Solar Installation

As I have mentioned, we're starting 2013 (actually ending 2012) with a new Winnebago which remains unnamed at this time.  Funny, it was December of 2009 when we bought the Jayco.  I guess December is a time of transitions.  We left the solar installation on the Jayco when we traded so I had the distinct pleasure of preparing and planning a new solar installation on the new Winnebago.  I thought I'd go through the process of how we decided on the equipment we would purchase for this new installation, which began with thinking about the energy we used for the past two years and what might be different on this rig.

First, let's mention the cost of installation, what's our price range.  I'd like to mention that often when I speak with folks about installing solar panels, they ask about "payback".  I've taken to asking them about their payback for that morning coffee at the local coffee shop, or payback for the game tickets they buy etc.  To me this is a lifestyle choice.  It's a choice to join in the experiment of using solar energy to fuel our world.  So having said that, I really don't care about payback because it's immediate.  (There is a time I started to calculate payback but gave up.  I mean, we can roughly say that we potentially save at least 30 dollars a month because of the solar and this installation cost under $2,000, so that's about five to six years I guess.)

I might also mention that the Winnebago Vista 30T that we bought, lends itself well to solar installation.  In the purchasing process I looked the roof over, imagined where I would run the wires and checked out the battery box.  I had a good picture of how it would go before we committed to the new rig.

Equipment:

    Let's start with batteries.  The new rig came with 2 Group 24 NAPA dual purpose batteries rated at about 105 amp hours at 20 hours. (right I'm not sure what that means either)  Anyway, our last set up had about 300 amp hours of battery (three X 100 ah group 31 batteries) so I wanted one more battery.  I would have rather had group 27 AGM batteries for this installation, but I already had two brand new group 24s so I opted to run to NAPA (on my bicycle) and pick up one additional matching flooded battery.  I got a few extra cables, reworked the tie down system but just changing the bolts to rubber straps and now we have 315 ah of battery bank.  

Here are the three batteries installed.  These are just inside the step to enter the coach.  Nice location if you ask me.

   Now for the Controller.  I did some checking around before deciding on the charge controller.  Even though I was quite happy the the controller we had before (MorningStar TriStar 45 MPPT) I just wanted to know if there might be something more suitable to our setup.  Also I was hoping for something with a slightly smaller footprint and mounting position.   I had decided to put the controller in a basement cabinet just beside the battery box so there would be a short wired run between the controller and batteries.  I figured the run from the roof to the controller in this case would still be only about 20 feet, so everything seemed to be going together well.  

      So.... after all this processing, I finally decided on the TriStar, just like the one in the last installation.  I ordered the controller, breaker boxes and wiring from Northern Arizona Wind and Sun.  

      I'll talk about ordering the solar panels in a minute, but I had gotten all of the materials from Northern Arizona so I went ahead and installed the controller and breaker box with most of the wiring while waiting for the panels.    Here's a photo of the installed TriStar controller and breaker box.

And remote meter installed just inside the entry door to the coach.

The exterior cabinet that holds the controller and breaker is just to the right of the entry door to the coach.  The batteries are under the second step coming in the entry to the coach and the meter is just on a wall to the left as you walk into the coach.


 Solar Panels.  I saved quite a bit of money by shopping around a bit for panels.  I found the three 175 watt panels we purchased at Sun Electronics at 189 each, so a little over a dollar a watt.  The last panels we bought were more like a little over 2 dollars a watt. Shipping was a little more because the panels were bigger but it all worked out quite well.  I saved about a hundred dollars on shipping by having them shipped to a local lumber yard (instead of the RV park just across the street) and picking them up there.

    Also, based on recommendations from the various discussion forums, I opted for high voltage panels.  We got Suntech 175 watt panels.   I don't entirely understand the electronics involved in this, but I'm told the high voltage panels work much more efficiently with the MPPT controller.  Because they are high voltage (35.2 vmp) I can wire them in parallel on the roof, which means that if one of the panels happens to get shaded, the others will remain at full power for one thing.  Also at the higher voltages, the TriStar MPPT can work better at using the MPPT technology.

