Noob needs more help (pics inside)

[max2k]

Is there any issue to installing the panels 2-3 weeks before any electrical hook up is done (besides using up life prior to being able to capture the energy)? I would like to get the panels placed and mounted before the wind comes.

none that I'm aware of, especially if you know how are you going to do grounding and how you going to connect them in strings afterwards: if you place them close to each other it could make it difficult to access middle ones later. OTOH you have ground mounted array so you should be able to access any of them at any time from the back. The good recommendation here was also to connect '+' and '-' MC4 connectors of each panel to each other to prevent their oxidizing. While it will effectively 'short' the panel nothing bad will happen to it as panels won't ever exceed its Isc current and those connectors designed to sustain that easily. After all panels don't 'produce' energy, it was there to begin with so they can't possibly 'overheat'.

On my roof mounted array I used rails and according to the mfg specs had to put special 'lugs' to the rails to wire grounding wire through. The lugs and grounded wires ended up under the panels and I had to complete the grounding wiring along with panel installations as it would be impossible to do later without removing panels first.

[diegodog]

Is there any issue to installing the panels 2-3 weeks before any electrical hook up is done (besides using up life prior to being able to capture the energy)? I would like to get the panels placed and mounted before the wind comes.

[max2k]

Yikes!

I totally get the math on this one and get it now. Thanks Max and Butch.

I also prob wrongly assumed the bus was 200 due to the breaker size. If the bus bar is 125 then it appears I have a hot mess on my hands.

hope this won't be that bad. I'd make sure I get at least 200 A MSP given it's a new construction.

The panels are Hyundai Heavy Industry - HIS-M305TI

now we're talking- these are 305W rated panels so the STC power 60 of them can possibly produce: 305 x 60 = 18, 300 Watt which on AC side will produce: 18,300 / 240 = 76.25A. Your inverters would still be 'clipping' it to 75A but I doubt you'll ever see it- that 18,300W is the 'rating' in reality you won't see them above 90% (16.5kW) very often.

[diegodog]

Yikes!

I totally get the math on this one and get it now. Thanks Max and Butch.

I also prob wrongly assumed the bus was 200 due to the breaker size. If the bus bar is 125 then it appears I have a hot mess on my hands.

The panels are Hyundai Heavy Industry - HIS-M305TI

Thanks again guys.

[max2k]

Here is my "learned enough to be dangerous post of the day" Thank to Max and Tyab for getting me thinking on this track and learning a ton!

6 strings of panels. Each string is 451 volts 8.8 amps
SMA inverter (x3) 25A max out put on the AC side

We have the 25A x 3(inverters) = 75A * 1.25 for safety = 93.75A - 100 AMP breaker will be needed in the MSP

My MSP is 200A I multiply 1.2 x 200 and get 40A as the Max I can connect to the MSP which does not work (I need to do 100 AMP in the MSP) according to the above calculation.

Here is my question and the part I'm not getting.

My panels will put off a max AMP of 6 strings x 8.8A. That is 52.8 AMPS (at absolute full throttle).

Why would I double the amount needed up to 100 AMP for something that will max out and most likely never hit at 52.8 AMP. I can see leaving some safety up to 60 AMP but going to 100 AMP and crippling my MSP from 200A to 125A seems like a bad idea.

What am I missing?

If someone is on the side of follow the book go 100AMP can you please explain exactly the risk of how the 52.8 AMPS on the 60 AMP breaker causes disaster and how the 100 AMP breaker would perform better? Is there a scenario which you could throw out to help me see why one would go 100AMP

Thanks again!!!

since you're converting one DC voltage to another AC voltage the only thing which remains constant is the power (minus losses). Let's assume your 6 strings can produce 451 V x 8.8 A x 6 = 23,812 Watt. When converted to 240 V AC (L1/L2) it would produce current: 23,812 W / 240 V ~ 99 A. In reality inverters will be the limiting factor as each is rated to 25 A max so they can produce 75 A max together, this is the max current you can possibly feed back to MSP. Now the standard breaker for that is probably 80A and I believe you don't need 125% upgrade as 80A is its continuous rating. So, here you have MSP with supposedly 200 bus bar and backfeed 80A solar breaker. You can 'overload' your bus bar by 40A so you'd need to change your main breaker to 160A so it could accommodate your 80A backfeed: 160A + 80A = 240A.

BTW, I looked at the pics of your MSP and either I'm reading it wrong or it has 125A bus bar inside. Hope more experienced members would correct me there.

What is the model # of your panels? I'm trying to get their exact specs.

[Mike90250]

Ah, you meant loops in the wire, not the PVC conduit. That's better. Always use big service loops, just in case...

[ButchDeal]

Here is my "learned enough to be dangerous post of the day" Thank to Max and Tyab for getting me thinking on this track and learning a ton!

6 strings of panels. Each string is 451 volts 8.8 amps
SMA inverter (x3) 25A max out put on the AC side


My panels will put off a max AMP of 6 strings x 8.8A. That is 52.8 AMPS (at absolute full throttle).

