Noodle time on a small grid tie?

[Rednecktek]

OK, so I like the idea of string inverters over micro inverters, they make more sense to me. I've been eyeballing the Growatt MIN 5000TL for a while now and I'm noodling out a small grid tie system just to offset some of the bill for the little bit of time I'm up there. I have a half dozen panels already up there collecting dust. As I understand it the panels aren't allowed to overhang the roof which severely limits me as the panels are longer than the peak-to-edge distance of the pump house. Here's my basic concept doodle:



So a few thoughts and questions for y'all:

Washington is under NEC2020, and the Growatt is UL1741 so does that make it work by code?

As I understand it the racking and standoffs to the roof have to be UL listed? What kind of standoffs and racking does that entail for regular metal roofing (I.E NOT the standing seam or wavy corrugated)?

I also understand that NEC2020 requires all the wires to be in metal conduit? Is that between the panels as well or just from the panels to the inverter or just the output of the inverter to the main power panel? If it's between the solar panels, how the hell do you get all the terminals in there?

Rapid shutdown, is that a button switch between the panels and inverter or the inverter and the main power panel? Or does the "anti-islanding" feature of the Growatt satisfy that?

The Growatt would just go to a double pole breaker in the main panel, correct? Or am I going to have to get a second meter mounted by the PUD that the growatt ties into directly?

What are the little "Gotcha!'s" that y'all have run into trying to DIY a grid tied system?

Thanks y'all!

 

[MisterSandals]

As I understand it the panels aren't allowed to overhang the roof

I think there is supposed to be 3ft on all sides, including the ridge for firefighters and others to be able to access and move around.

 

[MisterSandals]

What are the little "Gotcha!'s" that y'all have run into trying to DIY a grid tied system?

The red info/warning labels on everything, including the conduit at specific spacing. Some inspectors are sticklers for where they go and how they are worded.

 

[Shimmy]

I think there is supposed to be 3ft on all sides, including the ridge for firefighters and others to be able to access and move around.

Not an occupied structure so should be ok.

 

[Shimmy]

Rapid Shutdown is the TIGOs on the roof, one per panel. That is where the microinverters make things much easy on a small system.

 

[Rednecktek]

Wasn't planning on TIGO's or optimizers, trying to keep this on the cheap and simple.

 

[Shimmy]

Wasn't planning on TIGO's or optimizers, trying to keep this on the cheap and simple.

Does the pump house have four walls? If so I think avoiding them is going to be a challenge for a grid-tied system.

 

[Rednecktek]

Does the pump house have four walls? If so I think avoiding them is going to be a challenge for a grid-tied system.

I'm missing the joke... or the cat.

 

[Shimmy]

I'm missing the joke... or the cat.

If you only have three walls it is a shed and not a building.

Can you ground mount?

 

[pvgirl]

Gird tie in requirements are going to be determined by your power supplier, you should check with them on requirements for the inverter and any other requirements. Many require a locking disconnect to be installed to isolate the inverter. That inverter seems to have the required listings, but with the wiring setup on it I don't think you can get a NEC compliant wiring install.

Being installed on a building rapid shutdown is required you will need a transmitter and receivers on each panel, unless you are able to get an exception from the local officials due to this being an unoccupied building.

There are plenty of options for listed roof mounts, check with iron ridge or snapNrack for options.

PV circuit conductors from the panels to the inverter only need to be in metal conduit if they are inside the building. PV wires only need to in conduit once they leave the array. Metal conduit is commonly used from the roof to the inverter for protection of the wiring. Output of the inverter can be any NEC wiring method. Disconnects for the PV input and output of the inverter will need to be provieded within sight of the inverter. PV input disconnects are common on inverters. The inverter can tie in to a breker in the main panel, the most common configuration is a breker placed on the outside end of the breaker panel's bus from the main, as long as the sum of the main breaker rating, and the 125% of the inverters output amps, does not exceed 120% of the panels bus bar. If this is not the case there are other options as well.