Solar Photovoltaic Panel Install
Dave and Helen Damouth www.damouth.com
16 July 2005
Introduction
This solar charging system was originally purchased in 1996 and installed on our first RV. When I sold that travel trailer, I removed the solar components. I'm reinstalling the old solar panels on our "new" 2002 Winnebago Journey DL 32TD, (three 75-watt Siemens SP75 panels) but have purchased a new, better, charge controller (Trace C-35).Although much of the general information given here should be generally applicable, the details are only valid for the Winnebago Journey 32. Mine is a 2002, but I believe the layout is the same for all model years up through 2006.
Panel Mounting
I chose to mount the solar panels near the center of the roof, where
there is adequate clearance from other roof protrusions, and where the
wire length to the existing electrical panel (located above the microwave oven in the
kitchen) is minimized.
This photo is looking toward the front of the motorhome. The wire from the panels can be seen disappearing through the roof about midway between the vent pipe and the back of the folded TV antenna. Excess wire, needed when the panels are tilted up, folds neatly under the lowered panel and isn't seen. A portion of the shower skylight is visible in the lower right corner of the photo.
For other motorhome layouts, it may be possible to find a shorter path to the batteries instead of going to the electrical panel, by mounting the charge controller near the batteries. In this case, one should choose a charge controller which supports a remotely mounted meter/control panel. It will then be necessary to run wires from the charge controller and/or battery to a convenient place to mount the remote panel (presumably on one of the existing electrical panels.) These wires are small diameter and not length-sensitive. (Actually, if you already have a good battery monitor which reads battery current using a shunt mounted near the battery, you may not need a remote control/monitor for the solar controller. Once you've completed the initial setup of charging parameters for the solar charger controller, you can pretty much ignore it, except for monitoring its performance via the battery ammeter.)
I mounted four 8" square pads, made of
5/8" thick canvas-reinforced phenolic laminate - a rather old-fashioned plastic that
is quite rigid and is easy to machine with ordinary tools. (I cut these pads
to size using a carbide woodworking blade on my 10" radial-arm saw). A local plastics supply
company had a dusty odd-sized piece that was big enough for me to cut the
four pads. I found that the roof is thin fiberglass-reinforced plastic
bonded to thin (looks like 1/4") plywood. I was concerned about screws
holding in this thin material, so I used large "Molly" style
reinforcements - the ones designed for very thin walls, using a 1/4"
machine screw, and mounting in a 1/2" hole. Four of these are used for
each of the mounting pads.
A piece of 1.5" (1/8" thick) aluminum angle stock 7" long is bolted to the pads, with 5/16 flat-head machine screws, with the screw heads countersunk into the bottom of the pads. A bead of polyurethane sealant was applied between the pad and the roof all the way around the edge of the pads, with extra sealant around the bolt holes. When bolted down, this sealant spread into a thin layer between pad and roof, extruding out just beyond the edge. This serves to keep moisture from getting under the pad and also provides additional adhesion between roof and pad. Polyurethane is an excellent adhesive as well as sealant.
The aluminum angle rails which support the solar panels overlap the short aluminum rails on the roof, and a single 5/16" bolt connects them together, near the outer edge at each corner.
When two of the bolts are loosened and the other two
removed, the panels
can be tilted up to face the sun. In the winter, this can provide up to
40% more
power. Additional pieces of aluminum angle are cut to the right length
to go between the raised edge of the panel and the existing mounting pads.
It's also possible to tilt the panels to the side.
To do this, I remove all four
mounting bolts and tilt the panel with the panel rail laying loosely on the
roof rails. The raised edge is supported with aluminum angle cut to the right
length, with an extra right-angle bracket at the bottom.
Use a 1/4" drill bit to slightly ream out
the bolt holes at the lower edge so that a 1/4" bolt will fit through at an
angle to anchor the panel rail to the roof rails. In the photo of the
side-tilted panel, I'm using the same support pieces as
for the front-to-back tilt, simply drilling addditional holes part way down.
This results in the supports extending beyond the top of the panels. This is
temporary, and I will cut new side-tilt supports that are the correct length.
This upward exension can cast a shadow on the panels at certain time of day,
greatly reducing the power output. (Because of the way the individual
cells are series-connected in the panel, shading one cell greatly reduces
the output from the entire series-connected group of cells.)
Running the Wires
The wires run through a new hole in the roof
into the blind space between
the kitchen cabinets over the sink and the electrical panel over the microwave.
I secured the wires to the roof adjacent to the hole with a small plastic wire clamp
screwed to the roof, and covered the hole and clamp with a blob of sealant
(again I used the polyurethane). Enough slack must be left in the wires to allow
the panels to be tilted up - in all tilt directions. Measure carefully with
the panels raised.
I cut a hole in the side of the
kitchen cabinet over the sink to provide convenient access to the wires
from the roof, and
this also provides access to the wiring channel which runs down to
the basement. The wires coming through the roof are visible in this
picture. An electrician's fishing tape is shown, ready to pull wires
up from the basement.
