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

live4soccer7

Solar Enthusiast
Are the fuses on the PV panel side of the breakers? I'm just trying to get all components lined out for my drawing.
 
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MarkSolar

Solar Enthusiast
Since you have more than 2 series strings, you need to fuse each string before they can be combined. I put my fuse/combiner box on the array mount under the panels to keep it out of the sun and rain. Immediately after the fuse/combiner box (I have 3 strings) I ran it into a Square D DC disconnect that's rated for 600v. I don't think the disconnect was necessary because the inverter has a DC disconnect on the input. But if there's a fire in the building where the inverter is located it seemed like a good idea to be able to disconnect the array outside.
 

live4soccer7

Solar Enthusiast
None of them will be combined. Each one will be separate and go to its own MPPT within the inverters.

So... I could fuse them out at the panels, as you've suggested and that will double as a junction box at the end of both arrays so I don't have to worry about pulling enough wire through to reach all the series runs at the beginning and end.

@MarkSolar Is your DC disconnect on the inverter something manual or automatic if a fault or other issue is detected?
 

MarkSolar

Solar Enthusiast
@MarkSolar Is your DC disconnect on the inverter something manual or automatic if a fault or other issue is detected?
Fronius inverters have a built in DC disconnect on the input. I'd love to know how it works because it's a small plastic handle attached to a small plastic box inside the inverter and it must carry the full input current/voltage. The square D DC disconnect is about 10 times the size. The disconnect is manual, and I don't know if there are conditions that would cause the inverter to automatically disconnect the DC.
 

wattmatters

Solar Addict
None of them will be combined.
Fusing arrays for the Fronius isn't required. Unless you have some local code requiring it.

At most you are running two strings in parallel with these MPPTs. They are high DC voltage / modest DC current systems. The off-grid type systems are typically lower voltage / higher current, often with more strings in parallel and this is when fusing each string matters more to protect each string.

As Mark says the Fronius inverter has a DC isolator switch built in (it's located underneath the inverter), but you can also add your own if you wish, which might be more conveniently located but also enable independent isolation of each MPPT input. Here's a pic from of underneath my Fronius Symo showing the in-built DC isolator but I also have external isolators, one for each MPPT input (20 panels each MPPT, 2 x 10 in parallel).

IMG_3139.jpeg
 

Sanwizard

Photon Sorcerer
Are the fuses on the PV panel side of the breakers? I'm just trying to get all components lined out for my drawing.
Yup, PV side. This is the way it looks hooked up. Water tight. Overkill with both fuses and breakers, with each string going to a separate MPPT in my inverters. (Each LV6548 has 2 x 4000 watt PV inputs at 250V 18amp)
I added lightning protection to it also.
 

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Hedges

I See Electromagnetic Fields!
I just built my own. Alibaba breakers/fuses and home depot electrical boxes.

You have Delta lighting arrestors mounted.
Do you have any illusions they will provide some protection?
How about a report of measurements verifying what they can actually do?
 

Sanwizard

Photon Sorcerer
You have Delta lighting arrestors mounted.
Do you have any illusions they will provide some protection?
How about a report of measurements verifying what they can actually do?
Its just to pass inspection if needed. I went cheap on them. Everything is well grounded though.
 

Hedges

I See Electromagnetic Fields!
Its just to pass inspection if needed. I went cheap on them. Everything is well grounded though.

Shouldn't matter to an inspector.
If you have utility grid connection, ought to have something there to swallow surges.
PV array can pickup coupled spikes from nearby lightning, so recommended there too.

Here's my test result:


Other parts that did work as expected:


Midnight has videos of their guys and a lab testing their lightning arrestor and the Delta.
 

Sanwizard

Photon Sorcerer
Shouldn't matter to an inspector.
If you have utility grid connection, ought to have something there to swallow surges.
PV array can pickup coupled spikes from nearby lightning, so recommended there too.

Here's my test result:


Other parts that did work as expected:


Midnight has videos of their guys and a lab testing their lightning arrestor and the Delta.
Yup, I saw those. Midnight is a much better solution. I even like the little lights. I have all the good stuff on my HAM antenna, including an 8' ground rod.
The stuff I built for this particular solar solution will be replaced at a later time with a commercial solution. This is a test bed for me to play with and learn.
Its amazing to me that I started in Feb, and feel like I now have at least a freshman college education on Solar energy due to all of you on this forum. I learned a LOT from you especially, so thanks for being so sharing with all your knowledge!
 

