8awg Solar Prewire, now what?

[AirMiles]

Originally Posted by thewarden

I am also at this cross roads, use factory prewire on series/parallel or install 4 AWG to accommodate 4+ panels on parallel.

If anyone has installed upgraded solar wire on a 27 FB I would really appreciate any info you have regarding where to thread the cable from the roof to the front compartment. I have been searching for days without any luck.

After receiving a large estimate to have this done, I am more than willing to give it a go myself. It just so happens that I have 25' each of red and black 4 AWG tinned copper marine cable in the garage, which hopefully is enough.

I also had the same issue/concern on my 27FB Queen. There are no cabinets running the full length of the front bedroom in which to hide the new heavy-gauge solar cables. (Another reason to use the factory prewire on a 27FB Queen.) But I did find a solution. You can use cable channel to span the visible area through the front bedroom. Just pick the size and color that would work best in your Airstream (probably grey). There are many different brands, so here is a random example: https://www.amazon.com/One-Cord-Chan...72F0P58HW&th=1 This was the only soution I could come up with for installing heavy-gauge solar cables in a 27' Queen. I chose to use the factory prewire to avoid drilling holes and adding a visible cable channel.

[GMFL]

Originally Posted by AirMiles

I also had the same issue/concern on my 27FB Queen. There are no cabinets running the full length of the front bedroom in which to hide the new heavy-gauge solar cables. (Another reason to use the factory prewire on a 27FB Queen.) But I did find a solution. You can use cable channel to span the visible area through the front bedroom. Just pick the size and color that would work best in your Airstream (probably grey). There are many different brands, so here is a random example: https://www.amazon.com/One-Cord-Chan...72F0P58HW&th=1 This was the only soution I could come up with for installing heavy-gauge solar cables in a 27' Queen. I chose to use the factory prewire to avoid drilling holes and adding a visible cable channel.

Why not run the cable as far as you can through the cabinets. And the drill the floor and run the cable under the floor to the bed compartment?

[Kalashnikov]

Originally Posted by pcskier

Whoops. I didn't calculate the length of the round trip, which is how I wound up with 6 awg from the roof...good to up to 18 feet at 2 percent loss for my four panels in parallel. My run was certainly more than 9 feet *each* way, so the chart prob would have called for 4 awg. So my losses might be higher than 2 percent after all. Fortunately my system has been working great for me though I'm probably not wringing every last watt. But I do float every day, so life is good!

Then you're ok


I'll be using the factory prewire, don't plan on losing any sleep over it. My dual AC units will shade much of the array anyway - that's the biggest "loss."


600W of panels will make up for it

[gator.bigfoot]

If there is a pre-wire then they would have run it in a conduit. That's the way mine was. I simply ran a fish tape through and pulled in the 4 gauge wire. If you look carefully you should find conduit. Mine was buried under the couch arm under the carpet. From there is ran under the credenza and then out under the dinette bench. From there it was an easy pull behind the fridge and up to the roof.

[gator.bigfoot]

Originally Posted by Kalashnikov

Then you're ok


I'll be using the factory prewire, don't plan on losing any sleep over it. My dual AC units will shade much of the array anyway - that's the biggest "loss."


600W of panels will make up for it

I think you'd be surprised by how much you're losing through the shading effect. Avoid shading from roof mounted stuff at all costs. You panel is pretty much putting out nothing. My brother in law just mounted his panel much higher to avoid this. At the same time he used a 72 cell panel. It puts out an insane amount of power. He also has the ability to tilt the panel in multiple directions.

[daleyocum]

Originally Posted by thewarden

I am also at this cross roads, use factory prewire on series/parallel or install 4 AWG to accommodate 4+ panels on parallel.

If anyone has installed upgraded solar wire on a 27 FB I would really appreciate any info you have regarding where to thread the cable from the roof to the front compartment. I have been searching for days without any luck.

After receiving a large estimate to have this done, I am more than willing to give it a go myself. It just so happens that I have 25' each of red and black 4 AWG tinned copper marine cable in the garage, which hopefully is enough.

I ran my 6 gauge wire on a FC25 down behind the triangular panel that conceals the vent pipe in the bathroom. It really is easy but yes you do need to drill a hole at the top of the run through both the ceiling and the roof. I used Sikaflex and VHB tape to hold down a AM Solar combiner box right above that vent pipe area. On a FC25 the vent pipe makes a few turns before it emerges through the roof so going straight up worked out great.

