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Can I believe the Sunsynk inverter's measurement? - Zero export power


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Posted

Hi All

I have zero export ticked on my installation with a grid trickle feed set at 20W. 

See screenshot for the test scenario.  It was a bright and clear day so the solar power and loads at the time of testing were stable. I measured 2 amps on the main eskom utility feed which at 230 V is +- 460W.  I found this very peculiar as it should be close to zero at +- 20W corresponding with the measurement? 

I am using a Major Tech MT723 which is a decent True RMS meter so should be reasonably accurate. 

Has anyone popped a current clamp meter on the main utility feed when sufficient solar is present to zero the meter?  What readings do you get?  

Thanks all, your feedback would be appreciated.
 

IMG_5005.jpg

Posted

Hi Halcyon,

I would tend to believe the RMS meter that is reading the amps from the mains supply. 

There seems to be lots of little niggles with the Sunsynk hybrids. 

I hope you update this thread if you find an answer.

Posted

My 5kW Sunsynk is set to zero export and zero grid feed but the prepaid meter still shows 0.22 kwh usage a day. Looking at the Solarman graph I can see the odd export and import over a 24 hour period.

Still I shouldn't complain with 6 units a month currently being used😃

Posted (edited)
57 minutes ago, Pumba said:

My 5kW Sunsynk is set to zero export and zero grid feed but the prepaid meter still shows 0.22 kwh usage a day. Looking at the Solarman graph I can see the odd export and import over a 24 hour period.

Still I shouldn't complain with 6 units a month currently being used😃

I see the same with my Goodwe. It's set for zero export, but there are some imports and some exports on even the sunniest of days. There was some discussion a while back (which I have tried to find) as to why a hybrid inverter might behave like this. I had thought it was because the inverter has to sample the grid so that it can match it's output voltage and phase to the grid, but the draw is too high to be only that.

As to the exports, I believe that it is the inverter trying to zero the meter by feeding back what it has drawn, when it is able to do so. In my case this appears to be intermittent, not constant, though I have no way to be measuring between grid and inverter to see if there is some small, constant current.

Edited by Bobster
Posted

Hi All

After a lot of testing, investigation and a repair job, this is what I figured out.

- My CT coil is extended and installed +- 30m from inverter using a high quality, shielded, twisted cable to reduce risk of interference.

- The Sunsynk CT coil (50ma/100A version) is accurate. I did a test over 4 days to compare the import/export power measured at CT and recorded by Sunsynk logger and my street meter. They are aligned with +- 1% variance.  (Street meter actually logs a little less KWH used....yay).

- One will measure current on the utility feed using a clamp meter even if CT shows zero on inverter screen. In my case at least 2 amps when zero exporting.  Luckily the street meter does not measure this current flow as power used. If I switch off the local grid input at the inverter this current draw immediately dissapears so it is definitely created by the inverter.  It is possible something to do with reactive power however Sunsynk have not confirmed the science behind this.

https://www.allaboutcircuits.com/textbook/alternating-current/chpt-11/true-reactive-and-apparent-power/


- It is possible that the actual CT coil measurement by the machine can manifest an issue which happened in my case. I noticed that my CT coil measurement started looking out of the ordinary over December 2021. It started under reading by +- 40%. The machine went in for testing and the issue was confirmed. Sunsynk replaced all the boards and I got a new serial number.

- One can test if there is interference on your CT coil. Do at night with no solar and time of use switched off. Unclip the CT clamp from the main utility feed. Observe if a value remains on the the screen for CT measurement. If you remove the black and white wires from the contacts and this value dissapears it indicates you may have some interference on your cables causing a fictitious value. Most likely if any interference it will be minimal and wont make a material difference to the workings.

- One can adjust the CT coil ratio in case a different CT model is used than the supplied 50ma/100A version. This version needs to be set on 2000:1 - It does seem Sunsynk is rolling out support for their machines to use other types of din rail power meters as opposed to the supplied CT coil, however detail on this is a little scant.

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  • 8 months later...
Posted

Hey @Halcyon

Did your repair job on the inverter actually fix this problem? I.e. after repair did you stop measuring this 2 amp draw? I have the same 'problem' (oddity perhaps?). Sunsynk 5kW inverter, 3 days old, the grid side has a constant current measurement of about 2 amps, when inverter is set to 20 W grid trickle, and no other non essential items are drawing power. It's even confirmed by the status screen on the inverter (see attached screenshot)


The numbers don't line up, or am I missing something? 244 V * 2.2 amps = 536 Watts, not 21?

630b23ae-253d-4c77-bad1-99421033c0a7.jpg

Posted (edited)
10 hours ago, Elroc said:

Hey @Halcyon

Did your repair job on the inverter actually fix this problem? I.e. after repair did you stop measuring this 2 amp draw? I have the same 'problem' (oddity perhaps?). Sunsynk 5kW inverter, 3 days old, the grid side has a constant current measurement of about 2 amps, when inverter is set to 20 W grid trickle, and no other non essential items are drawing power. It's even confirmed by the status screen on the inverter (see attached screenshot)


The numbers don't line up, or am I missing something? 244 V * 2.2 amps = 536 Watts, not 21?

630b23ae-253d-4c77-bad1-99421033c0a7.jpg

A pity your load power is not visible. Your battery is powering your essential load and not the grid. The 21W from grid seems right. The only way to confirm what you suspect is to measure the power flow from the grid with clamp meter or if you have a prepaid meter. 

While measuring the power from the grid you might find if you switch off the grid only the 21W from grid will fall away. 

Edited by Scorp007

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