New 40' container power house build.

Hedges

Photon Sorcerer
Put 2 in series. Repeat for a total of seven strings of 2. Then parallel those. "2S7P"
One problem with 7 panels in parallel, connected in series with another 7 panels in parallel, is if some strings were unplugged, current from 7 panels would be forced through fewer panels - that's too much current for the diodes. Or the wires.

There should be fuses or breakers for each string. Here are some ideas:




 

mopat

Solar Enthusiast
I am getting confused, Original Poster, bought 3 breaker combiner panel, BUT discussion was about 6 breaker combiner boxes.
OP has 7 pairs of PV in parallel.
 

Hedges

Photon Sorcerer
Reading first post, he has 20 panels.
I think he's trying to put in 7 pairs of panels, maybe because that hits wattage limit of charge controller.
But as I said earlier, he could use all of them if at different orientations. So I think 10 strings of 2 panels is good.

 

DCDave

New Member
Mopat and Hedges,

From: Sep 16, 2020
I need an 2S 7P configuration, per Ian delivering 125volts and 42Amps at the charge controller, keeping voltage under the required 145VOC /Vdc.
So my current systems is limited to 14 of my 20 panels, in a 2-Series x 7-Parallel to achieve this maximum panels used.

I need to keep the Controller under 145 volts VOC, each panel is 64.9VOC and 6.46A ISC.
1. As my new path is to create a group of 14 panels, each pair in series, then parallel the 7 strings, which will not fit in my combiner box but only requires one breaker at 63A (70A if Midnight solar made one, they skip from 63A to 80A).
2. The 64.6A ISC x 7 panels = 45.22A. Multiplied by 1.5 for excess per code is 67.83A for a Breaker, which Midnight solar does not sell, and 80A is too large. My question is; At multiplier of 1.4 = 63.08A is that big enough?
3. I assume there is no issue with delivering the 7 strings to a pre-combiner box, with a 8 position bus bar for positive and one for negative. Then feed the single wire into the Midnight combiner box with the breaker and I have met my need to both shut off power and protect the inrush voltage to the Charge Controller. Is this a safe assumption?
4. I suppose can put 7 breakers in a 6 breaker box if necessary, they simply clip to a DIN rail, I can have a 7 breaker bus bar cut out on a water jet if necessary, like this 8 position bar.
1601164725143.png
 

Hedges

Photon Sorcerer
Mopat and Hedges,

From: Sep 16, 2020
I need an 2S 7P configuration, per Ian delivering 125volts and 42Amps at the charge controller, keeping voltage under the required 145VOC /Vdc.
So my current systems is limited to 14 of my 20 panels, in a 2-Series x 7-Parallel to achieve this maximum panels used.

I need to keep the Controller under 145 volts VOC, each panel is 64.9VOC and 6.46A ISC.
1. As my new path is to create a group of 14 panels, each pair in series, then parallel the 7 strings, which will not fit in my combiner box but only requires one breaker at 63A (70A if Midnight solar made one, they skip from 63A to 80A).
2. The 64.6A ISC x 7 panels = 45.22A. Multiplied by 1.5 for excess per code is 67.83A for a Breaker, which Midnight solar does not sell, and 80A is too large. My question is; At multiplier of 1.4 = 63.08A is that big enough?
3. I assume there is no issue with delivering the 7 strings to a pre-combiner box, with a 8 position bus bar for positive and one for negative. Then feed the single wire into the Midnight combiner box with the breaker and I have met my need to both shut off power and protect the inrush voltage to the Charge Controller. Is this a safe assumption?
4. I suppose can put 7 breakers in a 6 breaker box if necessary, they simply clip to a DIN rail, I can have a 7 breaker bus bar cut out on a water jet if necessary, like this 8 position bar.
View attachment 23760

"So my current systems is limited to 14 of my 20 panels, in a 2-Series x 7-Parallel to achieve this maximum panels used."
Ah, but as I keep saying, you can hook up 20 panels, 2S10P, and not exceed wattage or current that would come from 12 or 14 panels, 2S6P or 2S7P.
Just aim the 10 strings in various directions. If they are at an angle to each other, area presented to the sun at any given time is less, so amps and watts is less. But earlier and later in the day, it will make more power than a single orientation would. Spreads your production over the day.

"but only requires one breaker at 63A"
Needs one fuse/breaker per string. That is what the "maximum fuse" spec on your PV panel label is for. If there is a short in a panel, the other 6 strings dump 35A into it and melt something. (That's why we like like high voltage series strings and no more than two strings, e.g. 7S2P, if our charge controller can take that high a voltage. All my stuff is designed around 600V absolute max. Look Ma! No Fuses!)

"My question is; At multiplier of 1.4 = 63.08A is that big enough?"
The idea was to get 1.25 x continuous current to avoid nuisance trips. Cold day, current can be higher than label. But your charge controller won't be operating panels at Isc, rather at Imp. Worst that can happen is breaker trips, so you should be fine. If we were sizing wire to operate with no breaker, then would want to use worst-worst case figures.

6 awg rated 90C has ampacity 75A (in bundle of 3), or 105A (single conductor in free air.) So I don't think you really need a breaker on that size wire.