Coming down it that area made it really easy to get to the batteries and electronics I put under the curb side twin bed in my front bedroom trailer.

My year's trailer has 10ga wire so there was no choice in my mind than to upgrade because I wanted to go parallel. If my trailer came with 8ga and I only wanted to put four panels on the roof I probably would have just used the standard wire.

One thing people haven't talked about is if you upgrade the solar wire, that means you have power for something else going to the old Airstream solar box on the roof. I used that for my Garmin backup camera but it would also be handy for a self contained Cell hotspot.

[Greatlaker]

Hermes,

Thanks. Having a front bedroom, I will penetrate the roof and come into a chase in the bathroom, whereas I will be right next to the curbside twin, which is where all my business ends reside....

How was it, wrestling the #4 into the AM Solar C-box busbar? I'm only mounting 4 panels, so it appears there is ample room inside.

[Hermes]

Originally Posted by Greatlaker

How was it, wrestling the #4 into the AM Solar C-box busbar? I'm only mounting 4 panels, so it appears there is ample room inside.

Here is a picture of the C-Box with the wiring. Needed to drill an additional hole (bottom left side in picture). Could most likely do the same on the other side to go to 600w. As far as the #4 wires, they are bulky but the bus bars can handle them as you can see from the picture.

[Hermes]

Here are two pictures where you can see the panel layout on both sides of the trailer. The combiner box is installed a few inches from the fridge vent.

[thewarden]

Originally Posted by gator.bigfoot

If there is a pre-wire then they would have run it in a conduit. That's the way mine was. I simply ran a fish tape through and pulled in the 4 gauge wire. If you look carefully you should find conduit. Mine was buried under the couch arm under the carpet. From there is ran under the credenza and then out under the dinette bench. From there it was an easy pull behind the fridge and up to the roof.

If they ran my prewire in a conduit I will be shocked, pleasantly shocked, but shocked nevertheless. Mine is a 2016 27 FB Int. Maybe because yours is a Classic, AS went the extra mile with conduit.

[Hermes]

No conduit in mine (an Int'l). Ran the #4 wires (taped together) under the stove and galley counter from the fridge cabinet to the front. There is other wiring under there as well, tied to the wall.

[Moodywelman]

I would pose the question to AM Solar. They do this all the time and they are happy to discuss it over the phone or via email. They did my install and I’m very happy with it.

[lilboomer]

Originally Posted by nvestysly

The discussion is centering around 4 AWG not 4/0 AWG. 4/0 is extremely large diameter wire.

Can't help you on the routing although I have heard a number of installers say they route the wire down through the exhaust vent of the refrigerator if the trailer has a roof-mounted exhaust vent. Using this method, no holes are needed through the skin of the trailer.

This Sport 22FB has no refrigerator roof vent. A wild guess is the factory wiring starts at the roof connection box and follows the AS ribs down to floor level then forward to emerge under the front bed. But I can't figure out how to confirm this guess.

[Rzrbrn]

I am not electrically knowledgable. However, I read somewhere that going 24V instead of 12v might be preferable when the cable runs are long because the 24V system uses smaller diameter (larger gauge) wires. But what you gain in efficiency may be lost due to the step down to 12V.

[AirMiles]

Originally Posted by Rzrbrn

I am not electrically knowledgable. However, I read somewhere that going 24V instead of 12v might be preferable when the cable runs are long because the 24V system uses smaller diameter (larger gauge) wires. But what you gain in efficiency may be lost due to the step down to 12V.

This is what I do by using series-parallel configured pairs and an MPPT controller with the factory prewire. Victron actually recommends running their solar controllers at 24V for their "highest" efficiency. Series-parallel configured pairs running at 24V on 10 gauge wire will have nearly equal efficiency as the same number of parallel configured panels running on 4 gauge wire. You can verify this efficiency by using a voltage loss calculator https://www.calculator.net/voltage-drop-calculator.html

Actually I noticed on the above voltage calculator link that 10 gauge wire has a resistance of 0.9989 O/kFT and 4 gauge wire has a resistance of 0.2485 O/kFT. A series-parallel configured solar pair has twice the voltage at half the amps which reduces resistance by a factor of four. So 0.9989 divided by four is equals 0.2497. This easily demonstrates that a 10 gauge wire's resistance of 0.2497, when panels are configured series-parallel pairs, is nearly identical to the 0.285 resistance of a parallel pairs of panels on 4 gauge. An added benefit of a series-parallel configuration is that there is significantly less wire needed between the panels and the rooftop box (about half as much) which actually makes the series-parallel configuration the most efficient of the two. And with 8 gauge, the series-parallel configuration would be 37% more efficient!

