SMA Sunny Island wiring set up?

[callmeburton]

It shouldn't be a problem for transformer's 120/240 windings to be in parallel with two Sunny Island. That will help a bit with balancing.
I think I would use transformer as auto- rather than isolation, when only 120V sources are available.

Are you suggesting I run both SI's to the transformer in parallel on the 120vac side, then run the 240 v side to the load panel?
Does this change configuration of the SB's at all?

I thought the SI's did their own load balancing on each leg?

Btw, the unit I got is a 6048, $1800 used for a short period of time then sat for five years so it looks pretty much new but nothing included less the mounting bracket. Will need to read the manual to know what other parts I need to order to link it to the other SI

 

[Hedges]

No transformer is needed with SI, unless you have only one (producing 120V) and you need to connect something 240V (like Sunny Boy.) For grid-tie, a second transformer on the primary would be useful to split the power between grid L1 and L2.

With 2x SI connected for 120/240V split phase, each Sunny Island will deliver up to its 5750W continuous (or derated at elevated temperature.) If you had more than that on one phase, an auto-transformer would partially shift the load. A large enough isolation transformer would let all power from both SI be on a single phase.

If you have a transformer, I would suggest wiring it as an auto-transformer through a breaker, and leaving it switched off. If one SI goes down, you can configure to use just the remaining SI and switch in transformer. Put battery temperature sensors in both master and slave, and have a way to swap any control wires.

 

[callmeburton]

Working on ordering hardware for this setup and I was wondering if I should bother with GFCI for the outdoor AC coupled side of the SB since it is going to be a good 300ft from the main living area.

It seems like it would be more of a PITA to deal with it ever had issues being tripped. While more expensive a standard breaker / box combo seems like it would be better in this case than the squareD spa box combo.

 

[Hedges]

I don't believe there is any requirement for recommendation for GFCI on hard-wired AC circuits like that.

GFCI is required for convenience outlets, originally wet location now maybe everywhere, but I think an exception for difficult to access outlet behind a refrigerator.
GFCI is required for wiring on a dock. Probably a run to a Sunny Boy on a boat dock should have it.

PV DC is required to have 1A GFCI for at least some locations of installation.

 

[callmeburton]

I was thinking more in the realm of nuance potential vs required by code. I agree code doesn't require this to be a GFCI for the outdoor AC Coupling of the SB.

There are Square D boxes, sold as a package, targeted toward spa owners which is cheaper than buying the same box + standard breaker if I recall but the spa box has a GFCI breaker pre installed. I was weighing the cost savings vs how often, if at all, the GFCI would fault being 300ft from the home :D

I have the PVDC going through 600vdc MN breakers in one of their boxes, then to the SB .. both at the panels.

 

[Hedges]

I doubt there is a risk that GFCI would be needed for, for AC to Sunny Boy.

Sunny Boys provide DC GFCI and AFCI (which can be turned off.)
AC wires to Sunny Boy aren't likely to have ground fault, and a hard fault would trip breaker. Purpose of GFCI is to detect a high leakage, e.g. through your body, that isn't enough to trip a circuit breaker.

There can be a problem with capacitance to ground (e.g. EMI filters) tripping GFCI. But not likely for symmetric 120/240V split-phase. More likely if connected to 208V (two legs of 3-phase) or 277V (single phase). Unevenly loaded 3-phase is a source of such tripping in industrial systems.

 

[callmeburton]

This is actually selling me on the GFCI combo as it saves us money If it isn't likely to have faults and we get similar protection then it comes down to cost savings ... and every time we can save money and do something safely and to spec we go for it :D

 

[Hedges]

Shock hazards from portable plug-in devices, when you are in a wet location, are a real concern.
If electrical system has proper ground wire and appliances are solidly grounded, that should make them safe by tripping breaker.
I never liked the L1, L2, Ground connection of dryer, with motor current being carried through ground. I replaced it with 4-wire, also installed GFCI (mine is on the porch outside.)

