Cisco Systems 4500 manual Calculating System Heat Dissipation, Output Power

Chapter 2 Preparing for Installation

Ventilation

Appendix A, “Specifications,” lists the operating and nonoperating environmental 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 Appendix A, “Specifications,” are those 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.

Calculating System Heat Dissipation

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

Output Power

1	- Catalyst 4506 with fans	50 W
1	- Supervisor Engine IV	145 W
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

Note 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

Output Power

1 - Catalyst 4506 with fans

1 - Supervisor Engine IV

1 - WS-X4248-RJ45V with no phones

50W

145W

72W

	Catalyst 4500 Series Switches Installation Guide
2-16	78-14409-08