Hedges

I See Electromagnetic Fields!
You're welcome!

You might be surprised at how detached from reality the college freshman, undergrad, graduate education can be.
I challenged a contractor's submission regarding how a circuit would respond to higher frequencies. The response was a SPICE simulation showing that at the frequency of concern, an RC filter provided 200 dB (10,000,000,000x) attenuation. That misses the basic 2nd order characteristics of lumped components - "R" and "C" both contain "L" which becomes dominant at higher frequencies. At some level of isolation, inductive and capacitive coupling between separate components also shows up. (These things will matter, maybe in a beneficial way, for fast transients you're trying to protect against with surge arrestors)

The theoretical things taught are good for doing some modeling and calculation, while hands-on experience and seeing what worked in the past helps by kickstarting a useful implementation. I'm presently working on EMI issues with an SEM/FIB expert. First thing he did was use a microamp AC clamp meter to check currents running in system vacuum components, facility plumbing, ground wires. Star ground wiring and Mu metal are beneficial, but have to develop ways to deal with large loops inherent in the system (it isn't just circuit boards where ground scheme can be implemented as desired.)
 

wattmatters

Solar Addict
@live4soccer7 One thing to consider which I can't recall being mentioned is to consider including a Fronius consumption monitor "smart meter" in your main grid supply circuit board. It then connects to the data manager card inside one of the inverters via a data cable (and subsequent inverters).

The version of this you have in the USA is different to ours but I think functionally it's the same:

It provides a plethora of data on your grid imports and exports, which combined with your inverter production data enables you to have a great understanding on your system performance, your household consumption as well as a whole range of data points.

These are the data channels the inverter provides (this is via Fronius Solarweb). My system is three phase so some data channels reflect that:
Screen Shot 2021-09-24 at 5.53.38 am.png

And below are the addition data having the smart meter enables:
Screen Shot 2021-09-24 at 5.53.57 am.png

Screen Shot 2021-09-24 at 5.54.27 am.png



The Fronius has built-in relay controller which can be used for things like when a hot water service operates and programmed based on PV production or excess/export production values.

Data can be polled via your own systems if you want and there are Home Assistant integrations available as well which can of course be part of home automation actions:

e.g. perhaps you set up certain circuits or appliances to operate when a particular combination of events occurs (be it time of day, weather, excess solar production etc).

Just some stuff to consider down the track for which having the data metering can enable.
 

live4soccer7

Solar Enthusiast
@live4soccer7 One thing to consider which I can't recall being mentioned is to consider including a Fronius consumption monitor "smart meter" in your main grid supply circuit board. It then connects to the data manager card inside one of the inverters via a data cable (and subsequent inverters).

The version of this you have in the USA is different to ours but I think functionally it's the same:

It provides a plethora of data on your grid imports and exports, which combined with your inverter production data enables you to have a great understanding on your system performance, your household consumption as well as a whole range of data points.

These are the data channels the inverter provides (this is via Fronius Solarweb). My system is three phase so some data channels reflect that:
View attachment 65978

And below are the addition data having the smart meter enables:
View attachment 65979

View attachment 65980



The Fronius has built-in relay controller which can be used for things like when a hot water service operates and programmed based on PV production or excess/export production values.

Data can be polled via your own systems if you want and there are Home Assistant integrations available as well which can of course be part of home automation actions:

e.g. perhaps you set up certain circuits or appliances to operate when a particular combination of events occurs (be it time of day, weather, excess solar production etc).

Just some stuff to consider down the track for which having the data metering can enable.
Thanks! I'll definitely take a look at that. I always like to look forward a bit to leave options open.
 

live4soccer7

Solar Enthusiast
I still need to make 100% certain that fronius primo can do frequency watts. I do wish it had the SPS functionality, similar to the sunny boy as well.

Even if I wanted to do SMA, it seems the max input DC current is 10A / MPPT. That definitely would not work since the panels I'm looking at are all higher than that (around 11A)

1632430113910.png
 
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wattmatters

Solar Addict
I still need to make 100% certain that fronius primo can do frequency watts.
I can't imagine they don't. Stacks of Tesla Powerwalls in AC coupled systems with Fronius Primo inverters here, and the PW uses grid frequency control to moderate the inverter's output when operating in off-grid mode.

