Can poke-through devices contain fires as well as feed power and communications services?
September 11, 2001. On this infamous date in our history, eyes opened and people finally realized the importance of firestopping. The structural design of the World Trade Center saved thousands of lives by standing for well over an hour after the planes crashed into its twin towers. Having a strong structural design involves proper firestopping, an act all too often overlooked.
Firestopping should occur any time a wall, ceiling, or floor is breached for conduit, duct, or poke-through cable distribution. When you breach a wall, ceiling, or floor, you create a hole for a potential fire to poke through (no pun intended) to a room filled with unsuspecting, innocent people. This hole needs to be filled with a firestopping device for safety reasons, but at the same time, it must be able to allow cabling to pass from one room to the next. With the addition of putty, poke-through devices can fill the hole in your floor/ceiling.
A typical poke-through device feeds power and communications services to open-space areas from the floor/ceiling below. Common poke-through devices fit snugly into a cored hole, but they can't stop a fire from passing through to the next room. A poke-through device needs the assistance of putty, an intumescent. The design of the device and materials used to make the poke-through work with the putty to help slow down the fire and smoke attempting to pass from room to room. This month's Product Update is intended to educate you about what is available in poke-through devices (see table on page 62), dispel any myths, and tell you what to expect.
Non-obtrusive design
Today's poke-through devices have a design that blends in with the room's environment. This is done for safety reasons as well as to create an aesthetically pleasing atmosphere.
Older poke-through devices use "flip lids." When you flip-up this lid, you can plug into the receptacles. "Some people don't like flip lids because they can create a trip hazard," warns Mike O'Brian, product manager, Wiremold (www.wiremold.com). Wiremold's RC3, RC4, and RC7 Series poke-through devices feature individual slide cover protection for all of the receptacles, as opposed to using a flip lid. Instead of using metal, Wiremold's poke-through covers are manufactured from textured polycarbonate or PVC.
Versatility of these fire-retardant materials makes this feature possible. The slide cover slides back to the duplex receptacle, and then you can plug-in to it so that the device is still flush with the floor. This non-obtrusive receptacle cover snaps back into place when the receptacle is not in use, offering "dead-front" protection.
"You can plug directly through the slide cover," explains O'Brian. "In other words, the slide cover has holes in it to meet up with the receptacle itself." When you unplug, a spring pushes the slide cover back over the receptacle. It is a convenience feature, and at the same time, the receptacles are protected from dirt and debris. Also, if the poke-through device is flush to the ground, it blends in with the room's environment and doesn't get into anyone's way.
To help the poke-through stay flush to the floor, Wiremold's RC3, RC4, and RC7 use carpet flanges to secure the device. The flanges use steel retaining rings that hold the unit in place after installation. "If you wanted to take the poke-through out of the floor, the only way you could do it would be to remove the trim flange assembly at the top," says O'Brian. "You won't be able to pull it up because of the steel retaining rings."
Poke-through devices do not have to be flush to the floor to be non-obtrusive. Hubbell Premise Wiring (www.hubbell-premise.com) offers both flush and pedestal models. These different covers are offered to "blend-in with the dècor of the room," explains Randy Minor, product manager at Hubbell. Hubbell's flush-style covers are available in gray, black, or brass. On the pedestal side, the company offers either a brushed aluminum or gray color. Most poke-through devices have covers in different colors to match your needs.
Unique Fire Stop Products Inc. (www.uniquefirestop.com) also offers efficiency-minded devices to feed power and communications services to open-space areas. But Mike Tobias, the company's CEO, refers to its devices as sleeve systems. "Sleeve systems are a vessel of containment," explains Tobias. "These devices allow the intumescent material to expand when exposed to the heat and flame, and it lets you control and direct that expansion."
The Split Sleeve system is a non-obtrusive solution designed for quick retrofits. Composed of four slotted square washers and a piece of rigid, threaded conduit split in half, the Split Sleeve is designed to turn violation cables into an Underwriters Laboratories Inc. (UL-www.ul.com)-classified system without disrupting the existing system. It is wrapped around the violation cables and stuffed with fire-rated caulk or putty to restore safety without any network downtime.
The Smooth Penetrator, another system offered by Unique Fire Stop Products, is designed for new penetrations in drywalls. This system is non-obtrusive in that it does not create a big mess when being installed. The Smooth Penetrator features drywall-cutting teeth that let you create the right size hole for the fire barrier penetration. At the same time, the teeth hold the device in place once installed. This feature is similar to Wiremold's steel retaining rings.
High capacity
The main function of a poke-through device is to feed sufficient power and communications services through a confined space. The device must be able to service the above floor's communications needs in an efficient manner.
"Poke-throughs started out with a 2-inch core because they were primarily allowing just a few power cables to come up through," says Minor. "And then as the requirements for offices began to grow with the need for more communications cables to be able to come through, the 2-inch core grew to 3 inches." Today, many poke-through devices are manufactured with a 4-inch core, allowing even more cables to come through. Hubbell Premise Wiring's flush and pedestal poke-throughs have a 3-inch core for retrofit. "Most of the holes drilled in the past 15 years have been 3 inches so our product will fit right in," continues Minor.
Wiremold's RC4 series poke-through device provides both flush power service as well as flush or recessed communication service. The RC4 is a multiple-service device that offers two duplex receptacles, giving you four power outlets in the unit, plus four communications outlets. Most poke-through devices today provide both power and communication service. Rated for optical-fiber devices, the RC4 can handle normal Category 5e or Category 6 communications jacks, voice, or data applications.
"Not all poke-throughs on the market can handle fiber-optic connectors because of their design," says O'Brian. "With the fiber-optic connectors, you need to be able to recess the [poke-through] device so that the connector is not sticking out above the flush part of the connector." Wiremold's RC3, RC4, and RC7 Series poke-throughs also contain a built-in junction box. Having a junction box already installed in the unit instantly adds capacity and reduces the amount of wiring you have to do.
Importance of intumescents
Why can't the design of the poke-through device classify it as a firestopping device? "Poke-through devices must have a firestop material," explains O'Brian. "All poke-throughs need a firestopping material such as an intumescent (putty). That is what makes them unique compared to floor boxes." Firestop putties do not shrink, nor do they harden like most caulks and sealants. Most firestop putties will expand with heat or flames to help seal off any leaks around the poke-through device, preventing the spread of fire through fire barriers. This is ideal for the poke-through since it rests in a cored hole. Putties are also non-obtrusive.
Some poke-through devices have the firestop putty built-in to the device to save time and effort during installation. Not having to add the firestop putty is a convenient feature and translates to no obtrusive messes. Hubbell Premise Wiring's poke-through devices come with round disks made from intumescent material. These are applied right to the product and stuffed into the hole. Mike Tobias of Unique Fire Stop Products refers to the built-in intumescent in his company's sleeve systems as "fill material." In other words, the device and the putty are separate entities, but the sleeve system depends on the putty to make it sufficient for the application.
Ryan Cliche is assistant editor for Cabling Installation & Maintenance.
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