I'm about ready to install a solar system on our 28' 2011 Jayco TT. Solar panels will be on the roof with the wires from each going to a roof combiner box, then a pair of wires from the roof combiner box going down to the pass through storage, where my solar controller, inverter, etc, will be mounted on a piece of 3/4" plywood opposite the two 6V batteries on the tongue.To minimize voltage loss, I want to route the wires from the roof combiner box, which will be in the center of the roof at the front of the TT, to the solar controller in the pass thru storage via the shortest possible distance. The shortest route is down through the front center of the TT, between the front cap and the paneling on the inside wall. In the pic below, you can see the inside wall. I removed the decorative headboard which is held by 3 screws, and behind that is the same paneling.I don't know for sure what is behind that paneling. I recently drilled a hole for another project in the rear wall of the TT, and the insulation there was solid styrofoam. Should I expect that the insulation between the front cap and the inside paneling is also styrofoam? Or would it likely be a different material?If it is styrofoam, any suggestions on the best way to route a wire from the roof down through it? I can take my oscillating multi-tool and from the inside cut one or more access openings into the front wall, behind where the decorative headboard fastens. For obvious aesthetic reasons, I don't want to cut any access openings into the paneling above the headboard. If the insulation is styrofoam, I wonder how hard it would be to get a wire from the roof through the styrofoam and down to the pass through storage. Does anyone have any experience with a similar project?Thanks for any tips and suggestions!

crcr wrote:To minimize voltage loss, I want to route the wires from the roof combiner box, which will be in the center of the roof at the front of the TT, to the solar controller in the pass thru storage via the shortest possible distance.You can minimize V loss, and ditch the combiner box by wiring in series.

2oldman wrote:crcr wrote:To minimize voltage loss, I want to route the wires from the roof combiner box, which will be in the center of the roof at the front of the TT, to the solar controller in the pass thru storage via the shortest possible distance.You can minimize V loss, and ditch the combiner box by wiring in series.Thanks, but I have studied this and have already made the decision that I will be wiring in parallel, and I will use substantial gauge wire from the roof combiner box to the solar controller. Parallel wiring because we camp in Forest Service campgrounds and state park campgrounds, and very often during the day, parts of the roof will be shaded, and parts will not. By wiring in parallel, if one or more solar panels has it's output cut drastically by shading, and other solar panels are still in full sun, I will still get a decent amount of amps.

How many watts of panels? What controller? How thick is "substantial"?

Unfortunately I'm going to bet your front wall is the same Styrofoam as the rear making it impossible to just push a wire through. What gauge wiring are you running down the wall? Can you hide it on the surface behind some white or tan channeling? LinkIt looks like you have cabinets on either side of the trailer that comes down most of the front wall. And I'm assuming there's a night stand table feature under the cabinets leaving a gap between the two of about maybe 18 inches. I would take the voltage drop hit and extend the wire over to the drivers side front corner and come down inside the cabinet. Then it's only a short run of visually exposed channel under the cabinet to the night stand and then across to the batteries. I'll bet after a week you wont even notice the channeling unless you actively remind yourself it's there and look at it. You could even put something in front of the exposed channel like a framed picture of the family or a vase of silk flowers velcroed down so it doesn't move during travel.

This idea may or may not help you:When I installed my Winegard Traveler satellite dis, the instructions said to route the wiring thru a hole I was to put in the roof... It had some sort of plastic cover to install over it.I wasn't too keen on that idea. So I opted to run the wires to the back of the TT (only about 4') and down the roof ladder. All the way to the bottom, then thru the underbelly to where I wanted to come up thru the floor with them. It worked great, and will not ever be a roof leak issue.

Routing Solar Wiring from Roof to Pass Through Storage

15 Replies

Vintage465
Nomad
Dec 04, 2019
babock wrote:
crcr wrote:

Thanks, but I have studied this and have already made the decision that I will be wiring in parallel, and I will use substantial gauge wire from the roof combiner box to the solar controller. Parallel wiring because we camp in Forest Service campgrounds and state park campgrounds, and very often during the day, parts of the roof will be shaded, and parts will not. By wiring in parallel, if one or more solar panels has it's output cut drastically by shading, and other solar panels are still in full sun, I will still get a decent amount of amps.
You are still better off running in series. If your panels have bypass diodes(most do) the effect of shading only affects the panel that is shaded.

I think the best bet is to get “enough controller” and a spacious enough combiner box to be able to wire it either way to see what really works best. At some point that’s what my plan is.
babock
Explorer
Dec 04, 2019
crcr wrote:

Thanks, but I have studied this and have already made the decision that I will be wiring in parallel, and I will use substantial gauge wire from the roof combiner box to the solar controller. Parallel wiring because we camp in Forest Service campgrounds and state park campgrounds, and very often during the day, parts of the roof will be shaded, and parts will not. By wiring in parallel, if one or more solar panels has it's output cut drastically by shading, and other solar panels are still in full sun, I will still get a decent amount of amps.
You are still better off running in series. If your panels have bypass diodes(most do) the effect of shading only affects the panel that is shaded.
Vintage465
Nomad
Dec 03, 2019
I was able to route #4 Welding Cable(red and black)from the combiner box over to the left side of the coach, then I intercepted it in the left wardrobe closet and brought it down to the night stand, where it came out of the bottom of the wardrobe and became exposed in the corner.

