feed the grid, though have never actually put a clamp meter to this to verify if it is actually happening. If I keep the shore input to 20a or less on each inverter, they operate flawlessly regardless of shore power connection type (or when strictly off-grid/inverting), which is basically what I have been doing for the last year as we live & travel full-time in our RV.

2) Secondary, and less important issue is that I pop the GFI on any 120v 15a or 20a GFI-protected receptacle within 5-10 seconds of connecting to it, if that happens to be my shore power connection.

After doing much reading on this forum and elsewhere, I think what I need to do is simply disconnect from shore power, connect my Multiplus' together (via RJ45/Ethernet), and connect one of them to my laptop via RJ45/Ethernet cable and program them in Split-Phase through the VictronConnect app (I have a Victron USB MK3 Dongle). But before I do this, I wanted to reach out to all of you to see if there is anything else in my setup that is of concern, or that would prevent me from doing this. Again, please see the attached PDF single line drawing that includes my hardware details.

If I go this route (Program to Split-Phase), it is my understanding that when on a 240v 50a shore connection, the Multiplus' will each pass through 50a to one side of my AC breaker panel, and that everything will work as expected with ample power available. When connected to a 120v 30a (or 20a or 15a) shore connection, one inverter will pass through that amount (or use to charge batteries), plus the "Assist" wattage will also be available from that inverter. The second inverter will reject the incoming shore power (since it is the same phase) and will operate in Inverter mode only, up to its maximum inverter wattage. Do I understand this correctly?

The other option I have considered is to go the parallel route, but it is my understanding that some re-wiring would need to be done to facilitate this, and that I would always be limited to the maximum amperage of one leg of any shore connection (ie 50a total on a 240v 50a shore connection). Is this correct?

Greatly appreciate any advice or feedback you can offer - thank you!

Josh

Details on hardware & wiring:

AC Wiring To/From Shore/Inverters/AC Panel: 6/2 & 6/3
DC Wiring: 4/0 To/From/Between Batteries, 4/0 To Multiplus' from Lynx Distributor

6 - Battle Born 12V 100Ah
2 - Multiplus 12/3000/120-50 120v VE Bus
1 - Victron Lynx Distributor
1 - Victron BMV-712 Battery Monitor
2 - Microair EasyStart 364 (One on each Air Conditioner)
2 - VE.Bus Smart dongle
1 - Victron SmartSolar MPPT 150/85
1 - Battery Guard AutoSelect
6 - Canadian Solar 305w solar panels
 

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  • Solar & Battery Wiring Line Drawing.pdf
    110.9 KB · Views: 53

rv_solar

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May 15, 2022
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Just a shameless bump back to the top in case anyone here might be able to help. Thanks!
 

corn18

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Sep 9, 2021
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I looked at the diagram and don't see any glaring issues. I wish I could help with the dual Victrons, but I know nothing about how they work together.
 

jwelter99

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Dec 6, 2020
Messages
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The diagram looks good. And you do need to program these to split phase as you point out. Their is a wizard to do it now as well on the iOS app to make it easier.

Also note these units will only draw 120V/25A each from shore power. To get above that it will use PowerAssist to supplement that shore power AC via the inverter and battery banks.

Your RV is setup for each phase to be 50A so you may have have to reduce your expectations on what you can run.
 

rv_solar

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May 15, 2022
Messages
5
The diagram looks good. And you do need to program these to split phase as you point out. Their is a wizard to do it now as well on the iOS app to make it easier.

Also note these units will only draw 120V/25A each from shore power. To get above that it will use PowerAssist to supplement that shore power AC via the inverter and battery banks.

Your RV is setup for each phase to be 50A so you may have have to reduce your expectations on what you can run.
Hello!

Thanks for the reply and details - greatly appreciated. It turns out the Parallel/Split-phase/Mulit-Phase setup on the iOS/Mac OS VictronConnect app is somewhat limited in functionality. Specifically you need to disable a function called "Switch as Group" to allow shore power on L1 to pass through when on a single phase shore connection (I am currently on a 120v 30a connection). If you do not, the system will reject shore power on all legs when it doesn't receive a true 180º split phase shore connection. The iOS/MacOS VictronConnect app does not have this "Switch as Group" option to deselect. I did attempt to program them into split-phase with the MacOS app and successfully got them into Split-Phase, but the system rejected shore power on both legs and would only invert on both inverters.

