Photo courtesy East Coast Lightning Equipment, Inc.
Surge protector
Any wire entering a building is a potential path for lightning. In addition to power lines, contemporary buildings can be connected with wires for:
- telephone and cable TV services;
- satellite dishes and antennas;
- irrigation controls;
- electric gates;
- wells;
- fire pumps;
- surveillance cameras and security systems;
- site lighting and remote power receptacles;
- building-mounted lighting and signage; and
- photovoltaic (PV) collectors and generators.
In addition to protecting against lightning, these surge protectors resist transient voltage from other external sources. However, since they do not protect against surges that originate within a building, individual pieces of equipment may still require their own surge protectors.
Surge protectors can burn out due to lightning strikes or other surges; they should be equipped with indicator lights or connected to a monitoring system to facilitate inspection.
Surge-protective devices are usually furnished as part of the lightning protection work as their selection is integral to a complete lightning protection system. However, installation is typically performed by an electrical contractor because few lightning protection installers have the electrician license necessary to install surge-protective devices.
Site work
Tall trees next to buildings can present a problem when stuck by lightning, either by falling on the structure or by causing the lightning to side-flash and strike building walls unprotected by air terminals. NFPA 780, therefore, recommends installation of lightning protection in trees with trunks within 3 m (10 ft) of a building or that overtop a building. Consideration should also be given to protecting valuable specimen trees and other items onsite such as pole-mounted lights required for security concerns.
Photo courtesy East Coast Lightning Equipment, Inc.
Items installed in open areas, such as pieces of equipment or small temporary structures, can be protected by a mast-mounted air terminal. Large areas—such as docks and military encampments—in which a multitude of masts would not be practical, can be protected by conductors draped between widely spaced poles. This overhead shielding approach is called ‘catenary lightning protection’ after the shape assumed by the cables. It has been proposed as a means to protect arenas and other large outdoor venues where it is impractical to evacuate a crowd to safety when lightning approaches. The conductors can also be used to support lighting fixtures for a dual-purpose catenary lighting and lightning system.
*Deep snow accumulation is unlikely at the exposed locations where air terminals are generally required. One should consider tall, braced terminals if required. At large sloped roofs, especially metal or other slippery roofs, sliding snow can damage lightning protection components installed at the eaves or mid-roof; consider locating conductors on fascia or soffits instead of on top of roof and providing snow retention devices to protect roof-mounted components. While winter thundersnows are rare, a video of one in Montréal can be viewed here .
** Damage due to condensation on lightning protections system penetrations through a building’s thermal envelope is rare, but should be considered if high interior humidity and extremely cold exterior temperature is expected.
Jennifer A. Morgan, CSI, is an officer of East Coast Lightning Equipment Inc., a UL-listed manufacturer of lightning protection components, and an officer of the Lightning Safety Alliance. She can be reached via www.ecle.biz.
Michael Chusid, RA, FCSI, CCS, is an authority on building materials and a consultant to building product manufacturers specializing in product innovation and marketing. He can be reached via www.BuildingProduct.guru.
