Noob needs more help (pics inside)

[diegodog]

Hey guy's I'm very thankful for the info. Some I understand and some I don't (will be studying the next few days). My knowledge level is very basic as I 'm finding out.

It looks like I made a mistake by buying the tin plated lugs. I watched a solar tutorial from Penn State University and they recommended Stainless or Tin coated as the tin to copper connection does not suffer from galvanic corrosion. The tin lugs do have the toothed washer to get passed the coating on the aluminum frame . For 60 bucks I better switch out to stainless to be safe as the damage caused by the corrosion is fast and devastating from what I have seen.

Inverter's are going on the back corner of the building right next to the Meter/ACDisconnect (Never occurred to me they could be placed at the array) however the building works better as I will have feet and feet of snow on the ground for months at a time to contend with. The back side of the building receives little sun so that's another advantage.
I'm completely broken on the electrical side. I was fairly sure I was lost and then I read your guys answers and now know for certain I am!

For getting wire to the inverter I like Max2K #2 idea (because that's the one I understood!)

- run 2x6 DC wires from each string + 6AWG for ligtning protection. Advantage- 450V DC would have about x4 times less losses compare to 240AC with the same wires. Given max current of 8.8 A and 80% reduction due to > 6 current carrying conductors in the conduit you only need to pass 11A so even 14 gauge will be satisfactory and 12 of them will be easier to pull. This option would obviously require inverters mounted on the side of the house.

With my limited understanding of things I need to get DC power to the one side of the inverter. So a straight shot to the inverter from right off the panels seems like the safest most straight forward option for a rookie. 12 wires (6 strings x 2 wires). I like the idea of stepping the wire down a size (after checking the charts for distance) to save a few $$. Since the DC disconnect is on the inverter I'm assuming If I kept it 10awg I would go from the panel to the DC disconnect/inverter with no equipment in between. If I step down a size on the wire I would need a junction box after the panels then a straight shot to the DC disconnect/inverter. Is this a correct line of thinking? If so it makes sense to me and I can get this line buried before the snow hits.

Panel's wires are PV type wire while the 'home run' wires are THWN-2 so somewhere at the array you need a box with terminals switching from one to another..
I don't understand this one. Does this mean I cannot connect the dc disconnect/inverter up to the PV wires coming off the panels directly? I have to switch them to THWN-2? Was this statement made assuming the inverter was at the panels and not the building? I may also be completely lost and not getting what your putting down.

One question on the grounding and I'm going to stop as the electric box talk got me scared.

You guys gave awesome information on the grounding. Thanks to both Max2K and Tyab.

Here is my plan
For grounding I'm using 6 awg all around. I will hook all the panel frames together with 6 awg. Once the panels are hooked together I will send (1x) 6 awg to a grounding rod in the field by the panels. Then I will send (1x) 6 awg to a 2nd grounding rod in the field by the panels but making sure they are the proper distance apart. And finally I will send (1x) 6 awg along the run to the barn to go to the inverter. Is this a correct understanding and blending of what you guys were saying?

Let me stop there so I don't get to far ahead of myself.

Butch I need to study more on the electric panel over the next few days so I can better understand what your saying. I'm sure I'll have a question or two!

Mike, Butch, Tyab and Max2K I thank you very much for responding and helping me accomplish as much as possible before calling in the electrician. I'm very grateful.

[ButchDeal]

Question 3
What is the path the AC current takes after the inverter. I'm not sure if I go from the inverter to my breaker box or if it goes to the current AC disconnect or if I need a 2nd separate AC disconnect. Can you give me an idea on the equipment that AC currnet hits (in order) as the power runs through the AC side with this setup.

Most AHJs require a single AC disconnect to shut the entire system down, so you will need an AC combiner.

Planning on using 10 awg and 30 amp breakers. I have 15 open slots on my panels 200 service.

Thanks again for everything

30a breakers are good in the AC combiner, then disconnect, then to your MSP But here is where it gets tricky.

You can't just land 3 X 30A breakers on your MSP, you need to combine them. Regardless depending on your MSP you cant feed 90a into it, you are most likely going to need a special MSP or a line side tap.

