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Sunsynk, feeding back to grid


Warren Porteous
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Hi - Hope the forum can offer guidance. I had a Sunsynk 5.5 installed during the week. There is a problem in surplus power feeding to the grid. During high PV production the flow back to the grid reaches 3.5kw (and over). As I am not sure where the "grid" reading takes places (at the inverter or at the board) I switched off all non critical loads at the board to check whether flow reduced. Unfortunately the negative flow continued. So, the power from PV banks does not reduce in cases where AC1, AC2 and non critical loads are less than production and the balance flows to the grid. Also my Eskom P160 Customer Interface Unit has also stopped reading. A few questions to help me understand where the problem might be

- which sensor provides the "grid" reading on the sunsynk? is this read at the CT or at the grid input on the inverter?

- are there settings, in the management system, to prevent feedback to the grid?

- alternately, are there settings that enable the reduction of PV generation when the CT detects a negative flow? (i.e. power being returned to the grid)

 

If there have been similar experiences in overcoming power returning to the grid, I'd greatly appreciate your guidance on problem areas to investigate.

 

Lastly, what is Eskom's stance on this. I know returning power to the grid is not allowed. Is there some tolerance allowed in setting up a new inverter and working through snag lists. Or should I shut down the whole system until the installer is able to solve the problem?

 

Thanks

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3 hours ago, Warren Porteous said:

Hi - Hope the forum can offer guidance. I had a Sunsynk 5.5 installed during the week. There is a problem in surplus power feeding to the grid. During high PV production the flow back to the grid reaches 3.5kw (and over). As I am not sure where the "grid" reading takes places (at the inverter or at the board) I switched off all non critical loads at the board to check whether flow reduced. Unfortunately the negative flow continued. So, the power from PV banks does not reduce in cases where AC1, AC2 and non critical loads are less than production and the balance flows to the grid. Also my Eskom P160 Customer Interface Unit has also stopped reading. A few questions to help me understand where the problem might be

- which sensor provides the "grid" reading on the sunsynk? is this read at the CT or at the grid input on the inverter?

- are there settings, in the management system, to prevent feedback to the grid?

- alternately, are there settings that enable the reduction of PV generation when the CT detects a negative flow? (i.e. power being returned to the grid)

 

If there have been similar experiences in overcoming power returning to the grid, I'd greatly appreciate your guidance on problem areas to investigate.

 

Lastly, what is Eskom's stance on this. I know returning power to the grid is not allowed. Is there some tolerance allowed in setting up a new inverter and working through snag lists. Or should I shut down the whole system until the installer is able to solve the problem?

 

Thanks

Hi 

The CT sensor will limit the flow back to the grid. First is to make sure it's installed in the right location. You can check this by the information on the display when clicking on the load icon on home screen 

Can you share this screen. 

There are settings that you can use to limit any feedback. You will need to share a screen of settings page. 

If you have an old spinning meter then the meter will spin backwards. This can be an issue if your current reading is less than the previous reading. 

If you have a prepaid meter then it could either trip and go into tamper mode or it will bill you usage when feeding back. 

What kind of meter do you have? 

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5 minutes ago, Achmat said:

Hi 

The CT sensor will limit the flow back to the grid. First is to make sure it's installed in the right location. You can check this by the information on the display when clicking on the load icon on home screen 

Can you share this screen. 

There are settings that you can use to limit any feedback. You will need to share a screen of settings page. 

If you have an old spinning meter then the meter will spin backwards. This can be an issue if your current reading is less than the previous reading. 

If you have a prepaid meter then it could either trip and go into tamper mode or it will bill you usage when feeding back. 

What kind of meter do you have? 

Thanks Achmat, gladly problem solved.. the (rather confusing) options on the "System Mode" panel were the key. Although the "Zero Export" button was checked there are two conditions under which this is overridden underneath the check box, "Sol exp bat full" and "Limit to load only". Both of these were checked and therefore allowed power to flow to the grid. 

"Sol exp bat full" means it will allow solar to be exported when the battery is full (even though "zero export" is checked).. so its a conditional function.

"limit to load only" means solar will be available for solar loads only (i.e. critical loads) anything else, is pushed back to grid.

I have unchecked both and the push back has stopped. The flow from grid is now the min 20w and the panels are throttling back.

 

Re the meter, I have a digital meter but its not prepaid, rather debit order. In my house I have a CIU (customer interface unit). The CIU is used by prepaid customers to load credits. 

I think the meter was charging me for the solar being pushed back to grid as the reading was increasing. 

 

 

Thanks

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2 hours ago, Warren Porteous said:

Thanks Achmat, gladly problem solved.. the (rather confusing) options on the "System Mode" panel were the key. Although the "Zero Export" button was checked there are two conditions under which this is overridden underneath the check box, "Sol exp bat full" and "Limit to load only". Both of these were checked and therefore allowed power to flow to the grid. 

"Sol exp bat full" means it will allow solar to be exported when the battery is full (even though "zero export" is checked).. so its a conditional function.

"limit to load only" means solar will be available for solar loads only (i.e. critical loads) anything else, is pushed back to grid.

I have unchecked both and the push back has stopped. The flow from grid is now the min 20w and the panels are throttling back.

 

Re the meter, I have a digital meter but its not prepaid, rather debit order. In my house I have a CIU (customer interface unit). The CIU is used by prepaid customers to load credits. 

I think the meter was charging me for the solar being pushed back to grid as the reading was increasing. 

 

 

Thanks

Just a correction on the limit to load function. 

If this is not ticked it can send solar generation to loads before the inverter of you have any. Normally high powered loads such as geysers and pool pumps are not put after the inverter. With the CT coil connected at the right location, the inverter can calculate the total coming from the grid and what the loads on the inverter is using. The difference between these two would be loads before the inverter. It can then send excess to these loads while trying to keep the meter close to zero. 

I'm not sure if you have any loads before the inverter or if your while house is connected to the inverter. 

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3 hours ago, Achmat said:

Just a correction on the limit to load function. 

If this is not ticked it can send solar generation to loads before the inverter of you have any. Normally high powered loads such as geysers and pool pumps are not put after the inverter. With the CT coil connected at the right location, the inverter can calculate the total coming from the grid and what the loads on the inverter is using. The difference between these two would be loads before the inverter. It can then send excess to these loads while trying to keep the meter close to zero. 

I'm not sure if you have any loads before the inverter or if your while house is connected to the inverter. 

Thank you Achmat, this evening I noticed the battery draining rapidly and your description explains this. with the limit to load unchecked and with no solar it was using battery for non critical loads. Now with it checked I presume battery depletion will reduce. looking forward to tomorrow to see if the grid feedback problem remains resolved.
 


 

 

 

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