DIY 32.2kw off-grid Oregon farm system--advice?

[PNW_Solar_Guy]

Hey everybody,

Well I signed up on DIY Solar Forum last year, which was when I did the bulk of the work on out off-grid system as far as purchasing and building goes.

Now I'm at the point where I need to pull my wires, get everything wired up and turn the system on. I'm a little stumped though on where I need to install fuses, disconnects or any other shutoffs. I'd like to run some points past some more experienced DIYers, as I'm definitely not that, this being my very first solar system.

Here is a sketch of the system and plan as an overview.


Here is what I've got done so far.

I bought 2 pallets of 460w bi-facial BluSun panels, 70 panels in total. Designed and had fabricated adjustable racking, and I have 2 of those fully set up with panels mounted, which you can see in these photos.



We decided to pour concrete below each array to meet wind load needs with the added benefit of light reflection onto the backs of the panels, and no need for mowing or weed abatement under and around the arrays.

Each array is 16 panels, two separate 8-panel strings in series (the two strings on each array are not paralleled). I don't have photos included here but you can sort of see where I trenched and laid conduit stubbed up through the concrete on each array pad. All 1" conduit then comes up behind the 2nd array, between the forest and the backside of that array (you can see the grouping of pipes in a few of the photos).


We rented a trenching machine and trenched 300' through the forest. I have 300' of 1 1/2" conduit as well as a separate 1" conduit (for future expansion of the system if needed). Those conduit stub up next to the solar shed that we built on the other side of the 300' of trees, shown here.

Our well head for this field is just out of the frame of this photo. The pressure tank for this well is also going inside the solar shed, and pipes were trenched and set as shown here, before the concrete pour. Those are the water line pipes going to the various outbuildings and garden areas.

Here's the same shot now with the pad poured. I buried two parallel 2" conduits with sweeps. My plan is to run my lines from the inverters through those, under the slab, and up into the load panels on the opposite wall (nearest the camera).


Completed. This shot also shows the well head there next to the pressure tank.


Here is the back side of the solar shed, which shows the trench and the two conduit pipes stubbing up just exterior to the solar shed. The wires from all 6 arrays will enter the backside of the solar shed there, right in the middle.

Here is a sketched plan for what I plan to mount on the backside wall of the solar shed (where the PV wires all enter from the forest trench).


I see that I'm only allowed to attach 10 photos to this post, so I'll leave out the photos of the interior of the solar shed for now.

The inverters will go inside the shed as shown in the sketch above. I bought (4) EG4 6500-EX inverters, with the plan to get 4 more eventually (again, as shown). I will be adding server rack batteries to the system. For now I own (5) Pytes 48v 5.12kwh LiFePo batteries, will likely be adding Signature Solar batteries going forward.

Signature solar also shipped (4) IMO DC Disconnect Rooftop Isolator Switch, as well as (4) Nader DC Circuit Breaker | 60V 200Amp.

I'd love to hear any feedback in general on the system. I'm also happy to answer any questions if anyone has them.

I am about to pull all of the wires (10AWG) from the arrays to the solar shed, probably in the next 1-2 weeks.

For anyone who knows their stuff, I'd love to hear your thoughts on these questions I have about what's left for my system:

1. QUESTION #1: I plan to bring all 12 pairs of red/black 10AWG wires into a large weatherproof box at the back of the arrays, where my conduits all stub up. This will be for system shutoffs (perhaps the IMO DC disconnects here), one for each of the 6 arrays. Then the wires will all go into the 1 1/2" conduit through the forest and into the solar shed. My question here is, are DC disconnects required there by the arrays, or just a good idea (in case of emergency, so you can shut them off right there and then)? If required, should I use the IMO disconnects, or some other kind of DC disconnects?
   
   
2. QUESTION #2: Is a DC disconnect also required on the outside of the solar shed, before the wires enter that building? This seems redundant, but I seem to remember someone saying NEC code requiring this as well?
   
   
3. QUESTION #3: Does code require me to ground all of my arrays? If so, what do they need to be grounded to? I do have a ufer buried next to my solar shed, but I would prefer not to run a grounding wire that full 300' to the solar shed for that.
   
   
4. QUESTION #4: What fuses and disconnects do I need to purchase (if any, aside from the 4 200A Nader DC circuit breakers) for my inverter and battery setup inside of the solar shed? My aim is to make that inverter wall very clean with no exposed wires, by using metal pipe underneath each inverter routed right into a long wireway. This is the part I have the most questions on so I'm hoping to get some help on that solar shed wall setup.

Let me know if any questions or more photos needed. Like I said, I was only able to attach 10 to this post, so I can post below this if needed.

