Off-grid Giandel inverter with 2 AC outputs wired into 2 separate RCBOs - weird or normal RCD behaviour?

[GeeGee50]

Hi All,

Looking for some advice into my build.

What I've basically done is add additional RCD protection to my 100% off-grid 12V 3300W Inverter system by adding RCBO breakers to both AC outputs of the inverter (12V Giandel 3300W 240V).

Things you should know for context:

• Inverter has no N-G bond
• Inverter has no RCD protection
• Inverter 2 AC outputs / receptacles
• each AC output is running into separate RCBOs via the consumer/sub panel (see images & schema)
• N-G bond made in the consumer panel

My assumption
- If a get a ground fault on one of the AC outputs, then only the RCBO for that output should trip

Here's what is actually happening:

• If I simulate a ground fault on AC output 1 (I do this using the Low Impedance (LoZ) feature on my Digital Multimeter (DMM) by touching the DMM prongs on the RCBO), then both RCBOs trips
• Same behaviour goes for AC Output 2, i.e. if I simulate a ground fault then both RCBOs trip

Here's my questions:

• Can someone please explain what is going on here? I don't understand why a ground fault on one of the AC outputs is causing both RCBOs to trip. It's as if both AC outputs are on the same circuit?
• Is this behaviour because of the way the inverter is internally wired OR because I added a N-G bond? Can I do additional tests to confirm which?
• Am I causing potential safety issues with my wiring?

Kinds Regards
GeeGee


Basic Schema

Consumer Panel