diy solar

diy solar

AC side MPP LV6548 connections, critical load panel, wiring

After some consideration and calculation, I think I'm going to mount the panels directly to the side of the garage through the studs at 90 degrees (vertical). Hopefully my reasoning below makes sense.
I think your reasoning makes perfect sense! I'm actually rather surprised by how little the angle to the sun, and orientation in general makes (within reason). If you have room, adding more panels seems to make a much larger difference than minor improvements in angles.

I thought my south wall array might generate more per panel than the roof array does. Not so far!! It has many more hours of direct unshaded sun, but in this case at least, size really DOES seems to matter ;)
 
I think your reasoning makes perfect sense! I'm actually rather surprised by how little the angle to the sun, and orientation in general makes (within reason). If you have room, adding more panels seems to make a much larger difference than minor improvements in angles.

I thought my south wall array might generate more per panel than the roof array does. Not so far!! It has many more hours of direct unshaded sun, but in this case at least, size really DOES seems to matter ;)
Thanks Scott. I think that is the plan now.
Quick question about the shading. Am I right that the shading from a fence like the one that I've attached would reduce significantly the production if I add a second row? I know there are a lot of variables with this but this type of fencing will create a shade of lines along the panels rather than covering up a complete panel.
I've attached the solar panels spec sheet (310W is what I'm using).
Thanks!
 

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Thanks Scott. I think that is the plan now.
Quick question about the shading. Am I right that the shading from a fence like the one that I've attached would reduce significantly the production if I add a second row? I know there are a lot of variables with this but this type of fencing will create a shade of lines along the panels rather than covering up a complete panel.
I've attached the solar panels spec sheet (310W is what I'm using).
Thanks!
Based on my limited antidotal experience, a Chain link fence a couple of feet away is not going to affect them drastically, if at all. You could play with what it looks like, though, using cardboard or paper cut to the size of your panels. Put those up on the wall in the spots you're most worried about and see what sort of shading you have over the course of the day. Keeping in mind the sun will be higher soon (so less shading, but also at a higher angle). Or you might save the work of the cardboard or paper just look at the wall itself several times during the day. My guess is a few lines crossing the panels will likely not have a drastic impact, certainly not enough to not want the extra power they generate.

A lot depends on if you already have the panels, or would need to buy more. In my case, I bought a pallet and have extras. My limitations had more to do with wiring them to be within the specs of the LV6548 PV inputs. In my case, I can't have more than 5 panels in series and still have enough voltage head room for cold mornings, and I can't have more than three strings in parallel to keep the amperage within reason. Even three is considered over paneling based on the published specs, but the tech support at MPP felt as long as I don't go over 250Voc the LV6548 would handle up to 25Amps fine. 3 strings in parallel is just under that for my panels.
 
My guess is a few lines crossing the panels will likely not have a drastic impact, certainly not enough to not want the extra power they generate.
If you have a little shading on the lower row of panels, it would likely be good to wire them in a separate series string from the ones that you suspect will have full sun. My limited understanding is that even partial shading of one panel will bring the output down on the other panels in that series. Depends on what you've got to work with... For my set up, I've found that more panels is better, regardless, but still wired them as strategically as I could.
 
Scott - I think you're right based on what I've seen as well. If there are panels that are going to be shaded, put them on a separate series. What's nice with the LV6548 is having two sets of solar inputs.

One question that I've received different answers to from the companies I've dealt with is the VOC decreasing for used panels. I purchased these used panels and I wanted to put 5 of them in series. However, the VOC for the five panels in series during the coldest time in my area (Southeast Michigan) is calculated as 254V (more than the VOC that the LV6548 can handle). One company told me that the panel's VOC decreases over time and I'll be fine (the company that sold me the panels). Another company told me that VOC does not deteriorate over time - only the amps.

Any idea who is right?
 
One question that I've received different answers to from the companies I've dealt with is the VOC decreasing for used panels. I purchased these used panels and I wanted to put 5 of them in series. However, the VOC for the five panels in series during the coldest time in my area (Southeast Michigan) is calculated as 254V (more than the VOC that the LV6548 can handle). One company told me that the panel's VOC decreases over time and I'll be fine (the company that sold me the panels). Another company told me that VOC does not deteriorate over time - only the amps.

