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Air Plenum
In some data processing environments, the underflow area is used as an
air plenum, with cool, controlled air flowing under the raised floor and
distributed to the heat loads out in the data processing area. Return air
is routed back to the tops of the process control HVAC units.
This can create some potential problems:
• Concrete sub-flooring should be sealed, but often is not. Concrete
continues to ‘shed’ over its lifetime and will add to humidity control
problems.
• Improper cable routing can and does cause air flow distribution
problems.
Cable routing
Most data processing environments use the space under the raised
flooring to route data and power cables. Since this is often not closely
controlled, potential problems may arise such as:
• Air flow impedance and misrouting
• Electromagnetic interference from parallel runs in close proximity to
one another
• Liquid spills beneath the floor may go unnoticed for long periods.
• Where cable breaches raised floor, abrasion may cause severe shock
hazards.
In general, cables should be routed parallel to the air flow, and not
horizontal to it. Additionally, extreme care should be given to ensure that
data and power cables are not routed close together in a parallel fashion.
In fact, these cables should be separated by a minimum of 6 inches
wherever physically possible.
Safety Hazards
Most electrical codes dictate that if an electrical shock hazard exists,
some method to curb this must be used. For instance, “any non-current
carrying metallic part of a structure that could be energized and touched
by personnel has to be grounded.” With all of the power and data cables
routed beneath the flooring and pulled up into the data are, the chances
for short exist. As the tiles are metallic clad, it is conceivable that the
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