Prime numbers problem

[Rednecktek]

So I've got a sailor buddy who pinged me about doing solar on his barn out at his place in Eastern WA and gave me a bit of a head scratcher.

He's got a barn style shed out there that he wants to split into 3rds for an apartment/garage/shop and run the whole thing on solar since it's a couple miles to the nearest power and at $4/ft that adds up right quick!

The "Plan" he's doodling out is to use a pair of the EG4 6.4Kw AIO's in parallel since he needs 240v split phase for the well, the welders, the plasma cutter, and a real size AirCon mini-split. The plasma cutter and welders both want 50a outlets so he figures just get the 6.5k's which should leave him plenty of capacity. A stack of the Trophy heated batteries (because it's COLD out there when he's at sea!) and a rack and good to go. He was smart enough to never get married so he can actually afford all this.

Here's the conundrum though, the panels. Like I said, it's a barn style roof and the building faces N/S so he's got the idea to put an 8s string of Trina 240w panels on each of the slanted sides AND right down the center of the roof. My confusion is this:

An 8s3p setup with those panels gives him about 320v and 8a per string (rough numbers) but each AIO is only going to have the inputs for 1 string, so where do you stick the 3rd string?

Would you do:
1: 8s2p into EG4-1, 8s1p into EG4-2?
2: 8s1p into EG4-1, 8s1p into EG4-2, 4s2p into an EPEver 200v model?
3: Some magical MPPT that can take 400v PV input and put the 3rd string in parallel?
4: Some other magical option?

Ideas on which way would be best and why?

Thanks y'all!

 

[wiseacre]

Some magical MPPT that can take 400v PV

here's a few magical beans that will cost about a whole cow

Victron Energy SmartSolar MPPT RS 450/100-Tr
Schneider CONEXT MPPT 100A 600V SOLAR CHARGE CONTROLLER
Morningstar TS-MPPT-60-600V-48 TriStar MPPT Charge Controller 60A 600VAC 48VDC

 

[wattmatters]

4: Some other magical option?

Use fewer much higher power rated panels for 2 strings only.

 

[robby]

So I've got a sailor buddy who pinged me about doing solar on his barn out at his place in Eastern WA and gave me a bit of a head scratcher.

He's got a barn style shed out there that he wants to split into 3rds for an apartment/garage/shop and run the whole thing on solar since it's a couple miles to the nearest power and at $4/ft that adds up right quick!

The "Plan" he's doodling out is to use a pair of the EG4 6.4Kw AIO's in parallel since he needs 240v split phase for the well, the welders, the plasma cutter, and a real size AirCon mini-split. The plasma cutter and welders both want 50a outlets so he figures just get the 6.5k's which should leave him plenty of capacity. A stack of the Trophy heated batteries (because it's COLD out there when he's at sea!) and a rack and good to go. He was smart enough to never get married so he can actually afford all this.

Here's the conundrum though, the panels. Like I said, it's a barn style roof and the building faces N/S so he's got the idea to put an 8s string of Trina 240w panels on each of the slanted sides AND right down the center of the roof. My confusion is this:

An 8s3p setup with those panels gives him about 320v and 8a per string (rough numbers) but each AIO is only going to have the inputs for 1 string, so where do you stick the 3rd string?

Would you do:
1: 8s2p into EG4-1, 8s1p into EG4-2?
2: 8s1p into EG4-1, 8s1p into EG4-2, 4s2p into an EPEver 200v model?
3: Some magical MPPT that can take 400v PV input and put the 3rd string in parallel?
4: Some other magical option?

Ideas on which way would be best and why?

Thanks y'all!

Why is he planing on using 240W panels? Even is he had all three connected he would only have 5760W going into two 6500W Inverters. He hardly has enough PV to power one much less two!

I assume he has a roof space limitation or he would not be using the North facing side of the roof?

I am also not sure by what you mean by putting "a string down the Center of the Roof" Do you mean panels lying flat? That would create shade on the South and North facing Panels.

I would think that Larger Panels like 400W Panels made into 4 strings should solve most of his issues. I cannot even reccomend a brand as I have no idea what he is willing to spend and what will fit on his roof.

 

[Rednecktek]

OK, a couple quick answers between watches:

Why is he planning on using 240W panels? Even is he had all three connected he would only have 5760W going into two 6500W Inverters. He hardly has enough PV to power one much less two!

Because he already has a stack of 25 and he won't be there for months at a time. He doesn't need the 12Kw all the time, just those rare instances where he's firing up the plasma cutter or the welder. His regular usage is well under 20Kw a day, he's been running on a 3500w generator while he's out there and just firing up the big 8Kw when he starts cutting & welding.