Was able to track down a windows-based system and got the VE.Configure tools downloaded. Successfully configured everything into Split-phase yesterday and everything appears to be working as it should. Disabled "Switch as Group" and have L1 passing through 30 amps (current shore power is 120v 30a) and L2 is operating in inverter-only mode as expected. Also disabled the Ground Relay on the L2 inverter, as apparently this should only ever be done on the L1/Master inverter.

Won't be able to fully verify this has solved the strange behaviour when shore input is set to more than 20 amps until I move to a different RV park in a couple weeks, but I am optimistic this is a big step forward!

Also just to confirm, my understanding is that when setup as a split-phase system, and on a split-phase shore power (as in a typical 240v/50a shore connection at an RV park) I will have the full 50a available as pass through on BOTH legs. If I had programmed (and wired appropriately) as a Parallel system, I would only have 50a available total, as Parallel systems only use L1 and ignore L2. So in that case, I would be limited to 25a per inverter (50a total split and balanced across the two inverters). Do I have that correct?

Appreciate your help - thank you!
 

B-ManFX4

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Jan 17, 2022
Messages
28
Not that you want to spend additional money but adding an Autotransformer would allow you to realize the full power of both inverters on either side of your RV breaker panel. (When in parallel mode the Autotransformer is out of the loop.)

This is a busy drawing but it is exactly how my dual set-up is configured. I plug into the Multiplus with my phone and an OTG cable and use the Victron Connect app to switch between 30A parallel and 50A split-phase configuration. It is super simple, fast and mistake proof. Then I flip the switch to the correct configuration and the wiring is correct and works like a champ.

I went with 24V to reduce wiring size and all the associated costs but the AC output is the same.
 

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  • RV Power System 1 - Copy.pdf
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rv_solar

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May 15, 2022
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Not that you want to spend additional money but adding an Autotransformer would allow you to realize the full power of both inverters on either side of your RV breaker panel. (When in parallel mode the Autotransformer is out of the loop.)

This is a busy drawing but it is exactly how my dual set-up is configured. I plug into the Multiplus with my phone and an OTG cable and use the Victron Connect app to switch between 30A parallel and 50A split-phase configuration. It is super simple, fast and mistake proof. Then I flip the switch to the correct configuration and the wiring is correct and works like a champ.

I went with 24V to reduce wiring size and all the associated costs but the AC output is the same.
Thank you so much for this detailed response and clear drawing - it is appreciated! Not sure I'm going to go the route of adding an autotransformer for now, as I have successfully reprogrammed my system to Split-phase and things are working well, even on my current 120v 30a shore connection. L2 is inverting only (no pass through) but most of my regular heavier loads are on L1 anyway. If I end up running into regular needs for better utilization on single phase connections I'll definitely look into this further, and will likely use your drawing as a guide. Thank you!

One quick question in case you may know - I programmed my two MP's in 180º split-phase. I may run into situations where I get a 3-phase 120/208v 50a connection at certain RV parks. Is there any downside to just programming my setup into split-phase floating (VictronConnect calls this "Split phase 180 (Auto)) and leaving it that way indefinitely? Just wondering why they give you the option of 120º/180º/Floating. Why not use floating all the time? Thanks again!
 

B-ManFX4

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Jan 17, 2022
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I wish I knew more about Victron programming. From my limited exposure to the older apps I saw they had a "visual" connected with each setting - it appears the Auto selection might indeed accomplish what you describe. As far as why everything doesn't use "Auto" I can only surmise that for people with three phase configs that want the system to shut down if one of the phases fail it would make sense to have the system programmed with set phase output? That is only a guess though.
 

rv_solar

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May 15, 2022
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5
I wish I knew more about Victron programming. From my limited exposure to the older apps I saw they had a "visual" connected with each setting - it appears the Auto selection might indeed accomplish what you describe. As far as why everything doesn't use "Auto" I can only surmise that for people with three phase configs that want the system to shut down if one of the phases fail it would make sense to have the system programmed with set phase output? That is only a guess though.
Thanks - that makes sense about those who specifically want set a phase output. Cheers!
 
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houlster

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Mar 31, 2022
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Also note these units will only draw 120V/25A each from shore power. To get above that it will use PowerAssist to supplement that shore power AC via the inverter and battery banks.

Your RV is setup for each phase to be 50A so you may have have to reduce your expectations on what you can run.

Why is that? User manuals for both the Multiplus & Multiplus II 3k units clearly show max output on L1 to be up to the 50A input plus 25A of power assist, so 75A total.

Obviously, if shore power isn't 50A you can't get that, but if it is, there's nothing about the MP that limits how much of it can be used.
 
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