Then where it became exposed I cut out a piece of trim to to cover it. The "blemish" at the top is actually a reflection of the 12v outlet.

From there it went to the controller and down thru the belly to the batteries

I ran #2 welding cable down to the batteries.
Harvey51
Explorer
Nov 29, 2019
The refrigerator vent is a surprisingly easy route for running heavy cable down from the roof.
crcr
Explorer
Nov 29, 2019
camp-n-family wrote:
Does your tt have a moulded fibreglass type front cap? If so there is likely a hollow open void between the cap and the front wall of the tt. You wouldn’t have any way to secure the wiring through there but you could remove a side cabinet and cut a small access hole.

Thanks. No, does not have the molded fiberglass front cap, has the older traditional style. I can't know for sure, but given there is styrofoam in other walls, that is why I suspect there might be styrofoam behind the inside paneling on the front of the TT.
camp-n-family
Explorer
Nov 29, 2019
Does your tt have a moulded fibreglass type front cap? If so there is likely a hollow open void between the cap and the front wall of the tt. You wouldn’t have any way to secure the wiring through there but you could remove a side cabinet and cut a small access hole.
CA_Traveler
Explorer III
Nov 28, 2019
I've run wires through styrofoam walls using the common household wire puller to penetrate, pull a string, rope and then wire.

If you are going to use a PWM controller then you don't need the larger wire. PWM controllers use the panel amps so as long as the voltage at the controller is 14.8V or more so larger wire won't help. ie The typical voltage drop from the 12V panels (about 18V) to 14.8V at the controller doesn't get used, just the panel amps.

Serial panels with bypass diodes and MPPT controller are generally more tolerant of shadows than parallel panels.
Lwiddis
Explorer II
Nov 28, 2019
“...a short run of visually exposed channel...”

That’s what I did. Appropriately painted or stained no one will notice.
crcr
Explorer
Nov 28, 2019
Huntindog wrote:
This idea may or may not help you:
When I installed my Winegard Traveler satellite dis, the instructions said to route the wiring thru a hole I was to put in the roof... It had some sort of plastic cover to install over it.
I wasn't too keen on that idea. So I opted to run the wires to the back of the TT (only about 4') and down the roof ladder. All the way to the bottom, then thru the underbelly to where I wanted to come up thru the floor with them. It worked great, and will not ever be a roof leak issue.

Thanks, but that would be way longer wire run than I want for DC amperage -- too much voltage drop. Re the possibility of the roof leaking, I will use a 4" x 4" x 2" deep plastic gasketed box from HD. I will epoxy two bus bars inside for the wires to all connect. The down wire will go into the roof from the bottom of the box, box will be screwed the the roof and I will seal the bottom of the combiner box with Dicor. Lots and lots of folks install solar roof combiner boxes this way with no leaks.
crcr
Explorer
Nov 28, 2019
opnspaces wrote:
Unfortunately I'm going to bet your front wall is the same Styrofoam as the rear making it impossible to just push a wire through. What gauge wiring are you running down the wall? Can you hide it on the surface behind some white or tan channeling?
Link

It looks like you have cabinets on either side of the trailer that comes down most of the front wall. And I'm assuming there's a night stand table feature under the cabinets leaving a gap between the two of about maybe 18 inches. I would take the voltage drop hit and extend the wire over to the drivers side front corner and come down inside the cabinet. Then it's only a short run of visually exposed channel under the cabinet to the night stand and then across to the batteries. I'll bet after a week you wont even notice the channeling unless you actively remind yourself it's there and look at it.

You could even put something in front of the exposed channel like a framed picture of the family or a vase of silk flowers velcroed down so it doesn't move during travel.

Thanks. Yeah, that is roughly my Plan B. And yes, it may be near to impossible to route a wire down through styrofoam, if that is the insulation. The left and right cabinets are roughly only 12 inches above the built-in nightstands, so yeah, I could route the wire through one of the "wardrobe" cabinets, down into the back of the nightstand, and then into the pass through to the solar controller. As you say, the only place the wire would be exposed is between the wardrobe and the nightstand, at the back, hardly would be noticeable, or I could run it in the corner and cover it with something.

I'll probably run 4 gauge wire down from the roof combiner box. I was going to run 6 gauge, but 4 gauge wire is a bare few pennies more per foot, so I'll just run 4 gauge and have minimal voltage loss.