V: Installing a PV System:
Safety First:The first order of importance on any job site is safety. Solar panels put off voltage and current as soon as the sun hits their surface. Electric shock can be fatal and it is important practice safety on the job site. Grid Alternatives is by far the safest company that I have ever worked for in my life. The two most threatening hazards on the job site are dehydration and sunburn. It is vitally important to wear protective clothing, as well as to drink enough water during the day. Beyond that, we practice not walking backwards on the roof, treating all wires as though they are live, wearing hard hats, and using eye and ear safety with power tools.
For profit companies tend to neglect safety by prioritizing speed and profits. In fact, it is well understood in the construction industry in California that if you are an employee who speaks up about safety, then you will most likely be fired. Since solar energy is forecasted to grow in the coming years, a larger part of the dialogue about solar energy includes worker's rights. Using mindfulness as a business model, each work site is sure to have sunscreen, drinking water and personal protective equipment.
Locating Roof Rafters:
To locate the roof rafters from above, have a team member hold up a straight line (i.e. measuring tape or builder's square) directly above where the rafter hits the rooftop while standing on a ladder. The team member on the roof marks the location of the rafter with a chalk mark. Measure the same distance from edge of roof to rafter mark above and below, then snap a chalk line on the roof between the two marks. In order to precisely locate the other end of this rafter, we use an educated guess-and-check method by creating small holes until we find the center of the rafter. The maximum amount of holes needed is 3. One if you go too far to the left, one for the right, and then the center. The holes made in error must be sealed properly so that the roof does not leak!
Install Flashings & Racks:
From here we install the flashings first, and then the racks. These are the first Balance of System (BOS) components used on the job site. A flashing refers to a metal object designed to fit securely onto the rooftop. There are various designs, and the correct one needs to be chosen for the job. All photovoltaic flashings must also be matched to the racking equipment that is to be attached on top of them. The racks are measured according to the number of modules in each string and assembled to size on the ground. The completed racks are then sent up to the roof team to be connected to the flashings. There are pole mounts, self-ballasted mounts, racking systems that allow the modules to track the sun through the sky, and many more interesting types of equipment to design a unique solar energy system.
Connect Grounding Wire:
Once the racks are connected to the roof, we install the grounding wire. This is usually an AWG 8 bare copper wire that is connected to the racks with a metal clamp. This is for security in case there is an electrical short circuit or another problem in the system; the electrical current will be able to go to the Earth via a large metal rod that is sunk deep into the soil. Grounding correctly is a large part of the inspection process.
Install Micro-Inverters and/or Modules on Racks:
This next step depends on the type of system being installed. If using micro-inverters, then these need to be connected to the racks before the modules themselves. Micro-Inverters turn the DC electricity from each individual module into AC directly underneath each module. The electrical line coming down the roof from the solar panels is already AC and may be directly plugged into the service panel. The other option is a wall mount inverter, which must be mounted near the main service panel. This is also the stage when the proper amount of end clamps and mid clamps may be placed on the rack with WEEBS, ready to secure the module and ground it electrically once it is set down.
Connect System to Inverter and/or Main Service Panel:
At this stage, we must bend conduit that will bring the wires from the rooftop, down the side of the house, to the inverter and/or main service panel. It is standard in the industry to use Electrical Metallic Conduit (EMT), which are metal tubes that can be 1/2", 3/4", 1" or more in diameter. The amount of wires that may fill the conduit, the amount of bends that may be made in the conduit, the labeling and securing of the conduit are all controlled by national and local code. A hobbyist should never do the interconnection of wires to the inverter and/or the main service panel! Remember that as soon as the solar panel is being hit by sunlight, it is creating electricity, and that it takes only 1/3 of an amp for electricity to cause serious injury to humans. In addition, the main service panel is constantly feeding 240V of electricity into the house from the other side. That said the correct sized circuit breaker must be plugged into the bus bar on the main service panel. While doing an install in Seaside, CA, I had the pleasure of viewing an old meter that actually began to spin backwards as soon as we plugged in the PV circuit!
Commission the System:
Commissioning the system is the process of going through the walkthrough with the inspector to insure that everything is wired properly, and that there is proper safety labeling and security. The state and/or county official will ensure that the paperwork is satisfactory as well. All grid-interconnected PV systems must go through a commissioning process before they can begin to supply energy to the grid.