High-Capacity Poke-Thru Device

Poke-thru devices provide capacity and flexibility to meet the demands of open plan spaces by delivering power, voice, data, and audio/video services precisely where they are needed without impacting the fire rating of the floor slab. However, as the demand for such services at workstations increases, conventional poke-thru devices may not have sufficient capacity. In fact, it is not uncommon for contractors and building owners to "double up" by installing two poke-thru devices to serve a single workstation. With the high cost of installation, especially in occupied spaces, there is clearly a need for high-capacity poke-thru devices. These devices should also support and protect a wide variety of connectivity and power devices, including GFCI and hospital grade receptacles. And, of course, any new poke-thru device must be a fire classified product.

The solution to these challenges is to increase the size of the core-drilled hole. This enables greater capacity, improved flexibility, and enhanced long-term performance.

Fire Rating and Structural Integrity

Poke-thru devices employed today are installed in core-drilled holes of 3" or 4" diameter. In order to increase capacity, the size of the hole must be increased to 6" or 8". These larger holes not only afford more space for devices, they also allow the devices to be recessed below the finished floor level for maximum protection and longevity. This feature, in turn, permits new cover designs that are truly flush, not raised above floor level, as is the case with conventional poke-thru devices. These design enhancements maintain the most important feature of a poke-thru device - the fact that it is a fire classified product that maintains the fire rating of the floor slab.

Because poke-thru devices are installed in holes that have been core-drilled through concrete floors, the number and placement of the holes is governed by standards relating to the fire rating of the floor slab, as well as by structural considerations. The UL fire resistance directory details the standard for poke-thru penetrations as a "minimum of 2 ft. on-center and not more than 1 insert per 65 sq. ft. of floor area in each span." These standards are in effect up to an 8" core-drilled hole. In other words, the same standards that apply for smaller poke-thru devices also apply for those that require larger floor slab penetrations.

Nonetheless, the structural integrity of a floor slab must always be taken into account. Wiremold/Legrand commissioned an independent analysis of a typical office floor (30' x 30' column bays, steel beams spaced 7' 6", and 4" thick concrete on a steel deck). This analysis determined that 6" and 8" holes pose no threat to the integrity of the floor slab. It must be stressed, however, that such an analysis should always be conducted for any project as a matter of sound engineering practice.

Design Advances

In summary, the parameters for the design of a next-generation poke-thru device were:

• Greater capacity
• Recessed devices
• More durable covers
• Maintain fire rating

High Capacity
In order to create greater capacity, new poke-thru devices are designed to install in core-drilled holes of 6" or 8" diameter. An 8" diameter hole doubles the capacity of the highest capacity conventional poke-thru on the market. Higher capacity creates more "real estate" for locating receptacles and data, communications, and audio/video connectivity devices. This extra space affords more design flexibility, including allowing the poke-thru to accept GFCI and hospital grade receptacles. Many poke-thru devices are sold in standard, factory-installed configurations that can not be altered. The new poke-thru design allows receptacles to be installed in the field and changed out at a later date if necessary.

Recessed Devices
In profile, a conventional poke-thru device has a head that is nearly flush with the floor and a stem then extends downward through the core-drilled hole. Until now, wiring devices were located in the head of the poke-thru, above the point where the stem passes through the floor. Larger core holes and higher poke-thru capacity allow devices to be recessed below the floor surface, affording additional protection for the devices.

Because the new poke-thru design places all connection points within the device, the cover swings open to provide access to the devices inside. Wires and cables exit through slide covers located around the perimeter of the cover. In this sense, the next-generation poke-thru devices are more like recessed floor boxes in terms of capacity and wiring flexibility. But unlike floor boxes, which must be encased in concrete, the new poke-thru devices can be used in retrofit applications while maintaining the fire rating of the floor slab.

Cover Design
The design of the new poke-thru device makes it practical to use a durable all-metal cover. Sliding covers at wire egress points are also made of metal and are spring loaded so they close tightly around exiting wires and cables. Integral gasketing enables these devices to meet UL514A "scrub water" standards. An all-metal cover design provides enhanced durability and improved aesthetics. This feature makes possible new poke-thru applications, such as feeding part-time kiosk locations in malls, airport concourses, and office and hotel lobbies. When the poke-thru device is not in use, it is flush with the floor and strong enough to withstand foot traffic.

Maintain Fire Rating
In conventional poke-thru designs, intumescent material is placed around the stem at the level where the poke-thru penetrates the floor slab. When exposed to high temperatures, the material expands to fill any space between the fitting and the floor slab. In the new poke-thru design, the devices are recessed below floor level, so the entire casing around where wiring devices are mounted is a fire stop material. This allows the poke-thru to be fire classified since in the event of fire or high temperature, all space within the floor slab penetration is quickly filled by the expanding intumescent material.

Conclusions

The next-generation poke-thru device adds significant capacity to avoid core drilling extra holes and "doubling up" of devices in order to provide adequate workstation services. Increasing the size of the hole does not increase the installation labor cost, nor does it impact the regulations governing the placement of poke-thru devices. This next generation of poke-thru devices also offers enhanced protection by recessing receptacles and connectivity devices below floor level and by allowing for more durable covers. As a result, poke-thru devices continue to provide services in open spaces, even as the demand for these services grows.