The other concern is fire safety. PV panel strings on a residential roof can start a fire that endangers occupants. Maybe DC GFCI helps. AFCI should help, so long as it doesn't nuisance trip due to interference. RSD is supposed to be fireman safety but greatly increases the number of mixed-species MC4 connections. After the fact (fires), code changed to require UL listed inter-species pairs. I like to avoid as much newfangled electronics as possible due to unintended operation.

GFCI breakers had an extra pigtail wire in the breaker panel. With those required throughout house, more cluttered. There are "plug-on-neutral" panels to reduce extra wires, but now 1 million units recalled to check torque of a screw. KISS.

 

[beastman]

Yes, you can use a transformer. Either auto- or isolation. SMA used to sell one (with transfer switch as well) for this application.
Plenty of used transformers on eBay.

An isolation transformer, needs to be VA at least as high as Sunny Boy wattage. At least whatever wattage comes from SI or grid, if you put loads on 240V. Used as auto-transformer, needs to pass through half the wattage (may be labeled full wattage.

You aren't likely to have a need for 83.3A at 120V.

SI supports 56A pass-through, so 6.7kW max PV if grid-tie. Off-grid, can put 12kW of SB on one SI.

quick question on the 56a and 6700 watt pv limitation- if using a pair of 5048s with a sb7000us, can we double the 6700 watt figure when grid tied? the sb7000us puts out 6.7kw max and is 240v providing power on each phase, so that should be pushing appx. 23a on each 5048 on the ac1 side. pls let me know my assumption is correct. thx- B

 

[Hedges]

Yes.
With 2x SI 5048US or 6048US, the 240V GT PV inverter's current will perfectly go through both.
The actual limit is 56A, not precisely 6700W x 2, because wattage varies with voltage.
Voltage will usually be above 240V when you backfeed, so you're likely to get that many watts though.

With 4x SI, can't count on current splitting evenly across two parallel relays, so would need to stay somewhat under 112A and 6700W x 4

 

[beastman]

Yes, you can use a transformer. Either auto- or isolation. SMA used to sell one (with transfer switch as well) for this application.
Plenty of used transformers on eBay.

An isolation transformer, needs to be VA at least as high as Sunny Boy wattage. At least whatever wattage comes from SI or grid, if you put loads on 240V. Used as auto-transformer, needs to pass through half the wattage (may be labeled full wattage.

You aren't likely to have a need for 83.3A at 120V.

SI supports 56A pass-through, so 6.7kW max PV if grid-tie. Off-grid, can put 12kW of SB on one SI.

quick question on the 56a and 6700 watt pv limitation- if using a pair of 5048s with a sb7000us, can we double the 6700 watt figure ? the sb7000us puts out 6.7kw max and is 240v providing power on each phase, so that should be pushing appx. 23a on each 5048 on the ac1 side. pls let me know my assumption is correct. thx-

Yes.
With 2x SI 5048US or 6048US, the 240V GT PV inverter's current will perfectly go through both.
The actual limit is 56A, not precisely 6700W x 2, because wattage varies with voltage.
Voltage will usually be above 240V when you backfeed, so you're likely to get that many watts though.

With 4x SI, can't count on current splitting evenly across two parallel relays, so would need to stay somewhat under 112A and 6700W x 4

awesome, this means i can use the extra sb6000us i have to load another 5k watts for both grid tie and battery charging. with tax incentives i might as well bump up the batteries to 60kw and never pay for ev charging by plugging into the protected panel on ac1.

 

[Hedges]

Yup. 6000 + 7000 = 13,000 is a perfect fit for 2x SI.
Is that wattage fine with your utility? Used to be 10kW before more involved application in my area, maybe now 30kW? Probably still depends on utility transformer. One guy paid to have the "pole pig" upgraded.
Do multiple orientations of PV into each inverter if you can, should allow 50% over-paneling without clipping.

How well you can utilize batteries on SI while grid-tied, I don't know. I haven't tried, but without external control by networking, I don't think SI supports anything besides connect/disconnect. Other models SMA promotes for gaming time of use and spot markets.

