DVN 5000
Environmental Guidelines
12
24-10520-22 Rev. –
This document contains confidential and proprietary information of Johnson Controls, Inc.
© 2009 Johnson Controls, Inc.
If the equipment room does not have the ability to remove the heat generated by the
rack(s), then all of the following calculations will have little meaning. Whatever
heat is removed from the rack should not raise the room temperature by more than
3
F.
For digital equipment, the room itself should be no hotter than 75ºF (24ºC). This
gives a 10ºF (5ºC) temperature difference between the room and the recommended
85ºF (29ºC) internal rack temperature for optimum equipment life.
The cooler the room (as long as the room temperature is above the dew point so
condensation does not occur), the fewer vents or fan CFMs will be needed.
All necessary information is included within this document to calculate the total
BTU/Hr. that will need to be removed.
Rack Placement
Heat generated by equipment in racks needs to be removed. The hot air from the
enclosure must be replaced with cooler room air. In general, it is more effective to
work with natural convection and remove the heated air from the top of the rack
while letting cooler room air enter at or near the bottom. Several examples are
shown later in this document.
Since fan noise is often not welcome in a work area, equipment racks are housed in
closets. Ambient (or room) temperature will be much higher in closets, and heat
should be exhausted out when the ambient air inside the closet exceeds 75°F (24ºC).
When using a single rack in a non-air-conditioned closet, use a fully louvered closet
door and monitor the temperature at the front of the DVN.
In an air-conditioned room (without a raised computer floor), have the supply ducts
and diffusers in front of the racks, and the return ductwork and registers in the rear
of the room.
Avoid locating the racks directly under supply ductwork. Cold air falls, and the flow
of the hot air that rises from the top of the rack should have no impediments on its
way back to the return air (intake) duct. See Figure 4.
When supplying cool air to a dedicated rack room or closet, it is always best to
provide a separate zone in the HVAC system, along with properly placed supply and
return ducts, to ensure consistent air flow and proper room temperature.