How to add a 2nd Victron MultiPlus ii 48/3000/35-50 120 volt in Parallel

[SteveBrown]

I have studied the manual, watched numerous YouTube videos and searched google for information. I have ordered an identical Victron Multiplus ii 48/3000/35-50 120 volt inverter to the one I have been using for the past year. I have been very confused about how to wire it into my existing system and how to configure it. I want to configure them in Parallel. I finally found today a diagram showing how I want to wire the 2nd multiplus into my system. Does this diagram look workable? I want to connect my breaker box L1 and L2 wired as described in this diagram. I want the AC1 Out on master(my old multiplus) wired to my L1 6-curcuit Transfer box and the AC1 Out on the new slave multiplus wired to my L2 6-circuit transfer box. With this arrangement I can select any or all of 12 circuits to run off my solar system. I currently have the AC1 Out on my Multiplus wired to both of the tranfer boxes and it's too easy to overload my current Multiplus.

 

[HangglidingPilot]

I assume you have watched this video regarding how to connect two multiplus ii

 

[740GLE]

Did you cross check your serial number on with the unit you’re buying to verify they are compatible to be run in split phase.

Victron has a caution that the Serial number of the units “shouldn’t be off” from each other when running split phase. IE order two units at once.

No idea if that’s just a caution, but I’d hate for you to find out the hard way some small change of a 2023MY unit won’t work with your new unit.

 

[SteveBrown]

I assume you have watched this video regarding how to connect two multiplus ii

No, I had not seen this video. Thank you very much for sharing this. I was planning to cannect them in "Parellel" but now I'm thinking I should select the "Split Phase 180" option.

 

[SteveBrown]

Did you cross check your serial number on with the unit you’re buying to verify they are compatible to be run in split phase.

Victron has a caution that the Serial number of the units “shouldn’t be off” from each other when running split phase. IE order two units at once.

No idea if that’s just a caution, but I’d hate for you to find out the hard way some small change of a 2023MY unit won’t work with your new unit.

No, when ordering from Amazon I only tried to select an identical unit to the one I have. I'm probably getting myself into a mess. I'm really getting worried about my future with this project. My single Multi has been working so nice I just wanted to make my system a little better. I started a year and half ago knowing hardly nothing about DIY solar. I've learned a lot but still a beginner.

 

[SteveBrown]

I have studied the manual, watched numerous YouTube videos and searched google for information. I have ordered an identical Victron Multiplus ii 48/3000/35-50 120 volt inverter to the one I have been using for the past year. I have been very confused about how to wire it into my existing system and how to configure it. I want to configure them in Parallel. I finally found today a diagram showing how I want to wire the 2nd multiplus into my system. Does this diagram look workable? I want to connect my breaker box L1 and L2 wired as described in this diagram. I want the AC1 Out on master(my old multiplus) wired to my L1 6-curcuit Transfer box and the AC1 Out on the new slave multiplus wired to my L2 6-circuit transfer box. With this arrangement I can select any or all of 12 circuits to run off my solar system. I currently have the AC1 Out on my Multiplus wired to both of the tranfer boxes and it's too easy to overload my current Multiplus.View attachment 283932

Could someone please verity that this wiring diagram will NOT WORK when configuring 2 multiplus in PARALLEL? I just read about phase rotation. It seems to me that L1 connected to AC1 IN on 1 multiplus and L2 connected to AC1 IN on the 2nd multiplus would cause a phase rotation alarm and the system would iqnore the grid and only work using the inverter from the battery. So it appears to me that I MUST wire AC1 IN on both multiplus's from either L1 or L2 in my breaker box.

 

[Glock24]

Your diagram looks good for split phase operation, but you need to configure them to operate in split phase.

Operation in parallel is different as that will add the output of both inverters and I think the wiring is also different.

Edit: Yes, parallel connection is indeed different. Here's the diagram.



You can run them in "parallel" the way you have them as long as you don't wire anything for 240V split phase. The way you have them each inverter will power each leg on the distribution panel but they will not be synchronized correctly, so only 120V operation is possible. Using anything in 240V split mode (with a connection to L1 and L2) will result in equipment damage or worse.

 

[SteveBrown]

Your diagram looks good for split phase operation, but you need to configure them to operate in split phase.

Operation in parallel is different as that will add the output of both inverters and I think the wiring is also different.

Edit: Yes, parallel connection is indeed different. Here's the diagram.

View attachment 284381

You can run them in "parallel" the way you have them as long as you don't wire anything for 240V split phase. The way you have them each inverter will power each leg on the distribution panel but they will not be synchronized correctly, so only 120V operation is possible. Using anything in 240V split mode (with a connection to L1 and L2) will result in equipment damage or worse.

Okay. This makes it very clear to me. I appreciate the diagram. I guess I'll forget wiring my slave to L2.

 

[HangglidingPilot]

No, I had not seen this video. Thank you very much for sharing this. I was planning to cannect them in "Parellel" but now I'm thinking I should select the "Split Phase 180" option.

Glad i can help. Keep us posted on how split phrase 240v works. I plan to add secondary multiplus-2 24v 3000va to create split phrase as well in next few months.