Lean-to Shed Solar Power for Year Round Use

nicorellius

New Member
Very cool, things are getting clearer. Thank you both for the prompt replies! I really like the idea of a control box, but my understanding of these is a bit behind the curve.

One follow up:
Here's a 'combiner diagram' example for your 4 panels arranged in 2s2p + 24v Battery going thru a circuit breaker for ON/OFF. Crude/messy but hopefully get's the idea across.
I see that you are "combining" the positive and negative leads (2x of each) in the box. I was under the impression I needed MC4 Y/branch connectors for the parallel part (which would be 1x positive and 1x negative going in). Is there any advantage to doing it one way or the other? Or am I missing something else?
 

OffGridInTheCity

Solar Addict
Very cool, things are getting clearer. Thank you both for the prompt replies! I really like the idea of a control box, but my understanding of these is a bit behind the curve.

One follow up:

I see that you are "combining" the positive and negative leads (2x of each) in the box. I was under the impression I needed MC4 Y/branch connectors for the parallel part (which would be 1x positive and 1x negative going in). Is there any advantage to doing it one way or the other? Or am I missing something else?
Great question!

The MC4 Y/Branch connectors would 'combine' out at the panels and 2 wires would run into the control box. The diagram has 4 wires running to the control box... with a circuit breaker on each string... and then combining.

If the distance if long (like 100-200ft) then combining at the panels saves $ / wire. But if the panels are close - then 4 wires is not big $ compared to 2 wires. For my trailer's 4 panels - the longest wire is 7 ft, so 4 wires are cheap/easy. For my house, I have the combiner box / breakers out the panels - 1 breaker for each string (30 wires) - and then 6 wires from there to the charge controllers 150ft away.

For me, I prefer running the 4 wires with a circuit breaker on each string at the control box to allow me to turn on/off each string independently (or both to disable PV power while I work on things) so I can check each string in isolation to verify it's working. If you do the 7/Branch it's all or nothing by the time it gets to the control box / PIP.

There's no wrong choice here - its just a nuance I'm sharing :)

Some people use the Y/Branch out at the panels and run the wires directly to the PIP - and don't have an intermediate control box or circuit breaker near the PIP. I (personally) prefer having a control box with breakers - at the equipment panel. If you did Y/Branch and only have 2 wires coming in - you could still do a breaker just before the PIP so that you could disable the current flow to work on things. IF you do 1 breaker, then it's easy to do 2 and have that diagnostic option on each string.

You may get other comments/advise and I do not claim 'my way' is the only or best way - just sharing a perspective from being further down the road on all this. Take it all in and choose what makes sense for you! :)
 
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nicorellius

New Member
The MC4 Y/Branch connectors would 'combine' out at the panels and 2 wires would run into the control box. The diagram has 4 wires running to the control box... with a circuit breaker on each string... and then combining.
Perfect answer, thank you. I figured this was the reasoning but wanted to confirm.

One other reason I was asking is that I'm about ready to buy solar panel wiring and if I combine with the Ys closer to the panels (which I'm not even sure is a good idea), I would run two leads from the array on the roof to the combiner and LV2424. Your method makes good sense, but would require more 10 gauge wire and connectors (not exactly 2x as much, but maybe 1.5x as much).

Here's a rough sketch I've been working on. If I don't use Y/branches, I'll need to reconfigure my shopping list ;-)

1626900600519.png
 

OffGridInTheCity

Solar Addict
Yes sir - looks good. From a wire perspective - I'm sure you'll be < 10a per string. So you can go down to 14awg (15a rated) if you wanted 4 wires and keep the $ down. However - I don't know your physical setup....

One of the reasons I use 10awg is because 'PV wire' is typically UV protected whereas home 14awg (15a) Romex is not - and you want exposed wire to be fully protected. Another reason if it's a long distance (100ft or more) then 10awg running <10a or even if you combine at <20a - will have a little less power loss than if you use 14/12awg.
 
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nicorellius

New Member
I priced out 10 AWG (UV resistant, etc) for the solar wire and it's a bit more expensive than 12 AWG, but it seems the most versatile in the long run. And if there is no reason aside from a few more bucks, it seems prudent. Especially since I'm not really dealing with all that long of lengths.

@OffGridInTheCity When you say PIP, what do you mean? The LV2424? What does that stand for, acronym-wise?

