Critical loads causing excess export when setting modbus register 37

[christophedm]

I am sending -500w to modbus regster 37 on unitid 228 (VE.Bus)
To feed back 500w to the grid.

I am also reading back the value from modbus to ensure I had written it correctly, no issue here.
I am reading what I am writing.

But in actuality I am getting ± 857w feed back to the grid.
I dont understand why, when checking the VRM I can see Critical Loads being added to the grid feedback?

Can I disable the critical loads import ? I have connected the wiring up to AC OUT 1.
And ofcourse AC IN.

VRM :

Readings :

Thanks for any insights/help.

[lxonline (LX)]

Help me understand here.

1. You have a load ln the inverter output
2. . You are discharging from battery to grid (target 500W)
3. You don’t want the battery to discharge to the load- where do you want the power to come from for the load?

The target to grid is being met (shy of a few watts).

What is being discharged from the battery is load + grid is how i understand your vrm upload.

[christophedm]

Hi LX,

I would expect if I send -500 that I would get approximately -500 feedback to the grid.
I dont understand why this “Critical Load” is also added ontop of the feedback, generating a surplus on the requested feedback.

I would be very happy if only the left side was fed back (-480).

Any ideas how to improve or how other people deal with this ?

[DuivertNL (Marc)]

Its called critical loads for a reason, so that means it always have to have power…

System is functioning as it should, supply power to critical loads and still keep your grid at setpoint…

[lxonline (LX)]

They have their grid set point at 0w and allow battery discharge.

[christophedm]

1. Is there anyway to disable the critical loads ?
2. Is there some calculation behind it ? What is the logic here ?

I am still not understanding why if I say -500, it will trigger the critical loads also.
Here are some more examples

Value : -100, no effect, works as expected, I am feeding back to my grid 84w

Value : -200, adds 296w of Critical Loads, I am feeding back to my grid 502w

Value : -500, adds 377w of Critical Loads, I am feeding back to my grid 857

Then when I request the battery to charge, there is also a surplus of power draw.

Value : 100, getting 147, still acceptable for me in a way.

Value : 200, getting 511, more then double of what I requested.

Value : 500, getting 1168w, again more then double of what I requested.

I must be missing a big clue or have something misconfigured.

If it is normal behaviour can you please explain the logic behind it so I can take it into account when steering the charging/discharging of the battery.

Thanks!

[lxonline (LX)]

@christophedm

misconfigured

Do you have a grid meter? Where is it physically vs where is it in software position?
It is likely that as an issue.

Do you actually have loads on the output?

[DuivertNL (Marc)]

Maybe make a drawing how your system is connect to grid and house (grid meter?) ac loads, ac in, ac out 1/2?

[christophedm]

Marc, here is the wiring.

[christophedm]

@lxonline

Do you actually have loads on the output?

It is physically exporting that value, I can see it in the homewizard app, see my initial post, the one with the graphs purple and green.

[DuivertNL (Marc)]

You clearly dit not read the manual… get the ac out connection out asap, connect only ac in

why did you do that?

Thats causing weird issues

Whats connected to ve bus?

[christophedm]

@DuivertNL I have removed the bridge between AC IN and AC OUT 1.
Looks alot better now, I did read the manual but failed to find the info on which AC the feedback would occur, apparently it can just go out on the AC IN.

[christophedm]

@DuivertNL

Whats connected to ve bus?

MK3 to usb

[DuivertNL (Marc)]

You cant connect a mk3 at the same time with the GX running…

[DuivertNL (Marc)]

Yes its like a normal pv inverter so thats how it feeds back to grid

[christophedm]

@DuivertNL the MK3 is just connected and wired through a cable gutter to an electric box, if I need it I can just grab it from there without needing to unscrew the Multiplus at the bottom again, I had already noticed it goes into “Blocked” when MK3 is connected.

Thanks for your help

[DuivertNL (Marc)]

Ok!

[lxonline (LX)]

Also on the GX, you can switch in software ac output not in use as well. (Under ess settings)