Randy White,
The Wiremold Co.
Problem
Before the development of fire-rated poke-throughs, it was necessary to install firestopping material to maintain the fire-retardant capabilities of concrete floors when core-drilling them to run wiring. These firestopping operations could not always be adequately policed, leading code-enforcement agencies to limit this installation practice.
Solution
The solution was to incorporate firestopping material into the poke-through fittings themselves, guaranteeing that each penetration of the floor maintains the slab`s fire rating. Until such time as the poke-through is required to function as a firestop, it remains completely unobstructed and fully functional, permitting electrical wiring and low-voltage communications cabling to be installed through core-drilled openings in concrete floors while maintaining the fire rating of the floor slab. This is especially useful to installers in maintaining their flexibility to provide services in open-floorplan spaces.
How poke-throughs work
Poke-throughs serve as firestops because they incorporate one or more rings of intumescent material and phenolic spacers around the conduit stem at slab level. When exposed to high temperatures, intumescent material expands to fill any space between the fitting and the floor slab. In poke-throughs that support both electric service and low-voltage cabling, the electric wires are run through the stem of the fitting, while the low-voltage cabling runs outside the stem through holes in the intumescent rings. In the event of a fire, these holes, like the slab penetration itself, are quickly filled by the expanding intumescent material, effectively blocking flames and maintaining the slab`s fire rating.
Tips on selecting poke-throughs
1) Poke-throughs should be listed and classified by Underwriters Laboratories (Northbrook, IL) or some other testing agency.
2) Installers should note the fire-resistance rating of the device. Poke-throughs manufactured by Walker Systems, a Wiremold Co., for instance, generally have a fire-resistance rating of 2 hours, although some are rated for 4 hours. In many instances, the fire rating of the poke-through may exceed that of the surrounding slab.
3) Ease of installation is also a consideration. Walker rci poke-throughs, for example, offer a patented one-step installation procedure, which depends on a retaining system that holds the fitting securely in place, eliminating the need for a second installer working below the slab to lock in the device.
4) A variety of poke-through profiles, activation fittings, service heads, and covers are available for electric service, dedicated communications cabling, and wiring combinations.
Poke-through fittings in a variety of configurations provide communica-tions cabling and electric power to open-space locations. Intumescent rings (lighter bands on the fitting stem) expand when exposed to high heat, completely sealing the slab penetration.
Randy White is product business manager for Walker Systems, a Wiremold Co. (West Hartford, CT).