Floating Neutral

[mainline]

I back fed the system, via an unused cooker breaker
in the kitchen

, I have found, but not yet purchased a special
change over breaker, where the Grid is on the top at one
side, the solar is diagonally across at the bottom and the
consumer unit is on one of the other empty places, I don't
remember which

, I need more information, to see that it is
robust enough, to be safe, similar to the one below, which
is 125 amps.

 

[MikeM3]

Don't worry mainline, I have no intention of going into
the home, grid, electrics, I just wanted to see if it was
possible, but with no earth, it is dangerous, this will
be a stand alone off grid system, the whole project,
was an experiment.

I learned some interesting stuff during the process.

Mike.

 

[MikeM3]

German energy suppliers are in crisis, all because of solar energy
and lack of control, below is a copy and paste, of their version of
the problems, plus a short video explaining, "Balcony Solar", which
is retailed on the open market and is legal there, it isn't legal here
and that is why I am off-grid!

Mike.

The drop in Germany's electricity production as well as in total energy consumption in early 2024 was in part caused by weaker economic development, warm weather, and high energy prices, said energy industry initiative AGEB earlier this week.6 Jun 2024

 

[mainline]

Hi Kim, I back fed the system, via an unused cooker breaker
in the kitchen, I have found, but not yet purchased a special
change over breaker, where the Grid is on the top at one
side, the solar is diagonally across at the bottom and the
consumer unit is on one of the other empty places, I don't
remember which, I need more information, to see that it is
robust enough, to be safe, similar to the one below, which
is 125 amps.

Mike.

View attachment 117138

The change over switch should be ok to isolate the mains from the generator.
They also do automatic ones that can disconnect the mains when the generator comes on or vice versa.

 

[Spanners]

Hi Kim, I back fed the system, via an unused cooker breaker
in the kitchen, I have found, but not yet purchased a special
change over breaker, where the Grid is on the top at one
side, the solar is diagonally across at the bottom and the
consumer unit is on one of the other empty places, I don't
remember which, I need more information, to see that it is
robust enough, to be safe, similar to the one below, which
is 125 amps.

Mike.

View attachment 117138

Hi Mike,
Pretty sure you can't safely ground one side of a floating Neutral invertor. So that maybe a big problem.
Dependant on the type of house earthing arrangement, TNC-S (pme) TN-C, TN-S, etc of the supply, the DNO may require some specific changes (N- Earth bonding switching) when you go into Island mode. You can't do any of this without checking requirements with them anyway. You may not have to comply with G98 as you don't connect to the grid but your installation still has to pass close inspection and testing.
Out of interest how do you know the RCBO or circuit breakers you have will meet the 0.5sec L-N short circuit disconnection times when off mains when powered from the invertor.
Do you know what happens to the invertor during a short circuit? What fault current can it supply for how long? or does it trip.
Your lighting RCBO tripping maybe something to do with where you are conneting Invertor outputs into the board. You turned the incomming L-N mains power off but the Earth is still connected to Neutral and some RCBOs have a white wire that goes to Earth, but look its all very unathodox and again I say just don't go there.

Regards kim

 

[MikeM3]

Tanks again Kim,

One of the reasons not to connect to the grid, is the RCBO on the lights,
it trips and I assume, it is because there is no earth, strangely the RCD
didn't trip.

Having spent days and hours of searching for answers, I haven't found
any, that explains earthing a floating neutral, it may be another live as
somebody said that there may be.

I have seen copper pipes being driven into the ground and a floating
earth from a generator attached to it, but only after a link between the
neutral and earth was installed, there is no such thing inside an inverter,
the only conclusion I can see is a balancing/equalising transformer, you
only need live and neutral in and it gives out the same, plus earth, but
the price for a 4Kw one is too much, so some stand lamps will do for
light I think.

There are several coils inside the inverters, so the neutral must be as it
is because of the electronic side of the magic. Below are two images of
the innards.

Mike.

 

[newfutile]

I cant believe the panels are 12 volt 1 KW that would be 83 amps per panel, i suspect some chinese figure manipulation is going on here.
In any case you cant connect it in any way shape or form to an existing installation.this can only ever be a stand alone system maybe in combination with some batteries and a charge controller.

 

[MikeM3]

I have 6 panels, newfutile, with 6 controllers, 4 heavy-duty batteries,
the system will stand an electric Kettle of 2.4Kw, so there is some
power available.

Mike.

 

[Spanners]

Tanks again Kim,

One of the reasons not to connect to the grid, is the RCBO on the lights,
it trips and I assume, it is because there is no earth, strangely the RCD
didn't trip.

Having spent days and hours of searching for answers, I haven't found
any, that explains earthing a floating neutral, it may be another live as
somebody said that there may be.

I have seen copper pipes being driven into the ground and a floating
earth from a generator attached to it, but only after a link between the
neutral and earth was installed, there is no such thing inside an inverter,
the only conclusion I can see is a balancing/equalising transformer, you
only need live and neutral in and it gives out the same, plus earth, but
the price for a 4Kw one is too much, so some stand lamps will do for
light I think.

There are several coils inside the inverters, so the neutral must be as it
is because of the electronic side of the magic. Below are two images of
the innards.

Mike.

View attachment 117148
View attachment 117149

Hi Mike,
Floating Neutral. I'm really over simplifying below, but using generators as an analogy is possibly easier to understand.
In a large 3 phase 4 wire generator the winding centre point is Neutral. This is usually (but not always) tied down to the metal of Larger output generator frames.
Small single phase generators are often multi voltage. i.e 1 x 220VAC and two lots of 110V maybe. In any event think of it as two seperate sets of windings in the generator. So 4x ends all of which you could call live. No true Neutral. Dependant on how the generator selection switch is configured you either series up these two windings to get 220VAC or you configure so you have two seperate windings each putting out 110V to two seperate 110V sockets.
Think of floating Neutral as no Neutral until you tie the end of a winding down to ground (Ground being tied to Neutral back at the substation). Some small generators (Honda for sure) do have options to ground one of the outputs but this is not so straight forward when you have various voltage outputs possible. You have to be guided by the manufactures information and grounding can open up another set of regulations you have to conform with. The same with the invertor.

If you think of a lower cost invertor as small generator. It says it has a floating Neutral, meaning in this case, a source of electronic voltage generatation designed to be used isolated from true terafirma ground. You at present are choosing to ground one side of your output. This may or may cause damage. What does the manufacturer state on this? The device you have is really for use feeding a few bits of equipment in a small isolated from Earth system, segregated from your house, where it is safe. You may have an Earth point on the invertor case that can be grounded, but often electronic equipment uses what might be called a technical earth, which is just connected to capacitors and chokes and used to comply with CE requirements to reduce emmisions interference. Also manufactures may tie down one side of the DC input to the tech earth, complicating the issue more.
Thats it from me. Hope that helps.