Inverter Install Compliance

[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