2017 is particularly exciting for the lightning protection industry because our lightning protection code gets updated. The National Fire Protection Association (NFPA) has recently released their updated version of the lightning protection code. The Lightning Protection Institute (LPI) will be releasing their 2017 version later this year along with Underwriters Laboratories (UL). These are the three codes that lightning protection installers use to ensure that lightning protection systems will keep the structure safe that they want to protect. Each of these codes has their own certification, and these codes correlate very closely with few differences.
What Do Lightning Protection Codes Say?
The scope of these codes includes anything that relates to lightning protection, anything that could affect your home or office building or the Taco Bell you ran through for lunch today. NASA has spent time researching how lightning works and what happens during a lightning strike. These codes then take that information and decide how a lightning protection system should be created in order to curb the affects of dangerous lightning strikes.
Basic Concepts of Lightning Protection Code
The whole point of lightning protection is to keep a structure from getting struck. In order to do this we install strike termination devices (The acronym is STD. And yes, people actually use it). We can use an air terminal, sometimes referred to as a lightning rod, or we can use an existing piece of metal under a certain set of criteria. These strike termination devices typically can’t be farther than 20ft. apart and must be at least 10in. above anything you are trying to protect. These devices do not attract or repel lightning, but sit just high enough off of the structure that it will intercept the lightning bolt just before it hits the building. These strike termination devices also need two paths to ground. We’ll get to that in a second.
Path to Ground
Once the lightning is intercepted by the strike termination device it has to have a place to go. We use conductor to bring the charge safely to ground. Conductor can be a number of different types of metals, but copper and aluminum are the most common. You can also use existing metal as conductor if it meets certain criteria. Like we mentioned before, two paths to ground is critical. If a charge becomes too much for one path to handle or if one path is blocked because the cable has been cut by maintenance men from other industries over time there is always the other path as a backup. According to NFPA 780, the only time you don’t need two paths is if you are protection a pole no higher than 25ft.
The ultimate destination for lightning once it hits the strike termination device is the ground. The whole purpose is to divert lightning away from a structure by giving it another path into the ground. The resistance in the ground is measured by ohms, which can be measured by hooking the system up to an ohm reader. The code requires that any given downlead has less than 25 ohms of resistance, but suggests less than 5 ohms.
Do Building Codes Require Lightning Protection?
Depends on where you live. Lightning protection is required in certain instances in certain states. In the state of Florida, any commercial building taller than two stories is required by state law to have lightning protection. Florida just passed a law that requires all new construction commercial buildings have lightning protection installed. Areas that have high density lightning strikes are starting to require lightning protection by law. Here in Atlanta, even though lightning protection isn’t required by law, many building opt to have it installed because of the high strike density in Atlanta.
At the end of the day, lightning protection is about protecting people. The lightning protection code is designed to help educate and enforce good workmanship in the lightning protection industry and keep Moms and Dads coming home to their kids every night, and protecting your home so that you can sleep well knowing disaster won’t strike in the form of a lightning bolt at night.