"I suppose can put 7 breakers in a 6 breaker box if necessary, they simply clip to a DIN rail, I can have a 7 breaker bus bar cut out on a water jet if necessary, like this 8 position bar."
That is the thing to do (the breakers on DIN, at least.) Lots of commercial parts are tinned aluminum. I think copper would be the way to DIY.

"water jet"
You kids with your newfangled toys! I grew up with an arc welder and oxy-acetylene torch. Want to see how I get a 1.25" nut off my tractor when I don't have enough air and the right wrench to do it?
I need to make a breaker panel cover with a rectangular cutout for DIN transfer switch. Water jet would be a way if I had access. I don't have a neat way to make rectangular inside cuts, just round holes with a Greenlee Slug Buster.
Such a busbar I'd probably drill and chop with bandsaw. But your CNC water jet is going to be more steady than me with bandsaw. I don't even have access to a Rotex punch like I used in school. Picked up a cheap used HF drill/mill lathe, but the vertical spindle is stiff.
 

mopat

Solar Enthusiast
OK, sounded like you bought a Midnight Solar 3 breaker combiner box.
So feed it with 3 pair and 4 pair;
14 x 327 = 4578 watts That SPF3000TLLVM-48P is rated 4500, it will be fine.
You can use their 63 amp Over Current Protection Device on each string as a PV disconnect.
MC4's can combine the (3pair, 4pair) strings; they'll be under 30 amps. 10AWG fine to combiner box.
 

DCDave

New Member
My Combiner box is a re-purposed 125a service panel with a new Din rail and two 63A breakers installed with the buss bar pictured in my response above on 8/26 with 8 connections for breakers. (I'll attempt adding photos later). Made a custom breaker cover plate, using 22 gauge galvanized, and had the hole for the 7 breakers cut out with the water jet, Just $10 for labor. Nice clean hole with great square corners, (See blue tape in pic.) No need for an oxy acetylene torch here.. ;#D
I'll lay out two strings of two panels near these boxes on my patio for testing/mock up tomorrow. I will say the cabling has been challenging with all the 2AWG and 6AWG connections and finally determining how to attach safety disconnects and though panel connectors, proper welding wire sheathing etc. None of the 3/8" ends, butt connectors, orange sheathing etc are available locally, even Red 2AWG welding cable is non existent here in Lake Havasu.

The Midnight Sun 3 breaker box is now mounted on the steel lid of the battery box/ power wall, as it was too small for the seven, 10AWG wires and all the combining. This little box now supports, an 80A double breaker that accepts the 2 AWG wire directly. (My Growatt supports up to 80A charging).

Tomorrow I mig weld the new flat panels created to flatten the box top to allow for the small Midnight Solar 3 breaker box to provide my battery shut off on the battery case.
 

Attachments

  • IMG_20201006_162652263_HDR.jpg
    IMG_20201006_162652263_HDR.jpg
    243.5 KB · Views: 3
  • IMG_20201006_162659653_HDR.jpg
    IMG_20201006_162659653_HDR.jpg
    59.2 KB · Views: 3
  • IMG_20201006_162644166_HDR.jpg
    IMG_20201006_162644166_HDR.jpg
    96.3 KB · Views: 3

DCDave

New Member
Any suggestions on "Near free ware" for creating visual image of the flow of PV to Charger/Controller, with batteries, switches and disconnects? Something like this one? Interactive-Solar-Wiring-Diagram-Facebook-Image-1024x538.jpg
Note: On Youtube I found someone posting several diagrams, he listed a service to draft up one for you, but at $375,/hr that is about three times what my back surgeon makes at Stanford University Hospital.
 

michael d

Solar Enthusiast
We are starting this off grid project with the following equipment just received:

Parts, starting place;
* 40' container located at 6800' Summer 97 degrees, Winter 10 degrees.
* Growatt 3000w 120v output, 48vdc input from Watts247
* 20 solar panels, 327w used Sunpower
* 800KW Lithium, 48v BMW batteries, from Battery hookup
* 2awg cables with disconnect below the panel, 60w breakers on each of the two battery packs to de-rate them a bit.
* Plan to string second Growatt 3000 to add input charging and run the AC on camper next summer.

Loads:
* Small RV Camper, one AC unit, microwave
* Charging battery powered tools
* Laptop

Unkowns:
How to group and connect the 327w solar panels to not exceed voltage limitations.

* 80A MPPT / 6.5Amps per solar panel + 12.3 panels.

Growatt's limitations.
* 48v
* Input 80A MPPT
* Input 40 from Generator

Solar panels limitations;
* Rated power max 327 Watts
* Voltage 54.7 Volts
* Current Input 5.98 Amps
* Open circuit VOC 64.9 Volts
* Max series fuse 15 Amps

** By my calculations, I can only attach 12 panels to the Growatt 3000w. Even if I chose the 6000w unit I gain 220v AC but can only attach some 15 of my 327w panels. I am not sure which is the better option.
I bought these 327-watt panels and also found to be limited to 2s configuration then parallel them in a combiner box as I also bought outback 80 amp flexmax scc. seems like I am on a similar path as you. i built an insulated 8x8 shed for batteries inverters and scc. good luck with all.
 
Top