Inverter Install Compliance

[hartdev@hotmail.com]

I have had issues with Onesto breakers now on a few occasions. In one case a 7kw Instantaneous Water heater was running on a 20amp Onesto circuit breaker and there was no tripping.
I think we all know how dangerous that was.
I have been using Schneider circuit breakers almost exclusively for 2 years now and not had one failure, 2 years is not very long but so far i'm impressed.
I found this thread very interesting and informative.
I have almost completed the electrical installation in a nice new home in Cape Town. The company which installed the solar and battery backup inverter etc were very quick, in and out on a day I was not on site. They have requested that i rewire the D.B to isolate backup circuits from the non backup circuits. By doing this i would have to disconnect the backup circuits from the earth leakage device. The solar installers don't seem to have an earth leakage device at all in their though so I am trying to find out if the backup inverter has some sort of built in earth leakage protection, I downloaded a manual and saw nothing mentioned. (Victron 24/3000/70).
Does anyone know if we require a specific type of energy dispenser to allow our client to feed back into the grid? This is something I was told the solar installers would see to but no change has been made to the standard ED installed by ourselves.
The solar has not yet been switched on to feed back into the grid, i am worried it could cause some sort of damage.

[Tonye]

I have almost completed the electrical installation in a nice new home in Cape Town. The company which installed the solar and battery backup inverter etc were very quick, in and out on a day I was not on site. They have requested that i rewire the D.B to isolate backup circuits from the non backup circuits. By doing this i would have to disconnect the backup circuits from the earth leakage device. The solar installers don't seem to have an earth leakage device at all in their though so I am trying to find out if the backup inverter has some sort of built in earth leakage protection, I downloaded a manual and saw nothing mentioned. (Victron 24/3000/70).

I will try and answer your questions to the best of my ability & also with reference to SANS 10142 regulations.

If alternate power is to be fed into a DB board together with Grid power, you need to have a split neutral bar. One for Grid power & one for the alternate power.
Both power sources earth terminals need to be earthed to the main earth terminal.
You also need to have a seperate main switch to disconnect the alternate power to the main DB.
Also a power on indicator (visible or audible) shall be provided together with a notice indicating that the alternate power main switch shall also be switched off in an emergency.

With regards to the earth leakage, to my knowledge no inverters have built in earth leakage protection. This is because inverters have a floating neutral with no reference to earth. By measuiring voltage on the inverter output, one usually finds Live-Neutral = 220v, Live- Earth = 110v & neutral- Earth = 110v.
To resolve this problem & ensure correct operation of an earth leakage unit, you need to bridge the neutral to earth on the inverter output.
Some inverters have an auto neutral to earth connection when the inverter is running in inverter mode.
Bear in mind, if the inverter does not have an auto neutral to earth connection and you bridge the neutral to earth on the inverter, the supply to the inverter charger (if it has a built in charger) cannot be fed from a circuit breaker connected to the grid fed earth leakage unit.
The earth leakage would trip, as it sees the bridged neutral to earth as a fault.

The regulations also state that if alternate power feeds plug circuits, they have to have earth leakage protection.

If not all plugs are being fed from the alternate power source, you would have two earth leakage units. One for grid fed plugs & one for alternate power fed plugs.

I have just completed an inverter installation on a three phase board feeding single phase loads with split neutrals. The same would apply on a single phase supply.

I have attached a basic wiring diagram showing essential wiring

wiring diagram new.pdf

Hope this helps

[AndyD]

To resolve this problem & ensure correct operation of an earth leakage unit, you need to bridge the neutral to earth on the inverter output.
Some inverters have an auto neutral to earth connection when the inverter is running in inverter mode.
Bear in mind, if the inverter does not have an auto neutral to earth connection and you bridge the neutral to earth on the inverter, the supply to the inverter charger (if it has a built in charger) cannot be fed from a circuit breaker connected to the grid fed earth leakage unit.
The earth leakage would trip, as it sees the bridged neutral to earth as a fault.

I think it's against the regs to have a neutral-earth connection within the installation itself, there's implications for fault current alternative paths etc. I'd need to comb the regs when I've got time in the office to find the relevant paragraph.

[DieterT]

@Tonye
Just to add

In regards to plug circuits being under earth leakage. All plug circuits shall have earth leakage protection wheter or not from mains or alternative supply.

It's only dedicated circuits which can be taken off earth leakage protection.

*take note of conditions to be adhered*

Cutting a normal plug top off and putting on a dedicated plug top so to fit the half earth plug socket does not make the appliance acceptable for use on non-earth leakage protected plug sockets

Also, where visual (light indication)/audible indication is required for alternative supply is where the alternative supply has automatic change over. Where manual change over is used, notice of alternative supply is sufficient. Also rember that all DB boards fed from alternative supply should have this indication, including sub DB boards.

@Andy
You are very much correct in saying that. The earth neutral bridge is only allowed on the supplier side (thus a little box between the alternative supply and DB board with earth neutral bridge plus indication of such is sufficient)

Can't remember the page in SANS10142, but it basically says that the earth neutral bridge is not allowed to be made on the consumer side, thus on the DB board.

[Dave A]

I think it's against the regs to have a neutral-earth connection within the installation itself, there's implications for fault current alternative paths etc.

Bear in mind any given portion of the installation is only going to be powered by one supply at a time. The trick is to configure everything in such away that the neutral-earth connections are only on the (various) supply sides. (i.e. on the supply side of the crossover switch).

That said -
This is normally easily achieved where the alternative supply is a generator (excluding V-0-V generators with a centre tap to earth). The situation where the alternative supply is an inverter and the crossover switch is essentially incorporated in the inverter supply device does look like it might pose some special challenges.