The Institute is Getting Solar Panels — Part IV: Installation

Avid readers will notice that we haven’t been posting much over the last month. That’s because every free moment has been given over to installing our solar panels (see the earlier posts here). Here I’ll recap the physical installation of the panels and other components. In the next post, we’ll go through how we ended up rewiring our house.

The Structure

Before installing the panels, we had to reinforce our garage roof. Our garage started out as an exterior kitchen for our 1850s home. It must have been built in the early 1900s judging from the true 2-×-4-in lumber and stud framing (as opposed to balloon framing). In the 1970s, our home got an addition built on the back and the kitchen was pulled by a tractor with rolling logs over to a new cement foundation. It was expanded out the back to accommodate cars as it was converted to a garage. To achieve this, the whole back wall was cut out and a beam put in place to bear the load of the roof. Unfortunately, this was done with plywood and dimensional lumber in a way that is not acceptable today. Therefore, I had to remove and replace the beam with a LVL (laminated veneer lumber) beam.

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The old beam (center above), new beam components (to left and right), and temporary stud wall (far left and right).
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The old beam coming down as well as new beam members and stud wall.
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The new beam seated in place on a new post.
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The new beam without through-bolts.

First, I had to bring in the extremely heavy members that would make up the new beam and place them below the old beam. Then I had to build temporary stud walls on either side of the old beam. Once secure, I could safely cut away the old beam and lower it down. Then it was cut into manageable sizes and moved out of the way.

The new beam is composed of four large boards (essentially 1 3/4-in-thick plywood measuring 22 ft long by 18 in tall). Each one had to be lifted and slotted into place over new posts on either end. Once in place, holes were bored through all four members and through-bolts were installed to hold it together as one beam (not pictured). Finally the support stud walls were removed. It took me two days to do this alone (with a little help from a neighbor to maneuver the LVLs into place).

The Buried Conduit

To connect the solar panels on the garage to the house, we had to bury a power cable. This was accomplished by using a trenching tool (which is now available in the tool library). It took about three hours do dig out the approximately 50 ft between the buildings. If we didn’t have a concrete sidewalk that I had to tunnel under, it would have been done in half that time.

I started by pulling masonry string between the corner of the garage and the house. The trenching tool is essentially a narrow shovel and lets me dig out 6 in of soil depth at each pass. When the bottom reached 18 in, I laid out the 10-ft segments of PVC conduit on the surface near the trench. I pulled the bundle of wires through the conduit a piece or two at a time. Once the wires were through, I glued each end of the PVC together to form a water-tight run. At each end of the trench, I used 90º bends to turn the conduit up to transition into metal LBs (junction boxes that help electricians pull wire through conduit). Inside the house and garage, the conduit must be metal, but in the ground, the PVC has better longevity and performance. The conduit enters the house and garage through drilled holes near the foundation, sealed (around the outside and also inside the conduit) with caulk.

The Panels

The most visible part of the system are the solar panels. Panels are mounted on lightweight but strong aluminum racks. To install the racks, I first measured out the correct location of each footing. These must be directly over rafters both to hold the weight and to accept the screw that helps hold the foot on the roof in high winds. The best way to find the location of rafters, in my case, was to use an 8-in-long, 1/8-in drill bit to poke a hole through the rafter below up through the shingles above. From this reference point, I could measure the distance between rafters for the rest of the footings.

The most important part of installing the feet is flashing, or using inserting metal sheeting to keep the roof water tight. We have wooden shingles, which are harder to flash than asphalt shingles, which simply lift up and allow fasteners and flashing to be installed below their flaps. Wooden shingles are not flexible and the flashing must be pushed up under the rows above during installation to cover the screws that hold the footing. Those screws are stainless steel and fit through a hole in the footing. Usually they are 4 in long, but we had to switch to 6 in because of the wooden roof. All the screws, bolts, and fasteners have torque values, so a torque wrench is a must-have tool.

Once the footings are in, the rack itself is easy to assemble. Bolts hold the bottom of the upright supports and the horizontal bar fits together with splices held in place with tap screws. It is held to the uprights with square-headed bolts fed through a slot that runs the length of the rack. Take your time to get the horizontal bars both level and square, which will make the installation of your panels go much easier.

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The rack for the center group of panels.
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The bottom and half of the middle group of panels installed. Another row will go above the two pictured.

Just like in every project, the visible part goes quickly after all the prep work is done. The panels are easy to place. A mark must be made on the side of the panels to indicate where they meet the horizontal bars beneath them. Special bolts called universal fastening objects (or UFOs) slot into the rack and then sit above the rim of the solar panels. When tightened, they bond the panel to the rack. The hardest part is maneuvering the large, light, and expensive panels into place on a roof.

The Components

Inside the house, we have added an inverter, battery, and other necessary components to convert and store the DC energy into usable AC power for the house and grid. Plan this stage (and all others, for that matter) carefully.  I installed all the components once, only to have to tear them out to make space for the new electrical panel. Each component requires clearance space around them, especially the battery, transformer, and inverter, as they generate heat. In my case, I had to drill into concrete and use anchors to hang each piece on the wall.

Unfortunately, we had to get the entire panel rewired. One is only allowed to generate 20 percent of the bus rating (maximum amperage) of the electrical panel, and our 100-A panel was too small for the 35 A we might be generating, so a new 200-A panel was needed. This went in the space on the left in the photos, requiring me to move all of the components pictured to the wall to the right of the photo.

In the next post, I’ll detail the wiring and finalization of the system.


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