Environmental Guidelines
DVN 5000
24-10520-22 Rev. –
19
This document contains confidential and proprietary information of Johnson Controls, Inc.
© 2009 Johnson Controls, Inc.
Most front-intake equipment exhausts between 50 and 150 CFM. If a fan is required
for the top of the rack, ensure that this fan’s CFM rating is at least the sum of the
CFM ratings of all the equipment. With proper fan placement, hot air will not
short-circuit
and re-circulate between equipment, as the fan will draw air from all
openings. A solid rear door is recommended in this situation to control airflow from
front to rear. However, adequate (6” minimum) clearance needs to be between the
rear door and rear exhaust outlets of the equipment.
It is important to note that Fan CFM is a maximum rating, as if you mounted it in
free air. As soon as you connect it to an enclosure, the flow rate decreases because of
bends and turns that slow the air flow.
Figure 8: Incorrect Use of Forced Air with Front Intake on Equipment
Note that Figure 9 on page 20 (Correct Use of Forced Air with Front Intake on
Equipment)
shows no vents in the upper rack face, no vents in the upper rear door,
and no vents in the upper 6 spaces of the rack. This will prevent the
short-circuiting
of air at the top of the rack.