[tyab]

digodog - Here is a partial answer to #2 and covering GEC (grounding electrode conductor) and GE (ground electrode). You are required to electrically tie all the panels together and have a local ground electrode at the ground mount. Since your not using any sort of listed rail system, you are forced to use #6 solid copper wire to every panel approach. Think of it this way - one long continuous wire starting on one panel to the next in a long big S shape, with the wire finally heading into two ground rods, both 8' deep and the rods are at least 6' apart right at the ground mount. Those ground rods can be put into the ground up to a 45 degree angle so find that area where you have deeper rock to pound them in. There are other ways to do a ground electrode, see 250.52(A) if the ground rods simply will not work for you. This will be your compliant 690.47(D). Its important that the #6 wire be continuous unless you are familiar with the ways specified in 250.62(C)(1). As stated above, you can't let the copper touch the panel frames, so you need a listed lug that attaches to the frame - the panel frames will have one or more designated grounding holes. You can go expensive WEEB lugs - which will give a great connection or given you are trying to keep costs down you can use this:

https://www.garvinindustries.com/fittings/grounding-clamps-straps/lay-in-lugs/4-14al

They are bi-metal rated and here is what they look like on my system (I used them to bond various items).

https://www.flickr.com/photos/149650...3/31920780421/ (see the far right).
https://www.flickr.com/gp/149650329@N03/3vLP20 (middle)

They take a #12 stainless bolt - just make sure your panel hole can take that #12. Panel specs should have this info. You will need to get the stainless hardware, use mcmaster.com for a super wide selection. Hex bolt, external tooth washer on one side, external tooth washer and nut on the other. That lug has teeth on the bottom to help it compress into the aluminum coating to ensure a good bond (just not as good as the more expensive WEEB style). But they are only a buck and are UL listed.
Would also suggest using some aluminum anti-oxide on the aluminum to aluminum contact with the lug and on the external tooth washers to help keep that contact electrically good over time - something like this:

https://www.amazon.com/Ideal-30-030-Anti-Oxidant-Compound-Squeeze/dp/B000LDE7V4

I would suggest using anti-seize on the stainless bolts threads - this stuff is really good and a little goes a long ways but any stainless anti-seize will do.

https://www.albanycountyfasteners.com/Anti-Seize-compound-2400-Marine-Grade-p/1050-106.htm

[max2k]

Hello,
...
(3) SMA 6300 watt inverters (4 dc inputs possible - maxes out at 600 volts) - incorporated dc disconnect
(60) Hyundai 45.1 volt 8.8 amp panels
Using 10 AWG pv wire
Wiring in series
10 panels per string
2 strings per inverter
6 strings total.
grid-tie

looking reasonable IMO. Where are you planning to put your inverters- near arrays or on the building? There're 2 options:

- run L1, L2, N AC and 6AWG for lightning protection. Advantage- simpler circuit, disadvantage- thicker wires: 6300W SMA inverter has AC output rating of 25A multiplied by 3 gives 75A which would require 6AWG for L1, L2 and N which will be hard to pull through and probably more expensive.

- run 2x6 DC wires from each string + 6AWG for ligtning protection. Advantage- 450V DC would have about x4 times less losses compare to 240AC with the same wires. Given max current of 8.8 A and 80% reduction due to > 6 current carrying conductors in the conduit you only need to pass 11A so even 14 gauge will be satisfactory and 12 of them will be easier to pull. This option would obviously require inverters mounted on the side of the house.

Question 1
My plan currently is to run each string straight to the inverter (incorporated dc disconnect). No junction boxes, combiners, fuses, breakers. Each string gets a line straight from its last panel to its own input on the inverter with nothing in between. 451 volts and 8.8amps. This is a lot of wire obviously. Is there a better way to save on wire or is it better to keep it the way I'm planning. . Any disasters ahead? Missing something completely? Boneheaded?

Panel's wires are PV type wire while the 'home run' wires are THWN-2 so somewhere at the array you need a box with terminals switching from one to another..

Question 2
Grounding: I'm using the old school lug method (tin coated) as I have no rails for weeb or other fancy options. To be honest I'm completely confused on the grounding front. Once all the panels are connected with the grounding wire where is its first stop? To the rod in the ground under the meter or into the inverter? If the answer is rod in the ground should I use the one close to the building or should I put one out in the field somewhere? If I go from panels to rod in the field does it need to work back to the ground rod at the building or it terminated in the field? Is 6 AWG what is needed for the job?

you need to use special stainless steel grounding lugs to connect grounding wire to the panel's frames to prevent aluminum corrosion of the panel frames. You have to make sure your 6AWG copper wire never touches panel's frames directly. Someone with experience on ground mounted arrays might help with the solution.

Are those concrete blocks have any rebar you could connect to? If so I'd connect panel frames with 6AWG and then to the rebar below. Then I'd run 6AWG between rebars and through the trench to the building grounding rod.

Question 3
What is the path the AC current takes after the inverter. I'm not sure if I go from the inverter to my breaker box or if it goes to the current AC disconnect or if I need a 2nd separate AC disconnect. Can you give me an idea on the equipment that AC currnet hits (in order) as the power runs through the AC side with this setup.

Planning on using 10 awg and 30 amp breakers. I have 15 open slots on my panels 200 service.

