Preferred route for main solar feed FC25FB

[daleyocum]

I'm adding 500W of solar to our 2018 25' Flying Cloud FB Twin. Much as I'd like to use the factory prewire I just can't bring myself to drop a volt thanks to the miserly 10ga wire AS installed. So, what's the conventional wisdom as to the best way to get 6ga wire from the roof to under the curb side (twin) bed? Down through the refrigerator vent and then under the trailer? Can I use the existing wire to fish a new bigger wire? I'm not sure what route it takes.

[alano]

If you're using an MPPT charger, you could consider a series/parallel panel configuration. You're voltage losses would probably be around 2%. Seems like a small price to pay for the convenience. And if you do wind up running 6 AWG wire, you've lost nothing. That's how I'm configured.

[SSquared]

Lewster here on the forums is a professional installer that has done many AS installs. On my 25FB twin, he went down the fridge vent, then down to the floor (I didn't watch him for that bit, so I don't know the details), then under the closet, under/behind the shower, and through the street side and front storage compartments. He used some aluminum channel in the storage compartments to protect the wires.

[daleyocum]

Originally Posted by alano

If you're using an MPPT charger, you could consider a series/parallel panel configuration. You're voltage losses would probably be around 2%. Seems like a small price to pay for the convenience. And if you do wind up running 6 AWG wire, you've lost nothing. That's how I'm configured.

I was all set to do that (I do have a MPPT controller) until I learned more about the extreme drop off of in efficency from shade on even one cell.

[daleyocum]

Originally Posted by SSquared

Lewster here on the forums is a professional installer that has done many AS installs. On my 25FB twin, he went down the fridge vent, then down to the floor (I didn't watch him for that bit, so I don't know the details), then under the closet, under/behind the shower, and through the street side and front storage compartments. He used some aluminum channel in the storage compartments to protect the wires.

That’s more or less what I thought I’d do. I was tempted to drill one hole and drop down inside the closet and then inside wire molding for a foot into the bed. Much less wire.

[alano]

Originally Posted by daleyocum

I was all set to do that (I do have a MPPT controller) until I learned more about the extreme drop off of in efficency from shade on even one cell.

I've seen this a while ago and here are my criticisms:

1. It's unknown whether or not the panel includes bypass diodes. The number of diodes is unknown.

2. MPPT controllers have proprietary algorithms for adjusting the maximum power point. It's not clear how fast the controller in this example responds and if the test allows sufficient time for the converter to adjust.

3. Blanketing areas of the panel with no (zero) sunlight whatsoever seems unrealistic. Real-world use conditions rarely result in such a pessimistic test.

4. Series connected panels in home installations are a popular configuration in use all across the world.

I personally think the tradeoffs of using a series or series/parallel configuration vs a parallel installation are minimal and re-using the existing 10 AWG wiring entices folks to perform the solar installation themselves by lowering the difficulty level. Your mileage may vary

[daleyocum]

Originally Posted by alano

I've seen this a while ago and here are my criticisms:

1. It's unknown whether or not the panel includes bypass diodes. The number of diodes is unknown.

2. MPPT controllers have proprietary algorithms for adjusting the maximum power point. It's not clear how fast the controller in this example responds and if the test allows sufficient time for the converter to adjust.

3. Blanketing areas of the panel with no (zero) sunlight whatsoever seems unrealistic. Real-world use conditions rarely result in such a pessimistic test.

4. Series connected panels in home installations are a popular configuration in use all across the world.

I personally think the tradeoffs of using a series or series/parallel configuration vs a parallel installation are minimal and re-using the existing 10 AWG wiring entices folks to perform the solar installation themselves by lowering the difficulty level. Your mileage may vary

Do you have your panels in series or series/parallel? If so do you have a sense as to how well they are performing in the real world with real world shading?

[alano]

I've got 4 100W panels in a series/parallel configuration. Since each set is angled differently, I wired the panels that are angled in the same direction in series.

Although I probably go on 10-15 outings per year, probably only 3-5 of them are without hookups. In the few times where I've been boondocking and shady, the shade that I've experienced so far hasn't been very dense. In the vast majority of cases when boondocking my battery monitor indicates that my batteries are back to up 100% by noon.

For the moment I probably only have about 90-100 Ah of usable capacity anyway since I'm currently using the stock lead-acid batteries. One of the reasons I put 400 W on the roof was to make sure that I have sufficient solar power even if shading is a problem, but so far my experience has been very good and I see no reason to mess with routing wires in the interior of my Classic for what could be negligible benefits.

[daleyocum]

According to the the voltage drop calculator at 20’ and 30amps at 18 volts (parallel panels) you save about 4% by going from the stock 10 gauge prewire to 6ga. If I went in a series / parallel arrangement the wire voltage drop would be less but I fear, in the kind of camping we do in the Northwest with a lot of shade, that loss would be minimal compared to shading losses.

As a test I took one of the panels I plan to use, the top of the line Renogy Eclipse 100w panels and measured it’s output voltage under various shading scenarios. If the whole panel is in direct sun everything is dandy. Once a few cells are shaded from direct sun (not blocked to zero, just not getting direct sun) things drop in half or worse. If the panels were in series I fear the whole string would fall off a cliff. I didn’t get out two panels to see if that’s true. I think I’ll run that test if we ever see the sun in Portland! Maybe with MPPT, series is still better, because each panel can still contribute something?