Why would I double the amount needed up to 100 AMP for something that will max out and most likely never hit at 52.8 AMP. I can see leaving some safety up to 60 AMP but going to 100 AMP and crippling my MSP from 200A to 125A seems like a bad idea.

What am I missing?

If someone is on the side of follow the book go 100AMP can you please explain exactly the risk of how the 52.8 AMPS on the 60 AMP breaker causes disaster and how the 100 AMP breaker would perform better? Is there a scenario which you could throw out to help me see why one would go 100AMP

Because you are changing volts in the inverter.

here is the equations Amps X Volts = Watts

on your strings you have 451V and 8.8A = 3,968.8 watts
You are converting that to AC 240V so it is 16.54 amps on the AC side.
16.54a X 8 strings = 132 amps (there is loses and clipping in the inverters)

Also keep in mind the volts will not always be 451.

[diegodog]

Here is my "learned enough to be dangerous post of the day" Thank to Max and Tyab for getting me thinking on this track and learning a ton!

6 strings of panels. Each string is 451 volts 8.8 amps
SMA inverter (x3) 25A max out put on the AC side

We have the 25A x 3(inverters) = 75A * 1.25 for safety = 93.75A - 100 AMP breaker will be needed in the MSP

My MSP is 200A I multiply 1.2 x 200 and get 40A as the Max I can connect to the MSP which does not work (I need to do 100 AMP in the MSP) according to the above calculation.

Here is my question and the part I'm not getting.

My panels will put off a max AMP of 6 strings x 8.8A. That is 52.8 AMPS (at absolute full throttle).

Why would I double the amount needed up to 100 AMP for something that will max out and most likely never hit at 52.8 AMP. I can see leaving some safety up to 60 AMP but going to 100 AMP and crippling my MSP from 200A to 125A seems like a bad idea.

What am I missing?

If someone is on the side of follow the book go 100AMP can you please explain exactly the risk of how the 52.8 AMPS on the 60 AMP breaker causes disaster and how the 100 AMP breaker would perform better? Is there a scenario which you could throw out to help me see why one would go 100AMP

Thanks again!!!

[DanS26]

I would NOT put big loops in. Hell to pull wire through. Lay it in the trench, like a snake. If there is any curve in the bundle of PVC, alternate the bend, so you have a lazy S pattern in the trench, zig zags from left wall to right wall. Bed it in sand. Or follow local construction advice/practice

Mike, I meant 4" loops at the connections in the inverters and J boxes at the array. Standard electrical practices in cold weather areas.

[Mike90250]

I would NOT put big loops in. Hell to pull wire through. Lay it in the trench, like a snake. If there is any curve in the bundle of PVC, alternate the bend, so you have a lazy S pattern in the trench, zig zags from left wall to right wall. Bed it in sand. Or follow local construction advice/practice

[DanS26]

OP......not to complicate an already complicated project....but are you aware or have investigated expansion joints for your long conduit run? Since your conduit will not be very deep you will need to take the freeze/thaw cycle into greater consideration. Big loops at the connections at least. Your electrician probably knows this but maybe not.

[diegodog]

The OP must be smiling now or else beating his head up against a wall......here we are recommending fused connections and/or Schedule 80 conduit buried 18 inches in solid rock (see post #1).........heck just lay that high voltage DC on top of the rocks in conduit of course.......no one will bother it........

HAHA!!

I was able to get about 1 foot down for the wire ditch!!!! Some sections I can get down a bit more. It will be shallow none the less. I ran ethernet/coax from the main house to the barn about 1000 feet away. Ran the entire thing in conduit even though the lines were direct bury. Seems too risky to just throw it in there. There are sections of that run which are only 1-2 inches down due to the ledge (bedrock). The ledge causes massive headaches for any type of construction. And makes every job complicated.

I originally tried going below the freeze line for the 10 piers (6.5 feet down) due to the heaving issues. Took about 6 months before I gave up on that dream. As one dream gets crushed it normally opens up a better situation. Hopefully these slabs will be able to heave quite a bit since they are all independent from each other aside from the wiring. This project has been horrible for me as I know enough to get into trouble each step of the way and then hit a brick wall.

Building the house and barn were cake compared to this. I didn't realize about the mess I have with the breaker box as well. Though all those empty slots were going to be the ticket. Nope! Just another brick wall!!!

Thanks again guys.

[diegodog]

So here is a bit on the MSP placed on the inside for the barn. 200 amp main breaker at the top.

[DanS26]

The OP must be smiling now or else beating his head up against a wall......here we are recommending fused connections and/or Schedule 80 conduit buried 18 inches in solid rock (see post #1).........heck just lay that high voltage DC on top of the rocks in conduit of course.......no one will bother it........

[max2k]

Wire will be in conduit the entire run.

If I hit the line with the tiller or plough I would think there will be much bigger issues. I just assume I get crispy if I do it. It is not in a farming area so hopefully I don't do anything that outrageous but .....

Nothing will happen to you as what you're building is 'ungrounded' system meaning none of DC wires is tied to the ground. This also means your digging tool cutting the wire won't actually put current through your body to the ground as there's no return path for it. It might get sparky for a second though .