I upgraded my system from a 5 kVA MultiPlus II to a 10 kVA MultiPlus II, but I’ve suddenly run into a problem.
I have this system because my house connection is 16 amps, single-phase, and I have an electric car, boiler, etc. Since the 5 kVA was just barely sufficient, I upgraded my system to a 10 kVA (connected in the same way).
The system consists of:
Several MPPT chargers
Cerbo GX
MultiPlus II 48/10000/140
Everything runs through the MultiPlus, so the measurement is done internally in the inverter.
I’ve seen this problem come up before, and suggested solutions were:
Wires too thin (AC in is 4 mm², AC out is 4 x 6 mm² on out1 and out2 )
My AC input is not very stable (under load the voltage drops quickly, and when feeding back it rises quickly, but still within 10%)
Disabling UPS mode (I’ve tried both options)
Changing the grid code (I’ve already tried EU grid code and no grid code)
The issue shown in the video occurs after 2 minutes or after 10 minutes (completely random), sometimes once, sometimes several times in a row, with or without loads connected, and with or without the load connected to the output (the house is on a 2-position switch).
Does anyone have an idea in which direction I should look for the cause of this problem?
Aside from the small cable which introduces a whole host of things… Se the input current limit down as far as 10A set weak ac on. (So no grid code) Treat it like a poor undersized generator.
You have a poor/high resistance connection somewhere. It could even be in the contacts in a breaker.
Are you actually trying to feedback? Not advised until it is installed with decent cabling.
The DC side should have 2x50mm² there and a battery that can supply the surge. If your ac is weak its fine when the DC is robust. If there is poor crimping and not so great connection there, it will also contribute to stability issues.
all the sound that you hear are from the multiplus 95% shure but i will check if i hear any arcs
i will put the gridcode agean on “no gridcode” and the current limit on 10 ampere and weak ac (done it before but maby i missed something)
i will install a new main breaker just to be shure
the cables 4mm2 in is the same size as my main cable, in the old situation with the 48/5000 i feeded 3300 watt in by a seperate solar inverter becouse my victron inverter is not feeding back (the mppt’s are charging the battery, when the battery is full they stop charging).
the dc cables are 70mm2, 50 cm between the inverter + and fuse box and 70cm between the inverter negative and negative busbar. there are the mppt’s connected to, 35mm2 150 cm to a 100 amp mppt and 150 cm to 95 amp smaller mppt’s. and 2 x 70mm2 150 cm to 560 ah lifepo4 battery’s.
i checked the temperature of the cables and connections after i 1 hour of inverting 6500 watts and more at the output with a heat camera.
do you think i need even more cables or are these fine
Is this still happening?
The surges (where everything goes really bright) being seen on the video are really not good for anything.
What does the GX record in terms of voltage fluctuations?
My main suspect here is a bad neutral, either from grid or in the house/inverter installation.
The other is a poor earth connection.
The arcing can be the transfer switch in the inverter, that is a bad thing. It is interesting how it does not happen. Ervy time there is a connect.
Switch off grid charger in the inverter as well that is technically a load. If your solar is sufficient then that will also be a good move to lessen the issues.
While this is a good check on any installation; power generating and stability run on a whole lot of other laws of physics. I have found in many installations where the minimum dc sizing (from the manual) is not met there is the installation with many weird problems.
Are you running the ess assistant?
If you are, switching more to an ac ignore set up would probably be better with no grid charging so you can have some grid assistance for loads direct when needed but keep solar for battery charging and load support when grid is disconnected.
