Calculating System Heat Dissipation - Cisco 4500 Series Installation Manual

Chapter 2 Preparing for Installation

Calculating System Heat Dissipation

Note
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Appendix A, "Specifications,"
site requirements for the switches. To maintain normal operation and ensure high
system availability, maintain an ambient temperature and clean power at your site.
The environmental ranges listed in
within which the switch will continue to operate; however, a measurement that
approaches the minimum or maximum of a range indicates a potential problem.
You can maintain normal operation by anticipating and correcting environmental
anomalies before they exceed the maximum operating range.
To calculate the expected heat dissipation from a switch, add the total amount of
power drawn from power supply by the system's configuration, then divide the
total amount of power by the efficiency of the power supply. Multiply the result
by 3.415 to get the system heat dissipation in BTUs/hr.
First example (System without any powered devices):
Components
1 - Catalyst 4506 with fans
1 - Supervisor Engine IV
1 - WS-X4248-RJ45V with no phones 72 W
total output power 267 W
Total heat dissipated by system = (267/.75) * 3.415 = 1215 BTUs/hr
All Catalyst 4000/4500 power supplies have different efficiencies, An average
efficiency figure of 75% was chosen.
Second example (same system but this time with one IEEE class 3 device):
Components
1 - Catalyst 4506 with fans
1 - Supervisor Engine IV
1 - WS-X4248-RJ45V with no phones 72 W
lists the operating and nonoperating environmental
Appendix A, "Specifications,"
Output Power
50 W
145 W
Output Power
50 W
145 W
Catalyst 4500 Series Switches Installation Guide
Ventilation
are those
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