Author Topic: E-Panel for SMA switches Sunny Boy between AC1 & AC2  (Read 840 times)


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E-Panel for SMA switches Sunny Boy between AC1 & AC2
« on: January 12, 2021, 04:05:29 AM »
I have a somewhat nitty-gritty question about the use of the E-Panel with SMA Sunny Island and Sunny Boy inverters.
The built-in bypass breakers in the E-Panel (with mechanical intertie) serve to switch the SB and critical load panel from the AC1 to the AC2 terminals of the SI.
The purpose, of course, is in case the SI needs service or any other reason you wish to shut it down, while keeping the loads energized by the grid, and keeping the SB inverter working.

My question is whether any parameters in the SB need to be edited when this switchover is made.
Because when the SB is connected to AC1, the SI is performing the anti-islanding per UL1741.
Whereas when the SB is connected to the grid, it must handle UL1741 requirements for anti-islanding itself.

My SB will be the latest model, SBx.x-1SP-US-41.
My understanding is that the -41 models no longer require RS485 comms between the SI and SB to shift the latter into FSPC (frequency shift power control) when connected to AC1 on the SI.

I've posed essentially this exact question to SMA America tech support dept, and they replied it's a question for Inside Sales. I forwarded it to Inside Sales, but am not confident they will be able/willing to answer it.
I need to find someone who REALLY understands how the SI and latest SB work, and work together.

SMA's installation manuals and other documents always show the SB connected to AC1 on the SI; they never include any bypass switches, that I've been able to find.
If doing the bypass is NOT a good idea (in spite of the fact it's done that way in the E-Panel!), then I can alternatively leave the SB permanently connected to AC1, and ONLY switch the critical load panel back and forth when I need to bypass the SI. Because of the distance involved between my SES (where the production meters, disconnects, and critical load panel will all be located) and the battery shed where all the PV and inverters will be located, I need to figure this out earlier rather than later. Because it affects the ampacity of the 200+ foot long cables running in trenches between the two locations.


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Re: E-Panel for SMA switches Sunny Boy between AC1 & AC2
« Reply #1 on: January 12, 2021, 06:02:52 PM »
In case anyone is wondering, I believe I've found the answer to my question.
The -40 and -41 version US Sunny Boys are compatible with CA Rule 21 and UL1741-SA.
Up to now I hadn't paid attention to the CA rule because, well, I'm not in California!
It turns out these "extensions" to UL1741 (anti-islanding) add requirements for frequency shift ride-through, among other things.
And they include the optional "frequency-watt" control, AKA freq-watt or what SMA terms FSPC.
Phase 1 of Rule 21 was enacted in CA in late 2017, with Phase 2 (monitoring of your inverter by the grid operator) and Phase 3 (control of your inverter by the grid operator) coming later (2018-2019 I think).
I'm not sure which, if any, of the other 49 states require this stuff (Hawaii has its own very stringent requirements).

So as I now understand it, the newer versions of Sunny Boys will happily implement FSPC, if they are set for Rule 21 operating mode, regardless of whether they are connected to the Sunny Island AC1 terminals or directly to the grid. This means no parameter changes are required when switching back and forth. That's as far as I understand, but I still haven't heard anything authoritative from SMA.

I'm still not sure whether this might have been an issue, requiring parameter changes, for pre-40 Sunny Boys used with Sunny Islands and the E-Panel bypass switching. Because in previous models of Sunny Boys, absent the RS485 comms from the SI, a slight increase in line frequency (say 1 Hz or less) would shut down the SB output entirely. Perhaps tripping the bypass switch would have stopped the SI from telling the SB to go into full island mode?

I suspect this stuff is all "old hat" to quite a few active solar installers; but for me, I'm still learning about it.