I'm leaning towards starting out without a "control box" as it adds a bit of cost to the overall project (box + wires + breakers ~ $300). I've got a pretty clear picture how to do this. And I can always save up for a control box/wires/breakers and install those in phase 2. Given that, and the size of this system, what is the minimum protection I need for fuses/breakers? I guess I'm still a bit unclear on when/where to use fuses and/or breakers.

As a reference, in the LV2424 video in which Will presents the hand truck solar system, he uses a simple 125 A circuit protector between the battery bank and the LV2424 (on the positive lead). This video seems to show a system that is very similar to what I'm going for.
 

OffGridInTheCity

Solar Addict
@OffGridInTheCity When you say PIP, what do you mean? The LV2424? What does that stand for, acronym-wise?
Yes. As I understand it - "MPP Solar" is the overall company. PIP is a short-hand term for *off-grid* models as apposed to hybrid models. The LV2424 is an off-grid model.

I'm leaning towards starting out without a "control box" as it adds a bit of cost to the overall project (box + wires + breakers ~ $300). I've got a pretty clear picture how to do this. And I can always save up for a control box/wires/breakers and install those in phase 2. Given that, and the size of this system, what is the minimum protection I need for fuses/breakers? I guess I'm still a bit unclear on when/where to use fuses and/or breakers.
Most jurisdictions require a fireman's quick-disconnect (an off switch or breaker) near the panels on the outside. This can act as the off switch for you to work on things on the inside in lieu of a switch near the PIP - you just have to walk outside to toggle it. For me - its much easier to have a switch(breaker) right next to the PIP.

You should also
1) Bond/ground the panels/
2) Have a surge (lightning) arrestor on the panel wires coming in https://www.solar-electric.com/mnspd600.html

But no judgements - my goal is just to share info. For me - it took some operational time for all these things - ground, lightning arrestor, circuit breakers, control box - I ignored them all until I had some operational experience and circled back on things. Perhaps the key thing at this point is to leave room for it in your setup for the future. :)

As a reference, in the LV2424 video in which Will presents the hand truck solar system, he uses a simple 125 A circuit protector between the battery bank and the LV2424 (on the positive lead). This video seems to show a system that is very similar to what I'm going for.
OK - 125a will give you 25a headroom if you overload the Inverter for very long.

The *key* thing here is to allow the max current to the LV2424 that it can use but low enough to blow if:
1) A short occurs. The PIP could melt inside ?!? (not likely) or you could touch wires - e.g. if a short occurs you want the breaker to flip before....
2) Do not allow so much current the wire will melt! If you use 2/0 wire, you could easily go much higher than 125a.

As you get this system up and running - I'm hoping you'll post a pic or 2 - it will be fun to read that you have it going :)
 

nicorellius

New Member
@OffGridInTheCity I need to remind myself to buy you a beer (or suitable beverage); your assistance has been invaluable so far. I've been building software for 15 years, so I use the StackExchange boards (StackOverflow specifically) more than any other Q&A forums. I can definitely say that my experience on this forum so far is more/equally responsive and informative than SE. This is saying a lot since those boards get millions of views regularly (50+ billion total from recent query). Big thanks to @Will Prowse, as well, for all your efforts.

Most jurisdictions require a fireman's quick-disconnect (an off switch or breaker) near the panels on the outside. This can act as the off switch for you to work on things on the inside in lieu of a switch near the PIP - you just have to walk outside to toggle it.
You should also
1) Bond/ground the panels
2) Have a surge (lightning) arrestor on the panels wires coming in https://www.solar-electric.com/mnspd600.html

But I'm not an inspector, its your DIY build, no judgements on my part. For me - it took some operational time for all these things - ground, lightning arrestor, circuit breakers, control box - to make sense. Perhaps the key thing at this point is to leave room for it

I do have an 8 foot ground rod I intend to install by the shed for proper ground. I can use this to ground whatever I need to. The surge/lightning protection I hadn't even considered, so... more research is needed. But, I agree, setting something up with room to grow is a good idea. I get the impression that best practices dictate protection at every point in the system, but also that it's common to start with the basics and implement the rest as you are comfortable doing so. I really want an operational system ASAP so I'm begining to chomp at the bit.