   
Mounting to the roof.   After talking with various people on the discussion boards I opted to build my own z brackets by buying, drilling and cutting some aluminum angle.  Also, based on recommendations, I decided to draw an installation plan.  I can't say how happy I am that the forum gurus convinced me to do this.  I had a whole different picture in my mind of how the panels would be.  This turned out to be a great installation, mainly because of this drawn up installation plan.

  I've included some photos below with captions.

Here's the drilling of the holes in the new Z brackets.
The drill press and cutoff saw were loaned to me by a new friend, James, from Early, TX.

Here's a photo of yours truly drilling the aluminum.

And then cutting.

Each Z bracket is made up of two L's bolted together  which will facilitate removal of the panels if necessary at some point.  Each bracket is 3 inches long and made from 1 and 1/2 inch aluminum L giving me 4.5 inches of glue surface for mounting to the roof.

 

Here I'm installing the Z brackets (feet) to the underside of the panel (I hope that's the underside)

The feet were mounted to the underside of the panel with
two stainless steel bolts then the panels were glued to the
fiberglass roof with 3M 5200 fast cure marine adhesive.

There aren't any screws driven into the roof at this
time but I could add one on each bracket
if I want to at some point.

Here the panels are attached, wired and working.  The panels are
wired in parallel and use mc4 type wire and connectors.

The Escapees Discussion Forum was most helpful in the process as was Jack Mayer's website on RV solar installations.  On this forum we spoke about using the 3M glue and with or without screws into the roof.   Of course this is often a concern for someone installing panels on the roof.  I can tell you from our last (first) installation, it was a difficult thing to drill into a perfectly good roof.  The Jayco had a rubber roof and I opted to drill.  I drilled the hole the size for the #12 x 1 inch stainless steel screw for each foot.  Then I put dicor in the whole put the screw right into the dicor sealant.  Then I put more dicor on top of each screw to seal it up.  There was no problem at all in the two years we had the panels in place.   This new roof is fiberglass and I was told that with fiberglass well adhered to the plywood underlayment, the 3M 5200 fast cure would be fine by itself.  I researched a lot and I feel quite sure that this is a permanent bond that will hold the panels just fine.  Having said that, I also plan on going up on the roof on a nice day in a month or so (or before we move next) and evaluating the bonds.  I'll probably inspect each foot carefully, and give a tug or two on the panels in various places as part of the inspection.  At that time I'll probably drill the glue that oozed out of one of the holes in each leading foot, drill for a screw, add dicor and install a #12 x 1 inch stainless steel screw in each leading edge, covering it with dicor.  This is just a bit of added security so I don't have to think about it someday when we're driving in some windy and weather.  I may, however, opt to leave it alone and inspect it again after our first major road trip.  

In Operation:

    Solar Volts and Amps.  I double checked the wiring and then powered up the system and right way I was treated to a lovely reading of 42 volts DC from the solar array.  As soon as I had the system working I switched off the breaker to the 12 v converter charger that came with the coach.  This monitors the battery and keeps it charged while providing all of the 12 v power for the rig.  That's lights, furnace blower fan, and water pump, not to mention some small dc loads from the electronics of the fridge, water heater and furnace.  Now the only ac power we use (when we're able to harvest solar energy... see below) is the 110 outlets in the motorhome.  All of our lighting, water pump and furnace blower energy comes from the sun now.

We've been up and running for a couple of weeks at this point and for the most part they've kept up quite well.  We just entered an expected stretch of overcast and rainy weather so I switched the breaker back on to let the converter/charger keep the batteries just until Friday, when the sun will be back.  The panels almost keep up, but it's also cold and the furnace draws a fair amount of that energy.

The TriStar has a connection that allows me to gather data from it on my computer and therefore track how the panels are working and the daily state of the batteries.   I plan on keeping a spreadsheet of this data for a while at least.

Thanks for reading,  I'm glad to answer questions if you just ask.

Martin Bates