Fronius IG4000 Sting Inverter - question regarding string configuration

[JanS48]

Greetings everyone - I'm getting a bit closer as I'm putting the RI Solar permit together. In RI you get a Solar permit where they must approve your racking plan before rack installation and then inspect the racking before you can install the panels. I'm getting all that together now. At the same time you need to pull an electrical permit to wire the Inverter to main panel. Then you need to arrange for the Net-Meter commissioning & installation.
I have a question regarding string arrays - do most string array installations use optimizers? Does approx $ 50. each sound about right? Any particular brand that is better than others?
Thanks in advance
Jan

[bcroe]

I have a question regarding string arrays - do most string array installations use optimizers? Does approx $ 50. each sound about right? Any particular brand that is better than others? Jan

Optimizers can be useful if you have shade issues or badly matched
panels in a string. But if not, they will increase cost, failure modes,
radio interference, and some losses. Lots of string systems were built
before optimizers were invented, and are still being built. Bruce Roe

[JanS48]

@bcroe
Ok, thanks for the heads up. The array I'm planning has all the same panels and all will receive the same amount of sun 99% of the time. The only advantage I can see is that should one panel go bad or way under-perform the rest continue on. I was curious what the consensus was here on their use when installing new string arrays. Cost - I was not thrilled about spending another $ 50. per panel installed but I could live with it if optimizers were the way to go. Per your comments I'm leaning towards skipping the optimizers.
Thanks
Jan

[scrambler]

If You have no shade issue, you definitely do not need optimizers, but you still probably need rapid shutdown devices.

Tigo has modules that will give you that and also individual panel monitoring. The model is TS4-A-S, see all the variants below
TS4 Flex MLPE | Tigo Energy

[azdave]

@bcroe
Ok, thanks for the heads up. The array I'm planning has all the same panels and all will receive the same amount of sun 99% of the time. The only advantage I can see is that should one panel go bad or way under-perform the rest continue on. I was curious what the consensus was here on their use when installing new string arrays. Cost - I was not thrilled about spending another $ 50. per panel installed but I could live with it if optimizers were the way to go. Per your comments I'm leaning towards skipping the optimizers.
Thanks
Jan

KISS works for me. I would not add any extra failure points into the system, especially more components on the roof, if they do not have to be there there. I have 26 panels with 13 per string which is really handy to compare the two. My monitoring routine amounts to looking at the collection totals I'm provided daily by my POCO and an occasional glance at my inverter that I go by 4-5 times a day anyway. My inverter display screen always shows the two strings output side by side. No buttons to push or menus to scroll through. It takes two seconds to check if they read the same value or not. After almost 9 years, the two strings are still within a few watts of each other. Doesn't get any easier than that.

[JanS48]

@azdave
It sounds like you have a great system going there. I'm a long time fan of KISS.
What brand and size of inverter are you using? And a question: If you were going to install an additional 20 panels would you install string arrays or go with individual inverters like an Enphase 8 or similar?
Thanks
Jan

[azdave]

@azdave
What brand and size of inverter are you using? And a question: If you were going to install an additional 20 panels would you install string arrays or go with individual inverters like an Enphase 8 or similar?

My system was installed 9 year ago so the inverter is no longer made but is a Power One Aurora (previously ABB) PVI 6000W. After a test grid-tie program with the local POCO I was paid for my trouble by being given an identical inverter that is packed away in a cool place for future use. That was a nice score.

If I had to install a new system today under the same conditions, I would choose a string inverter but would need panel-level rapid shut down since that was not required when my system was installed.

[bcroe]

KISS works for me. I would not add any extra failure points into the system, especially more components on the roof, if they do not have to be there there. I have 26 panels with 13 per string which is really handy to compare the two. My monitoring routine amounts to looking at the collection totals I'm provided daily by my POCO and an occasional glance at my inverter that I go by 4-5 times a day anyway. My inverter display screen always shows the two strings output side by side. No buttons to push or menus to scroll through. It takes two seconds to check if they read the same value or not. After almost 9 years, the two strings are still within a few watts of each other. Doesn't get any easier than that.

