Frequently Asked Questions
Tate has put together a document which answers many of the Frequently Asked Questions regarding access flooring, underfloor HVAC and modular wiring. Complete FAQ document
Below is a sampling of the questions answered.
How should an appropriate panel grade be selected for a project? Panel grades are typically selected based on three loading criteria: concentrated, ultimate and rolling load capacity. Concentrated and rolling load ratings for panels are based on tolerable deflection and permanent deformation allowances under design loads. Ultimate load capacities are based on tolerable safety factors. The task for the project specifier is to match expected floor loads with floor capacity. For an explanation of how to translate panel load ratings into actual floor capacity numbers for concentrated and rolling loads, see Section 3 of the Best Practices Design Manual, Access Floors.
How do you translate a panel's rolling load rating into rolling load capacity of the floor? A panel's rolling load rating represents its capacity to support one loaded wheel crossing it at a time. To translate the rating into actual floor capacity, you need to map the wheel spacing of your moving device. If the device has four wheels spaced more than 24 inches apart, then the load will be distributed to four separate panels. If this is the case, and the load is evenly distributed, then the floor's capacity forthat device (with payload) is four times the panel rolling load rating. For example, ConCore 1000 panels, rated at 600 lbs., will provide a floor with a maximum rolling load capacity of 2400 lbs. – for moving devices with wheels spaced more than 24 inches apart. In another case, if a four-wheel device is less than 24 inches wide (but has front-to-back wheel spacing more than 24 inches), then the capacity for that device on a ConCore® 1000 floor is 1200 lbs. This is because the front and back sets of wheels have the ability to traverse a single panel at a time – thereby loading a panel with 600 lbs. – the panel’s rated capacity.
Where can I learn more about underfloor air distribution (UFAD)? There are many resources available to lean about UFAD systems. Tate recommends finding non-biased sources when researching the performance and benefits of UFAD to conventional air distribution (CAD) systems. That’s not to say that all those who support or question UFAD are biased however both sides must be evaluated before forming a decision. Associations that are open to participation/sponsor from anyone such as ASHRAE, The Center for the Built Environment and the government supported website: Whole Building Design Guide are good examples of non-biased sources.
Organizations such as SMACNA and SMWIA and the research generated through their non-profit organizations NEMI and NCEMBT should be evaluated with the knowledge that underfloor service distribution systems significantly reduce (up to 90%) the amount of sheet metal ductwork required to deliver conditioned air to an occupied space.
Our recommendation when evaluating information is to always consider the source, search for alternative view points, and draw your own conclusions.
Can I use ADPI to evaluate an Underfloor Air Distribution System? The goal of using ADPI methodology is to achieve a perfectly well mixed system and uniform conditioned space. Applying this methodology as a measure of the performance of a UFAD system is neither correct nor realistic. Well-performing UFAD systems are not designed to create a well mixed space instead they seek to promote some amount of stratification in the occupied zone (up to 5°F, according to ASHRAE Std. 55-2004). Under partial load conditions this 5° stratification becomes more prevalent and will decrease ADPI values below the acceptable levels recommended for overhead systems.
Furthermore, ASHRAE Standard 113-2005, it is clearly stated in Appendix B on page 7: "The ADPI method for mixing systems should be applied to traditional overhead air distribution systems under cooling operation only."
How do I help ensure the underfloor air delivery plenum is properly sealed? Tate has provided three best practices guides to aid in the proper design and construction of an underfloor air distribution (UFAD) system. Trade specific guides have been created for the Architect, General Contractor, and Commissioning Agent extracted from lessons learned through Tate’s experience working on a wide range of UFAD projects. These guides will help to ensure the proper sealing and reduction of underfloor air leakage in an access floor air plenum. Furthermore, Tate believes a holistic approach to design and construction should be used and recommends regular consultation be held with key individuals on the design and construction team throughout the entire process. You can also take our online constructability course and receive continuing education credits while you learn how to reduce the risk of uncontrolled air leakage.
What happens when the underfloor air plenum area gets dirty? Prior to installation of the flooring system, the concrete pad should be cleaned and sealed. By the time the flooring is installed, most of the dust creating construction work should be completed. Little dirt should get into the plenum area after construction. If material does get into the plenum, it can be vacuumed out. If debris gets into the MIT unit, it can be wiped out with a damp cloth, or cleaned out with a vacuum cleaner.
Where do you locate the return air grilles? If you have a drop ceiling, put them around the perimeter directly above the glass in order to capture the chimney effect. If you do not have a drop ceiling, use high wall rectangular or linear diffusers. In general they should be away from the core areas.
What is Modular Wiring? Modular Wiring is a totally modular branch circuit distribution system (3-phase, 4-wire) entirely prefabricated and factory assembled including cabling from the power panelboard board to the convenience outlet receptacle. This ‘relocatability’ feature is becoming increasingly important because of the need for constant floor plan changes in the workstation environment found in today’s buildings. Because Modular Wiring is so quickly and easily put in place, its installed cost can be 40-70% less than traditional pipe and wire configurations (which are almost impossible to relocate).
Why is the wiring described as ‘modular’? The primary reason is because you can plug or unplug the entire system from the panelboard to receptacle. The ‘workhorse’ of the system is the Extender Cable. It can be used anywhere along the system. There is absolutely no need to fuss with a lot of different cables. The Extender Cable is inter-changeable anywhere along the entire length of the system.