On the morning of April 21, I finished flashing the L-feet and sealing them with roofing cement before James and Steve, the Current Plus Electric guys (http://www.currentpluselectric.com/), arrived. After a bit of organizing and planning, we got to work installing the ground wire and microinverters. The PV kit included several grounding lugs with "WEEBs" (http://www.we-llc.com/WEEB.html)--special grounding washers--to ensure the racking was properly grounded. The grounding lugs and matching WEEBs went on first. We used stainless steel nuts and bolts, securing them at the manufacturer-recommended 10 foot-pounds of torque.
Next we installed the microinverters. The microinverters are nifty devices from enphase (http://www.enphaseenergy.com/products/index.cfm) that convert the DC from the PV modules into 240 volts AC current. Each PV module requires its own micro-inverter. The use of microinverters maximizes production because they allow optimal power production for each PV module (an excellent feature for a partially shaded site), as compared to using a single inverter for a series of PV modules. In addition, enphase's system uses an interface that monitors the output from each microinverter, and pushes data to a web service that allows real-time and long-term system performance monitoring (see an excellent example here: http://www.arttec.net/SolarPower/9_Stats/index.htm). The microinverters attach to the rails under the PV modules, using two stainless steel machine bolts that fit neatly into the open channel at the top of the rail. Following installation of the microinverters, we ran a #6 ground wire in a loop, attaching it to each of the microinverters and to the aforementioned lugs at the end of each rail.
Next, we installed the PV modules. These particular modules are hefty at nearly 50 pounds each; they are also large and cumbersome. Although I originally figured I would do the installation myself, I quickly realized that messing with these things on a roof alone can make for some expensive mistakes--there are too many tripping and dropping hazards on a solar job, and the larger modules could catch the wind easily. It really does make sense to have two or three guys to do most home-scale PV installation jobs.
To help get the modules to the roof, I built a ramp-and-sled system from lumber. I had participated in some solar hot water projects in 2010 wherein we used a gang of guys to muscle 150-pound collectors up parallel ladders to a second-story roof. That experience was kinda scary, and I didn't really want to do that again. So, the solution I came up with involved a 12-foot-long ramp built of 2 x 4 lumber in which a chipboard "sled" slid. The PV module rested on cleats on the sled, and I attached eye screws, hooks, and heavy cord to the top end of the sled. One or two guys on the roof can then pull up the PV module on the sled, fasten it in place with a hook, and then remove the module from the sled. This system worked out pretty well--it sure beat trying to lug the modules up a set of ladders, and was significantly less risky. We discussed a number of ways this system can be improved upon. Jmes, of Current Plus Electric, did an on-site improvement that elevated the PV module higher, allowing for easier grasping on the roof.
Removing the first PV Module from the sled
The PV system kit came with the requisite PV module mounting clips--specially built for the racks and the modules, and a specialty bolt that slips into the "T" channel at the top of the rail. Although the system came with standard machine nuts that could be tightened by a standard socket wrench, I opted to spend a little more money for theft-resistant nuts, which I purchased elsewhere. In addition, the PV kit came with some additional WEEBs that were designed especially for the the UniRac rails; they serve to ground the PV modules to the racks when the aforementioned clips are used to secure the PV modules.
As with a lot of other projects, installing the first couple of PV modules required a good amount of time to ensure that everything was lined up properly. We used a combination of tape measures, levels, and squares to accomplish this. The remaining panels went more smoothly. I think we installed the first 14 modules in about 4 hours.
End of Day 2, with 14 of the 16 modules installed.
You can see photos of Installation - Day 2 here, together with additional explanation of the steps: http://tinkeringcavemanspvproject.shutterfly.com/pictures.
We left the last two PV modules for the Installation Day 3, as well as the main part of the standard electrical work. That included:
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