2016 Classic Solar

[Kringle]

I’m looking at a 2016 Classic that I understand is prewired for solar. What is required to complete the system?

[pcskier]

Solar panels, solar controller, a cutoff switch, a 30 or 40 amp fuse, and depending on a few factors, some wire and cable (and connectors.) Most people also add a good battery monitor such as Victron or Trimetric.

Then there is another issue...depending on how many panels/watts you want, you might have to bypass the factory prewire and run new wire from the roof to the electrical area where the controller will be. This is because depending on the size of the prewire, it might be 10 awg or 8 awg, the losses will be too great, and bigger wire will be required. Likely 6 awg, on a Classic that might have longer wire run, even 6 awg. But on that topic, is another thing to contemplate, you can avoid bigger wire if you wire the panels in a certain way. "Series/Parallel" would allow more panels with pre-wire, but technically, any shade on one panel in a pair can impact both panels that are wired in series. Whereas "parallel" wiring will require bigger wire (if you install 400 watts or more), but the panels will be completely independent of each other.

Fun, huh?

Check out the thread "Solar Show & Tell" for plenty of debate regarding series/parallel vs. parallel. User "Airmiles" chose to install 400 watts (four panels) using factor prewire in a series/parallel configuration and is getting excellent results with the data to prove it.
http://www.airforums.com/forums/f448...ll-181608.html

[AirMiles]

The factory prewire can easily support 400W of Solar as demonstrated in the Solar Show and Tell thread mentioned above. I’ve recently purchased a 27’ Airstream and will be installing 600W in a series-parallel configuration on the 10 gauge prewire and will continue to post results on the Solar Show and Tell thread. I have no doubt 600W of series-parallel will perform well based on line loss calculations and my experience with 400W. Stay tuned to the Solar Show and Tell thread for further updates.

[alano]

AirMiles is correct - the solar pre-wiring can easily support up to 600W with very low losses. I installed a 400W system in a series/parallel configuration and my losses are less than 2%. Reusing the solar prewires makes the DIY installation fairly easy for someone with basic DIY skills. I was also able to reuse the existing CAT5 cable to locate the remote head and battery monitor for the BlueSky IPN ProRemote.

[gator.bigfoot]

If you park a lot in the shade the series/parallel approach falls apart. As soon as one panel is shaded it will limit the power of the other. For best results only wire in parallel. Upgrade the wire and do it right.

[AirMiles]

Originally Posted by gator.bigfoot

If you park a lot in the shade the series/parallel approach falls apart. As soon as one panel is shaded it will limit the power of the other. For best results only wire in parallel. Upgrade the wire and do it right.

If you park in the shade, all solar configurations don't work very well. I've documented over 200 days of use with my series-parallel configured solar array in the Solar Show and Tell thread. Anyone interested can look at my data and see for themselves that panel shading has not been an issue for me.

I prefer the more efficient series-parallel configuration and would configure in that fashion no matter what size wire was going to the controller. It just so happens that the factory prewire is completely sufficient for up to 600W of solar with less than a 2% voltage drop when using a series-parallel configuration. No need to waste time and money upgrading the solar prewire.

[gator.bigfoot]

Originally Posted by AirMiles

If you park in the shade, all solar configurations don't work very well. I've documented over 200 days of use with my series-parallel configured solar array in the Solar Show and Tell thread. Anyone interested can look at my data and see for themselves that panel shading has not been an issue for me.

I prefer the more efficient series-parallel configuration and would configure in that fashion no matter what size wire was going to the controller. It just so happens that the factory prewire is completely sufficient for up to 600W of solar with less than a 2% voltage drop when using a series-parallel configuration. No need to waste time and money upgrading the solar prewire.

I'm talking of one panel in the shade and the other in the sun. Which happens quite often when I'm camping. Sure the efficiency is lower in the shade, but it still works and the panels are still outputting something.

The size of wire matters and is a proven fact. But you can do as you wish. The law of physics doesn't change. Voltage drop is a real. But if you have one panel in the shade and the other panel in the sun then your output is close to zero so no wonder you proclaim that it's not a problem. Zero output will be just that. I always camp in the shaded spots and don't have an issue. I rarely get all panels in the sun for more than a few minutes a day. So I will take the parallel approach.

[AirMiles]

Yes let’s stick to physics because the series-parallel will win. You get higher voltage across any size wire with series-parallel and therefore more Amps of battery charging. This is exactly why the Victron owners manual states: “Recommended number of cells for highest controller efficiency: 72 (2 x 12V panel in series or 1 x 24V panel)." See attached picture of owners manual.

Again, over 200 days of successful documented usage and an owners manual that recommends series-parallel verses opinions of those who have no experience with the configuration.

This summer I spent over 60 nights using only solar charging in NC, ME, VT, NH, Up-MI, WI, and MN. All locations with considerable tree canopy and not once did I need to boost charge with my generator (see documentation in Solar Show and Tell thread). If series-parallel did not work great, I’d spend the money to convert to full parallel in one minute. But it works perfectly and I would not reconfigure against the owners manual’s recommendation.