SB 7000US is 7000W
SB 8000US is 7680W @ 240V, 8000W @ 277V

https://www.solaris-shop.com/content/7000US%20Specs.pdf

These inverters aren't UL-1741-SA. Are you allowed to use them for grid-tie net metering?
(If you're not backfeeding the grid, 56A limit doesn't apply. Sunny Boys can be 2x the wattage of Sunny Island)

With batteries and EV charging, I'm not sure that SI would supply 100% of loads from PV + battery, zero from grid. I don't think it would invert from batteries except if grid current limit setting was exceeded. Or if disconnected from grid. (back to that power shaving function that I don't think it has.)

 

[beastman]

Yup. 6000 + 7000 = 13,000 is a perfect fit for 2x SI.
Is that wattage fine with your utility? Used to be 10kW before more involved application in my area, maybe now 30kW? Probably still depends on utility transformer. One guy paid to have the "pole pig" upgraded.
Do multiple orientations of PV into each inverter if you can, should allow 50% over-paneling without clipping.

How well you can utilize batteries on SI while grid-tied, I don't know. I haven't tried, but without external control by networking, I don't think SI supports anything besides connect/disconnect. Other models SMA promotes for gaming time of use and spot markets.

SB 7000US is 7000W
SB 8000US is 7680W @ 240V, 8000W @ 277V

https://www.solaris-shop.com/content/7000US%20Specs.pdf

These inverters aren't UL-1741-SA. Are you allowed to use them for grid-tie net metering?
(If you're not backfeeding the grid, 56A limit doesn't apply. Sunny Boys can be 2x the wattage of Sunny Island)

With batteries and EV charging, I'm not sure that SI would supply 100% of loads from PV + battery, zero from grid. I don't think it would invert from batteries except if grid current limit setting was exceeded. Or if disconnected from grid. (back to that power shaving function that I don't think it has.)

I am on my own transformer (in rural area on 50 acres) that I paid for in 2009, every person in my area does not share a transformer,so I don't think i'll have an issue there. Main panel is 225a Eaton w/ meter socket on single phase. Other solar owners in my area are going up to 13k watts using solaredge. My business is next door to a solar and roofing company and that is what they claim for our area and are a solaredge dealer and use sonus lithium batteries which are $700 per kw.

I have the sb7000us grid tied since 2015 and have an ETOU-B time of use plan with about an 8,000w array. Max output on the sb7000us is 6.7kw and I haven't ever seen over 6400 watts at the inverter. It is fully permitted w/ the county and PG&E.

The sb6000us I received w/ the two sunny islands has the rs-485 card installed and I have the cable. My sb7000us does not, but I assume I can just move the card from the sb6000us to the sb7000us before turning up another array. I don't know if the sb6000us or sb7000us would need any programming. The sb6000us previously was setup for off-grid 100%. I have another 5k watts in older mono panels that are sitting in storage which can be used w/ the sb6000us and put on the house. I'm not planning on pulling another permit.

The grid-shaving should somewhat work when the solar is offline for the day; we would want to fudge the voltage numbers on the SMA-NET canbus so the SI's should backfeed current to the grid on ac2 thinking the batteries are a bit overcharged to somewhat match the current being used from the main meter socket panel. At least it's a theory at this point. While the sun is out grid shaving really isn't necessary. As long as the batteries are topped off, the SI's should pass-through the power from the GT (sb7000us) on AC1 to AC2 and thus the system should still function properly w/ grid tie and grid-backup. The SI's will connect to my 200a sub-panel in the metal building on a 60a double breaker via ac2 connections to Si1 and Si2. The sb7000us currently uses a 40a breaker connected to the same sub-panel, but this will get a new sub-panel and route through the two Si's on AC1 connections.