I assume he has a roof space limitation or he would not be using the North facing side of the roof?

The barn faces north/south so he can use the east and west angled sides and the flat strip down the middle. See krappy MSPaint attached.

I am also not sure by what you mean by putting "a string down the Center of the Roof" Do you mean panels lying flat? That would create shade on the South and North facing Panels.

It shouldn't, he's pretty sure the strip down the middle is wide enough to accommodate a string there.

I would think that Larger Panels like 400W Panels made into 4 strings should solve most of his issues. I cannot even recommend a brand as I have no idea what he is willing to spend and what will fit on his roof.

He's trying to keep it between $15k and $20 including a stack of the 220Ah Trophy heated batteries. He's already got a couple dozen of the 240w panels and he might be able to score more matching ones when he gets home. Doing a 12s string puts his VoC at about 460v which is too close for a place that stays below freezing for months at a time.

Mind you I'm just coming into Guam and he's just passing Alaska so there's a lot of guess & check involved and neither of us can swim out there and whip out a measuring tape.

 

[robby]

Well that cleared up a lot of things but I still see no way for him to get sufficient power with three strings of those 240W panels. One of the Inverters is going to have only one string and I just don't see that as being sufficient PV for that Inverter.

 

[Rednecktek]

Well this is still in the noodle phase, my question though was the best options for incorporating an oddball number of strings. If it was 4 or 6 strings that would be easy, but that one strip up on top of the roof is kinda throwing me for a loop.

I know that dual 6.5Kw inverters is way overkill for his likely needs, but it's more about future proofing up front. Can a pair of 3Kw's run a good size mini-split? Sure. Could a pair of 3Kw's run a deep well pump (yet to be drilled)? Maybe. Could a pair of 3Kw's run the plasma cutter and stick welder in the thicknesses he usually works with? Absolutely.

Can a pair of 3Kw's do all that at the same time? Not so much. Future proofing so he doesn't have to replace his AIO's later. Once one of us gets back (and it's kind of a race, he's on month 6 of his 4 month rotation) we can get measurements and try to max out the roof space. I think he's getting those panels for about $60ea, and we could stick 10-11 in series per AIO if the physics say so.

 

[wattmatters]

Put the top panels on tilts, 4 in landscape each facing same way as the East and West roofs.


Then you have 2 sets of 12 panels in each direction.

That gives 6S2P x 2

 

[robby]

A better plan but I still cannot see how he is going to run all this heavy duty split phase equipment when one inverter is getting very little pv in the morning and the other is suffering later in the day and we don’t have enough PV on any single string to combine an East and west string on a single mppt. This would be a great plan if we where actually over paneling the system and not under paneling it.

 

[Kornbread]

Build ground mounts and add more panels as $ allows.

 

[Zwy]

So I've got a sailor buddy who pinged me about doing solar on his barn out at his place in Eastern WA and gave me a bit of a head scratcher.

He's got a barn style shed out there that he wants to split into 3rds for an apartment/garage/shop and run the whole thing on solar since it's a couple miles to the nearest power and at $4/ft that adds up right quick!

The "Plan" he's doodling out is to use a pair of the EG4 6.4Kw AIO's in parallel since he needs 240v split phase for the well, the welders, the plasma cutter, and a real size AirCon mini-split. The plasma cutter and welders both want 50a outlets so he figures just get the 6.5k's which should leave him plenty of capacity. A stack of the Trophy heated batteries (because it's COLD out there when he's at sea!) and a rack and good to go. He was smart enough to never get married so he can actually afford all this.

Here's the conundrum though, the panels. Like I said, it's a barn style roof and the building faces N/S so he's got the idea to put an 8s string of Trina 240w panels on each of the slanted sides AND right down the center of the roof. My confusion is this:

An 8s3p setup with those panels gives him about 320v and 8a per string (rough numbers) but each AIO is only going to have the inputs for 1 string, so where do you stick the 3rd string?

Need panel specs..............

These? http://www.solardesigntool.com/comp...175/TSM-240PC05/specification-data-sheet.html

Personally, I'd forget the EG4 and purchase the LV6548's with dual MPPT's. Run 4S2p per PV input. If this is the correct spec sheet, that would be about 150VOC and 16A per string max, one input open. That's under the rated 4000W per LV6548 input, both for VOC and amps. One advantage of splitting up series into smaller parallel strings is output under cloudy conditions. Just because you have the ability to run higher VOC doesn't mean you harvest more electrons.