Any idea who is right?
I'd measure them. That's what I did with mine, which are also used. And I happened to have a chilly day with bright sunshine. Not near as cold as it can get, but cold enough to put the 5 year old panels well over their rated VOC.

I was surprised to see the record low here actually hit -20°F at one point. I've never seen it lower than -6°F, and that only maybe 3 times in 27 years. I decided to stick with 5 panels in series.

You may have already seen another thread where we hashed this out:

Thanks to the super helpful forum folks I worked through having WAY to many panels in parallel in the first part of that thread, hoping to mediate the partial shading and different locations. I had completely misunderstood the LV6548 specs for amps! Later in the thread I was helpfully stopped from frying it with too many volts.

You'll see included in that thread a really cool suggestion of rigging a low temperature charging disconnect (such as would be used for a LifePO4 battery) as shut off for the solar panels on those super cold mornings. I didn't explore it, electing to go with 5 panels in series instead of 6, but it is a compelling idea.
 
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Hi Scott - I started to look at that link but am now back to figuring out something for my permit plan revision. I'll get back to that link later and probably have questions then.

My question is is it possible to simply bolt the panels directly to the side of the wall? I thought it would be but I can't figure out what I would use for hardware (and still not cost me a lot). I could go the Iron Ridge route and do it the same way as on my roof, but I have a hard time thinking that is necessary (and is more $ than I was hoping for something that I thought could be done more cheaply).

I realized today, while working on my revisions, that I cannot simply say that I'll not use the mounting system that I was planning on using and that I'll simply bolt them to the side of the wall. I think they'll want more information than that, such as what bolts etc are being used.

Any recommendations? Each module weighs approx 60 lbs.

Thanks again,
Paul
 
Hello Paul,
It depends on your wall. In my case it was brick. But regardless, you want to have the panels at least a couple of inches off of the wall to provide good air circulation between them and the wall. I'd use sections of treated lumber as stand offs anchored to the brick or through the siding into the studs. Then I'd lag bolt channel strut to that, and secure the panels to the channel strut. There are several different styles and sizes of nuts that slide into the channel strut. My panels had holes for 1/4" bolts. I went through those with 1/4" galvanized bolts into the nuts captured in the channel strut, but it was a royal pain, and might be even harder without having them angled out from the wall.

One advantage to that system was I could pre-attach the bolt through the panels and into the nuts that fit the channel strut, then sort of hang the panels into top channel strut using the nut and slide them into position before tightening. I lost sleep over the logistics of lifting the panels into position and securing them to the channel strut. I did it all myself using scaffolding to support the panels on the bottom while securing them to the top rail. Then attached the bottom rail afterwards. My set up was facilitated by having the top rail hinged. It would all be much easier with help.

BTW, I used channel strut for the roof installation too. Prices vary, but the box stores tend to have 10 foot 12 gauge sections for between $24 and $30 each. It's more fiddly than Iron Ridge or other systems designed for solar mounts, but it's sure a lot cheaper!

The smaller 100W panels I used for my sailboat and storage shed project came with little brackets. It might be possible to use those bolted to the panels and then lag bolted to the treated lumber stand offs, but it would involve some man power or some sort of rig to hold the panels up against the wall to line everything up and mark it for drilling, etc...

It's a little daunting to think of how to document any particular DIY mount solution for the type of permit application you seem to be dealing with. It might be worth a call to talk through exactly what they need. I refined my installation on the fly after getting the permit, for which I simply described the hardware I planed to use, and took pictures of the existing structure.
 
Thanks Scott for the reply. I think you're right in that I should ask the plan reviewer what he needs for my type of situation. Otherwise I could go way overkill with documentation or simply not enough.

The price for the super strut here (galvinized) is around $30. For three panels in landscape mode I'll need at least 5 pieces of 10 feet. They are a little less than 6.5 feet in length. Plus either clamps or the bolts that you suggest. Not as cheap as I was hoping for but much cheaper than what the awning style (30 degrees tilt) was going to cost me. Plus no shipping.

Thanks again for your help. I appreciate it!

