Philadelphia Museum of Art - Lightning Protection
Philadelphia Museum of Art - Lightning Protection, by Bob Gumaer
The tip of the air terminal needs to be at least 10 inches about the object being protected which in this case is the ornaments. Air terminals taller than 24 inches must be braced so in this instance the tallest air terminal possible without a brace is used and the swivel gets the ornaments in the zone of the air terminal.
This installation is unique because of the need to protect the decorations without mounting to them.
The `pedestals’ are a combination of a base, which holds the air terminal to the building and connects it to the main conductor, and a swivel adapter,
he air terminals were installed that way to place the decorative features at the perimeter within the required protection distances. The projections are about 22” in height, so we elevated 24” air terminals in order to avoid having to install tripod supports for the rods.
The angling of the rods was to keep the lightning protection back from the edge and minimally visible from grade, while still keeping the outer edge of the decorations within 24” of the rod tips.