Sungrow SH25T - Unnecessary Import on One Phase

[maknij]

I'm having a very strange situation and hoping for some insights. I have a Sungrow SH25T 3-Phase inverter, PV and battery, installed as per the manual with a separate 3-Phase meter on the main DB feed - at the moment I'm not exporting to the grid (Export Limitation is enabled and set to export 0%).

When a particular phase is running a higher backup load at any point in time then it seems to be importing from the grid for that specific phase, and at the same time exporting the proportional amount back to the grid on the other two phases. See attached screenshot from the meter on the main DB feed - this shows:

Phase A - importing 1.6kW
Phase B - exporting 1.2kW
Phase C - exporting 0.4kW

Cumulatively the three numbers combined = 0, so the inverter doesn't think it's importing anything (in fact it reports 0 import and export as I would expect) since the numbers balance out to 0. The real net effect though is I'm unnecessarily pulling 1.6kW from the grid on Phase A.

At the time of these values I had a high load on Phase A, low load on Phase B, and medium load on Phase C. If I turn on other appliances to move the high load to a different phase then I see the same thing on that phase - power imported from the grid on the highly loaded phase, and a proportional amount exported back to the grid for the other two phases, again always balancing out to 0.

This is costing me unnecessary grid consumption (backed up by the utility bill). There are a bunch of settings on this inverter but I can't identify any which might influence this behavior. I've made 100% sure there is no phase mismatch anywhere and the meter at the main DB feed is measuring the correct phases too.

Interestingly, if I enable grid export then it masks the problem as long as PV is available (it manages to export enough to not try importing anything), however as soon as PV is unavailable then it's back to the same behavior again.

Any ideas would be welcome!

 

[timselectric]

I'm not sure if there's a solution for this situation.
It's doing exactly what it should. It's designed to balance out the 3 phases of import and export to zero out your utility bill. But if you don't have an export agreement with the utility company, they will only count your import.

 

[maknij]

I hear you, but here's another factor: the installation company had swapped my unit out due to an issue with the original unit (won't go into that now). I've attached two screenshots, a before view from the utility company (previous unit) and current view from the utility company (unit I have now) - it's chalk and cheese; the previous unit wasn't consuming anything from the grid unless the battery was run down. Nothing else has changed in the installation besides the inverter swap out.

 

[timselectric]

It could be something different in the settings, between the two units.
But I don't know what that setting would be.
I know that my Deye has separate settings for zero export and solar sell.
They can override each other if they aren't both set properly. Maybe you can look into something like that in the settings.

 

[maknij]

That's what I'm thinking too - I've gone through everything over and over again and tried countless config changes (and reverting them again) - just can't get this unit to behave like the previous one.

 

[timselectric]

That's what I'm thinking too - I've gone through everything over and over again and tried countless config changes (and reverting them again) - just can't get this unit to behave like the previous one.

I'm not familiar with that unit, or it's settings.
Hopefully, someone else can provide more help.

 

[maknij]

I've managed to resolve this issue if anyone has the same problem.

My inverter boasts 100% unbalanced per phase capability which got me thinking there must be a setting around this, after more digging I came across a setting on my inverter this morning only visible when connecting via Local Access through the iSolarCloud app (can't even be seen when directly connecting to the web interface on the WiNet dongle) – this setting being 'Feed-In Limitation for Each Phase'. Once enabled and set to 0 my export/import totals on the smart meter immediately dropped to practically 0, solving my current issue. I've read this might not be ideal for the inverter itself in the long term, so I'll undo this later on once I resolve the situation with the utility company as I believe they or the external 3-phase meter supplied by them should be netting the export/import totals instead of charging me the import amounts.