Paul
 
A bit of an update - I saw online how companies had used unirac to do a wall mounted system. I contacted them and they said that it can be done and that they would tell me what I needed, noting that I would be responsible for hardware to the wall. I waited for a bit and they prepared a fabulous document for me, all for free. Also, the cost would not have been anymore than using superstrut. Possibly even cheaper. However, there's a problem.

After waiting and getting that document, I submitted it to the company that prepares the permit application for me (who have been really helpful). They advised me that I needed to have unirac indicate what hardware is necessary and that the calculations would need to be verified by a structural engineer.

Back to unirac, and they indicate to me that the hardware requirements ultimately fall on a structural engineer to determine based on the construction of my wall.

Now, perhaps this was a simple misunderstanding, but when I was told that I would be responsible for hardware to the wall, I thought this meant that they simply didn't sell the bolts, etc and that I would have to buy them elsewhere (like home depot). If I had known a structural engineer would be required for this, at $$$, it would have been a non-starter from the beginning and unirac would have saved resources and I would have saved some time.

Oh well...live and learn. Back to the drawing board. I am starting to think that the vertical mount may be too much trouble for the benefit I get.

Paul
 
A bit of an update - I saw online how companies had used unirac to do a wall mounted system. I contacted them and they said that it can be done and that they would tell me what I needed, noting that I would be responsible for hardware to the wall. I waited for a bit and they prepared a fabulous document for me, all for free. Also, the cost would not have been anymore than using superstrut. Possibly even cheaper. However, there's a problem.

After waiting and getting that document, I submitted it to the company that prepares the permit application for me (who have been really helpful). They advised me that I needed to have unirac indicate what hardware is necessary and that the calculations would need to be verified by a structural engineer.

Back to unirac, and they indicate to me that the hardware requirements ultimately fall on a structural engineer to determine based on the construction of my wall.

Now, perhaps this was a simple misunderstanding, but when I was told that I would be responsible for hardware to the wall, I thought this meant that they simply didn't sell the bolts, etc and that I would have to buy them elsewhere (like home depot). If I had known a structural engineer would be required for this, at $$$, it would have been a non-starter from the beginning and unirac would have saved resources and I would have saved some time.

Oh well...live and learn. Back to the drawing board. I am starting to think that the vertical mount may be too much trouble for the benefit I get.

Paul
Wow, perhaps I've lived in rural Kentucky too long, but this all sounds WAY more complicated than it needs to be...

Were you able to talk with someone that reviews the applications about what they require? Perhaps a structural engineer's report is part of it in your case, but I would think providing them with what unirac provided you along with researching best practices for connecting it to your type of structure, then documenting that along list of hardware would be sufficient.

When I first explored my options I got a bid from a company that sold the entire package for homeowner installation based on a questioner and pinpointing my property on google earth. They included all the documentation for the permit application in their package, but I'm pretty sure that was only for roof mounted panels. The bid came back just a little less than a professional installation would cost (about twice what I was expecting). In light of my limited PV potential and also being under TVA's horrible metering policy the payback was well beyond the life expectancy of the system (or my own, for that mater).

I suppose with more restrictive building codes that may be the only viable solution for the average DIYer. Hopefully you can find an affordable way to jump through the hoops.
 
Wow, perhaps I've lived in rural Kentucky too long, but this all sounds WAY more complicated than it needs to be...

Were you able to talk with someone that reviews the applications about what they require? Perhaps a structural engineer's report is part of it in your case, but I would think providing them with what unirac provided you along with researching best practices for connecting it to your type of structure, then documenting that along list of hardware would be sufficient.

When I first explored my options I got a bid from a company that sold the entire package for homeowner installation based on a questioner and pinpointing my property on google earth. They included all the documentation for the permit application in their package, but I'm pretty sure that was only for roof mounted panels. The bid came back just a little less than a professional installation would cost (about twice what I was expecting). In light of my limited PV potential and also being under TVA's horrible metering policy the payback was well beyond the life expectancy of the system (or my own, for that mater).

I suppose with more restrictive building codes that may be the only viable solution for the average DIYer. Hopefully you can find an affordable way to jump through the hoops.
I was able to talk to the person who rejected my original permit application. After telling him what I was looking at doing, he indicated he needed an attachment detail. Of course, with what unirac sent me, that's the one thing I'd be missing. I have the railing, L-Foot (to attach to the wall), mid and end clamp as well as the grounding lug. But...I don't have how the L-Foot is attached to the wall or the panels.

