diy solar

diy solar

Finally, the start of my 25kw Ground Mount grid-tie system

I was thinking of pvc conduit with a wye at each location of the beginning and end of a series for two wires to come out (pos and neg). All my series begin and end at the top of the railing, conveniently. This means I would need just 4 locations for wires to come out. Some thinking to do for sure. That would make 160' or more of conduit as well and conduit is ridiculously expensive at the moment. I could get away with 3/4" conduit with plenty of room to spare.
 
alrighty guys and gals. I need some more opinions on single pass vs dual pass. Wire is getting ridiculous in price and availability.

I can get single pass from thepowerstore for .36/foot or dual pass from them for .44/foot.

CED can get me single pass for .60/foot plus shipping.

My requirement is 1000' spools or greater. I'd even buy a 2500' spool if it were dual pass around the .30-.36 range.

Single pass 2000 x 2 = $1440
Dual Pass 2000 x 2 = $1760

I'm thinking I go dual pass. It has a much better UV resistance than the single pass. Pretty much the only thing that will be exposed is on the rack itself where it goes to the panels. But my thinking is that it is not worth the $300 to get something less UV resistant that will be outside for 30+ yrs.

Thoughts, opinions, suggestions. Shoot away. Please.
 
What are you guys using for lightning protection on the DC side? I would assume you would want to put that close to the panels on the rack. If I did that then I could use the single pass up to that point and then dual pass from there to the actual panels.
 
Here's what SMA uses on input to 600V rated GT PV inverters. I provided a link to similar parts from DigiKey.
You can select other voltages depending on your hardware. Should be high enough above max Voc it'll ever see so it doesn't clamp and burn up on the DC.
Theory seems to be that hardware can take a brief spike above its rating, and the MOV clamps it from going above what the inverter or SCC can tolerate even briefly.

diysolarforum.com

Testing Metal-Oxide Varistors (MOV)

Surge arrestors are used on AC and DC side of PV inverters for protection, to clamp high voltage transients. One inverter I have (actually several) are in the SMA family SUNNY BOY 5000-US / 6000-US / 7000-US / 8000-US. These come with a kit of MOV to protect the DC side: The MOVs are about...
diysolarforum.com diysolarforum.com

If you're worried about frequent nearby lighting, maybe install something at array as well as these at the electronics. Not sure, but gas discharge tubes might also be good.
 
Thanks. I'll do some reading. We don't get a whole lot of lightning here and it'll be insured, sooooo.......

I would like to put large enough junction boxes at the panels and at the inverters so I can add any of this stuff down the road, whether it be lightning protections, DC shutoff etc... I'll have to take a look at what home depot / lowes has for some water tight boxes.

I also need to get some EMT or galvanized pipe to make a freestanding setup for the inverters and all that stuff.
 
Not much money for discrete parts. I mean to add them someday. I decided the Delta arrestors I had were useless (but they might be good for clamping lightning.)

Some of the MOV have a thermistor to disconnect them if the short, so they don't burn up. With a 3rd lead, condition indication is available. I think Midnight uses that to turn on LED.

Gas discharge tubes:

Circuit Protection | Gas Discharge Tube Arresters (GDT) | DigiKey

Circuit Protection - Gas Discharge Tube Arresters (GDT) are in stock at Digikey. Order Now! Circuit Protection ship same day
www.digikey.com www.digikey.com

One example, 800V 20kA for $2:

 
I think a bit over my head at the moment. Not that I can't wrap my head around it, but I think the main focus will be to get up and running and leave the option to add this stuff down the road.
 
They exist, about 4 times the price, though.

www.homedepot.com

GE 200 Amp 240-Volt Non-Fused Emergency Power Transfer Switch TC10324R - The Home Depot

Run your backup generator with the GE 200 Amp 240-Volt non-fused emergency power transfer switch. This emergency power transfer switch offers a NEMA type-3R metal enclosure for outdoor use. For use with
www.homedepot.com

www.homedepot.com

Square D 200 Amp 240-Volt 3-Pole 3-Phase Fused Indoor General Duty Safety Switch D324N - The Home Depot

The Square D by Schneider Electric 200 Amp 240 Volt 3 Pole 3-Phase Indoor Fusible General Duty Safety Switch is designed for residential and commercial applications where durability and economy are prime
www.homedepot.com

www.homedepot.com

Square D 200 Amp 240-Volt 3-Pole 3-Phase Non-Fusible Outdoor General Duty Safety Switch DU324RB - The Home Depot

The Square D by Schneider Electric 200 Amp 240 Volt 3-Pole 3-Phase Outdoor Not Fusible General Duty Safety Switch is designed for residential and commercial applications where durability and economy are
www.homedepot.com

Always check eBay. I got one for about fifty bucks. And that was a "heavy duty" one (600V AC/DC)
 
I can't imagine it would matter if it were 3 phase or not.

Does it matter if it is "fusible"?
 
If 3 phase switch, you just use 2 of the poles for split phase.

"fusible" means has socket for fuses, which must be installed for it to work.
Unfused should be fine in series with a suitable breaker.
With (appropriately rated) fuse, it could be service disconnect equipment, e.g. connected to a line-side tap.

Mostly I've either found fusible general-duty single phase, or unfused heavy-duty 3-phase. But more models are available from the manufacturer. Get what is cheapest that meets the need.
 
It won't be connected to my breaker box due to doing a "line tape" on the original meter base. This is how they told me it would be done due to being nearly 200A at max output.

Could I use this shutoff switch as an "AC combiner" for the 3 fronius AC outputs? Would the fusible allow for current to ONLY flow in one direction. This is something I was thinking about. If you have 3 AC lines coming into a box that are all feeding it, what's to say that they couldn't try to backfeed each other at some point or in some scenario. A traditional "fuse" wouldn't really care which way current flows, but I don't know much about the ones that would go in these boxes. This has been a question on my mind for a bit now.
 
If a Line Side Tap connected directly to meter, no intervening fuse or breaker, then I'd think fusible is exactly what you would want. And should have only fuses capable of interrupting at least 22kA fault current, holders with something to prevent use of lesser fuses.

"Combiner" should have fuses or breakers for each inverter. Typically a breaker panel, but maybe mount DIN rail in this box and three 2-pole breakers or 6 fuses.

Current will flow both ways through switch, breaker, fuse.
 
iu
 
Thanks a ton for the pics and example.

Should I not be concerned about the inverters possibly back feeding each other on the AC side?
 
Nope.
They are all UL-1741 with anti-islanding. None of them will consume power. All they do is observe grid is up for 5 minutes, then shove all they can harvest from PV into the grid. If grid disconnects, voltage/frequency go out of range and they shut off. Anti-islanding ensures no funny load that somehow keeps AC cycling can trick them into staying up.

But, everything can develop faults like short circuits. There will be a maximum fuse/breaker rating for the inverter. And you have a wire size to it. Fuse or breaker must the the smaller of inverter requirement and wire ampacity. Were those 7700W inverters? If so, maximum 32A operating current so minimum 40A breaker recommended. Probably 50A breaker allowed. 8 awg would be good.
 
If you need DIN Rail, I have about 200 feet of it laying around.. I have slotted, solid, raised, etc..

If you're in Michigan, you could come pick some up free if you like.
 
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