Hi all, I have a question about the aux input/output that's on the typical 5kw SunSynk inverters. The manual is a bit contradictory hence my post here.

I am interested in understanding if it's possible to connect secondary (non-critical) loads to the SunSynk. Thinks like geysers, pool pumps etc, that do not have to be backed up by the battery but should still be able to benefit from the solar input. I've seen some inverters have a dedicated secondary output that can be used for this, allowing the user to define separate battery and solar parameters that determine when the output is on or off.

According to the SunSynk manual you use the Aux input/output for this, but then where do you connect a generator if that's the purpuse of Aux? Via the Grid input behind a change-over switch?

Another place in the manual they say the Grid input can be used as an input/output, allowing you to put non-essential loads between the grid and the inverter. But I'm not sure if this allows for the inverter to send solar power into these loads, and what will happen during loadshedding, when the inverter is in islanding mode and it switches off the Grid connection to prevent backfeeding into the grid.

The advice of the forum would be greatly appreciated.

6 minutes ago, suds7162 said:

I am interested in understanding if it's possible to connect secondary (non-critical) loads to the SunSynk. Thinks like geysers, pool pumps etc, that do not have to be backed up by the battery but should still be able to benefit from the solar input.

Yes it's possible. Just configure the auxiliary port as a Smart Load / Aux Load output. The battery state of charge (SoC) will determine when the auxiliary port puts out power and when it stops. Note that other than excess solar, power from the battery bank will also be available for Aux Loads until the set SoC. 

 

15 minutes ago, suds7162 said:

According to the SunSynk manual you use the Aux input/output for this, but then where do you connect a generator if that's the purpuse of Aux? Via the Grid input behind a change-over switch?

Absolutely correct. Once you use the auxiliary port as a Smart load/Aux Load output then the genset should be connected via the grid input behind a change-over switch.

 

17 minutes ago, suds7162 said:

Another place in the manual they say the Grid input can be used as an input/output, allowing you to put non-essential loads between the grid and the inverter. But I'm not sure if this allows for the inverter to send solar power into these loads, and what will happen during loadshedding, when the inverter is in islanding mode and it switches off the Grid connection to prevent backfeeding into the grid.

The grid input is bidirectional and can push back solar to non-essential loads between the inverter grid input and CT sensor (100% self-consumption) or even export to the grid past the CT sensor. Like ALL grid-tie inverters, this only happens when there is a reference from the grid and stops in islanding mode e.g. during loadshedding. 

 

Posted after Kilowatt Power. What he said.

 

45 minutes ago, suds7162 said:

I am interested in understanding if it's possible to connect secondary (non-critical) loads to the SunSynk. Thinks like geysers, pool pumps etc, that do not have to be backed up by the battery but should still be able to benefit from the solar input. I've seen some inverters have a dedicated secondary output that can be used for this, allowing the user to define separate battery and solar parameters that determine when the output is on or off.

According to the SunSynk manual you use the Aux input/output for this, but then where do you connect a generator if that's the purpuse of Aux? Via the Grid input behind a change-over switch?

Yes, the AUX/GEN port on the inverter can be used to supply this type smart load depending on battery and solar parameters. The same port can alternatively be used to operate a generator, or micro-inverters, but I don't think you can select more than one of these options at once.

 

45 minutes ago, suds7162 said:

Another place in the manual they say the Grid input can be used as an input/output, allowing you to put non-essential loads between the grid and the inverter. But I'm not sure if this allows for the inverter to send solar power into these loads, and what will happen during loadshedding, when the inverter is in islanding mode and it switches off the Grid connection to prevent backfeeding into the grid.

Yes, the inverter can do this, and push surplus power into the non-essential loads, or even export power to the grid, provided the CT coil is installed correctly and you select the right setting on the inverter, and only while Eskom is on. When the grid is off, the non-essentials are off.

If you search the forum, I'm sure there are more posts that go into more detail on this functionality.

Edited February 6, 20233 yr by GreenFields

Tanks guys, your answers are perfect.

I actually have more questions haha.

Specifically about grid-tied inverters, and how they would play along with a Sunsynk. Maybe this warrants another thread - let me know.

The use case I'm looking at is where we might require multiple PV sites, that are separated by some distance (50-150m). In my mind it's not feasible to lay DC cabling over those distances. So the route would be to use grid-tied or micro-inverters on each of the site, and then connect them all to the main hybrid inverter that sits in a central location with the battery bank.

My question is, would the Aux input have to be used for this (meaning I lose the ability to control non-essential loads), OR, are these grid-tied inverters simply connected to the rest of the AC "microgrid" that sits downstream of the main inverter. The literature on how grid-tied inverters work in this setup is a bit limited, and surely they must somehow communicate with each other? Or is this as simple as you just add as many grid-tied inveters to your internal grid as you need, and it just magically works?

Something like the below: 

I think you need to review how you use the words "non-essential loads." In the world of Sunsynk, the non-essential loads are connected to the grid input, with power supply to those loads being controlled by a CT coil.

The grid-tied inverters would then be connected to the AUX port, not to the backup loads.

You could alternatively put smart loads or the generator on the AUX port (nice-to-have, to be able to operate when the grid is up, but for the sake of clarity, rather don't call it non-essential), but not a generator on the grid input.

Just thinking though that it's best just to reference existing documentation for how these hybrid inverters are connected.

Granted, the image below is I think from Deye, but I guess it indicates what is possible for the Sunsynk too.

I have my geyser connected to Aux, set to only supply if more than 3 KW is available. It works perfectly when on Solar, but if there is little or no solar power, and we have load shedding, it tries to supply the geyser from the battery. If other power is consumed by essential circuits, it overloads, goes off for a couple of minutes, then 'recovers'  and powers only essential circuits. How do I set it to not power aux from the battery?

 

2 hours ago, Phil B said:

I have my geyser connected to Aux, set to only supply if more than 3 KW is available. It works perfectly when on Solar, but if there is little or no solar power, and we have load shedding, it tries to supply the geyser from the battery. If other power is consumed by essential circuits, it overloads, goes off for a couple of minutes, then 'recovers'  and powers only essential circuits. How do I set it to not power aux from the battery?

 

I don't think this is possible. It would be really smart if SunSynk added a trip-aux-first-on-overload option (rather than tripping the full inverter).

 

The alternative is you can move the geyser to non-essentials (assuming you've installed the CT coil) and let the inverter feed it like that when there's grid available; which it'll do using excess solar. This is common with SunSynk/Deye installs and it means you're not bound by the inverter/battery maximums (which one are you exceeding?) since grid takes the slack whenever solar is insufficient - with the caveat that the geyser is only actually powered-on when grid is present. I've less-than-halved both of my geysers' muncipal energy usage doing this since they run one-at-a-time mostly during the day (when there's usually sufficient solar);  plus just an hour or two in the evening to re-heat for the second batch of showers.

 

Aux is just an extension of load; so even with a tight Aux battery range (say, 94-98%), there's still the risk that when the power fails, the battery is in range, Aux is therefore on, and you trip if you exceed the inverter load maximum.

For this reason I'm going to be moving my smaller geyser to Aux (because I do want to be able to run it during extended outages - and maybe even load shedding); but I'm going to ask the installer to put up a change-over switch for it so that I can put it back on non-essentials if I find household demand exceeds the maximum supply with it on Aux. But indeed, Aux does require peak-load-management unfortunately...