I'd be making a call to Fronius HQ in the USA to ask the question and get them to point you to relevant documentation.
 

live4soccer7

Solar Enthusiast
I can't imagine they don't. Stacks of Tesla Powerwalls in AC coupled systems with Fronius Primo inverters here, and the PW uses grid frequency control to moderate the inverter's output when operating in off-grid mode.

I'd be making a call to Fronius HQ in the USA to ask the question and get them to point you to relevant documentation.
Great to know! I planned on reaching out. I'm sure I will sound pretty incompetent on the phone though. haha
 

MarkSolar

Solar Enthusiast
I still need to make 100% certain that fronius primo can do frequency watts. I do wish it had the SPS functionality, similar to the sunny boy as well.
I can find lots of vendor pages that say they do, but I've never found anything on a Fronius page that says they do. I'd call and ask them to point to a statement in their documentation.
Even if I wanted to do SMA, it seems the max input DC current is 10A / MPPT. That definitely would not work since the panels I'm looking at are all higher than that (around 11A)

View attachment 65983
Same problem I had, they were just a hair too low for me to use. The Fronius supports 33A on one of their two trackers, seems like a really big difference given the other parameters are relatively similar.
 

live4soccer7

Solar Enthusiast
I can find lots of vendor pages that say they do, but I've never found anything on a Fronius page that says they do. I'd call and ask them to point to a statement in their documentation.

Same problem I had, they were just a hair too low for me to use. The Fronius supports 33A on one of their two trackers, seems like a really big difference given the other parameters are relatively similar.
You would think they would have higher input currents on the SMAs given the higher power panels now. Looks like they need a new version. Might be why they are on sale at some places.

I'm definitely feeling good about the inverter selection for the project. If only I had 3 phase.
 

Hedges

I See Electromagnetic Fields!
I still need to make 100% certain that fronius primo can do frequency watts. I do wish it had the SPS functionality, similar to the sunny boy as well.

Even if I wanted to do SMA, it seems the max input DC current is 10A / MPPT. That definitely would not work since the panels I'm looking at are all higher than that (around 11A)

View attachment 65983

10A MPPT operation, 18A max Isc

"Parallel Operation of the DC Inputs A and B The DC inputs A and B of the inverter can be operated in parallel and up to three strings can be connected to it in parallel. As a result, as opposed to normal operation, up to three strings can be connected directly to inverters with two DC inputs and up to four strings to inverters with three DC inputs. The inverter automatically detects the parallel operation of the DC inputs A and B."

Presumably that means 20A operation and 36A Isc for paralleled inputs A & B.
That only lets you get one 11A Imp string fully utilized.

Connecting an 11A Imp string to a 10A max input could cause some clipping. 1/11th of power lost during peak sun, or less depending on how much voltage rises to reach 10A. The power/voltage curve is fairly broad, but it rolls off faster moving to higher voltages than to lower.

For PTC rather than STC ratings, it is voltage that decreases or current? With power 85% or 90% of STC, maybe that is within 10A.

If you had two parallel strings of different orientations feeding A & B, Imp would probably always be below 20A.


Earlier models accept as much as 36A, but they won't have the UL-1741 SA you probably need to connect.
 

live4soccer7

Solar Enthusiast
Not a whole lot to update yet. I'm having supply issues and problems getting quotes on ground mount framework components.

I have finished the site drawing and one-line in autocad. That was fun to use autocad again. It has been years. I'll post up when I get more time for feedback or if people are curious.

I've had a change of heard in part of the design though. I'm thinking that the Hyundai Bi-facial panels will be the way to go. I'm at a LAT of 47* and I was reading that bifacial is particularly beneficial above the 40* mark. I'm thinking of doing the panels at an angel of 45-47* (if I can get engineered plans). This will give me the best year round production numbers (month to month) and the "larger" angle will provide more benefits to the bifacial panel style as well. This leaves me open to replace them with bifacial again when necessary. Doubt that I'll actually care in 30 years or whenever that happens, but still planning ahead. ALSO I think this sets me up much better if the utility company really changes their billing style or net meter import/export setup so I can utilize batteries and get a closer monthly average from month to month through the whole year.

I'm sure I'm way overthinking it, but that's what I do best and I have time burning a whole in my pocket while I try to get info from suppliers, which has been quite challenging.

I'm going to call the utility company and see how long their application acceptance stands because my design depends on their accepting my system size, but if I can't get supplies then it may not happen immediately. I'm in a bit of a catch 22 with everything depending on each other between that and permitting as well.
 
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