Strange behaviour when Sunsynk 8Kw inverter is pushing back into the grid via AMI bidirectional meter

[c3poh]

Hi

I've had a Sunsynk 8kW inverter with 2 x 5kWh batteries with 14 x 405 W panels for about 6 months now.  Small house, heat pump, entire load covered by inverter.  It's been working just as expected, load is prioritised during the day, batteries charge and then discharge at night etc.  On sunny days, there is negligible draw from utility (Eskom).  At this point no feedback into the grid (normal prepaid meter).

A typical day looks like the first image posted and is entirely expected, viz, battery starts off low, sun comes up and PV picks up, covering load and charging battery, batteries get full and then PV drops off to cover load. Sun goes down and batteries cover the base load (+- 270W with spikes when heat pump runs). See first image (before.jpeg)

 

This week I got an AMI meter installed (City of Cape Town).  Apart from removing the prepaid meter, COCT didn't touch the PV setup.  The PV installer then logged on and configured the system remotely to push back to the grid using the following system settings (see second image: AMI-settings.png)

 

1. Work mode: Limited to Home
2. Solar export: [enabled]
3. Use timer [enabled] - this setting didn't change
4. Inverter Power Limiter: 5000
5. Energy pattern: Priority Load
6. Grid Trickle Feed: 20

Since the AMI meter installation and changes to the settings, I've noticed some strange behaviour.  The third image (today.jpeg) and fourth (flow-consumption.jpeg is the profile for today which illustrates this behaviour.  The flow screenshot was taken today at 20:46 - well after sunset.  Here's what I'm seeing

 

            

1. The battery doesn't cover the load at night and remains almost fully charged
2. Throughout the day and night there is a consistent 20W being fed to the grid
3. At night the no load on the house is present any longer (0W).  I would expect to see at least the base load (370W)
4. During the day, the batteries charge first back to 100% - this doesn't take long as they have hardly discharged, and then the load line almost mirrors the PV line throughput the day.  I can guarantee you that this is not the real load that the house is drawing.  

Its almost as if the load line has replaced the grid line, but on the other side of the graph (from digging into examples, I'm expecting the grid line to display negative as the power is fed back).

 

Does anyone have any idea what is going on here?

 

 

[GreenFields]

1 hour ago, c3poh said:

Hi

I've had a Sunsynk 8kW inverter with 2 x 5kWh batteries with 14 x 405 W panels for about 6 months now.  Small house, heat pump, entire load covered by inverter.  It's been working just as expected, load is prioritised during the day, batteries charge and then discharge at night etc.  On sunny days, there is negligible draw from utility (Eskom).  At this point no feedback into the grid (normal prepaid meter).

A typical day looks like the first image posted and is entirely expected, viz, battery starts off low, sun comes up and PV picks up, covering load and charging battery, batteries get full and then PV drops off to cover load. Sun goes down and batteries cover the base load (+- 270W with spikes when heat pump runs). See first image (before.jpeg)

 

This week I got an AMI meter installed (City of Cape Town).  Apart from removing the prepaid meter, COCT didn't touch the PV setup.  The PV installer then logged on and configured the system remotely to push back to the grid using the following system settings (see second image: AMI-settings.png)

 

1. Work mode: Limited to Home
2. Solar export: [enabled]
3. Use timer [enabled] - this setting didn't change
4. Inverter Power Limiter: 5000
5. Energy pattern: Priority Load
6. Grid Trickle Feed: 20

Since the AMI meter installation and changes to the settings, I've noticed some strange behaviour.  The third image (today.jpeg) and fourth (flow-consumption.jpeg is the profile for today which illustrates this behaviour.  The flow screenshot was taken today at 20:46 - well after sunset.  Here's what I'm seeing

 

            

1. The battery doesn't cover the load at night and remains almost fully charged
2. Throughout the day and night there is a consistent 20W being fed to the grid
3. At night the no load on the house is present any longer (0W).  I would expect to see at least the base load (370W)
4. During the day, the batteries charge first back to 100% - this doesn't take long as they have hardly discharged, and then the load line almost mirrors the PV line throughput the day.  I can guarantee you that this is not the real load that the house is drawing.  

Its almost as if the load line has replaced the grid line, but on the other side of the graph (from digging into examples, I'm expecting the grid line to display negative as the power is fed back).

 

Does anyone have any idea what is going on here?

