I have a Sunsynk 5.5kW Hybrid inverter that connects to solar, battery and grid. I have a CT clamp around the grid feed and my load is split between a critical circuit DB board and a non-critical/mains DB board. When the grid is connected/on then the voltage is between 240V and 250V which is the expected behaviour. However, when the grid goes off, then there is always a small grid voltage that the inverter reports, usually 4-5V. Even if I go to my mains DB board and drop the brakes to Eskom this small voltage is always reported by the inverter. I would imagine that if the grid feed is disconnected that the voltage should be zero

 

I'm wondering if this is something anyone else has observed and more importantly if someone can explain why this is observed. 

Edited March 14, 20232 yr by Jeans
Added a picture

We experience the same. According to the installer its normal on the sunsynks. Perhaps due to the capacitors or the like 

2 hours ago, Jeans said:

I have a Sunsynk 5.5kW Hybrid inverter that connects to solar, battery and grid. I have a CT clamp around the grid feed and my load is split between a critical circuit DB board and a non-critical/mains DB board. When the grid is connected/on then the voltage is between 240V and 250V which is the expected behaviour. However, when the grid goes off, then there is always a small grid voltage that the inverter reports, usually 4-5V. Even if I go to my mains DB board and drop the brakes to Eskom this small voltage is always reported by the inverter. I would imagine that if the grid feed is disconnected that the voltage should be zero

 

I'm wondering if this is something anyone else has observed and more importantly if someone can explain why this is observed. 

Interesting, although 5vac is insignificantly small in relation to the nominal working voltage of 230vac. 

Would be good excersize to verify the reading with voltmeter.  Or if you have a breaker in the gridfeed to the Sunsynk, then open it, and check if reading still there. 

EDIT : one thing is for sure, its definately not a feed from the Sunsynk as it  is entirely disconnected from the grid when grid is gone,both live and neatral. 

Edited March 14, 20232 yr by BritishRacingGreen

I connected a multimeter on the breaker where the inverter connects to the main DB, and I get a reading of 0.096V this is then the same voltage a get across all the switches on the main DB board. If I flip this same breaker off, then there is 0V's. on any of the grid-fed circuits, except the same 0.096V towards the inverter. This does not add up to the 4-5V I see that the inverter reports so this 4-5V must be related to the inverter itself.

30 minutes ago, Jeans said:

I connected a multimeter on the breaker where the inverter connects to the main DB, and I get a reading of 0.096V this is then the same voltage a get across all the switches on the main DB board. If I flip this same breaker off, then there is 0V's. on any of the grid-fed circuits, except the same 0.096V towards the inverter. This does not add up to the 4-5V I see that the inverter reports so this 4-5V must be related to the inverter itself.

Overhead power lines running in parallel do act like a capacitor. The longer the line the more capacity. This is a major problem in ZA due to the long lines from the Highveld generating power stations to say the Northern Cape. 

7 hours ago, Jeans said:

This does not add up to the 4-5V I see that the inverter reports so this 4-5V must be related to the inverter itself.

It's more likely to me that the inverter's measuring accuracy at low voltage is poor. Usually firmware will report all measurements less than a certain value, say 20 VAC, as zero. I'd say there is nothing to worry about, without knowing the details of your situation.