Thanks again for everything

What rating your MSP busbar has? The service is 200A but internal bus bar could be lower/higher. Basically you can 'overload' that by 20% IIRC which is only 40A if it has 200A rating. You can probably replace your 200 A main breaker with 160A one to get some room for your inverters 75A combined output. This assumes your solar output is on the opposite end of bus bar relatively to the main breaker.

You can wire each inverter individually to its own 30A 'double' MSP breaker using 10 AWG essentially creating 3 completely independent solar systems.

or you can combine 3 inverter AC outputs together using some AC combiner box and then 'backfeed' the combined L1, L2 into single 'double' 80A breaker in your MSP. 75A wires would need to be 6AWG, but luckily for short run between combiner box and the MSP.

[diegodog]

Whoa, You have to have a way to disconnect the PV from the inverter, for testing or troubleshooting. You need a 500V rated DC breaker , or DC disconnect switch

Wires, Yep, you got lots of them. 10ga PV wire is pointless, you are paying for UV & Weather & Abrasion protection that you don't need. When your wire goes into the conduit, you could transition to 8 ga Alum wire. Cheaper than copper, but you need to insure all the connections / splices etc are rated for alum wire. You will need larger conduit, count the wires and size the conduit properly. But it saves $$

Disconnect is built into the inverter.

Great idea on ditching the PV wire for the underground run.

Thanks

[Mike90250]

Whoa, You have to have a way to disconnect the PV from the inverter, for testing or troubleshooting. You need a 500V rated DC breaker , or DC disconnect switch

Wires, Yep, you got lots of them. 10ga PV wire is pointless, you are paying for UV & Weather & Abrasion protection that you don't need. When your wire goes into the conduit, you could transition to 8 ga Alum wire. Cheaper than copper, but you need to insure all the connections / splices etc are rated for alum wire. You will need larger conduit, count the wires and size the conduit properly. But it saves $$

[diegodog]

Hello,

I'm back for more help. This time with pictures.

Here are my mounts. Home made. There is bedrock 1 foot down in places and 6 foot down in others so I made slabs for each pier so they can float with the frost heave. Winters are extreme. Used wood instead of metal due to cost. The metal prices were outrageous to get it where I am at. Those concrete blocks are 4 foot by 5 foot and 18 inches thick. It was 10 yards of concrete. Full truck worth. The wood is all 6x6 and is very heavy! I will be using paint and EPDM to put a barrier between the aluminum and the wood for corrosion issues. There are no inspection type issues I am as remote as you can get with power.

The complete run of all 10 pads is 160 Feet


Wire Trench - The Trench is 107 feet from the corner of the closest pier to the front corner of the building - The breaker box (electric panel) is in the front corner while the meter/ac disconnect is on the back corner on the same side of the building. Building is 60ft long on that side so 60ft between meter and the electric box.



Here is the current Meter + Ac Disconnect that was installed by the electrician when the power was first put in. The grounding electrode is in the ground right below the panel.





** I am not planning on hooking this up on my own. I will be calling the same electrician that put the service in to do final hook ups. I would like to go 99.99% of the the way though before he gets there. I'm having issues understanding a few of concepts so its making pre-running the wire a bit difficult. The forum got me past my first hurdle a couple days ago and I'm coming back for seconds if you guys are still available. Your info really helped me out.

(3) SMA 6300 watt inverters (4 dc inputs possible - maxes out at 600 volts) - incorporated dc disconnect
(60) Hyundai 45.1 volt 8.8 amp panels
Using 10 AWG pv wire
Wiring in series
10 panels per string
2 strings per inverter
6 strings total.
grid-tie

Question 1
My plan currently is to run each string straight to the inverter (incorporated dc disconnect). No junction boxes, combiners, fuses, breakers. Each string gets a line straight from its last panel to its own input on the inverter with nothing in between. 451 volts and 8.8amps. This is a lot of wire obviously. Is there a better way to save on wire or is it better to keep it the way I'm planning. . Any disasters ahead? Missing something completely? Boneheaded?

Question 2
Grounding: I'm using the old school lug method (tin coated) as I have no rails for weeb or other fancy options. To be honest I'm completely confused on the grounding front. Once all the panels are connected with the grounding wire where is its first stop? To the rod in the ground under the meter or into the inverter? If the answer is rod in the ground should I use the one close to the building or should I put one out in the field somewhere? If I go from panels to rod in the field does it need to work back to the ground rod at the building or it terminated in the field? Is 6 AWG what is needed for the job?

Question 3
What is the path the AC current takes after the inverter. I'm not sure if I go from the inverter to my breaker box or if it goes to the current AC disconnect or if I need a 2nd separate AC disconnect. Can you give me an idea on the equipment that AC currnet hits (in order) as the power runs through the AC side with this setup.

Planning on using 10 awg and 30 amp breakers. I have 15 open slots on my panels 200 service.

Thanks again for everything