Everyone can choose how they configure their solar array. But I keep banging this drum so everyone has the facts before they make a decision based on flawed consensus opinion.

[ghaynes755]

Double dittos to what airmile wrote.

[AirMiles]

Link to 28 days of May/June 2019 solar performance on the tree-filled Blue Ridge Parkway in NC. Notice that the system "floated" nearly every day meaning the batteries were fully charged. http://www.airforums.com/forums/f448...ml#post2252491

Link to June 2019 performance in Ohio, Michigan and Wisconsin: http://www.airforums.com/forums/f448...ml#post2258949 Again floated nearly every day in these tree-filled locations.

Link to July 2019 performance: http://www.airforums.com/forums/f448...ml#post2271059 Again floated nearly every day in more tree filled locations in WI and MN.

These are not selected days of data here and there. These are 80 days of continuous solar performance in tree-filled locations. Now show me in this data where series-parallel did not work. Not one time in 80 days of solar camping in tree-filled locations did a generator need to be used to boost charge the batteries. If series-parallel has a problem with tree canopy, or overcast conditions, or rain . . . it would show up in this data.

[gator.bigfoot]

There is obviously no point in convincing you. My system only runs on solar. Never plugged in. No converter. The batteries are in all the time. And it charged through the winter at negative 20 with a foot of snow.

The wire I put in cost me less than 100 bucks and it took about 3 hours to put it in. Small price to pay for the added performance.

[Fair_Enough]

And away we go again.

[gator.bigfoot]

There is nothing wrong with the series parallel approach in systems that have the same exposure to the light. Rooftops, trackers and fixed systems have this all the time and it's a great way of saving on the wire costs as pointed out. But on RVs not so much.

[ghaynes755]

Airmiles, clearly your measurements are wrong. It can't possibly work. So therefore your system is poorly designed, badly installed and your batteries are never in float and therefore you have no power in your trailer. As Andy said to the warden at Shawshank, 'are you being obtuse?'

[evamcmahan]

Kringle, did you buy the 2016 classic, and what length is it? I have a 2016 classic 30 foot, and cannot find the red and yellow prewires in the ceiling. The owners manual states they are in front of the rear roof vent. There is no rear roof vent. An Airstream tech support person emailed me his resource and it states in front of the bathroom skylight, and to remove the bathroom light to access the wires. Well, there is no bathroom, because there is no bathtub. The wires are not behind the ceiling light in front of the rear hallway skylight. Nor are they behind either of the two lights in the lavatory. Did you get the trailer, and, if so, is it a 30 foot and did you find the wires.

[AKNate]

Originally Posted by ghaynes755

Double dittos to what airmile wrote.

Triple dittos to what airmiles wrote. I have 600 W on the factory prewire and it works great. Series-parallel systems still have plenty of parallelism to provide alternative paths if a panel is shaded and they have the added advantage of higher voltage so they still make power in very low light.

[warrantchief]

Originally Posted by AKNate

Triple dittos to what airmiles wrote. I have 600 W on the factory prewire and it works great. Series-parallel systems still have plenty of parallelism to provide alternative paths if a panel is shaded and they have the added advantage of higher voltage so they still make power in very low light.

Hey, in order to fit 6 panels on my 2017 Classic, I would need to have them tucked right up against the A/C, which would likely mean some part of one of the two panels will be shaded no matter what. Is that a dealbreaker? I don't really understand the details of how shade limits the other panel and by how much.

Thanks

[AKNate]

Originally Posted by warrantchief

Hey, in order to fit 6 panels on my 2017 Classic, I would need to have them tucked right up against the A/C, which would likely mean some part of one of the two panels will be shaded no matter what. Is that a dealbreaker? I don't really understand the details of how shade limits the other panel and by how much.



Thanks

The way I did mine is each panel is in parallel with the opposite panel on the other side of the airstream. Each of the three sets of parallel panels are in series. AC units partially shading one or two panels don’t make a huge difference since any shaded panel is in parallel to an unshaded panel. Modern panels also have bypass diodes built in, so shading part of a panel doesn’t bring down the whole thing like old panels. Another factor is the curve of an Airstream’s roof - panels are mounted at an angle rather than flat. If your AC is casting a shadow onto a panel, that means that panel is pointing away from the sun anyway and the opposite panel is the one pointing toward the sun and producing the most.
The downside is that each of your three sets will be limited to the current of the least producing set, so an AC partially shading one panel is essentially the same as it partially shading the other three panels on that side. Like I said though, that partial shading isn’t as big of a deal as some might believe.
The upside is your three sets give you three times the voltage, so your charge controller will be on and producing significant power even near sunset or on cloudy days, when a full parallel system may not make enough voltage to turn on.
Here’s my roof.