duerrd561
New Member
Only if breaker feeding SI AC2 is on.
If it is off, would not be sync'd and could blow up SB when input phase jumps. Its FETs could be fighting the grid. At least in theory, based on SMA's warnings.
One guy did put SI AC1 output across the grid and it simply tripped breakers. That was at the end of a long wire.
Yikes. But yeah, the breaker feeding SI AC2 is always on so long as something doesn't trip it. I've never had it trip in ~8 years of operation (knocking on wood), but I get your point here and its something to be aware of.
I think newer firmware allows Rule 21.
You're switching this direct onto grid? Island mode would not have anti-islanding. It would have wider voltage and frequency settings.
This defeats some of the lineman safety requirements. (conditions needed for it to backfeed a dead line aren't likely to be achieved, but UL-1741 is what is approved for safety.)
The SB 5.0 is wired in to a panel sitting behind the ATS, so my rationale here was that the ATS would essentially provide anti-islanding between the SB 5.0 and the grid. And on several occasions I've witnessed the scenario where we have an extended off-grid situation and accidentally deplete the batteries on the SI below the 40% SoC cutoff such that the load-shedding contactor is opened and the generator input to the ATS goes dark. Then the sun comes up and the solar panels start to produce. The SB 8000-US coupled to AC1 is running and feeding power back into the SI, recharging the batteries. But the SB 5.0 doesn't start outputting any power on the AC side until the SI re-engages the contactor and allows AC1 power to reach the generator input of the ATS, at which point the SB 5.0 then comes online.
Correct, regarding backup mode. Without RS-485 it would remain UL-1741.
It would work in offgrid/island mode. But would not perform anti-islanding. SI would perform anti-islanding. I avoid relying on that, based on what SMA Germany engineers documented (and reports of relays welding shut.)
Got it. Thanks.
I think Bfr is frequency; does it quote the frequency observed?
I think mine do. Could occur during dropped power, not just frequency shift (knock offline by going above 64 Hz prior to synchronizing (only if excess production, was above 60 Hz before trying to reconnect.)
Try measuring voltage and frequency.
Perhaps line impedance is different and more noise from SB 5.0 is seen. I haven't checked waveforms from my -41 yet.
I did see poor PF from a VFD upset a SB. Documents say if that error continues, it becomes locked. I was playing with SBS during a grid failure, connected to SI, and discovered my SunPower SB 8000US locked that error, is now bricked. I suspect but don't know SBS current waveform did that.
Unfortunately it doesn't show frequency. But it does show a voltage readying which shows 129V on the L1 leg. I believe there is a ~1s tolerance for voltage above 129.3V at which point the SB 8000-US would see a disturbance. At least this was what I read in the manual.
Monitoring SB isn't so important. Drop in system output, check the displays, use a clamp DC ammeter to check individual strings.
SB -41 with WiFi or SpeedWire, you should be able to hook up and read.
I agree. Once I found myself with 2 generations of SB technology that couldn't even talk to each other, let alone (reliably) to my Home Assistant system without me doing my own integration development (which I can do, but don't have time to with day job and life responsibilities), I rolled my own monitoring system using Shelly EMs + CTs for solar production monitoring and Shelly I4s for SI relay reporting. We live across the country now, and PG&Es rates only continue to go up, so monitoring the system is key to avoid huge PG&E surprise bills.
I'm sticking mostly with old stuff, but trying some newer products when they show up cheap on eBay just because. And need recent grid-support features for new system installs and permission to operate.
If I was you I would consider getting multiple SB of the 5000 ... 8000 series and use just those. 8kW + 5kW = 13kW is OK going through 2x SI so would put both on protected loads panel. (I considered switching additional SB to support twice as much PV.) It may be better not to have anti-islanding by SB when SI forms island (not sure if a problem or not.)
I *really* appreciate your suggestion, and respect where you're coming from. If I lived at the property full time as I used to, I'd likely go this same route as I'd be able to rewire the secondary inverter like you say, to source the used SB 8000-US, and to closely monitor things. Unfortunately now that I live across the country, I'm unable to be as hands-on with things and I'm stuck hiring electricians, etc. when things go wrong. I just need something reliable that works, is under warranty, etc. We run an Airbnb out of the house when we're not there so taking a 50% hit on solar generation as we are now really affects the bottom line, hence the need to make this a straightforward and inexpensive replacement that my original installer can do without me there.
If you use Rule-21, consider adjusting frequency limits for disconnect and/or frequency/watts settings of SB 5000US so they work together better without anyone getting knocked offline. This is 15+ years of products being made to work together. SMA invented frequency-watts long before the grid asked for Rule-21 and grid support.
I will likely have the old SB 8000-US available if anyone has interest in it.