Solar Panels supplying new build

[SSE]

So...who has experience in this on here?? Not me for sure. Basically roughed in a new build for someone, was told he was haggling with the local authority over the price for putting power to his house, it's in the countryside. So I basically kept plodding on, got it all just about done, fitted dual load RCD consumer unit then asked again about the power...turns out he's given up with them & going to run it off his solar panels that he has outside a big shed that contains batteries for storage. He showed me the setup he has, he's definitely spent a few quid on it for sure but it's not my area of expertise. He has no electric shower or electric cooker in the house so he will actually have enough to power it, just him & his wife in the house. Is there anything I should be looking out for, making sure of as I want to make sure it's done correctly. Just having a quick scan online & seeing the max zs values etc & they seem high high! He's going to install an earth rod, what sort of figures are acceptable for the main Ze etc for this. Is a dual RCD consumer unit ok for this kind of install or would it be better having separate RCBO's, does it matter? Any advice be greatly received.

 

[SSE]

Should have also said he’s done the solar side if things, inverter etc & run the supply cable, just up to me to do all the consumer unit work.

 

[timhoward]

Should have also said he’s done the solar side if things, inverter etc & run the supply cable, just up to me to do all the consumer unit work.

At this point is the inverter connected to anything, or is that yet to happen?

 

[plugsandsparks]

As well as the obvious earth arrangements and RCDs that can handle DC injection (check inverter data ) - i would expect he is going to need a generator otherwise his marriage will be at risk...........so think about how that is going to work. Its outside my experience as i only do grid connected but i can see where the issues will arise. There will be days when he has no meaning full solar and flat batteries so get ready for that realisation

 

[timhoward]

Two more questions:
1) Is it an inverter designed to run without a grid supply. I've only met ones which shut down in such circumstances, but I'm sure they exist
2) Does the inverter have a N-E link?

 

[SSE]

At this point is the inverter connected to anything, or is that yet to happen?

I’ve not been out yet but he says the inverter is connected yes, he’s been using it to power the caravan he has been staying in whilst building this house. He has an isolation switch that feeds a supply cable to the house but he says it’s turned off just now. He says there’s 230v at it but he’s saying the impedance is super high. He does have an old impedance tester but not sure what sort of condition it is in. He seemed to be having trouble getting a decent reading so says he had to move the earth rod but it’s still high.

 

[pc1966]

Not my area of expertise but for my 2p is this is probably a TN-S supply, though with an earth rod that may only be 100 ohms or so to true Earth. But that is not your fault impedance (i.e. Ze is really back to the supply = inverter via CPC, not earth-earth as TT implies) but what it is ain't so simple!.

If the inverter is anything like the various 5kVA UPSs I have played with then you might see reported PFC from around 100A to 2kA but you damn well won't ever see that level as they will just shut down for protection. The 2kA values I measured was just good voltage regulation when the MFT switches its internal load on/off to observe the voltage change and hence compute the supply's impedance and PFC, it is not measured under actual fault levels.

So while it is not TT, you most likely will still be depending on the RCD for fault disconnection for anything above the likes of a 16A B-curve MCB as the inverter just won't throw hundreds or even thousands of amps at any fault in the way the grid can.

As @timhoward has already suggested check the inverter is configured with a N-E link as a TN-S supply and is not floating IT style, etc.