Hi,
I have an off-grid Victron system that runs power to a pretty conventional cabin.
It’s come as a literal shock to realise the RCBO’s aren’t functioning properly.
I’ve been doing a bit of reading and think this whole situation might revolve around the “External ground relay” or rather a lack thereof.
Equipment rundown:
5kW PV
Victron MPPT
9.8kWh PylonTech LiFePo4 battery bank
MultiPlus II – 48/5000/70-50
Cerbo GX
Generator
We dug out and made a high quality grounding pit.
The AC1 Output of the Multiplus runs directly to a distribution board and has been (perhaps erroneously) treated just like a regular mains connection. Inside the distribution board is a few RCBO’s and the neutral is bridged/bonded to ground.
The assumption is: Using an external ground relay is going to fix this.
The questions are:
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Why are we treating AC power from the Multiplus inverter differently from mains? Would my system be described as ‘IT’ as opposed to TT or TN?
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What should the specifications of the ‘helper relay’ and the ‘external ground relay’ be?
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Will PowerAssist and PowerControl affect the appropriate sizing of the external ground relay if using this system with a generator?
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Should bridging/bonding of neutral and earth ONLY be done at the first distribution board and NOT at any downstream?
Please have a look at the description and wiring diagram I’ve provided.
I think the documentation states the ‘ext ground relay’ output of the Multiplus outputs 24v @ 200ma. I’m assuming this is 24vdc. Also, I’m running off the assumption both these relays should be normally open (NO) SPST type relays.
Helper relay: Will receive 24vdc @ 200ma at the coils. The power pins will then be used to connect the 230vac Multiplus line out to the coil of the ‘Ground relay’ and we will use a 2A inline fuse.
Ground relay: Sized to Multiplus, Will receive 230vac at one side of the coil. The other side of the coil will go to the Multiplus AC out neutral. The power pins will go to Multiplus out GND and neutral. This will effectively short the neutral to ground when the ground relay is triggered.
Thanks heaps