The more I look into this setup the more I realize why people spend the extra money on the sol-ark when considering all the extra connections, relays, etc required to make these work. I do all the work myself and am comfortable with it, but for others DIY this setup is madness. The flexibility is amazing on the SI's but it's a huge puzzle and each piece is going to take quite a bit of time to implement and test without blowing anything up. I believe my sb7000us was mfg in 2009 and the sb6000us was mfg in 2011. System recouped it's entire cost within 3 years, now it's all a bonus. The system is sitting on the southern side of a 40x60x16 building I finished in 2015 and started the permitting in 2007. The building sits 250' from the main meter which is a 10x12 pumphouse that connects the main house on a 300' run of 350MCM aluminum on a 200a subpanel, and the metal building is 250' from the pumphouse on 250mcm al. At the pumphouse resides a 16kw generac w/ 100a transfer switch that needs some work at this point and I may end up replacing it as i've owned it since 2009 and have had nothing but reliability issues with it since day one. I may end up selling that generator and keeping the 100a transfer switch to use w/ the SI's for transfering loads. At this point I a leaning towards doing 60kw of lifepower4 48v rack batteries, last year for the 30% tax credit so charging a Tesla up to a 70% charge should not completely deplete the 60kw bank and can store about a days worth of power in the summer from the solar array.

 

[Hedges]

225A panel, 200A main, 120% rule allows 70A PV breaker. 80% loading allows 56A continuous, at 240V 13,440W.

Fed by 70A breaker in main panel, 2x SI can work as UPS for downstream loads panel. Have a critical loads and PV aggregator panel for SB so always powered (also critical loads like alarm, communications), then a load-shed relay supplying important loads panel. Default that would be disconnected at 30% SoC.

Backfeeding an interlocked "generator" breaker of main panel, you can manually supply that as well. I have that on same 30% load shed, will move it to 80% SoC load shed relay eventually. Have to turn off 70A breaker feeding SI when SI feeds that panel.

Back in the Sunny boy 5000 ~ 8000US days, I think "backup" was by default off and it would not respond to RS-485 and frequency-shift power control. Have to get it running with PV and AC (frequency has to be within spec) before it will listed to an RS-485 master so you can configure it. While my SI was at 59 Hz it wouldn't connect, but with grid feeding at 60 Hz I could connect and configure it. Then it would switch to backup and work with wider frequency range. (Later models were shipped with backup mode enabled.)

Added PV wattage likely requires agreement with utility, and compliance to UL-1741-SA, which these older models don't support. Not that it matters behind SI, because SI will disconnect from grid at UL-1741 frequency limits. (Maybe a newer product would remain connected and let SB support grid at wider limits.) If only you had a way to export-limit at your agreement, added wattage would likely go unobserved. I don't know how to do export-limit with these inverters. Their production limit could be set over RS-485. I think dynamic adjustment for zero or limited export is supported on later models with SpeedWire. With your added PV wattage, whether PG&E notices or not depends on your loads, and what their programmers code into meter reading software.

If both SB had RS-485 then both would switch to backup mode and do frequency shift.
If both were set to off-grid mode, they would do their thing behind SI, and SI would disconnect from grid when grid was out of spec.
SMA America has given some recommendations about doing that for certain systems but I have misgivings - I think the "backup" rather than "off-grid" settings were planned by SMA Germany engineers to keep the system safe even in the event of faults (like stuck relays.)

Commands to SI probably would let it feed battery to loads or grid. Voltage, as you say, or grid current limit.
60A breaker feeding SI - 80% of rating would mean 48A continuous is max recommended. More than that and a thermal-magnetic breaker might nuisance trip. Consider 70A (although for one of AC1, AC2 manual says 56A breaker max?) Consider magnetic-hydraulic. Midnight/CBI 60A is guaranteed not to trip up to 63A (+5%), guaranteed to trip eventually at +30% or higher. Carlingtech the trip curve is +0% and +25%.

Is it still last year for 30% tax credit, or did that get extended for a decade?

I installed my system beginning around 2003, cost $8/W with rebate $4/W and utility rates were lower. That may have taken 15 to 20 years to break even. The SI addition is pure cost, but it was nice working in the home office with A/C going during power failures. I figure the home made cappuccinos cost me $1000 apiece.

Here's the SI-LS100-48 load-shedding contactor.
Maybe you can find a domestic source, and other parts could also work, but this one has an especially good economizer - high current relay pulls in, low current relay switched in series to hold.

