Sunsynk 8kW - Aux port for geyser behaviour

[suds7162]

New Sunsynk 8kW owner here. I have it installed such that the geyser is connected directly to the Aux port on the inverter.

I have the following settings configured in the Aux Load screen:

My understanding is that the inverter should behave as follows:

• Switch ON the Aux port when the battery SOC > 95%
• Switch OFF the Aux port when the battery SOC < 90%
  • This means that at night, while drawing on the battery, the geyser will not kick on and remain off until the next morning when I have practically fully charged my batteries.
• Completely switch off the port if there is no grid/loadshedding - ("On Grid always on" switch is set to OFF).

However, this morning I noticed the following things happen:

• The geyser did not kick on when the SOC exceeded 95%.
• The geyser did not kock on when the batteries were 100%.
• Only when I turned the "On grid always on" setting to ON, did the geyser switch on.

It then drew power from the sun+batteries until the the geyser clicked off, after which the inverter continued topping up the battery. 

The way I would expect things to work is that the moment the battery hits 95%, the aux port clicks on, and the geyser starts drawing power. Once the battery dips below 90% the aux port switches off, and the battery resumes charging back to 95% and then cycle between this until the geyser has had it's fill. If I have excess solar, then the battery will charge at a slower rate while the geyser is on (I have priority load set in the work mode screen). I was a little surprised this morning when it drew from solar + battery instead of solar + grid. But this is kind of understandable behaviour as the energy in the battery is "free". I need to decrease my geyser element size so that the load does not exceed the solar generation capacity.

For tomorrow morning's test I will change the Aux parameters to 95%=off and 98%=on. I want to see how the geyser is switched off prematurely when the battery dips below 95%. I think this morning it switched off on it's own just as the battery hit 90%

So my questions are: 

1. Why would the aux port only switch on when the battery hit 100%, in stead of as per my settings?
2. Why would it remain off even when there is excess solar and the batteries are full, and only come on when I turn on the "On Grid always on" setting?
3. Will the geyser switch on this evening, after sunset, and draw from the batteries? Or will it draw from the grid?
4. I have the power limit on the Aux Port screen set to 5kW. Does this somehow have an impact on the setup?
5. What on earth are the "AC Couple on Grid/Load side" settings? They are not on my inverter's actual screen, only via the web settings. But, in all the online literature I see these two checkboxes in screenshots, but it's nowhere explained. 

Thanks

[suds7162]

Ok I think I managed to somewhat figure things out.

The magic setting is the "Solar Power" setting. This number must be set to the minimum amount of available solar before the Aux port switches on. Mine was set to 5kW by the installers. In theory I have a nameplate capacity on my PV of 5.55kW (10 x 555W) but I have never reached this number before. 

So in practical terms you can set this number to 0, which means the aux port will come on as per your battery settings, regardless of the prescence of solar or not. This might be handy in situations where you have an essential-ish type of load, that you are happy to draw power from the battery. Things like ovens/stoves etc. You basically give that circuit permission to draw a certain % from the batteries before cutting out.

In my case, I am setting the solar value to 2500W. This is enough for my geyser (2kW element) and the house at idle (100-500W). If something in the house asks for more power, I will start drawing from the batteries or excess solar, depending on what's avaliable.

The "On Grid always on" setting is now OFF for me, because I DO NOT want this circuit to come on when there is grid but no solar. In my above example of essential-ish loads, this might be perfect, because then you will power your oven from the grid, and when there is loadshedding you give it permission do get some power from the batteries.

So my last question about the AC Couple on Grid/Load side settings remain unanswered for now. My setup works for me, so I'm not going to mess around more.

[iiznh]

23 hours ago, suds7162 said:

In my case, I am setting the solar value to 2500W. This is enough for my geyser (2kW element) and the house at idle (100-500W). If something in the house asks for more power, I will start drawing from the batteries or excess solar, depending on what's avaliable.

Thank you for reporting back on your findings, I think most people do not use the AUX port on their inverter and do not understand how it works. Your feedback will help many people.

I am interested to find out what web interface are you using to see & edit the settings?

[iiznh]

On 2023/04/07 at 2:43 PM, suds7162 said:

What on earth are the "AC Couple on Grid/Load side" settings? They are not on my inverter's actual screen, only via the web settings. But, in all the online literature I see these two checkboxes in screenshots, but it's nowhere explained. 

 I think these settings are related to connecting a generator/inverter to the inverter as a power source/input. AUX input mode

In your case you use the AUX port for output so those settings are not applicable. Aux output mode

[suds7162]

3 hours ago, iiznh said:

I am interested to find out what web interface are you using to see & edit the settings?

I convinced my installer to give me the requisite permissions to have full access to my inverter via the Sunsynk Connect app. It's only slightly more convenient than going out to the garage to mess with settings on the screen.