Lightning is a tremendously powerful and unpredictable force of nature. There are, on average, 22 million lightning strikes in the United States each year. Lightning strikes vary widely in frequency and power, but can easily reach 100,000 volts and 40,000 amps. In the United States, the threat of lightning to the building and its contents is outside the scope of the mandated national model building codes. The National Electrical Code (NEC) NFPA 70 only deals with the safe use of electricity. The only building code covering lightning is NFPA 780, Standard for the Installation of Lightning Protection Systems; however, installation of these systems is not mandatory. It is up to the building owner to perform a lightning assessment under NFPA 780 to determine if the building should have a lightning protection system (LPS) installed.
Therefore, most homes and buildings in America are not designed, nor built to withstand, damage from lightning. It is no wonder then that in 2009, insurance companies in the United States received over 185,000 claims for lightning damage, resulting in losses of almost $800 million. The number of claims is actually down from the five-year average of 226,000 claims per year, but it shows the susceptibility of damage due to lightning.
Without a lightning protection system, building structures, mechanical systems and especially electrical systems are vulnerable to a lightning strike. There are methods to reduce the chances of damage, including bonding and equipotential bonding; however, there can be no assurance that a building will have no damage from a lightning strike unless an LPS is installed.
The house’s electrical system must have a connection to earth to provide for its safe operation. When other systems are connected to the electrical system and its grounding, those systems are “bonded” to the electrical ground. Bonding is achieved by installing a wire of sufficient size from the bonded component to the electrical system ground. Equipotential bonding is achieved when all metallic systems in a structure are bonded to the electrical system ground. The systems that are bonded to the electrical system will have roughly the same electrical potential so that if energized, they will all be energized at the same rate and at the same speed. Thus, when the electrical system and the bonded systems are energized by lightning, the possibility that the lightning energy will arc or jump from one system to the other is reduced because all of those systems are at an equal electrical state.
However, if metal systems in the house are not bonded to the electrical ground, they will have a different electrical potential from other conductive systems in the house. In the event those systems are energized by a high voltage event like lightning, then it is possible that the electricity being conducted and traveling on one metal system may come to a point where it is close to an adjacent metal system that offers a lower resistance or impedance path to ground. It is possible that if the energy has enough voltage, it may jump over the air gap between the two adjacent metal systems, and use the second path to go to ground. When the energy jumps that air gap, it generates an electrical arc that has a high voltage.
The voltage level in the arc is dependent on a number of factors, including the amount of electrical energy in the lightning strike, the number and characteristics of the metal systems in the house, and the length and resistance of the metal system on which it is traveling. When the arc is created, it creates a channel through the air separating the two systems by which electrical current can flow between them. The amount and duration of that current will determine whether the system to which the arc is flowing will be damaged.
No properly bonded CSST system has been factually identified as the source of gas leakage due to damage from an indirect lightning strike that subsequently resulted in a fire.
This important fact of performance in indirect lightning strikes—along with performance in seismic events—demonstrates the value of CSST technology’s safety track record, making it the optimum gas-piping solution.