SMA Sunny Island Inverters

System manager for all types of energy generators.

www.windandsun.co.uk

SolArk has more features/functionality, and responsive support. Time will tell if quality and durability is there. People compare to similar products from same manufacturer at a fraction the cost, which may have cheaper alternate components. SMA costs a lot because it is an expensive product, both how much it contains and source of components. What's lacking in these older models is newer features, but if we can roll our own with comms, that is OK. Latest firmware could break some things - Midnight has an interface for their Classic SCC, and said update broke that.

 

[callmeburton]

Winter season is here and we backed of the solar stuff a couple months ago to focus on our slab pour (which is now done and put to bed for the winter)
Debating setting up an always on battery backup system with one of my SI's here at home which would only power the emergency loads I have already configured with a transfer switch. This is a Reliance transfer switch which has the power coming from the breaker to LINE then the load going to the wire originally in the breaker.
Everything would be bonded.
The transferswitch would be kept on GEN and the Source transfer switch would change during a blackout (after we notice it).
I wanted to do it this way so I can more easily "fix" it before selling this house if required.

 

[callmeburton]

Likely should add a load shed relay on the loads side ... now the fun part is finding one I can eventually use with my whole house install on the new build :/

 

[beastman]

225A panel, 200A main, 120% rule allows 70A PV breaker. 80% loading allows 56A continuous, at 240V 13,440W.

Fed by 70A breaker in main panel, 2x SI can work as UPS for downstream loads panel. Have a critical loads and PV aggregator panel for SB so always powered (also critical loads like alarm, communications), then a load-shed relay supplying important loads panel. Default that would be disconnected at 30% SoC.

Backfeeding an interlocked "generator" breaker of main panel, you can manually supply that as well. I have that on same 30% load shed, will move it to 80% SoC load shed relay eventually. Have to turn off 70A breaker feeding SI when SI feeds that panel.

Back in the Sunny boy 5000 ~ 8000US days, I think "backup" was by default off and it would not respond to RS-485 and frequency-shift power control. Have to get it running with PV and AC (frequency has to be within spec) before it will listed to an RS-485 master so you can configure it. While my SI was at 59 Hz it wouldn't connect, but with grid feeding at 60 Hz I could connect and configure it. Then it would switch to backup and work with wider frequency range. (Later models were shipped with backup mode enabled.)

Added PV wattage likely requires agreement with utility, and compliance to UL-1741-SA, which these older models don't support. Not that it matters behind SI, because SI will disconnect from grid at UL-1741 frequency limits. (Maybe a newer product would remain connected and let SB support grid at wider limits.) If only you had a way to export-limit at your agreement, added wattage would likely go unobserved. I don't know how to do export-limit with these inverters. Their production limit could be set over RS-485. I think dynamic adjustment for zero or limited export is supported on later models with SpeedWire. With your added PV wattage, whether PG&E notices or not depends on your loads, and what their programmers code into meter reading software.

If both SB had RS-485 then both would switch to backup mode and do frequency shift.
If both were set to off-grid mode, they would do their thing behind SI, and SI would disconnect from grid when grid was out of spec.
SMA America has given some recommendations about doing that for certain systems but I have misgivings - I think the "backup" rather than "off-grid" settings were planned by SMA Germany engineers to keep the system safe even in the event of faults (like stuck relays.)

Commands to SI probably would let it feed battery to loads or grid. Voltage, as you say, or grid current limit.
60A breaker feeding SI - 80% of rating would mean 48A continuous is max recommended. More than that and a thermal-magnetic breaker might nuisance trip. Consider 70A (although for one of AC1, AC2 manual says 56A breaker max?) Consider magnetic-hydraulic. Midnight/CBI 60A is guaranteed not to trip up to 63A (+5%), guaranteed to trip eventually at +30% or higher. Carlingtech the trip curve is +0% and +25%.

Is it still last year for 30% tax credit, or did that get extended for a decade?

