I am looking into having installed batteries in my home with three Victron inverters and a safe ‘island’ solution to keep my house powered whenever the grid falls out. I have done some preliminary research and it looks like this safe island can only be achieved if the AC is connected to the AC in (AC from the grid) as well as the AC out (AC to the house and the solar converters) of the Victron converters. The solar converters are already installed in my shed that is some 50 meters from the house (main switch). The batteries and the three Victron converters should also be installed in the shed. The issue I am facing is that there is only one AC cable running from the house to the shed and it is virtually impossible to get a second one in place. Even installing communication wires would be a burden. I have, however, ethernet connection between the house and the shed.
Is it possible to work with one AC cable between the house and the shed and keep the house powered during grid disconnection without compromising safety? What would be the best solution to achieve this?
Simple answer is no, not for an application that requires battery backup, no one ( three core cable ) of positive Negative and earth will not do, you need at least a 5core cable not cheap either
Many thanks Daza for your advice! Not the one I wanted but clear and not unexpected. I may have to find another spot to install the Victrons and batteries. May be one floor below the main switch. But my mississ may not like that.
Moving it near to the main switch would mean your able to interrupt the main with the multi, should you have the room to house everything, but remember now in the dwelling extra care and precautions, in the UK we are going away from installing in a dwelling or to put better a habitable room.
You also want to install a clamp meter on the solar so it knows how much is coming back from the shed, you may have to install the clamp inverter side of the cable as you said you have issues with getting cables to the shed location, Which shouldn’t present an issue.
Well, after some research I have decided not to install the Victrons and batteries in the house itself for reasons of safety (fire and gasses) and comfort (humming and fan noise). Am I right that, in the situation that I do not have a second AC cable from the main switch to the Victrons and the grid blacks out, I can still easily start up the Victrons, get my PV system up and running and provide my house with AC after having switched off the connection between my house and the grid (i.e. the main switch) manually? Or would that also require reconfiguring the Victrons each time the grid blacks out?
Not sure what you mean but the Victron will need to interrupt the main supply and everything you want to run on a grid down situation be connected to AC out 1 ie Critical load. Feeding back through the input of the Victron is just like peak shaving it will try to cover as much as it can but there is no home backup.
If your back to the shed you still need another three core run or at the least 5 core cable if you just want the one cable but might be wise to bury a pipe so it’s easier in the future. You don’t need two wires, you need a proper transfer switch inorder to separate the input and AC out so that it can be bypassed should the unit fail. The AC wiring on a Multi is only one grid input, any how you want the whole house backed up the multi has to be in the middle to act as a gateway device ie stopping back flow to the grid. There is no way to cheat this.