What continues to amaze me (as is the case with many technical projects) is that when you start to scope the project, it can seem straight forward: solar panels, charge controller, inverter, and batteries. Which might work fine in a simple use case... but of course, depending on the actual needs of your system, the scope creeps and you realize that the actual required components are more than you thought ;/

I hope to start putting this system together in the next week or so. I've got most everything either in my possession or ordered and on the way. Planning to build my own panel mounts, so we'll see how this goes. The brackets and hardware for tilted mounting seem expensive.

I'll definitely post pictures and I'm sure I'll flood this thread with plenty more newb questions!
 
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nicorellius

New Member
I received all my parts for my solar system. I've begun putting things together but encountered a problem. I think I screwed up... I used the links at https://www.mobile-solarpower.com/wire-and-connectors.html to find the wire I needed (based on the 2000-4000 W inverter, eg, the LV2424 is 2.4 KW) and this lead me to 1/0 AWG, which I purchased.

Now I'm seeing that the 1/0 AWG is too thick and will not fit in the receptacles on the bottom of the unit. The LV2424 manual says 1*4 AWG so I assumed the 1/0 AWG would work, but it's definitely thicker (0.3249 in vs 0.2893 in according to this table):

1627432438454.png

What's odd is that if I measure the copper in this 1/0 AWG, it comes in at right about 3/8 in (which is 0.375 in). That seems too thinck for this gauge wire. Am I missing something?

Since I spent a decent chunk of cash on this thick wire, is there a way to make it work (remove some strands so the diameter fits)? Or do I need to bite the bullet and buy something smaller (like 1-2 guage)? This was an oversight on my part so I'm trying to figure out the best way forward. And since the wire I received is thicker than the specification, I'm not sure how to trust that the wire I purchase will actually fit.
 
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OffGridInTheCity

Solar Addict
Now I'm seeing that the 1/0 AWG is too thick and will not fit in the receptacles on the bottom of the unit. The LV2424 manual says 1*4 AWG so I assumed the 1/0
Maybe it was trying to say "1 wire @ 4 AWG" - e.g. 4 AWG (80amp) wire is the max it takes.

Too-big wire is better than too-small wire :) Just just strip back a section of the big wire and cut it down to size and electrical tape it up.
 

nicorellius

New Member
Maybe it was trying to say "1 wire @ 4 AWG" - e.g. 4 AWG (80amp) wire is the max it takes.

Too-big wire is better than too-small wire :) Just just strip back a section of the big wire and cut it down to size and electrical tape it up.
Something like this?

IMG_20210727_190203.jpg
 
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nicorellius

New Member
Yes sir - looks exactly some of mine :)
If you're so inclined / run into difficulty, Ferrules can make it a bit easier to push loose wires into a screw connector (and create a better long-term connection) - https://www.amazon.com/RockDIG-Connector-Electrical-Terminal-Assortment/dp/B0818ZPCWC/ref=sr_1_21
Awesome, thanks. I'll look into ferrules. They look pretty useful.

The negative turned out better because I was able to separate the outer strands more evenly.
 

nicorellius

New Member
Ended up shortening the 1/0 AWG leads to better match the distance between my battery bank and LV2424. This gave me opportunity to make the ends nice and clean.

Hooked up batteries and AV input and output and everything works! Not sure why I'm surprised but I guess all this anticipation had me nervous. Did a load test with a heat gun and pulled 1 kW no problem.

Panels tomorrow...

Here's a pic...

IMG_20210727_212039.jpg

Went with 10 gauge and an XT90 tail for array connection. Batteries under the countertop, with a 120 A DC breaker in between battery and LV2424.

Ended up changing my plans quite a bit, regarding the shed, as well. After observing sun pattern for a couple weeks and evaluating the site surroundings more thoroughly, I decided that the shed roof is not a good place for the array; it has too much shade or other obstruction (especially in the winter).

Now I'm installing the array on my mudroom roof (similar dimensions) and the batteries and MPP in the mudroom. Much better sun and the climate control is less of an issue for batteries and MPP (indoor, with a fan). The only downside is that I'll need to now run an AC lead out to my shed to supply power. Would it be sensible to run the AC line to the shed with an endpoint at a small panel/circuit box? Or should I put the AC breaker closer to the MPP?

Since I'm planning to invest more in solar power anyway in the future, I'm not too discouraged about the change. I'm just happy I've made it this far.

