The sold Sprinter has a nominal 12 volt 135 watt panel that was the largest panel that could be shipped with UPS.  The major load in the Sprinter was the Dometic refrigerator which used 40 watts when it was running.  The house battery was a 255 amp-hr AGM and the solar controller was a Morningstar SunSaver MPPT.  What I found out was in full sun days the panel produced about the same amount of power that was required to run the refrigerator.  Panel could not keep up with the power usage on overcast days.  A year before the Sprinter was sold the 135 watt panel was replaced with a 205 watt high voltage panel.  The 205 watt panel eliminated the need for any charging other than the solar.  The backup for bad weather conditions was the vehicle powered inverter that provided 120 volt AC power to the shore power charger with the engine running.  I did cheat a few times by turning on the vehicle powered inverter which would run the refrigerator on 120 volt AC power and charge at the same time.

Did not want multiple panels that require a rack, a roof combiner box and multiple cables on the roof.  Multiple panels are better in partial shade conditions but that seldom occurs.  I am normally in either full sun or full shade.  System is simpler with a single high watt panel.

For the Transit build several improvements were made.  Bought a 300 watt panel that is the same physical size as the Sprinter 205 watt panel.  Increased the size of the vehicle powered inverter from 600 watts to 1000 watts.  The larger inverter allows the shore power charger to charge at its maximum 50 amps, the water heater heating element could be changed from a 450 watt to a 625 watt heating element and I could install a 750 watt electric air heater.

The same Morningstar SunSaver 15 amp MPPT solar controller was used in the Transit.  At peak solar times this controller may limit the charging.  A good assumption is the panel will never produce more than 75% of its rated output due to the incorrect orientation to the sun and high temperatures.  300 watts/32 volts x .75 = 7 amps.  The MPPT controller does not create power but it does convert low amperage high voltage power to higher amperage at the charging voltage.  7 amps x 32 volts = 16 amps x 14 volts.  There could be times around noon that the SunSaver would limit the charging to 15 amps.  Not an issue because the charging loss would be a small percentage of the total charging.  For any panel larger than 300 watts I would change to a 25 amp solar controller.  On a full sun day the system gets the house battery back to 100% SOC before noon so any loss around noon is not important.

The 300 watt panel purchased for the Transit is a LG Momo Neon and is 64.57 inches long x 39.37 inches wide.  Selected this panel because the aluminum extrusion frame is a tube instead of an angle.  Installed the panel without a rack.  Added feet using the existing mounting holes in the panel frame.  The mounting holes are about 12 1/2" from the end of the panel.  Bolted four 6" long 3/16" x 1 1/2" aluminum angles to the panel.  Bolted a 14 gauge stainless steel angle between the panel angles and the roof.  The stainless angles were bent to an angle a bit more than 90 degrees so angle sits flat of the van roof.  Four 11/32" holes were drilled through the roof for the panel mounting bolts. The location of the four holes was not close to the roof ribs.  The Transit roof is not strong enough to support the panel feet without bending.  Four 1 1/4" x 2" wood stiffeners were glued with polyurethane adhesive under the roof steel between the roof ribs where the roof holes were located to prevent the roof steel from deforming.  The panel is about 1" above the roof at the roof centerline.

The LG panel has two MC4 connectors for the positive and negative cables.  Wanted to retain these connectors as disconnects if panel needed to be replaced.  Wanted to locate the roof penetrations out of sight under the panel directly above the solar controller so could not use any of the existing Transit roof holes for the solar cables.  Punched two 7/8" diameter holes in the roof for the bulkhead fittings.  Used two 90 degree aluminum cord bulkhead fittings purchased from McMaster-Carr.  They are part # 8317-K2.  Bought a 15' MC4 extension cord with male and female connectors.  Cut extension cord in two for the cables through the roof between the panel and the solar controller.

Solar panel wiring is simple.  The solar positive 10 ga. cord terminates at a 15 amp Blue Sea circuit breaker so solar panel can be turned off.  There is a 10 ga. cord between the circuit breaker and the input positive terminal on the solar controller.  The solar negative cord terminates at the solar controller negative input terminal.  The solar controller positive output 8 ga. cable terminates at a Blue Sea 20 amp circuit breaker.  There is a 8 ga. cord between the 20 amp circuit breaker and the house system positive bus bar.  The solar controller negative 8 ga. cord is connected to the house system negative bus bar.

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LG 300 watt Panel Install Drawing # ODJ127-27                         

If you want more PDF menu choices, the drawing can be saved to your computer and then reopened with Adobe PDF Reader.  The Adobe PDF Reader is a better program to use for viewing.
 

 

INSTALLATION PROCEDURE
1.  Built an access platform on the back of my pickup.
2. Punched the holes for the positive and negative panel cords.  Installed the 90 bulkhead fittings.  Added a rubber o-ring to the fittings before inserting the fitting in the roof hole.
3.  Bolted the eight angles to the panel and a 1/8" x 1" aluminum flat across panel using two of the leg mounting bolts.  Flat used to tie wrap the solar cables to keep them off the roof.  Also used some foam pipe insulation around the two cables to hold them in the panel extrusion.
4.  Glued the four 1 1/4" x 2" wood stiffeners under the roof between the roof ribs where the mounting bolts would come through the roof.  Two were 19 1/2" long and two were 32 3/4" long.  The Transit roof would have sagged without the stiffeners.
5.  Put a blanket on the roof and put two of the solar panel legs on the blanket.  Slid the blanket and solar panel on the roof into the correct location.  Removed the blanket and added four rags under the feet to prevent scratching the paint.  Moved panel to final location and drilled one mounting hole through the roof and the wood stiffener.  Temporarily bolted one leg.  Checked the alignment and then drilled the second roof hole on that side of the solar panel and installed bolt.  Went to other side of panel and drilled those two holes through the angle mounting holes. 
6. Loosened the four bolts that connect the two angles on one side furthest from the 90 degree cable fittings so I could lift the other side of the panel.
7.  Removed the four angle bolts from the other side and held the panel up with wood blocks.  Put mastic under the SS angles and sealed the edges of the SS angle with Dicor 501LSW sealant.  Used the same method of sealing the angles as I had used to seal the roof vent.
8.  When panel was blocked up on the side where the cable bulkhead fitting were installed, the two MC4 cables were fed through the bulkhead fittings.  Both the cable entry and the base of the fittings at the roof were sealed with the Dicor sealant.
9.  Lowered the panel back down and reinstalled the four angle bolts loosely.
10. Repeated the procedure on the other side of the panel and then tightened all 8 bolts.
11. When connecting the cables inside of the van a blanket was put over the panel to eliminate power production.