I installed my system beginning around 2003, cost $8/W with rebate $4/W and utility rates were lower. That may have taken 15 to 20 years to break even. The SI addition is pure cost, but it was nice working in the home office with A/C going during power failures. I figure the home made cappuccinos cost me $1000 apiece.

Here's the SI-LS100-48 load-shedding contactor.
Maybe you can find a domestic source, and other parts could also work, but this one has an especially good economizer - high current relay pulls in, low current relay switched in series to hold.

SMA Sunny Island Inverters

System manager for all types of energy generators.

www.windandsun.co.uk

SolArk has more features/functionality, and responsive support. Time will tell if quality and durability is there. People compare to similar products from same manufacturer at a fraction the cost, which may have cheaper alternate components. SMA costs a lot because it is an expensive product, both how much it contains and source of components. What's lacking in these older models is newer features, but if we can roll our own with comms, that is OK. Latest firmware could break some things - Midnight has an interface for their Classic SCC, and said update broke that.

I ended up purchasing 31kw of sok batteries rackmount 48v instead of lifepower4. There are too many problematic complaints on here with lifepower4 and pre-charge resistor issues as well as some capacity/current issues. The SOK's were about the same cost with shipping and tax as EG4LL - they do offer a 3% discount for doing a wire transfer instead of credit card processing and the black friday sale put my total for 6 batteries, the rack and all cabling at $10,900 shipped including tax. Since they do support the sunny islands that is one less thing to worry about fudging for weekends on end.

Going to be rebuilding my pumphouse inside this month with some plywood on a 12' wall to mount all this. One issue I will have is that my solar resides on a barn 250' away w/ the sunny boy PV inverters, and i'll need to run a separate 4 gauge feed 250' away which is about another $800 or so. This is so I can island the sunny boy inverters and the sunny islands directly through a dedicated sub-panel setup. Once I start wiring it up and get the basics up and going i'll try to document here what I learn. Dexter at SOK is a great resource and says the issue he has seen w/ the sunny islands and the SOK batteries is the initial balancing of the stack - when the SOK sends a stop charge request the SMA does not immediately comply and the SMA's only ramp down the charge- this in some cases causes an overcharge alarm and the battery array goes offline. Once the cells get all balanced out running in VLRA mode (non CANbus) initially, switching to can after a few weeks then works perfectly. I am still planning to test my concept of doing my automotive microcontroller w/ two separate canbus connections to proxy the data between and re-write the voltage/SOC in some cases to the sunny island to attempt to discharge back to the grid. The can protocol from pylontech is pretty well documented and that is what the sunny islands use. It's going to be some coding and testing to see if I can make this work. If it's doable this is definitely such a huge reliable setup at that point. I think the discharge to grid feature is really only going to work when the sun is down and the sunny boys don't produce any more power. There is some options to limit current and such. Other part of this is going to be finding a good rs485/can unit to capture the voltage and current going through the main lugs on the panel to calculate backfeeding values sent over canbus. One piece at a time.

 

[callmeburton]

@Hedge
Where did you get your SMA load shed relay? I looked around a bit and nothing was popping up less stuff in Europe ... even emailed SMA USA to see where I could get one but they haven't responded

 

[Hedges]

Manual lists "SI-LSXX". I've only found 100A ones.

Searching for SMA "SI-LS100" price I found:

SMA Sunny Island Inverters

System manager for all types of energy generators.

www.windandsun.co.uk

Price is 95 GBP. I bought two, but shipping added a significant percentage, wish I bought more. Got mine a couple years ago, name on them was ABB



You can use other relays, 48VDC, 120VAC, 240VAC. But this one has a particularly good economizer. When open it draws 5A at 48V (through the 1A PTC fuse) but when closed inserts a high resistance coil in series so low holding current. Note the wires and auxiliary switch on side of mine. I presume the Schneider model has same?

 

[callmeburton]

Hedges, what makes you want more than two?
You have two SI's correct? This means you can control 4 relays?
All "US vendors" for this don't have it in stock ... European ones are backordered ... Tried to look on ebay but the ones I found there are not the same or they are the same but don't have the switching relay on the side.