Neutral wire voltage, Ground-bonding, and insufficient Short-circuit current measurement

[Tunnerus]

Hello everyone, we have the following challenging situation with our offgrid cabin setup, highly appreciative of any tips / help / questions from you!

We are expanding our electrical installations in a new building extension. The electrical panel had 5x10A 1x16A, now we are trying to add 3x10A and 6x16A for the new.

((Needless to say, our inverter is much to small for all of this and at some point must be upgraded to something bigger))

The issues started when our electrician (not familiar with offgrid at all) needs to make formal measurements of voltages and of short circuit current (amperage).

Firstly, he measured 80V in the N wire and 150 in the L (delta being 230V), which threw a fault in the "Fluke" meter he was using.

Then, after installing a proper grounding rod and connecting the ground to N in the electrical panel, the N was 0V and the L 230V, and the Fluke-meter was happy to start measuring short-circuit currents.

==> However, here the real problems started. Per regulation, our six 16A fuses require at least 100A short circuit current, and he was not able to get any Fluke-readings over 80A. (With effort, the three 10A fuses needing >62,5A passed their tests).

Any tips, thoughts, tricks, ideas?
* should we bond the neutral and ground in / at the inverter, or in the electrical panel (as-is)?
* Or must we change the inverter to a new one?
* Have newer (larger) inverters solved the issue of ground-neutral-bonding to secure zero volts in the neutral?
* Will bigger inverters create higher current results in such tests?
* Is it the age of the inverter which was creating the voltage skew from N0V/L230V to N80V/L150V? If yes, why do old inverters slide into this type of fault?

Here's the setup: MPP Solar's PIP-3024GK (3kW/24V installed 2018), 8x285Wp solar (2018), 3 LFP batteries (~100+135+280Ah, from 2020 and 2023), EU system i.e. 230V AC at 50Hz.

 

[wpns]

Yes, lack of N-G bond could have caused the N-G voltage, but that’s solved.
Not sure what he’s trying to ‘Fluke’ measure short circuit current with (or for), can you explain? If he thinks he’s going to get 100 amps from a 3KW inverter he’s not paying attention.

 

[wpns]

Yes, lack of N-G bond could have caused the N-G voltage, but that’s solved.
Not sure what he’s trying to ‘Fluke’ measure short circuit current with (or for), can you explain? If he thinks he’s going to get 100 amps from a 3KW inverter he’s not paying attention.

If he’s using (hopefully) short duration current pulses to test the wiring, maybe you just haul in a 25 kW generator for the day.

There are other ways of testing the wiring.

 

[Tunnerus]

Yes, lack of N-G bond could have caused the N-G voltage, but that’s solved.
Not sure what he’s trying to ‘Fluke’ measure short circuit current with (or for), can you explain? If he thinks he’s going to get 100 amps from a 3KW inverter he’s not paying attention.

Thanks @wpns! There appears to be a regulatory requirement to establish the amperage at which short circuits occur, and if they are too low, they will not trip the automatic fuse, in this case 16A. The electrician explained that a short circuit has no load and therefore the power / wattage may be slightly hard to assess. I am just relaying what the guy told me.

 

[Tunnerus]

He

If he’s using (hopefully) short duration current pulses to test the wiring, maybe you just haul in a 25 kW generator for the day.

There are other ways of testing the wiring.

Thanks for your reply! He claims to test not only the wiring but also that the fuses he installed will actually trip when a short circuit occurs.

 

[wpns]

He

Thanks for your reply! He claims to test not only the wiring but also that the fuses he installed will actually trip when a short circuit occurs.

When you say 'fuses' you mean 'circuit breakers' that you can reset? When he does his test, and the breaker doesn't trip, does the inverter shut down? You could argue that the output current protection device in the inverter trips, so it doesn't matter if the downstream circuit breakers do.

However, at the end of the day, he's the local expert (even when he's wrong), so rent a 25KW generator for the day and let him 'test' to his heart's content, and go on with your life.

And yeah, if you are expanding your loads you are going to need a bigger inverter, and more batteries and more panels, but that's a discussion for another day.

 

[wpns]

The electrician explained that a short circuit has no load and therefore the power / wattage may be slightly hard to assess

Which is the part that leads me to believe he doesn't know what he's talking about, which may or may not be relevant. If what you want is for him to do the wiring 'to code', and he wants to test 'to (what he thinks is) code', and he's got some fancy piece of test equipment, there's not much you can do but grin and bear it.

 

[Tunnerus]

Ye

When you say 'fuses' you mean 'circuit breakers' that you can reset?

Yes circuit breakers

 

[Tunnerus]

Thanks guys, I will for sure just let him install his 10A circuit breakers and then ask him to leave the 16A ones for when I get the larger power source.