I have checked the installation manual for my panels and it indicates that the panels are "not suitable for overhead or vertical glazing". I don't know what "glazing" is, but perhaps someone here can indicate.

My permit application company said that unistrut and superstrut will not require the engineering approval (if I go that route) since "the superstrut structure is predetermined and a DIY mounting". I think that I'm back to this now.

It is however very difficult for me to find out how solar panels of this size are connected to the superstrut. I've seen Z-brackets for the end brackets but hard to find out if it will support a 310 W panel. I think the bolting through the holes of the solar panels is the way to go, like you did.

Do you have any recommended hardware for doing this? I see in your previous posts that you used 12 gauge superstrut and that is what i'll use. Any other hardware help will be appreciated.

Thanks Scott,
Paul
 
.... I think the bolting through the holes of the solar panels is the way to go, like you did.

Do you have any recommended hardware for doing this? I see in your previous posts that you used 12 gauge superstrut and that is what i'll use. Any other hardware help will be appreciated.
Yes!

I used these:

But the springs were not as helpful as I thought they would be. I ended up removing the springs. You can buy them without:

You may be able to find them in smaller quantity, but I found this particular eBay seller was great to work with, and the price included fast free shipping.

I bought 1/4 20 galvanized bolts locally, along with washers. You may want to play around with the best length for your panels first.

This is assuming the holes in your panels are set up for 1/4" hardware. If not, you can get those unistrut nuts in just about any standard size.
Good luck!
 
Thanks Scott! I appreciate the info. That's given me a lot of help while I look up what I should do. A couple of simple questions:
1. Any reason that the HD nuts couldn't have been used?
Link to the HD ones:
2. Did you consider these:
I did some searching and found that some use them and say that they are easier to use than the others. Not sure about if this would interfere with grounding b/c of the nylon.
3. I'm confused as to the size of the nuts and bolts to use. I know this is construction 101, but I'm not even there yet. One installation manual I have indicates 14mm x 9mm for the size of the holes, and another indicates 1/2" x 5/16". I've attached screen shots of both.

Thanks again!
Paul
 

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I did some searching and found that some use them and say that they are easier to use than the others. Not sure about if this would interfere with grounding b/c of the nylon.
Nice find. (y)

Thanks for posting the link to the "Universal Cone Nut".
 
I played around with the nylon cone versions. I think they would work better than the spring versions. I don't think the nylon will interfere with electrical ground. The metal part of the nut is against the rails, and is also what the screws thread into. The panels are also going to be sitting on the rails. Our local box store didn't have enough of them, and since I used the same ones for the roof, buying a 100 piece box saved some bucks...
Apparently galvanized metal is less conductive than ungalvanized. but my guess is it should work.

1/2" is going to be way to be big, though. Your panels are calling for an M8 bolt in one of the figures, and M6 in other? That's odd... I don't think your going to find metric sized cone nuts, at least not locally. 5/16" would be the closest imperial match to M8, 5/16" = .316, and the M8 = 3.150. The hole in the panels is 9mm wide, which is 3.54, so you should be fine those. Or go with 1/4" which is .25", of course, and M6 is .236. Worth trying a couple of options before you buy a bunch of them, maybe.

The panel frames are aluminum. I'm used to fiddling with things on sailboats where we don't like to mix aluminum with stainless or galvanized without some sort of isolation, or we're in a world of hurt with galvanic corrosion. I think it's much more of an issue with salt water. My boat is in fresh, and I see it a little, but not near as much. Unless you're dealing with extremely high humidity you should be fine.

The caveat with dissimilar metals is checking whatever bolts you use actually thread into the nuts. When I tried the box store versions of galvanized bolts, they would not thread into the channel nuts they had even though they were the same size and thread pitch. I think the nuts were ungalvanized zinc (not a great choice for outside anyway)...
 
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I played around with the nylon cone versions. I think they would work better than the spring versions. I don't think the nylon will interfere with electrical ground. The metal part of the nut is against the rails, and is also what the screws thread into. The panels are also going to be sitting on the rails. Our local box store didn't have enough of them, and since I used the same ones for the roof, buying a 100 piece box saved some bucks...
Apparently galvanized metal is less conductive than ungalvanized. but my guess is it should work.