 

[SignatureSolarJames]

-DC disconnect by the inverters only
-wires must enter the building in metal conduit
-Ground arrays at arrays, common ground and dc ground is not needed
-no other fuses as long as you only parallel 2 or less strings per input

 

[PNW_Solar_Guy]

-DC disconnect by the inverters only
-wires must enter the building in metal conduit
-Ground arrays at arrays, common ground and dc ground is not needed
-no other fuses as long as you only parallel 2 or less strings per input

Thanks, SignatureSolarJames.

-DC disconnect by the inverters only
Do you know if there is NEC code to back this up? I ask because our local inspector mentioned that he thought I should have DC disconnects there as well as a mounted placard showing clearly which disconnect shuts of which array (for emergency responders to refer to if they are the ones shutting it down).

-wires must enter the building in metal conduit
Great. So box or no box, just as long as it enters via metal conduit?

-Ground arrays at arrays, common ground and dc ground is not needed
Would you mind explaining your answer in more detail for me? Just want to be sure I understand what you mean on that.

-no other fuses as long as you only parallel 2 or less strings per input
Gotcha. No strings will be paralleled.

Also, what about the (4) 200A Nader DC circuit breakers that Signature Solar recommended to me when I bought my inverters and IMO DC disconnects? Where are those to be placed in the system?

Thanks in advance James.

 

[SignatureSolarPeyton]

Not James, but I can help.

- NEC Article 690.13 states that the PV system disconnecting means shall be installed at a readily accessible location. Where disconnecting means of systems above 30 V are readily accessible to unqualified persons, any enclosure door or hinged cover that exposes live parts when open shall be locked or require a tool to open. Each PV system disconnecting means shall plainly indicate whether in the open (off) or closed (on) position and be permanently marked "PV SYSTEM DISCONNECT" or equivalent. Additional markings shall be permitted based on the specific system configuration.

- Yes, however, a raceway is preferred.

- 200A DC breakers go between batteries and the inverter (to protect the inverter). Make sure breakers are installed on the positive line of your batteries.

- Yes, all arrays need to be grounded.

 

[PNW_Solar_Guy]

Not James, but I can help.

Thank you, Peyton!

- NEC Article 690.13 states that the PV system disconnecting means shall be installed at a readily accessible location. Where disconnecting means of systems above 30 V are readily accessible to unqualified persons, any enclosure door or hinged cover that exposes live parts when open shall be locked or require a tool to open. Each PV system disconnecting means shall plainly indicate whether in the open (off) or closed (on) position and be permanently marked "PV SYSTEM DISCONNECT" or equivalent. Additional markings shall be permitted based on the specific system configuration.

But because the arrays are 300' from the solar shed and inverters, would it be acceptable for me to place one disconnect per array, limited to 6 per NEC, inside a weatherproof enclosure (as well as a "PV SYSTEM DISCONNECT" placard) at the solar array site as well as inside the solar shed (those there for convenience so I don't have to walk 300' through the forest when needing to disconnect PV power to work on inverters, etc)? Or is there another reason that would not be a good idea (besides the added cost)?

- Yes, however, a raceway is preferred.

Thanks. So to clarify, DC disconnects are not required on the exterior of the solar shed, and the wires entering here have to enter through metal conduit. Is that correct?

- 200A DC breakers go between batteries and the inverter (to protect the inverter). Make sure breakers are installed on the positive line of your batteries.

Great. For the sake of a clean install, can these 200A DC breakers be installed inside the wireway that is mounted horizontally on the wall (as shown in the sketch above)? Or do those have to be wired outside of the wireway somewhere? (I can install below the wireway before the wires enter the knockout if that is safer as it would be more accessible).

- Yes, all arrays need to be grounded.

Great thank you. Can you refer me to the relevant NEC code for proper grounding of our arrays that are mounted on concrete slab? I have been told a variety of things a out how to properly ground the arrays so I'm not sure who is correct on that.

Much appreciated.

 

[Quattrohead]

Fuses or circuit breakers protect the wires, so need to be at the solar panels. CB can also be used as a switch but as you have the PV disconnect switches, use those.
Ground at the panels/mount. Static and lightning protection for the frames only, not really the PV voltage as that should be floating.
I hope the FD have a chopper LOL.

 

[PNW_Solar_Guy]

Fuses or circuit breakers protect the wires, so need to be at the solar panels. CB can also be used as a switch but as you have the PV disconnect switches, use those.

That makes sense to me, thanks!

Ground at the panels/mount. Static and lightning protection for the frames only, not really the PV voltage as that should be floating.

Do you know what the requirements are for me to ground each of those 28'x12' arrays with 16 panels each? I have grounding lugs that will fasten to the superstrut, but I don't know whether I'm required to have a copper grounding rod, or something else? Each ground mount is bolted into concrete slab, and I used fiber in the concrete mix (vs rebar), in case that helps answer the grounding question.

I hope the FD have a chopper LOL.

Haha, I was wondering the same. We're in a fire prone zone, so it wouldn't be the first time I'd seen water transport helicopters over near our property.

