The Sans Regulations supersedes the inverters installation manual, the documents state that all installs should adhere to Sans10142

 

the bonding relay would make this a non compliant installation as the regulations require a permanent earth neutral bond on the output side of an alternate supply source before it is wired to the changeover switch input.

 

Non essential/essential loads needs a separate neutral bar, the inverter must have a separate grounding rod, reason being if the changeover is switched to the inverter the Bond is broken on the utility side and effectively on all essential loads if there is no earth spike with a bond the inverter wont have a zero voltage reference.

I haven't installed solar yet but I was thinking about this whole earthing issue and it seems to be overly complex with regards to regulations. I am wondering if an isolation transformer would not be simpler option and avoid violating any regulations?

In other words install a 230 to 230 VAC transformer between the supply/grid and the inverter with it's own supply DB (and RCD if required).

Then permanently ground the output of the inverter to earthing spikes so that the  downstream RCD in the main DB always works on the local earthing point. Then there is always an earth reference even though it is not connected to the grid earth. If one is practically off-grid and only needs say 1kVA to top up batteries on cloudy days then the "shore power" to be imported from the grid can be limited on the inverter settings. This keeps the isolation transformer small and cheap enough. It shouldn't matter if the two earths or neutrals on each side are not referenced to each other. If Eskom/Muni screws up and has a floating neutral on their side (I've seen that happen more than once) it also won't cause any issues on the inverter side because the voltages are decoupled and float relative to each other.

Would something like that work and still be legal or is there specific wording which forces one to carry the grid earth into the main DB for earthing requirements?

Edited October 13, 20223 yr by Surge

On 2021/03/22 at 6:17 PM, ianm said:

Okay, thanks, so then the circuit would be:

Thank you ianm for a great drawing!

 

I know this is an old Post, but this is how I plan to wire mine up. It makes perfect sense.

My question is regarding the Earth Wire

1) I assume that the main earth wire from the Grid is wired to the Grid "Input" terminal on Inverter.

2) I am confused about the Earth wire on the Load Side. Must this be wired from the Load terminal on the Inverter to the Earth bar? OR should I use the "DB earth" that was bonded on the load side?

 

Any help will be appreciated!

 

Kind Regards

Jason

 

Jason good question I also want to know. On Sunsynk documents it says not to connect anything to the load earth terminal if you in SA. 

I rang it out Jason, all 3 earth terminals on the 5kW Sunsynk is internally connected. So u only need to connect to one of them with your house earth.

On 2023/04/14 at 10:23 AM, Karl Daschner said:

Jason good question I also want to know. On Sunsynk documents it says not to connect anything to the load earth terminal if you in SA. 

Which SunSynk document is that? Do you have a link?

this one

1 hour ago, Karl Daschner said:

this one

This diagram is a bad example. The inverter does not get wired like this in South Africa. The load and grid neutrals have to be split. The diagram shows them wrong as connected together. 

2 hours ago, Karl Daschner said:

this one

This is the drawing I was also using that was confusing me.

I agree, this is not how a typical installation in SA is done.

I followed the drawing from @ianm but the earthing was not show.

Thank you so much for all the advice and input.

Really appreciated.

 

Kind Regards

Jason

On 2021/03/22 at 6:17 PM, ianm said:

 

What would the reason be to install the four 25A MCB in front of the SPD's?

7 hours ago, Vaal said:

What would the reason be to install the four 25A MCB in front of the SPD's?

So that they can trip and cause a break to the surge unit. Once tripped the surge will have to jump the gap to go further to cause damage. 

My own way of reasoning. 

2 hours ago, Scorp007 said:

So that they can trip and cause a break to the surge unit. Once tripped the surge will have to jump the gap to go further to cause damage. 

My own way of reasoning. 

But if the breaker trips, then there is no spd in that line. That sounds counter productive. There is no mcb in front of my spd's. The spd is a sacrificial device. 

Edited May 7, 20233 yr by Vaal

29 minutes ago, Vaal said:

But if the breaker trips, then there is no spd in that line. That sounds counter productive. There is no mcb in front of my spd's. The spd is a sacrificial device. 

You are spot on. Then there is no surge to clamp and no surge to get to the MPPT. 

As unproductive as you see it if you look into power supplies you will see it is very common. Only fuses are normally used as it creates a much longer gap. 

 

 

Fuse between connector and MOV. 

Edited May 7, 20233 yr by Scorp007

14 minutes ago, Scorp007 said:

You are spot on. Then there is no surge to clamp and no surge to get to the MPPT. 

As unproductive as you see it if you look into power supplies you will see it is very common. Only fuses are normally used as it creates a much longer gap. 

 

 

Fuse between connector and MOV. 

I would take a lead from one of our great installers. It does not mean if you don't have fuses/MCBs yours is done the better way. Yes cheaper for sure. 

39 minutes ago, Vaal said:

But if the breaker trips, then there is no spd in that line. That sounds counter productive. There is no mcb in front of my spd's. The spd is a sacrificial device. 

If you install breakers before a SPD, someone can easily restore power if the device shorted. There won't be surge protection on the system but someone sold four more breakers and a larger DB.

Now I missed you. You get a surge from grid side, due to what ever reason. As soon as the spike hits the spd it divert it down to earth and no more spike and possible the spd is no more anymore.

On the drawing there isn't any mention of pv input but I would think it will work the same way. If you get more than one decent spike and the spd is blown then the next "soft/sensitve" spot in line will take it on the nose and go poef. 

21 minutes ago, Vaal said:

Now I missed you. You get a surge from grid side, due to what ever reason. As soon as the spike hits the spd it divert it down to earth and no more spike and possible the spd is no more anymore.

On the drawing there isn't any mention of pv input but I would think it will work the same way. If you get more than one decent spike and the spd is blown then the next "soft/sensitve" spot in line will take it on the nose and go poef. 

Yes I agree. But once the fuse is blown then no 2nd spike and no poef either 😅

SPD can take a number of spikes it depends on the intensity. 

What about the solar panels? They are the example used. 

 

Edited May 7, 20233 yr by Scorp007

12 hours ago, Vaal said:

What would the reason be to install the four 25A MCB in front of the SPD's?

SPD’s fail in 2 ways.

1) open circuit

2) Short circuit

 

These MCB’s on there to protect against short circuit scenario 2)

 

The sizing is related to the cable size. It is there to protect cable.

 

It is also in the Sunsynk manual, but on the earth wire. Does the same thing.

 

Kind Regards

Jason

10 hours ago, jraydoran said:

SPD’s fail in 2 ways.

1) open circuit

2) Short circuit

 

These MCB’s on there to protect against short circuit scenario 2)

 

The sizing is related to the cable size. It is there to protect cable.

 

It is also in the Sunsynk manual, but on the earth wire. Does the same thing.

 

Kind Regards

Jason

Aha. Thank you Jason.

I thought they all expired in a open circuit condition. 

Please send me clear picture s of your wiring diagrams 

Just wanted to ask is it okay if I use a 40A MCB on the supply and output of the SunSynk 5kw inverter

 

Just wanted to ask is it okay if I use a 40A MCB on the supply and output of the SunSynk 5kw inverter

Yes but use correct wire size 10mm²