Talking Sense about...
In-Floor Utility Enclosures (Floor Boxes)
Exhibits in trade shows and other events held in modern exhibit spaces have crucial electrical, mechanical and communications requirements that the competitive convention facility must provide. Floor Boxes, also known as utility pockets or floor ports meet these needs best. They are installed flush with the exhibit hall floor as part a utility delivery grid. Specific utilities and their capacities will vary from facility to facility based on the type of exhibits held. The provision of up-to-date utilities is an absolute necessity for attracting a wide array of trade shows and exhibitors.
Most exhibit floor planning assumes a ten by ten foot booth area, usually along both sides of a ten foot aisle. Aisles are laid out in two counter directions, which create a module. This module is the basis for the layout of the floor boxes that in combination with the under-floor utility pathways form a utility system that can service all of the exhibit booths on the floor. Therefore a single box can service several modules without above floor utility lines crossing pedestrian aisles.
Floor boxes are connected by a system raceways or conduit, usually PVC pipe. One pipe will carry power, while others supply communications, audio/visual, air, and water. This enables the delivery of services to all or some of the floor boxes and eliminates above-floor hazards and clutter
Floor Box Design
Many serious convention center exhibit hall projects have demanded floor boxes that are built to order. One reason for this is the rapid rate of change in communications systems; another is the need for more devices than standardized floor boxes can accommodate. They have been built as large as a desk, but are usually less than three feet square and less than 24 inches in depth. Vendors with accumulated designs, patterns and experience can frequently apply these resources to avoid the need for a more difficult "dead special" design.
Floor boxes can be fabricated for any type of floor, the most common being slab-on-grade. The floor box is really an assembly of three fundamental components; first the box itself, which is fabricated from sheet or cast metal, or most preferably, PVC. It can be equipped with fittings to accommodate any type of raceway or conduit as well as drains and other types of mechanical fittings. It may be constructed so that one side of the bottom is lower than the other to direct any accumulation of fluids away from electrical devices and connections. Second are device plates, to which are mounted the various electrical, telecom, A/V, or mechanical devices. These serve to suspend the devices near the top of the box, away from dirt and fluids, and to facilitate access from above. The third component is an integrated frame and cover assembly. The function of the frame is to secure the box in place and transfer the load on the cover to the slab. The cover may be divided and secured in various ways, and in combination with the frame, bear such loads as trucks and forklifts.
Floor boxes are divided internally so that services are isolated from one another as dictated by code. Minimally these dividers or partitions must separate ‘high voltage’ power services from ‘low voltage’ services such as communications. The drains are usually located in the mechanical or wet compartment of the box, but may service the entire box by using weep holes to allow drainage from any of the compartments. Properly designed, the raceway and conduit serving the floor boxes may also serve as drainage or relief in case of inundation by large amounts of water.
Floor Box Utilities
Any or all utilities may be supplied by all or selected floor boxes. Most up-to-date exhibit hall floor boxes provide for power, data, several modes of communication, audio/visual, water and compressed air. Exactly which utilities are available from which box depends on the exhibit hall layout and the anticipated needs of the exhibitors. It is not always necessary to supply all services to all boxes.
An efficient layout will utilize the floor boxes as elements of a complete utility distribution system. In most cases adequate services may be provided throughout an exhibit hall with one or two floor box configurations. Even though the contents of the box may vary, it is rarely if ever useful to have more than one basic box dimension and configuration. It is also prudent that the device plate be common, even though the device selection may vary. Properly designed, the floor boxes and their raceway should enable the possibility of cost effective and quick retrofits should circumstances dictate. The demands by exhibitors for utility services are growing quite rapidly, and without proper utilities an exhibit facility can become uncompetitive in a short amount of time.
How to Do It Right
While the floor box is usually considered a part of the facility’s electrical system, it will also contain elements of mechanical functions. A custom, or special floor box specification that is not complete in terms of a precise requirement for a drain fitting, for example, and cannot be fabricated. The practice, all too common, of hoping that a fabricator bidding the job will find the time and have the inclination to provide free engineering that will actually work correctly is one that never succeeds. The floor box design and firm specifications should be complete, approved and in the hands of a fabricator at least eight weeks or more before its time to pour floor slabs.