 

[PNW_Solar_Guy]

Also, I just priced out the wire we'll need for the system (I was going to pull it in the coming weeks) and wow it sure is pricey.

I had planned on going with 10AWG copper stranded THHN wire to reduce voltage drop a bit. But now I'm wondering if I can get away with 12AWG copper stranded THHN instead, to save some money. Can anyone weigh in on this for me? Here are the panel details and total distances each string of panels will run from the solar field into the solar shed inverters:
All panels are BlueSun 460w bi-facial panels. Max Voc is 50.8v and Isc is 11.5a. So each string of 8 panels will be 406.4v / 11.5a.

Total length wire runs from panels to inverter:
Array 1: 409'
Array 2: 376'
Array 3: 388'
Array 4: 454'
Array 5: 428'
Array 6: 428'

I don't mind a little higher voltage drop as I have plenty of power and can add more in this field if needed, down the road. I assume voltage drop doesn't negatively affect anything else, except simply less efficient use of the system.

Right now I am able to source the 10AWG wire for $0.32/ft, and I think the 12AWG will be around $0.22/ft. Total wire needed is just shy of 10,000'. So I'm up over $3,000 for the 10AWG wire and I'll be closer to $2,000 if I can get away with the 12AWG wire.

If you have some suggestions or info to offer, I'd love to hear your thoughts.

 

[rodrick]

Also, I just priced out the wire we'll need for the system (I was going to pull it in the coming weeks) and wow it sure is pricey.

I had planned on going with 10AWG copper stranded THHN wire to reduce voltage drop a bit. But now I'm wondering if I can get away with 12AWG copper stranded THHN instead, to save some money. Can anyone weigh in on this for me? Here are the panel details and total distances each string of panels will run from the solar field into the solar shed inverters:
All panels are BlueSun 460w bi-facial panels. Max Voc is 50.8v and Isc is 11.5a. So each string of 8 panels will be 406.4v / 11.5a.

Total length wire runs from panels to inverter:
Array 1: 409'
Array 2: 376'
Array 3: 388'
Array 4: 454'
Array 5: 428'
Array 6: 428'

I don't mind a little higher voltage drop as I have plenty of power and can add more in this field if needed, down the road. I assume voltage drop doesn't negatively affect anything else, except simply less efficient use of the system.

Right now I am able to source the 10AWG wire for $0.32/ft, and I think the 12AWG will be around $0.22/ft. Total wire needed is just shy of 10,000'. So I'm up over $3,000 for the 10AWG wire and I'll be closer to $2,000 if I can get away with the 12AWG wire.

If you have some suggestions or info to offer, I'd love to hear your thoughts.

With 12 gage you will have a 6 percent or less loss with 10 gage you will be 3 percent if the loss is not a big deal to you 12 will work you will have to figure the cost/benefit

 

[niktak11]

Also, I just priced out the wire we'll need for the system (I was going to pull it in the coming weeks) and wow it sure is pricey.

I had planned on going with 10AWG copper stranded THHN wire to reduce voltage drop a bit. But now I'm wondering if I can get away with 12AWG copper stranded THHN instead, to save some money. Can anyone weigh in on this for me? Here are the panel details and total distances each string of panels will run from the solar field into the solar shed inverters:
All panels are BlueSun 460w bi-facial panels. Max Voc is 50.8v and Isc is 11.5a. So each string of 8 panels will be 406.4v / 11.5a.

Total length wire runs from panels to inverter:
Array 1: 409'
Array 2: 376'
Array 3: 388'
Array 4: 454'
Array 5: 428'
Array 6: 428'

I don't mind a little higher voltage drop as I have plenty of power and can add more in this field if needed, down the road. I assume voltage drop doesn't negatively affect anything else, except simply less efficient use of the system.

Right now I am able to source the 10AWG wire for $0.32/ft, and I think the 12AWG will be around $0.22/ft. Total wire needed is just shy of 10,000'. So I'm up over $3,000 for the 10AWG wire and I'll be closer to $2,000 if I can get away with the 12AWG wire.

If you have some suggestions or info to offer, I'd love to hear your thoughts.

I got my 10AWG THWN for exactly half that including shipping on ebay ($640 for eight 500ft spools). Check Facebook marketplace too if you can't find anything on eBay.

 

[PNW_Solar_Guy]

With 12 gage you will have a 6 percent or less loss with 10 gage you will be 3 percent if the loss is not a big deal to you 12 will work you will have to figure the cost/benefit

Thanks rodrick!

 

[PNW_Solar_Guy]

I got my 10AWG THWN for exactly half that including shipping on ebay ($640 for eight 500ft spools). Check Facebook marketplace too if you can't find anything on eBay.

Wow I haven't seen deals that good but I'll check again before making this purchase. I'd prefer to go with 10AWG but at this point it's too expensive, which is why I was considering the 12AWG.