[Ddobier]

I know this doesn't help you now but does anyone have influence at airstream to just have them use the 4 gauge on all new airstreams and this eliminate the problem? Just add it to the cost of a new one. Would save a lot of headaches as I see this question often. (And while we are add it if they could offer at least 400 watts from the factory and a 3000 inverter as that's what everyone wants that would be great.!)

[jimro]

If anyone has installed upgraded solar wire on a 27 FB I would really appreciate any info you have regarding where to thread the cable from the roof to the front compartment. I have been searching for days without any luck.

On our 27FB GT for 4-100W panels I ran a duplex 6 AWG (AM Solar) from a rooftop combiner box set directly over the wall space that's between the bathroom wall and the kitchen cabinets. My 1" hole came into this space where the cable runs down and out the bottom under the vanity. I drilled a second hole beside the water heater LPG gas line and ran the cable underneath the trailer to enter the front compartment via another new hole beside the battery cables. Wrapped the exposed cable underneath with split corrugated cable protector and ty rapped to the gas line.

[Rloftinbiz]

I find most information here good advice. Going solar makes the most sense to me. I believe higher voltages, 48V vs 24V vs 12V vs 6V, have have enough advantages to be a preferable choice.

On the other hand it is easier to deal with 12V because of its extensive use and availability. There are lots more 12V batteries and systems in common use than 24V+.

Parallel and series are standard electrical designs, each with its own issues! Trying to set a topology that works, meets your needs, and is safe is the basic question. It is important to do it right. I don't believe electricity is as much a mystery as the many opinions may make it seem to be.

Some considerations may be efficiency per square foot, what size of panel fit best (many vendors, many sizes), panels with built-in MPPT controllers, or panel optimizers with cutoff ability, multiple MPPT controllers, single vs dual phase AC, battery types, battery management and topology.

Given the roaming nature of the platform, shading will likely always be an issue

I have used AM Solar and feel they have enough experience and knowledge to rely upon. They are my feedback for any crazy stuff I dream up. Simple is usually better (even if that is not what I did).

Lastly if you have to take apart anything that allows you access to rewiring, if you do not know the exact extent of the system you may grow into, then accommodate the growth with higher capacity wiring. Although there is much more engineering to explore in how gauge wire size affects all components, suffice to say, pre-wired may serve future plans without doing it all again. While your at it consider extra pulls of whatever wiring, communications and electrical.

Victron and others take into account the resistance of its connections and suggest they be matched and equal length runs.

Find someone with real electrical engineering credentials, who has experience in home grown as well as commercial solar and work with them to get what you need.

No matter how complex the system is, a good and experienced engineer is gold.

Hope this helps!

[thewarden]

Originally Posted by jimro

If anyone has installed upgraded solar wire on a 27 FB I would really appreciate any info you have regarding where to thread the cable from the roof to the front compartment. I have been searching for days without any luck.

On our 27FB GT for 4-100W panels I ran a duplex 6 AWG (AM Solar) from a rooftop combiner box set directly over the wall space that's between the bathroom wall and the kitchen cabinets. My 1" hole came into this space where the cable runs down and out the bottom under the vanity. I drilled a second hole beside the water heater LPG gas line and ran the cable underneath the trailer to enter the front compartment via another new hole beside the battery cables. Wrapped the exposed cable underneath with split corrugated cable protector and ty rapped to the gas line.

Thanks very much. P.M. sent.

[AirMiles]

I think its important for beginners to understand that running series-parallel solar panel pairs at 24V over the factory prewire gets converted to 12V by the MPPT solar controller so you still use standard 12V batteries and stock 12V appliances. You can then choose to retain your stock 12V batteries with about 160AH (50% usable), or upgrade to a pair of quality 6V batteries (making 12V in series) with about 230AH (80% usable), or upgrade to 12V Battleborn Lithium batteries with 100AH usable per battery. There is no difference from the solar controller to the batteries when using 12V or 24V over the factory prewire. Its all 12V from the solar controller output.