Hello , I've got an Multiplus 24V/5000 W and 2 bluesolar Mppt 150v/70W, all six years old 
I am upgrading my system with a multiplus 24v/5000 and 1 bluesolar Mppt 150V/70W. theidea is to have an output of 10000W . Is the new Multiplus connectable to the old one . and the nes Mppt connectable to the old one ?
Hi @MSA666,
Please have a read through these previous similar questions. They will answer a lot of the other questions you might have about your options, and the limitations.
If you have any other questions after reading through those, please come back and we can build on that knowledge.
https://community.victronenergy.com/questions/32367/victron-multiplus-24v-3000w-in-parallel.html
Hello , I whent trough the answered questions . But there is one explaining you can mix old and new , just upgrade the firmware . Other says it is not possible . So there is not a clear view .
The idea for our installation is to have a back up multiplus and raise the power to 10000 Va , our habve two power sources for 5000Va . Our installator do not get advise from the victron dealer here . So we are tryijng to get it cleared out . 2 photos show the references inside the existing Multiplus
Regarding mixing a previously purchased unit with a new unit;
I am always looking for a more precise and succinct way to explain the situation. The current best way is in the opening section of the three phase and parallel manual marked Important;
https://www.victronenergy.com/live/ve.bus:manual_parallel_and_three_phase_systems
Did you read that parallel manual, including the document explaining the VE.Bus firmware and hardware numbering, and are still unclear?
Both answers of mixing old and new may be correct, the details of which is the correct answer for your units, and your situation should be explained in those documents.
The relevant firmware number is not shown in the images you attached. When trying to identify the firmware number of the Multi, , the relevant number is in the green highlighted box in this image, not the red ones.
I cannot emphasise enough how important it is to get an installer that has experience with Victron parallel systems, and the support of a local dealer before attempting this project.
@Guy Stewart (Victron Community Manager) as an aside, as I read it (and I have a few times to make sure) there is a contradiction between parallel and three phase documentation and the firmware documentation.
The parallel and three phase document under “important” says the first four digits Ie. model must be the same as well as the firmware while the firmware document says that only the firmware version must be the same:
“ All units in one system must be the same type and firmware version, this includes same size, system voltage, and feature set. The type is indicated by the first four digits of the firmware version number.”
Vs
“For example 1942150 can be paralleled with 2642150.”
I have an off roading RV and I am planning to install 2 3k multi in parallel to improve output and provide reliability to the set up. thanks for sharing this information, very useful