The hole is then neatly closed by adding matching
molding around the edges of the piece that I cut out. Unfortunately, the
molding I had available is oak, so the grain doesn't match the fake-cherry
paneling. The 1/2" x 3/4" molding is glued to the piece of
panel that was removed, extending about half the width of the molding
beyond the edge of the piece of panel. Two screws through the molding then
hold the assembly in place. There are vertical 3/4" x 3/4" strips of
wood glued to the paneling from the back to hold screws from the shelf
support brackets, on each side of the hole (this limits the width of
the hole). These wood strip also securely hold the new screws holding
the cover in place.
.
From this area below the roof hole, one can reach in and feed the wire from the solar panels around to the electrical panel area where the charge controller will be mounted. The negative wire from the solar panel runs directly to the charge controller. The positive wire goes to a high-current toggle switch mounted on the electrical panel, and then from the switch to the charge controller. Some installers omit the switch, but I like to be able to turn off the current flow from the solar panels, when troubleshooting or maintaining any portion of the 12v. system and its loads. Some charge controllers may have a built-in on/off switch - mine doesn't.
The wires from the charge contoller to the battery are led to the access hole in the kitchen cabinet, and then straight down to the basement, following the same channel that the roof vent pipe runs through, and then are led under the grey and black water tanks, but above the chassis rails, diagonally back to the battery compartment. It would be wise to put a corrugated protective plastic wire shield around the wires, at least in the areas where it might chafe against sharp corners of the chassis and perhaps for the entire exposed length. I didn't do this, but may eventually regret the omission.
Access to the area near the floor, where wires are routed under
the chassis, is provided by removing the laundry hamper in the
bathroom. Remove four small screws from the hinges at the bottom
of the hamper, and lift out the hamper, giving good access
.
Looking down from this access point, you'll see an existing big hole in the floor where other wire bundles and water lines are passed through. You can also see a bit of the grey water tank (not visible in the photo - you have to stick your head into the opening where the laundry hamper was, and look straight down through the hole in the floor). There is a gap of about 3" between the tank and a vertical aluminum/foam wall enclosing the tank compartment. At the bottom of this gap, another aluminum/foam panel forms the bottom of the grey water tank compartment and is also the top of the propane tank compartment. Use a power drill with a long extension to drill through this bottom panel from inside the RV, locating the hole as far toward the rear and center of the motorhome as practical, to minimize wire length. (It would be easier to drill up from the propane compartment, except that it's somewhat difficult to figure out exactly where to drill from that side. And you really don't want to drill into the tank!)
To run the wires, feed an electrician's steel fishing tape down from the kitchen cabinet access hole until it comes out in the area behind the laundry hamper. Tape the end of the two wires together (leaving one wire extending about 3" beyond the other) and feed these wires up from the ground past the propane tank through the hole you drilled and then up past the grey water tank into the area behind the laundry hamper. Tape the wires to the end of the steel tape (making sure there is a straight path for the tape and wires to follow, not wrapped around any of the other wires and pipes in the area). I also needed to run the wire for the battery temperature sensor from the house batteries to the solar charge controller, and this wire should be pulled through at the same time as the power wires.
From the kitchen cabinet, pull the steel tape and attached wires up into the kitchen cabinet. It will make it easier if you have two people at this point, one in the bathroom pulling the wires up from the propane compartment and helping them feed smoothly up into the wall, and the other person in the kitchen pulling on the tape.
Pull about three feet of wire into the cabinet, detach the wires from the tape, and feed the wires back throuth the access hole and around into the electrical compartment above the microwave.
Now feed the other
end of the wires diagonally in a straight path
from the propane compartment across to the battery compartment,
above the chassis rails. Use plastic cable ties to support the wires,
whereever they pass a convenient attachment point.
I had intended to mount a fuse holder for
the solar power feed on the wall of the battery compartment. But all
I could find on short notice was an automotive fuse holder with wire
pigtails, which is supported by its wires. I installed a 30-amp
automotive fuse (max current from my existing panels is about 14
amps), which is visible in the photo. I ran the positive wire to the
fuse, and then from the fuse
to the existing very large inverter fuse, which is mounted in the
positive battery lead, high on the rear wall of the battery
compartment. (This fuse may only exist when the optional
high-capacity inverter/charger is installed.)
I ran the negative wire from the solar
panels to one leg of the dual
current-measuring shunt for my battery monitor. I had previously
mounted this shunt high on the forward wall of the battery
compartment. The negative battery cable runs to this shunt.
This allows the previously unused "battery 2" position on my
Link 2000 monitor to read the current from the solar panels.
If you are using a charge controller which has its own built-in
meter, you'll run the negative wire directly to the negative
battery terminal. The actual length of wire from the solar controller,
mounted behind the electrical panel above the microvave oven to these
connections in the battery compartment was 24 feet. In addition,
there is about 10 feet running from the solar panels to the charge
controllers - I neglected to measure this length carefully.