Quick panel roof mount question... Anyone know of a good way to mount somewhat temporarily without drilling holes in roof? Like a rail system or bands along the length? Maybe a frame that connects the panels together to offer stability so wind doesn't blow it down? I could use 2 x 16 foot treated 2x4s, and bracket them to the facia (the mudroom is exactly 16 feet long) and mount the panels to these. I can even build the pitch mounts to this rail system.
 
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OffGridInTheCity

Solar Addict
Congratulations!
Would it be sensible to run the AC line to the shed with an endpoint at a small panel/circuit box? Or should I put the AC breaker closer to the MPP?
Hmmm This falls under standard AC wiring. I'm not an expert but there are some basic considerations
1) You should probably have a circuit breaker near the PIP output
2) If you have more than 1 circuit - yes you need a distribution box

Let's say you start with a small distribution box by the PIP with a circuit breaker.....
1) You could run 1 circuit from that to the shed that winds thru a series of 120v receptacles. Of course you need proper wire / conduit to make the run to the shed.
OR
2) You could run 1 single circuit to distribution box in the shed with circuit breakers for each circuit you run in the shed.

Quick panel roof mount question... Anyone know of a good way to mount somewhat temporarily without drilling holes in roof? Like a rail system or bands along the length? Maybe a frame that connects the panels together to offer stability so wind doesn't blow it down? I could use 2 x 16 foot treated 2x4s, and bracket them to the facia (the mudroom is exactly 16 feet long) and mount the panels to these. I can even build the pitch mounts to this rail system.
Sounds reasonable.
 

nicorellius

New Member
I've got my panels under the sun and want to do some testing. I have them set up in 2S2P:

panels_on_mudroom_roof.jpg

I tested the voltage and it's about what I expect: 65 V. But I want to test the short circuit current (ISC) but I'm hesitant to plug the MC4s together. This is how I tested the individual panels previously but since I have not done this before with the series in parallel, I don't want to mess anything up. I'm using a clamp multimeter (my standard multimeter 10 A fuse is still fried).

Is this the right way to go about this? I know, super newb questions ;/
 

OffGridInTheCity

Solar Addict
I've got my panels under the sun and want to do some testing. I have them set up in 2S2P:

View attachment 58098

I tested the voltage and it's about what I expect: 65 V. But I want to test the short circuit current (ISC) but I'm hesitant to plug the MC4s together. This is how I tested the individual panels previously but since I have not done this before with the series in parallel, I don't want to mess anything up. I'm using a clamp multimeter (my standard multimeter 10 A fuse is still fried).

Is this the right way to go about this? I know, super newb questions ;/
Its perfectly OK to short solar panels and put a clamp meter on them to test amps. I've tested all 50 of mine that way to make sure they were good when they arrived and again at 120v in the 3s before finalizing the combiner hookups.

It won't hurt the panels or the wires as they will max out a 9a per string or 18a in 2s2p and the 10awg wire / MC4s are good for 30a. 3p would not be good as it would exceed the wire specs. If you're shorting bare wires they can arc if you don't do it quickly and at 65v you can be shocked so be careful. But they will NOT do a Battery or Grid surge/run-away meltdown because they just max out at 9a or 18a and can't go any further. :)
 
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OffGridInTheCity

Solar Addict
Yes but it sounds like he is asking about testing his 2S2P array with a full short, which I would not recommend. (65V @ 20A)
To gently disagree... I've done this over 50 times now and I find it FUN... its the only case I know of that you can do a direct short and it doesn't harm anything. I had fun creating a deliberate arc of amps... and it can be dangerous for sure. But done carefully, the 20a is well within the wire specs.

I do agree that as in the handling of any electricity it can be dangerous.. and care must be taken to avoid shock and uncontrolled arcing.
 
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nicorellius

New Member
OK, so I'm a bit confused... We're talking testing individual panels versus an array of panels, right? I'm not hooking them up to the LV2424 yet; just wanted to make sure the voltage and current coming off the 2S2P was what I expected before hooking things up. I know that testing my individual panels in this manner was OK, so initially I thought testing the 2S2P this way would be fine... But...

Obviously, being new to all this, I'm trying to be as careful as humanly possible to not f*** anything up. So I came to the pros.

Logically speaking, or maybe academically, why would testing a single panel (~32 V at 8 A) be OK, but not the whole array (65 V at 16 A)?
 
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