[alano]

I wish I had access to a good simulator where different scenarios could be tried. Since I don’t I’m only relying on first principles and my understanding of power converters. If you can run 6 AWG without too much difficulty I would do just that. There aren’t many folks banging the table that a series configuration is better. There are frequently trade offs that seems pretty clear for some and are more difficult for others!

[jcslocum]

This is a simple good discussion of shading and the effects.

https://www.youtube.com/watch?v=1qD3mN8VotQ

Jon

[daleyocum]

I did some poking around in the trailer today and found a great solution. This only works for a 25’ Front bed twin, though, so a pretty narrow application. Turns out in the bathrooom next to the toilet is a 45 degree panel that, when removed, exposes the ABS vent pipe to the roof! As others have done, I’ll just feed the wire down through the first few inches of that pipe then drill through the side (patching well, of course) and then run the wires straight down this 45degree chanel and out the wall to the underside of the street-side twin bed where all the electronics are to be located.

Any thoughts about how to seal that half inch hole (with two 6 ga wires) in the ABS vest pipe? I’ll just glob on lots of silicone adhesive unless someone has a better idea.

[Wayne&Sam]

Originally Posted by jcslocum

This is a simple good discussion of shading and the effects.

Jon

That's kind of depressing in series or parallel.

[wponder]

Do you have a pic of the panel? I am wondering if its also on a 25FB International? I was going to drill though the roof above the master closet then down past the hot water heater and over to the queen bed where everything is.

[daleyocum]

Here’s a photo of the vent chase in my FC25 FB bathroom I imagine other trim packages would have a pipe in the same place, perhaps finished in a more elegant way. https://www.dropbox.com/s/kx9cpioaed...route.JPG?dl=0

Its almost like it’s custom made for getting solar wires down to under the twin bed. I’ll probably also drop the cell booster antenna through the same hole and mount to the cell booster on top of the panel in the bath with the antenna out in the hall.

With a queen you’d have to run the wires either under the trailer from that point in the bath and back up inside under the bed or use wire molding on the surface once you are in the bedroom.

[billrector]

I'm also planning a solar install on my 27' FC FB. Currently, I'm planning on also adding 400W (with 200W portable) in a series/parallel configuration. Each side of the AS would have the two panels in series ties to the combiner in parallel.

If I change my mind and decide to do a parallel configuration, then why can't one just remove the combiner box (factory installed on the newer ASs) and run a new cable down through the roof? Anyone do this? I'm making the assumption and this is where the factory 10 AWG wire goes?

[wponder]

thanks daleyocum. I will need to look at that closer. There is a closet on the other side of that wall in the 25FB International also the Twin I believe. I am trying to get to that closet. The bottom 1/4 of the closet has really easy access to the Water Heater and into the storage underneath the Queen Bed. That is where everything is going for us. I'll take a closer look!

[daleyocum]

Originally Posted by billrector

I'm also planning a solar install on my 27' FC FB. Currently, I'm planning on also adding 400W (with 200W portable) in a series/parallel configuration. Each side of the AS would have the two panels in series ties to the combiner in parallel.

If I change my mind and decide to do a parallel configuration, then why can't one just remove the combiner box (factory installed on the newer ASs) and run a new cable down through the roof? Anyone do this? I'm making the assumption and this is where the factory 10 AWG wire goes?

I asked the service guys that question and they seemed to think it wasn’t possible to use those 10ga wires as a guide to pull through bigger wires...too many bends and such. At least on mine that box is in the middle of the hall so the hole there isn’t much use. Would have been great if the wires were in a conduit but alas they aren’t.

If you are doing series/parallel at 400w or less I think the existing 10ga would be fine. Going all parallel at 400w or higher is where replacing the wire starts to pay off. There’s no question all parallel is better from a performance standpoint in partially shaded areas with big wires. It’s how much trouble do you want to go to for that last 10%. AS rates that combiner box at 500w max for what that’s worth.

My guess is you have a vent pipe as well in your bath somewhere. If so that’s at least a handy way to get a wire from the roof to under the trailer.

[wponder]

I looked at this closer today and this is a very intriguing path to take for me vs. drilling a new hole in the roof. The vent on the roof is very close to where I want to mount the combiner box. If I take this path I plan to poke a hole in the plastic screen under the vent cover and just run the cable out to the combiner. From the bathroom I would just notch the 45 degree panel in the corner at the bottom run the power behind the toilet, through the plumbing hole and straight over to my core system area.

Does anyone know if that pipe has another screen further down? I did not get a chance to pop the top off.

Thanks

[thiel]

Originally Posted by SSquared

Lewster here on the forums is a professional installer that has done many AS installs. On my 25FB twin, he went down the fridge vent, then down to the floor (I didn't watch him for that bit, so I don't know the details), then under the closet, under/behind the shower, and through the street side and front storage compartments. He used some aluminum channel in the storage compartments to protect the wires.

This is exactly the route I have planned. I know I can get behind the fridge, and I know I can get behind the shower through the back of the closet... and then after that I'm running through the backs of cabinets. Makes the run pretty long though...