Successfully meets new UL 1767 test standard and compliance program for ESFR sprinklers installed in rack storage with high clearances to ceiling (20 ft or greater) Viking Early Suppression Fast Response (ESFR) Dry Pendent Sprinkler VK504 is a fast response fusible element type sprinkler designed for use in storage areas subject to freezing and supplied from a wet system only, in an adjacent heated area. With a 16.8 (242 metric*) nominal K-Factor and special deflector, this sprinkler produces large, high-momentum water droplets in a hemispheric pattern below the deflector. This permits penetration of the fire plume and direct wetting of the burning fuel surface while cooling the atmosphere early in the development of a high-challenge fire. The dry ESFR sprinkler consists of a fusible element style ESFR sprinkler permanently secured to a special supply nipple. The sprinkler assembly features a sealed brass inlet that’s grooved or threaded. Also included with the ESFR dry sprinkler are two insulating boot assemblies (optional) to help seal the clearance space around the dry sprinkler barrel. The dry sprinkler boot assembly is intended to slow the exchange of air between the inside and outside of the freezer (or any dry sprinkler installation) to help prevent humidity and temperature differential in the area around the sprinkler. Condensation can lead to ice build-up, which could inhibit sprinkler operation or cause premature operation.