Hi
How would you do this since the Multiplus do not work without batterie connection.
Same applies when one Multi dies and needs replacement i think?
Either the phases connected with MPII are dead oder a transfer switch needs to be installed to bypass all Multiplus devices?
My system:
3x Multiplus II 5000 (one per phase)
DIY Battery 48 V 16S 14,3 kWh
MPPT for 4 Strings of solar (13,2 kWp)
Thanks !
For that cases a bypass switch is always recommended.
Hi Matthias
Any recommendations for such a switch?
At home I use pureley Hager components
Hager has those: HIM406 as an example
Hager doesn’t recommend those anymore but if you only switch them without loads connected there is no problem (switch off the grid, switch the HIM and switch on the grid).
The “Kraus & Naimer KG63B K950” is also recommended often.
What about Hager SFT440 or equivalent ?
I am interested about the I-O-II switchovers in this “build layout”. Sorry for expression, English not my primary language.
I use two SFT440’s
These should only be operated when both sources are disconnected.
Now, my english may also be a bit insufficient, but I try:
When switching sources while both sources are connected, the Neutral wire should contact first, else there may be the danger of a star point shift when 2 hot wires contact first and a 400V circuit is closed through shared neutral connections of some consumers, because that “N” is not yet connected and floating. For example: L1 → Consumer1 → Shared N → Consumer 2 → L2
(The SFT440 don’t have an early contacting Neutral I read. Maybe typical for this build kind?)
Not an Issue, if you obey the rules. But wouldn’t consider them bullet-proof.
Edit: Hager is outlining that switches as 4-pole switch with NO (0) Neutral contactors.
One phase system here…
ok, then that risk drops to … 0 
@alexpescaru
If circuit is not complete the following can occur:
@dognose do you have an alternative for the SFT440. In case the risk is that high why would the SFT440 be marketed?
It’s a device that is completly legit, when used for it’s purpose:
It is just not suitable for the purpose of switching the neutral wire. (Even though, beeing 4-pin makes one easily assume that)
Therefore the datasheet also outlines that it has no pin designed for the neutral wire.
I’m currently looking for something like that as well, beside many factors like Grid form etc, you should check the datasheet for this, for example on the
You’ll find the information:
Switching type: N leading
And this is, what would be required to avoid issues when switching sources, while both (to be precice: any) sources are connected
(Just found that one recently, did not yet read much details, so don’t take this as a recommendation by now 
)
Sure, one could place a Sticker along with the SFT440, saying: Switch Off main-breaker, Switch off Inverter-Breaker - then switch source - but depending on country this may just be non-compliant with local regulations.
@dognose I agree with your point. However I also see shops doing it incorrect. That big device is not workable as I have 4 changeover switches in my installation. I will create a procedure for it.
I’ve now decided to go with the “Kraus & Naimer KG63B”. If the datasheet does not explicit mention a early contacting neutral, it may be outlined in the schematics:
(Note the tiny edges on the “N”, indicating, it will open last and close first.)
I’ve also found a (german) blog that put certain switches to a Test.
First Image shows a Hager HIM406 (Hager does outline it’s NOT suitable for this purpose) - second two images are from the Kraus & Naimer, as it should be.
Him406:
Kraus & Naimer opening:
Kraus & Naimer closing:
