10 December 2012
Just as a chef requires special tools to grill, bake, or fry a chicken – all with the goal of preparing delicious food – there are various tools available to solar PV installers who strive for successful installations on multiple types of PV systems. Pitched-roof, flat-roof, and ground-mount arrays each have unique characteristics that require specific tools.
Safety equipment tops the list as the most important set of tools for a PV installer to have. This collection includes a rope and harness, safety glasses, gloves, earplugs, boots, hard hats, etc. These items are known as personal protective equipment (PPE). Each installer must have individual PPE and know how to use it properly.
Array layout/site assessment
Every installation begins with the layout of the array. In most cases, a 25-foot tape measure, a 100-foot tape measure, chalk or string line, marking pencil, and solar pathfinder will get the job done. Using the solar pathfinder to recheck the install location for shading allows for adjustments to the array before installation. Taking the time to design an accurate layout helps installation go smoothly and ultimately saves time and money.
Working on a roof requires a ladder long enough to extend three feet above the dismounting location. Layout on a pitched roof includes finding the roof rafters or trusses. Tapping on the roof with a hammer allows an installer to audibly determine the location of the structural support. Once the installer locates the first support, he/she marks it with a pencil and measures 18 to 24 inches to the next rafter. Once all the rafters are marked top and bottom, use the chalk line to mark the rafters lengthwise, and then the location of the stand offs and rails to complete the layout. Flat-roof installations are usually the simplest to lay out because the measurements only need to determine if the array will fit within the roof surface area.
The layout of a ground-mount system requires locating the support posts for the racking. Contacting the local utility to locate and mark underground lines is a free service and should be done before the layout. Using the compass on the solar pathfinder, a ground-mount array will be positioned according to the design azimuth angle. Adjustments must be made to the compass for the magnetic declination of the install location. Having the layout done by a surveyor may make sense for very large arrays.
The greatest difference between the mounting types, in terms of the tools needed, is how the structural support should be installed for a racking system.
Solar Installation Handtools
For pitched-roof installations, a cordless drill and impact driver, drill bits, sockets, a utility knife, and a caulking gun should take care of most installs. Drilling a pilot hole helps prevent splitting the roof rafters and makes installing the standoff anchor bolt easier with the impact driver. The roofing material often needs to be trimmed using a utility knife to install the flashing, and caulk may be required according manufacturer’s recommendations.
Flat-roof installations are much simpler, because installers commonly use ballasted racking systems. Weights, instead of physical connections, hold the PV array in place. A good push broom removes debris from the installation area. The challenge for a flat roof installation is getting the ballast weight onto the roof, as this could require renting a forklift or hiring a crane.
Ground-mount installations require holes to be dug in the ground to anchor the posts in concrete. Whether with a shovel or an auger, digging holes is difficult and time consuming. A level and string line will help install the posts straight and plumb, making the remainder of the installation much easier.
After installing structural supports, the racking and module installation is similar for each of the different mounting types. It is common to need only one socket size for the entire racking installation. Many manufacturers recommend a torque wrench to install all of the bolts. A cordless reciprocating saw allows one to install the rails long on one side of the array and trim to fit once all of the modules are installed.
All PV systems require equipment grounding, which can be accomplished with wire cutters, a flat-head screwdriver, and a drill for installing lugs. A stubby flat-head screwdriver makes tightening ground lugs on the back of roof-mounted modules possible.
Though connecting modules in series does not require the use of tools, taking modules apart may require tools specific to the connector. The next step is creating a home run wire, which uses a specialized crimping tool to assemble a connector on the wire that matches the module connector. After installing the positive and negative home runs for a string, one must check the voltage with a multimeter. Checking the voltage as each string is completed verifies proper installation and avoids troubleshooting later on.
The remaining parts of the system to be installed include the combiner box(s), conduit, additional wiring, disconnects, and inverter(s), which can be installed with an electrician’s standard set of tools.
Understanding the unique characteristics of different PV systems helps a solar PV installer select the best tools to get the job done right.
Written by John Conde, Field Instructor with Everblue