1/2" is going to be way to be big, though. Your panels are calling for an M8 bolt in one of the figures, and M6 in other? That's odd... I don't think your going to find metric sized cone nuts, at least not locally. 5/16" would be the closest imperial match to M8, 5/16" = .316, and the M8 = 3.150. The hole in the panels is 9mm wide, which is 3.54, so you should be fine those. Or go with 1/4" which is .25", of course, and M6 is .236. Worth trying a couple of options before you buy a bunch of them, maybe.

The panel frames are aluminum. I'm used to fiddling with things on sailboats where we don't like to mix aluminum with stainless or galvanized without some sort of isolation, or we're in a world of hurt with galvanic corrosion. I think it's much more of an issue with salt water. My boat is in fresh, and I see it a little, but not near as much. Unless you're dealing with extremely high humidity you should be fine.

The caveat with dissimilar metals is checking whatever bolts you use actually thread into the nuts. When I tried the box store versions of galvanized bolts, they would not thread into the channel nuts they had even though they were the same size and thread pitch. I think the nuts were ungalvanized zinc (not a great choice for outside anyway)...
Thanks Scott for the reply and continued help!

I've written to santan solar (where I purchased these from used) to find out what they suggest between the two installation manuals.

BTW, The Home Depot also carries the nylon cone nuts in 1/4" and 3/8" (not 5/16"). I've seen multiple locations refer to 3/8" as 9mm but that is (to me) not accurate. 3/8" appears to be 9.525mm.

In the absence of Santan's response (they've been good in responding in the past), I'll have to buy both and give it a try.

I too am concerned with rust with the bolts mixing with aluminum. I have read that if they are zinc plated then that will mitigate it greatly. I am no expert however.

Besides the bolt and the nylon cone nuts, do I need another nut to attach the bolt to the solar frame? I just have a hard time picturing this in my head.

Thanks.
Paul
 
Use stainless fasteners with the aluminum. While some galvanic reaction can occur over a very long period of time, I'll be pushing up daisies long before it is an issue using stainless fasteners with aluminum.

And yes, I customized boats 20 years ago and never had an issue. Saltwater I could see some problems but nothing compared to steel and aluminum.
 
Besides the bolt and the nylon cone nuts, do I need another nut to attach the bolt to the solar frame? I just have a hard time picturing this in my head.
Nope, that's it! I used a washer on the bolt before going through the panel with it, and then straight into the nut captured in the channel strut.

And yes, I customized boats 20 years ago and never had an issue. Saltwater I could see some problems but nothing compared to steel and aluminum.
I think it's mainly salt water that causes the more drastic reaction. I dream of getting my boat in some salt water some day, so I give a nod to best practices. I have not heard of anyone having issues with solar installations. But if were on the coast, I'd be a lot more worried.

My dad had (and my step still has) a place in San Diego on the beach. EVERYTHING there rusts, dissimilar metals or not. We call it the beach tax ;)
 
I finally received my permit from the city! Very anxious to get going on this project. I did decide to put in the application that the three wall panels will be completely flat against the wall.

Unfortunately, it's been a bit of time and I've forgotten so much of what I had already learned (which admittedly wasn't much).

A couple of questions I have right now:
1. All the large amp breakers I've seen are double pole. While I was wondering how to run two load wires from a two pole main panel 60A breaker to my single LV6548, I came across a single pole 60A breaker. I haven't seen these used (and they're discontinued at HD) so I'm wondering if there is any issue with using one of these in my main panel to go to the LV6548?:

2. Based on the discussion regarding grounding, I realize that the panels that I can purchase can be used as a subpanel so long as the neutral and ground bonding can be removed. I figure it's best to utilize the same manufacturer of the subpanel as the main subpanel (my main panel is Siemens) so that I can re-use the breakers in the subpanel that I take out of the main panel. Any issue using this one?:


Here is the final diagram submitted to the city. It does list a junction box to combine the solar panel arrays, and I will instead be using a Y connector.

final electrical plan approval diagram.jpg



Thanks for your help on this!
Paul
 
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