 

 

A couple of points:

1. You are using the grid-charge in every time slot, 1,2,3,4,5&6. This means that, since you are using the timer activated, that you are setting your grid to charge the batteries around the clock. I just don't see your full timer settings anywhere in your images. Might help to post that to see if there's any room for optimisation. In the absence of knowing what your timer settings are, I'd say to just turn of (un-tick) all your grid-charge boxes.

2. Since you said that your entire house is on the inverter, it's not clear whether you meant that the entire home is on the essential-load port, or whether you are in fact putting splitting out some non-essential loads like the heat pump onto the grid port. Please confirm, and if in doubt, ask your installer to confirm. Be that as it may, first step, change the work-mode setting to "Zero Export, Limit to Load Only." This will eliminate the current situation where the CT Coil is determining how much power to try to export.

Basically, something looks wrong with your CT coil. Either it is installed the wrong way around, and is possibly treating your 20W grid-trickle feed like an export. Otherwise, it could be that you have a similar situation like I had, which was that the CT coil's cable may have been manually extended if your inverter is placed more than 15-20 meters away from the DB board, in which case it's possible that the CT coil's output is indicating a lower current than what is actually flowing.

Bottom line, change to zero export to load first, and see if the behaviour changes to be more like something that you would expect to see. 

[GreenFields]

1 hour ago, c3poh said:

Hi

I've had a Sunsynk 8kW inverter with 2 x 5kWh batteries with 14 x 405 W panels for about 6 months now.  Small house, heat pump, entire load covered by inverter.  It's been working just as expected, load is prioritised during the day, batteries charge and then discharge at night etc.  On sunny days, there is negligible draw from utility (Eskom).  At this point no feedback into the grid (normal prepaid meter).

A typical day looks like the first image posted and is entirely expected, viz, battery starts off low, sun comes up and PV picks up, covering load and charging battery, batteries get full and then PV drops off to cover load. Sun goes down and batteries cover the base load (+- 270W with spikes when heat pump runs). See first image (before.jpeg)

 

This week I got an AMI meter installed (City of Cape Town).  Apart from removing the prepaid meter, COCT didn't touch the PV setup.  The PV installer then logged on and configured the system remotely to push back to the grid using the following system settings (see second image: AMI-settings.png)

 

1. Work mode: Limited to Home
2. Solar export: [enabled]
3. Use timer [enabled] - this setting didn't change
4. Inverter Power Limiter: 5000
5. Energy pattern: Priority Load
6. Grid Trickle Feed: 20

Since the AMI meter installation and changes to the settings, I've noticed some strange behaviour.  The third image (today.jpeg) and fourth (flow-consumption.jpeg is the profile for today which illustrates this behaviour.  The flow screenshot was taken today at 20:46 - well after sunset.  Here's what I'm seeing

 

            

1. The battery doesn't cover the load at night and remains almost fully charged
2. Throughout the day and night there is a consistent 20W being fed to the grid
3. At night the no load on the house is present any longer (0W).  I would expect to see at least the base load (370W)
4. During the day, the batteries charge first back to 100% - this doesn't take long as they have hardly discharged, and then the load line almost mirrors the PV line throughput the day.  I can guarantee you that this is not the real load that the house is drawing.  

Its almost as if the load line has replaced the grid line, but on the other side of the graph (from digging into examples, I'm expecting the grid line to display negative as the power is fed back).

 

Does anyone have any idea what is going on here?

 

 

Other comment, if you have got a bi-directional meter installed, there is no reason to keep the grid trickle feed at 20W in the inward direction. Just set it to 0 (zero). You are no longer trying to prevent a back-feed of power to the grid/meter.

[c3poh]

Greenfields - thanks so much for the advice. I’ve made the following changes:

1. Turned off the timer

2. Set the trickle to 0

3. Set the mode to “zero export limit to load”

I’ll post an update when during the day one we get some sun on the panels. 
 

Regarding the trickle feed (just getting my head around this). If I understand correctly when set (to say 20) this should ensure a minimum feed FROM the grid of 20w at all times. Interesting that in I’ve been seeing a feed of 20w TO the grid at all times.

 

 For the record, these were my timer settings. It’s off now. 
 

 

 

[c3poh]

Oh, and my inverter is right next to my db board. Unless there is a lot of loose wiring I’m assuming that the CT coil is of normal length (where can I read up about what this is)?
Quite possible that it’s backwards. Will ask the installer to confirm on Monday 

[c3poh]

Will follow up with installer as to how the load is split. At this stage I know that the entire house is powered (incl heat pump) even when the utility is down (load shedding). 
 

One other question. In advanced settings is “Equipment mode : slave” correct. Seems odd since there is only 1 inverter.