As a practical matter, a frequent scenario is that everyone wants to see cement mixers pouring concrete, so the first component of the floor box that needs to be shipped is the box itself. Therefore a facility design in which all the boxes, lids and frames are the same enables the fabricator to ship sooner, and supply devices and device plates later. The design, approval and tooling for cast boxes take eight weeks or so from the time drawings are approved for fabrication. Specifiers should understand that material costs for the boxes are a poor source for savings, which seldom if ever offset the added engineering costs involved with multiple or highly customized configurations. In terms of basic floor box configurations, less is more.
Most metal fabricators have a very difficult time with built to order floor boxes, especially if they have not done the work before. If a fabricator has not done successful work with load bearing products, or has not got experience in intricate electrical wiring, they will be learning this rather difficult work at the expense of the specifier’s client. Collapsed floor boxes with forklifts sticking out of them are not as amusing to facilities people as they are to other more casual observers on the scene. Floor box specifications frequently contain an item like this one:
"The frame and cover assembly shall meet a minimum load rating of HS-44 as defined by the American Association of State Highway Officials (AASHO), which states: For a (highway) truck with a maximum single axle load of 32,000 pounds and dual pneumatic tires, the maximum load on one pneumatic tire shall be 8000 pounds with an assumed footprint of 6” x 10”.
The largest, regularly available forklifts are capable of a lifting capacity of 33,000 pounds, so the maximum total load on the front axle is 65,250 pounds, 50% of which is about 33,000 pounds. This, regardless of tire size, footprint, or type, is what a serious convention center floor box may have to withstand.
Contractors often elect to provide devices, and in cases where there is substantial experience, this may be a good approach. Often it is an attempt to save money that fails when devices do not fit device plates. This sort of problem cannot be remedied easily as heavy gauge device plates cannot be reworked effectively in the field. Again, experience counts for a great deal. A “first article test”, in which the device plate is matched and wired with specific device plates, is well worth the short time it takes to do.
Specifying a PVC box can be a sound recommendation. PVC can be installed anywhere and does not deteriorate, so there is no need to waste time figuring out what metal the box should be made from or whether it should be cast or formed. In addition it is a commodity that is ready from stock.
The phrase “or equal” should not be used to describe devices that will have to fit precisely into 12 gauge steel plates.
Perhaps the most important thing to bear in mind regarding floor boxes for convention center exhibit halls is that without them the hall is a large empty, unproductive space. They are important and their design as a component within a critical system should be treated as a major priority.
Floor Boxes for Ballrooms and Meeting Rooms
While the requirements for utilities for these facilities are relatively modest, the need to deliver utilities without hazardous floor clutter remains. Floor boxes for this application tend to be smaller and contain less in the way of devices and utilities. In addition they usually have to be installed under carpet and be inconspicuous. The trend to use ballrooms in small facilities for local trade shows and the growing requirements for communication capabilities mean that some low cost conventional floor boxes cannot always do the required job well.
These facilities are not the same as offices. Floor boxes in Ballrooms and larger meeting rooms must be able to withstand the weight of furniture laden dollies, as well as the use of wet powered carpet cleaning systems. Recent proposed changes in the pertinent UL standard reflect the reality that commercial carpet cleaning systems have the same ability to deliver water into a floor box as does a wet mop on a tile floor.
Conventioneer CMB Series
The pre-designed CMB1212, CMB1414 and CMB1818 are the new industry-standards for hotels, casinos and office buildings, providing utilities under carpeted floors.
Conventioneer EXH Series
The pre-designed Coventioneer EXH Series is based upon thirty years of experience producing superior exhibition hall floor boxes. These industry-standard, multi-utility service distribution boxes are leading-edge and feature-rich, providing a near-custom solution at off-the-shelf prices. The Conventioneer EXH Series is specifically designed for exhibition halls without carpeting, and can be installed flush into a poured slab-on-grade or in a deck poke-through.
Conventioneer Custom Series
Our Conventioneer Custom Series are based upon your application specific floor box requirements and our experience. Designed for any application, our custom floor boxes provide high current value to the architect, engineer, contractor, venue owner, and end user.
Telematic ä telescoping floor boxes
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