The same approach works well here, not checked every day. No
rapid shutdown needed for the ground mount. Bruce Roe

[JanS48]

Thanks to all for the comments but as usual they bring up more questions. How do I know if I need rapid shutdown? I believe the Fronius unit I have shuts down should the grid go down but that does not sound like the same thing. So how do I know if I need rapid shutdown? I didn't see any mention of that in the permit questions but I don't dare ask that of the electrical inspector - as I'm not a contractor - the inspectors in RI make it as hard as possible for a home owner to do anything. If I asked that question they would almost certainly say yes.
Does a chart exist by state that has that requirement listed?
Thanks in advance
Jan

[scrambler]

Rapid shutdown is potentially a requirement of your local code.
Check with your permit office, or eventually ask local installers.
This is to disconnect the panels at the panel level, so it requires a module on the panel.

[oregon_phil]

Thanks to all for the comments but as usual they bring up more questions. How do I know if I need rapid shutdown? I believe the Fronius unit I have shuts down should the grid go down but that does not sound like the same thing. So how do I know if I need rapid shutdown? I didn't see any mention of that in the permit questions but I don't dare ask that of the electrical inspector - as I'm not a contractor - the inspectors in RI make it as hard as possible for a home owner to do anything. If I asked that question they would almost certainly say yes.
Does a chart exist by state that has that requirement listed?
Thanks in advance
Jan

Like @scramber said, check with your local permit office to inquire about rapid shutdown. Looking at RI statewide code, they are following NEC 2020 electric code which requires module level rapid shutdown. But even if RI wasn't following NEC 2020, NEC 2017 also requires module level rapid shutdown. You have to go back to NEC 2014 to get array level shutdown instead of module level shutdown. Odds are that you will be required to have module level shutdown since nobody I know makes NEC 2014 array level rapid shutdown devices.

Regarding your solar permit requirements found on the RI website (STATEWIDE-SOLAR-PERMIT-APPLICATION-12-6-17-FINAL.PDF). This permit requires a RI Professional Engineer to evaluate the existing condition of your house and certify that the proposed solar system will accommodate all said loads. I know you said there are people in your neighborhood that have DIY'ed their solar install. I think it would be a good idea to talk to those neighbors to find out who they used for the RI PE letter. If possible, have a look at the entire drawing package. Depending on how good you are with CAD, regulations, etc. , you might want to get a quote from a PE that works in the solar installation field to turn out a complete drawing package. Just like everything else, it's all about tradeoffs.

[JanS48]

oregon_phil well, thanks for the bad news about the module level rapid shutdown. What exactly am I looking for to do this? Is that feature built in to module optimizers?
As for the PE - i'm following a couple of leads now for one that will do a minimal drawing and a letter. It's looking like that's going to cost me the better part of a grand. I've watched a solar company come in and install everything in a day - they deploy inspector magic I guess.

[scrambler]

I gave you the reference of one of the main one from Tigo.

They make these modules in different configurations. You can have them as Rapid shutdown only, or you can add individual panel monitoring too, which for the small added cost is worth it in my opinion.

From my last post:
Tigo has modules that will give you that and also individual panel monitoring. The model is TS4-A-S, see all the variants below
TS4 Flex MLPE | Tigo Energy

[JanS48]

I spent the last several hours learning about Rapid Shutdown and all the Tigo offerings - By the time I purchase the modules, and RSS transmitters, and an Initiator - which I had trouble finding and the box to house same and the hookup of wiring for the multiple 12v supplies for the RSS transmitters - I'm better off not using the Fronius string inverter and going with an Enphase 8 system that does it all. Am I missing something here? Apparently I can string up to 11 of my 320 watt panels together and get by with #12 wire in conduit, going back to a double 20 amp breaker. I'll research best practices for the Enphase 8 installations a lot more but it's looking like that is the way to go given the complexity and cost of the Rapid Shutdown required in roof stings - what a blow to roof string installations.
Jan

[solar pete]

Hi All,

Rapid shut down, what a crock, we never let it in here and they have given up trying as everyone knows its a crock, I believe there is a ground swell starting in the USA to get rid of it, good luck with that peeps, cheers