Silly solar question for the day

larkim

Not so much a silly question, as a practical one this time. My installation is part complete, with the inverter and various switching things up in the loft, brackets mostly installed on the roof, and effectively just the panels slotting in and connecting up required.

There is a "twin & earth" cable running from my meter box up to the inverter, via an isolation switch and what I presume is the solar meter. Is this the cable which both powers the inverter and sends power down to the consumer unit too? I suppose the question I am asking is "is the same cable used for both power source and solar generated supply"? I had wanted to try to get an Owl meter tagged onto the output of the solar, but I know I need a separate earth or neutral for that to work, so wanted to see what I need to ask the sparky to do when he arrives to connect it up on Friday.

Cheers!

Matt

bjohnson

I think that you will find that the inverter is connected to a normal 3-pin socket for its power. The cable that you describe is feeding the power from the inverter to the mains board?

Brian99_2

Larkim - tell the electrician you want to use the OWL on the output of the inverter.

It needs to clip round the A.C. live cable. NOT round a twin (or triple) cables, it measures the AC current passing through. See its instructions.

My inverter AC output is connected to the generation meter, then its own safety-cutout-switching-box then to the main meter then the grid.

larkim

@bjohnson - there are no plug sockets in the loft anyway, but I don't believe you are correct. The inverter is a Fronius IG30 for which the manual does not show any "plug in" options. It has a terminal block for wiring in 3 core AC (which I am presuming is both the mains input (to power the unit) and mains output (of the nice 240V AC) to supply the house / grid) and then I think 6 sets of 2 core DC (to take the "strings" of panels, which in my case I believe there will be two of). It appears to me that there is therefore only one cable which connects the inverter to the mains, and that it must therefore by definition be two way.

@Brian99 - yes, I'm aware that it needs either live or neutral, not both. I was just wondering if I should be expecting (from a Fronius IG30) a cable which is just live or neutral. I expect that to get a live or neutral separate I would have to get the sparky to specifically add that in for me, based on what I have written above.

Matt

thenudeone

bjohnson wrote: »

I think that you will find that the inverter is connected to a normal 3-pin socket for its power

Mine certainly isn't. It's wired directly in to the fusebox (via a large isolator)

larkim

thenudeone wrote: »

Mine certainly isn't. It's wired directly in to the fusebox (via a large isolator)

And is yours wired the way I have described? i.e. one cable which carries both the power to the inverter to make it run (and monitor the mains voltage) and the same cable to feed any solar generated power into the circuits the rest of the house?

Cheers!

Matt

Brian99_2

Yes... the same cable for both functions. It did puzzle me for ages, how can the inverter accurately monitor the mains, while it is pumping power down same cable.

But it does !! Modern electronics

larkim

Thanks to all for the help. As it turned out, the installers merged my two supplies in the meter box, rather than behind the consumer unit, as my CU was quite difficult to access from the roof (its in an "odd" place!). They ran the live and neutral as separate cables in there, to which they were able to clamp the Owl widget, so I have a reading now available. The only downside is that the Owl has a tendency to over-read the current being drawn by the inverter at night (I know this is due to the sensitivity of the meter, and there is nothing I can do about this). So it looks like the inverter is drawing 0.081kW all through the night, when I know it isn't. This means that the cumulative figures shown on the meter are nonsense.

When there is some generation coming through, the Owl meter readings pretty much matched the Fronius inverter readings (though updated much less frequently, and with fewer "steps"; certainly enough for me to able to point to the meter and see what is being generated.

On day 1 of the operation (Saturday) we peaked at nearly 1kW output for a few fleeting seconds and generated all of 1 whole 1kWh during the day! Roll on the summer!!

Matt