Data crunching questions - why?!

[JTimbood]

Hi there,

We have a new installation comprising 8 panels run through 2 inverters (as on FiT) and with a 5kW battery. All is running well however, I am struggling to understand some of the data the app is presenting us, and was hoping you may be able to help

1) Why does there appear to be a relationship between PV generation and load, when one goes up the other follows, etc? I didn't expect to see this. I have attached a few screen shots. Is it something to do with inverter arrangement?

2) Why do I appear to be exporting more than I am generating (no additional generating sources)? The daily stats show me generating producing more than exporting (for example PV production = 20.20kwh, 7.10 to Load&Battery and 13.10 to grid). But the graphical display shows export > generation for example 4.33 kW export against 3.1 kW generation (see attachment).

3) For Load - the graphical data shows it being consistently quite high (say 1.2 KW) but then dropping when I put on a high load appliance. You can see this in attachment where the little blips are when the induction hob went on.

Any idea what is going on?

Thanks so much

[Dave Foster]

Can you provide a bit more information about the existing system, you mention 2 inverters - is the FiT inverter handling the solar 8 panels and the Fox system running as a battery storage device - or does the Fox system also have solar panels attached?.

[JTimbood]

Hi there. The FiT inverter (fox) handles about 4 panels I think, then second inverter (fox) handles the rest and has fox battery. I can only think that the two systems aren't talking to each other properly in the app when looking at real time. But end of day stats look correct.

Sorry, I only have basic understanding of the set up but can try to find out more from installer if needed

[Dave Foster]

What you can see from the traces as you say the load increases with PV, but the load should be in the opposite phase i.e. under the line that is because the battery inverter (hybrid) is seeing the export from the other inverter as negative load.

In a setup like this you should have a second CT clamp wired (CT2) from the hybrid inverter and clamped around the live output of the solar only inverter - it then knows how much is being exported and it can calculate the correct load and also be able to effectively use that export.

[JTimbood]

Yes, that sounds like the fix. Thanks very much, I'll contact the installers And hopefully sort something with them.

[JTimbood]

Sorry Dave, last question, why does the front screen on the app (showing the house and energy flow) show the right numbers and the daily summaries seem right, but the real-time graphs show wrong? And I guess the issue is mainly within the app and not actually affecting how the system operates?

Should I be looking to get this sorted as part of the initial install rather than additional work?

Thanks for the advice,

James

[Dave Foster]

The app will be doing some reconciliation as it has both inverters in the account but the real time graphs are coming from the data produced by the hybrid and because it can’t measure the amount of power from the solar inverter it is getting all of it’s maths wrong.

[JTimbood]

Hi Dave,

Sorry one more question, would the two systems not talking to each other impact how it operates? Or is it strictly just how the data is presented in the app? The reason I ask is that I notice that sometimes when the load is high and solar generation is low, the system seems to pull from the battery whilst still charging and almost full battery - why not just pull the juice from the battery as preference?

Thanks again for your help,

James

[Dave Foster]

Hi, yes this is mostly a statistical problem, the main CT clamp will tell it how much is being exported or imported and so the battery will charge with export and supply power if there is import from the grid - the main problem for the app real time date is that as the AC1 cannot see the magnitude of the solar power coming from the FiT system it will report your house load as lower than it really is but the system should work fine.