Solar Panel Layout?

[alliemac9]

Me again....have questions on the best layout and mounting for the panels I bought.

Panels = 58.27" x 26.58" x 1.38" (26.4lbs)

Roof dimensions are roughly 100" wide by 251" long. This was my initial thought:



Proposed solar panel layout on a Class C RV. Drawing is to scale. The front of RV is at the top.

The line in front of the panels and behind the front vent demarcates the overhead cab; the roof slopes down to the front from that point forward. That is why I tried to fit the panels behind that line, so they were all on level roof. The distance from that line to the front of the roof is about 42 inches (i.e. shorter than the length of the panels).

However, I recognize the AC is taller and will have more shadow issues than the vent cover (all vents have covers). The clear space on either side of the AC is about 35", so just about 8" wider than the panels. It was recommended that I line the panels up in two straight rows and push them forward even though the front two panels will then straddle the break between the flat roof and the sloped roof. Does this look best? I don't know the angle of the slope, so I can't do the math to figure out the height differential and what impact it may have on my mounting options.

Any thoughts on this?

Here's a roof sketch with dimensions. We are planning to remove the antenna.



Roof dimensions. Not to scale (and not well proportioned).

[Almot]

12V breakers from Midnite Solar, you can use them for both panel and controller disconnects. And MS have a neat enclosure for those breakers, called Baby Box and Big Baby box. You don't normally need a breaker for panel, just some sort of disconnect.

I don't see what portable panels have to do with permanent install. You'll get cables and connectors for portables if and when it comes to it.

[crcr]

Here is a pic from my last TT, inside right side of the pass thru storage, near the door. The 4 ga cables going to the left go to the controller. Then there is a Bussman resettable breaker, then terminals, then wires going out the bottom of the pass thru as I described earlier. So when I add solar panels to the roof on our new TT, the wires will come down off the roof thru the front bedroom wardrobe, into the pass thru, and connect to the terminals on the right in the pic. Throwing the breaker will cut off power feed from both roof and portable panels, handy if want to work on the system or some such. Sorry the pic is a little bit blurred.

[crcr]

alliemac9 wrote:
Another question for my plans....

If I may at some time want to also have a set of portable panels (likely only if I ever expand battery capacity and/or find I want options to augment shade issues), is there anything I could/should do during the initial install to facilitate that? I guess my vision would be the portable system would simply plug into a pigtail or connector on the RV. If you check out this video by the Wynn's at about 1:40 you'll see the connector they had on their RV for the portable system. Here's a photo of it for those of you not wanting to click through to the video:



I guess the more I see/learn about the wiring, it's probably reasonable to just do this add on later if/when I need to. It will likely just connect in to the current system pretty easily (especially if I buy a portable kit that has its own controller built in) and not require reworking any of the existing system. Would you agree? Anything I should take into account now?

I did this only kind of in reverse of what you are doing -- I put a solar system in our TT, including controller, inverter, & Trimetric meter. I started with a 120 watt folding panel. I built the system with provision to easily add roof panels. I have since sold that TT, but removed the solar system, all the components of which are mounted on a piece of 3/4" plywood that was in the pass thru storage, so was pretty easy to remove. The connection for our portable panel is an Anderson connector. The wires came out the bottom of the TT from the pass thru storage, and the Anderson connector dangled there. I enclosed it in a short piece of ABS sewer pipe, 3 or 4" diameter, forget which, with a threaded female connection that accepts a screw in ABS plug. This keeps the Anderson connector dry if driving in the rain. When I set up, I unscrew the cap and plug in the 8 gauge cables that go to my portable solar panel.

This off season, I will re-install the system in a longer TT we bought. And at that time, I plan to add 2 or 3 solar panels to the roof.

Good luck with your system!

[westend]

I'd suggest you figure out what is going to be the most robust layout for your wiring and modules, now, and install it. If that includes a fixture for auxiliary modules, I'd do it now and be done with it. Also, don't get sticker shock with using larger wire sizes. It's much better to have a little too much than spending good money for the modules and controller and losing power to a small wire.

The Anderson connector the Wynns used is a good connector. Mighty handy to run other DC devices outside besides a charge point connection.

[alliemac9]

Another question for my plans....

If I may at some time want to also have a set of portable panels (likely only if I ever expand battery capacity and/or find I want options to augment shade issues), is there anything I could/should do during the initial install to facilitate that? I guess my vision would be the portable system would simply plug into a pigtail or connector on the RV. If you check out this video by the Wynn's at about 1:40 you'll see the connector they had on their RV for the portable system. Here's a photo of it for those of you not wanting to click through to the video:



I guess the more I see/learn about the wiring, it's probably reasonable to just do this add on later if/when I need to. It will likely just connect in to the current system pretty easily (especially if I buy a portable kit that has its own controller built in) and not require reworking any of the existing system. Would you agree? Anything I should take into account now?

[brulaz]

alliemac9 wrote:
What type of inline fuse holder (60A) are people purchasing? I see them in photos of others' installs, but am not sure what they are? And where should I purchase?
...

I'm using Midnite Solar Circuit Breakers between the solar panels and mppt controller (15A) and after the mppt controller (30A) before the cable to the batteries. Got the breakers and baby breaker box at Northern Arizona Wind & Sun. NAWS

The + cable to the battery also has a charger on it and is protected right at the battery with a Blue Sea Terminal Fuse Block and 60A Fuse (nice but expensive) Blue Sea Fuse Block

[crcr]

alliemac9 wrote:
What type of inline fuse holder (60A) are people purchasing? I see them in photos of others' installs, but am not sure what they are? And where should I purchase?

Bought a ton of last odds and ends today....making progress. Fuse holders seem to be the only thing I couldn't find.

