Metal roofing has been popular for hundreds of years in various forms, and this is in no small part due to the durability of these roofs. The return on investment of a metal roofing system is usually better than most other systems, justifying the sometimes higher initial cost. While one might need to replace an asphalt shingle roof every 15 or 20 years, a metal roof often will have a serviceable life of 40 to 50 years or more.
With the advent of rooftop photovoltaics, a common concern became whether or not the existing roof would outlast the solar array. Most PV module manufacturers expect their modules to last 30 years or more. If a solar array is installed on a roof that requires repair or replacement during the life of that array, the expense will be compounded.
The right clamp for the job
The combination of a standing seam metal roof and a solar array is made even more attractive by the fact that in almost every case, it is possible to mount the array without physically penetrating the roof system. This is achieved by clamps that engage the standing seams themselves. The clamp must match the shape of the seam closely for the best performance. Choose a company that can help to identify the seam and can provide testing information on the clamp to seam connection, specific to your job.Be wary of generalized testing or claims that “one size fits all;” a proper system should be tailored to the roof panel.
Adhering to electrical standards
Without a path to ground, electricity can be dangerous and unpredictable. There are very specific standards for achieving this safely and uniformly. UL 2703 is the designation of this standard and adhering to it is of critical importance for a safe installation that will pass inspection.
The first step in grounding a rooftop mounted array is to bond individual solar modules to one another. There are a variety of ways to achieve this, and a great deal of innovation has occurred within this facet of the industry over the last decade. The prevailing method has been to use what is known as grounding lugs. Most commonly, they are made of copper and plated with tin to prevent the galvanic reaction that would otherwise occur between aluminum and copper. Lugs are affixed to the module frames, and then connected to an adjacent module with copper wire.
Another common grounding product is known as a WEEB (Washer Electrical Equipment Bond). These are manufactured from thin stainless steel and feature raised nodes designed to pierce the anodization of the module frame. This allows for current to flow through the WEEB and into the rail systems commonly used to mount solar modules on roofs. This speeds up the installation process and simplifies the process of replacing a module should this become necessary.
Micro-inverters simplify installation
With the rising popularity of micro-inverters, it has become increasingly common for a grounding system to be built into the microinverter itself. This system generally has a path to ground built in to the trunk cables that link the micro-inverters. This, in conjunction with grounding the rails, allows for one of the simplest installations on the market.
It is also possible to forego the rail entirely, bonding the modules directly to one another with a rail-less mounting system. The PV-Kit from S-5 (shown here) is one such option, and achieves bonding by means of its unique stainless steel support disc. This disc features nodes similar to those found on a WEEB, and these bond the panels to one another. This feature drastically reduces the number of grounding lugs that will be necessary.
S-5! zero-penetration clamps attach ancillary items to standing seam metal roofs without violating the integrity of the roof or the roof’s warranties. The patented clamps mount snow-retention and wind-performance systems, solar arrays, signs/banners, light fixtures, gas piping, stack/flue bracing, walkways, HVAC, lightning protection, equipment screens, conduit, condensate lines and more.
Written by Chris Stearns, Technical Support Specialist, S-5!