This is a case of just because a single input SCC has a higher VOC doesn't mean it can input the same as a lower VOC rated unit with 2 PV inputs or handle the size of the PV array.

Would you do:

4: Some other magical option?

Yes, magical with units that have 2 PV inputs.

Ideas on which way would be best and why?

Thanks y'all!

I think I have the math right, you can double check.

 

[Rednecktek]

Personally, I'd forget the EG4 and purchase the LV6548's with dual MPPT's.

The reason we nixed the 6x48's was that those will only put 30a to each leg and the welders call for 50a. The EG4's would put 60a to each leg.

That and they've become harder to find for some reason.

 

[Zwy]

The reason we nixed the 6x48's was that those will only put 30a to each leg and the welders call for 50a. The EG4's would put 60a to each leg.

6.5Kw is 6.5Kw. The EG4 and LV6548 are the same regarding inverter output, both peak and constant.

The EG4 has a different MPPT and different firmware.

That and they've become harder to find for some reason.

Watts247 Wholesale – Worldwide Shipping!

watts247.com

Look at the top of the page.........

 

[Rednecktek]

The panels (now that I've got a little bandwidth back) if I recall are the Trina 240w panels:
Rated Power: 240W
Open circuit voltage (VOC): 37.2 V (24v panels)
Max power voltage (VMP): 30.4 V
Short circuit current (ISC): 8.37 A
Max power current: 7.89 A

As for availability, heh, there's a Page 2 that has the bundle! Oops. My understanding was that the 5Kw and 6Kw split phase units were basically 2x smaller units in the same box. OK, so how about this for a thought considering 250v input per controller (Warning, krappy MSPaint incoming)

My other understanding was that the EG4 units handle startup surges (like a well pump or the air compressor) better than the MPP's and Growatts.

250VoC * 80% = 200VoC limit per string
37.2v * 5 panels = 186VoC
5s4p panels would be 240*5 = 1200w/string, *4 strings = 4800w of panels.
Same numbers with a 10s2p and 2 of the EG4's.
Grab a second controller for a 4s2p setup in parallel down the center line for an additional 1920w of panel and only have to get 3 more panels.

Keep in mind that 2 inverters and 3 of the 220Ah Trophy batteries are already eating up most of the budget. Sure, he could go buy 1000 panels, but with no battery it's kinda pointless.

 

[Zwy]

The panels (now that I've got a little bandwidth back) if I recall are the Trina 240w panels:
Rated Power: 240W
Open circuit voltage (VOC): 37.2 V (24v panels)
Max power voltage (VMP): 30.4 V
Short circuit current (ISC): 8.37 A
Max power current: 7.89 A

Looks to be what I found for specs.

As for availability, heh, there's a Page 2 that has the bundle! Oops. My understanding was that the 5Kw and 6Kw split phase units were basically 2x smaller units in the same box. OK, so how about this for a thought considering 250v input per controller (Warning, krappy MSPaint incoming)

Someone has been providing you misinformation or you aren't researching the subject. Or you seem set one the latest "kool kid on the block" mentality.

My other understanding was that the EG4 units handle startup surges (like a well pump or the air compressor) better than the MPP's and Growatts.

Wow, I have an oceanfront property in Kansas to sell you.

250VoC * 80% = 200VoC limit per string
37.2v * 5 panels = 186VoC
5s4p panels would be 240*5 = 1200w/string, *4 strings = 4800w of panels.
Either skip the center line of panels OR grab a second controller for a 4s2p setup in parallel for an additional 1920w of panel

Not following the line of thought here. I gave you the 4S2P in 3 strings which is 24 panels, each string to a MPPT input. The LV6548 has 2 MPPT's per inverter, the EG4 only one. There is one extra input that would not be used and a ground mount could be added later with another 8 Trina 240W panels or even larger.

I don't know where you are getting information from but if the source is the one selling you the product, I'd be very skeptical.

 

[Rednecktek]

Someone has been providing you misinformation or you aren't researching the subject. Or you seem set one the latest "kool kid on the block" mentality.

That's what I learned watching Will's and David's video reviews of the 5048 and 6048 units. And I've learned pretty much everything here, and that's why I created a post researching the subject.

I will freely admit I didn't see the Page 2 box at the bottom of the screen.

Wow, I have an oceanfront property in Kansas to sell you.

According to the manuals: EG4 6500 says 13Kw for 5 seconds same as page 45 of the 6548 manual, however the David Poz videos never turned out well for the Miter Saw Test on those MPP and Growatt units.

Also, the $650 price increase to get the MPP's goes a long way towards all the other stuff he's going to need like wire and lumber.