I use these Bussman Hi Amp Circuit Breakers in my solar setup. They are available in a number of amperages. They are convenient also because I can break a circuit easily for any reason, then restore it.

[alliemac9]

What type of inline fuse holder (60A) are people purchasing? I see them in photos of others' installs, but am not sure what they are? And where should I purchase?

Bought a ton of last odds and ends today....making progress. Fuse holders seem to be the only thing I couldn't find.

[Almot]

alliemac9 wrote:

We've been looking at pics of various mounting methods and the one my husband seemed to gravitate to involved aluminum angle mounted on the corners going down to angle mounted to the roof. Regardless of exact style, it seems like a lot of people mount using four feet at the corners. Is everyone getting lucky that their panels happen to be a length that lines up with their studs? Or are people not worried about hitting something structural? And is four enough or is it dependent on the size of the panel?

Mounting brackets:
Vertical aluminum angles straddling the panel corner is one way, and yes, it has to be bolted or riveted to another aluminum angle mounted on the roof. So this is a 2-part bracket.

I don't like multi-part items when I can avoid them. So I did what Mr. Wizard and Golden HVAC and other people here suggested - used 1 aluminum angle bolted to the side of the panel. Check the photo in my link some pages up. There is a rivet nut in the panel side, but you can also use a pin or a bolt and nut. Rivet nut makes for simpler attachment, as you only have to deal with one bolt.

To hit or not to hit the rafters:
It's better to hit them if you can locate them. If you can't, then you need more screws into the roof and/or really wide brackets to ensure sufficient area of support. I am not familiar with your MH roof, my trailer is a plywood roof. Check install by Westend, I like what he did there.

Lucky panel length:
Mostly, 24V panels are ~65" long, and this closely matches the spacing between the rafters of plywood roof. Few panels have weird shape, and 12V panels are different again. And your MH roof can be different from trailer, i.e. different spacing. Again, check the install by Westend and similar desings where they used a long aluminum angle to span over a few rafters, and mounted the panel legs on it.

[brulaz]

alliemac9 wrote:
Okay - I'll check out those cable options, thanks! Now a mounting question...

We've been looking at pics of various mounting methods and the one my husband seemed to gravitate to involved aluminum angle mounted on the corners going down to angle mounted to the roof. Regardless of exact style, it seems like a lot of people mount using four feet at the corners. Is everyone getting lucky that their panels happen to be a length that lines up with their studs? Or are people not worried about hitting something structural? And is four enough or is it dependent on the size of the panel?

I didn't mount at the corners but part way in where the holes were in panel's frame. There's some sort of engineering calculation you can do to find the optimum location for two supports under a beam, and that's where these holes were.

Couldn't find where the wood trusses were on my roof. So I just used 6" long 1.5" Al angle pieces and 3 SS screws each into the 3/8" plywood. Plus a lot of 3M 5200 marine sealant/adhesive. Seems pretty solid. We'll see.

[alliemac9]

Okay - I'll check out those cable options, thanks! Now a mounting question...

We've been looking at pics of various mounting methods and the one my husband seemed to gravitate to involved aluminum angle mounted on the corners going down to angle mounted to the roof. Regardless of exact style, it seems like a lot of people mount using four feet at the corners. Is everyone getting lucky that their panels happen to be a length that lines up with their studs? Or are people not worried about hitting something structural? And is four enough or is it dependent on the size of the panel?

[Almot]

westend wrote:
If you get a single cable length with male & female MC4 connectors like this, it is easy to chop it in half and use both connectors to the module and the cut/stripped ends into your combiner box.

Yep. This is what's called MC4 extension cable. Run them to interconnect the panels, and/or cut in half to connect from pigtail to combiner box. This is 3ft cable for $13, and Ulimited Solar store have them about 6 times cheaper, 10ft for $6 🙂

[westend]

alliemac9 wrote:
@Almot answered my next question without me even having to post a pic.

MC4 connectors...what is the typical process here? Do I need to find an outfitter that sells MC4 pigtail in the length/gauge I need to get to the combiner box on my roof? Like this?

If you get a single cable length with male & female MC4 connectors like this, it is easy to chop it in half and use both connectors to the module and the cut/stripped ends into your combiner box.

I ran AWG 4 from the combiner box to the controller. In fact, after I realized I had to buy a pretty good length of wire to get everything connected, I opted to connect nearly everything with AWG 4. It was easier to shop lugs, fasteners, heat shrink, etc. since everything was the same size. That, and I don't have worries about voltage drop and squandering that $10/W power I bought. As it is, I need to find some creative use for the power that I don't use and the additional harvest I could have.

Best of luck with your solar, it is really a great thing for RV's.:)

[Almot]

alliemac9 wrote:
MC4 connectors...what is the typical process here? Do I need to find an outfitter that sells MC4 pigtail in the length/gauge I need to get to the combiner box on my roof? Like this?

Usually people don't replace the pigtails for parallel wiring. Instead they pick up the closest length of MC4 extension cable to run from the pigtail to connector box. Or - from the MC4 Y-splitters that combine 2 pigtails, to the combiner box. There are places to order a custom length of MC4 extensions, but you can just use the closest length, err on the longer side, and use #8 rather than #10, between the panels and combiner box. Cut the excess cable off, together with one MC4 connector. Combiner box uses bare wire ends on terminals, not MC4 connectors.

I like Ulimited Solar - US made, reasonable prices, good assortment. Unknown Ebay cables may have poor quality wire, sometimes aluminum wire coated with copper, rather than pure copper.

Edit - PS:
If some pigtail is so close to the combiner box that you don't need an extension, you just cut MC4 connectors off the pigtail.