I’m designing a three-phase system to power my house, mainly throught solar power (15 to 18 kwp) with the help of grid power (currently I have a 27kva ongrid three phases system), and with some batteries on top of that.
I’ve been considering using multiples Victron MPPT solar charger with 3x Multiplus II 8000VA, I’ve read on victron Multiplus II datasheet that the Multiplus II 8000VA (and over) does not natively support three-phase system and that you need to add an external transfer switch (seems to be an interrupting capacity issue) : https://www.victronenergy.fr/media/pg/MultiPlus-II_External_Transfer_Switch_application/en/index-en.html
However the document states : Note that this setup is intended solely for generator-based systems and is not certified for use with grid-tied systems.
So here are my questions :
Is this required for grid-tied system, or should you just wire the system like a 3 x 5000VA system.
Also, is the firmware update recommended in the same document still needed ? (I can’t find this version of the firmware on victron pro support site).
In this case, no need for custom firmware or anything in this kind of setup ? I can just setup the phase binding and the ess assistant through the VE bus system configurator and VE configurator, as showed on the training videos ?
I may also have a sizing question … but I’ll think this through before asking something basic …
@M_Lange https://www.victronenergy.fr/media/pg/MultiPlus-II_External_Transfer_Switch_application/en/index-en.html
Referring to the contactor used in this example as a “transfer switch” I find is misleading. A transfer switch has 3 sets of terminals, a contactor only 2. In terms of functionality, a transfer switch will isolate one set of contacts, whereas the contactor example used leaves the inverter output paralleled to the load circuit. Maybe a bit picky in terms of terminology, but it could confuse people…
This document describes a way to replace the internal transfer relays with an external contactor.
AC IN is only used to measure the input voltage for synchronization and the internal transfer relays are always open.
The AC Out and the grid/generator are in parallel if the external contactor is closed.
It is referring to the contactor as a transfer switch - which it technically is not. The intent of the article is fine.
The contactor is being used as a Bypass relay .
In the Victron world the internal relays are always called “transfer relays” or “transfer switch”.
So it’s just logical to call this “external transfer relays”.