Not following the line of thought here. I gave you the 4S2P in 3 strings which is 24 panels, each string to a MPPT input. The LV6548 has 2 MPPT's per inverter, the EG4 only one. There is one extra input that would not be used and a ground mount could be added later with another 8 Trina 240W panels or even larger.

I follow, just wanted to double-check my math. I was thinking for only 1 panel more he could get 5S strings involved for a little more wattage. 5s on each input would be 4800w, throw the oddball string on with one of the others for a 5s/5s/5s/5s2p and with the lower amperage involved maybe eventually upgrade later into 5s2p's on the other three inputs as well.

Would the extra $650 be a better value than just adding in more MPPT controllers in parallel? Especially with the oddball string down the middle?

I don't know where you are getting information from but if the source is the one selling you the product, I'd be very skeptical.

Oh, I found this really cool site online.

 

[Zwy]

That's what I learned watching Will's and David's video reviews of the 5048 and 6048 units.

Completely different units than the LV6548. Will will tell you the LV6548 has worked very well, he is very impressed with it. As for Poz, I've never seen him have a LV6548. But I quit watching him, some things he does, well, I'll just leave it at that.

And I've learned pretty much everything here, and that's why I created a post researching the subject.

I will freely admit I didn't see the Page 2 box at the bottom of the screen.

According to the manuals: EG4 6500 says 13Kw for 5 seconds same as page 45 of the 6548 manual, however the David Poz videos never turned out well for the Miter Saw Test on those MPP and Growatt units.

Like I said, never saw a Poz video on the LV6548. Ian did a video on the LV6548 running just off PV and no batteries, was impressive. I had asked Ian before purchase about the 6048 and he told me the LV6548 was far better.

Also, the $650 price increase to get the MPP's goes a long way towards all the other stuff he's going to need like wire and lumber.

Either he ends up buying another SCC for the odd string (plus wire, fuses, etc) or spends the money for buying the LV6548. I consider Ian to have very good customer support, SS given the posts here, not so great.

I will say the LV6548 could have parts/software updates/hacks sourced easier than the EG4 which is proprietary. Second, I'm not a huge fan of large arrays running many panels in series if given the option to run more parallel strings simply due to shading from the local environment or clouds.

I follow, just wanted to double-check my math. I was thinking for only 1 panel more he could get 5S strings involved for a little more wattage. 5s on each input would be 4800w, throw the oddball string on with one of the others for a 5s/5s/5s/5s2p and with the lower amperage involved maybe eventually upgrade later into 5s2p's on the other three inputs as well.

You will have to factor in the temp coefficient of 5S if you really want to go that route. Considering the different angles and orientation of the barn, I don't 5S as a great solution.

Would the extra $650 be a better value than just adding in more MPPT controllers in parallel? Especially with the oddball string down the middle?

That $650 will be spent either way in my opinion.

Oh, I found this really cool site online.

Don't believe everything you read there.

 

[Skypower]

Completely different units than the LV6548. Will will tell you the LV6548 has worked very well, he is very impressed with it. As for Poz, I've never seen him have a LV6548. But I quit watching him, some things he does, well, I'll just leave it at that.



Like I said, never saw a Poz video on the LV6548. Ian did a video on the LV6548 running just off PV and no batteries, was impressive. I had asked Ian before purchase about the 6048 and he told me the LV6548 was far better.

Either he ends up buying another SCC for the odd string (plus wire, fuses, etc) or spends the money for buying the LV6548. I consider Ian to have very good customer support, SS given the posts here, not so great.

I will say the LV6548 could have parts/software updates/hacks sourced easier than the EG4 which is proprietary. Second, I'm not a huge fan of large arrays running many panels in series if given the option to run more parallel strings simply due to shading from the local environment or clouds.



You will have to factor in the temp coefficient of 5S if you really want to go that route. Considering the different angles and orientation of the barn, I don't 5S as a great solution.



That $650 will be spent either way in my opinion.


Don't believe everything you read there.

Remember that the LV6548 or the EG4 6500 will not properly operate in split phase mode if “battery less” is attempted! Don’t do that!

 

[Rednecktek]

Remember that the LV6548 or the EG4 6500 will not properly operate in split phase mode if “battery less” is attempted! Don’t do that!

Not a concern, trying to power your house at the whim of the weather just seems a stupid idea to us. Even grid-tie is in the Why-Would-Anyone-Ever-Bother category.

 

[Zwy]

Remember that the LV6548 or the EG4 6500 will not properly operate in split phase mode if “battery less” is attempted! Don’t do that!

The reason the video was linked was to show the ability of the LV6548 to run various high loads.