Cisco CEE 7/7 - IEC-C19 13-ft Europe CAB-CEE77-C19-EU= User Manual

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):

All 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):

Although a class 3 device needs 15.4 W to power up, 17.3 W need to be generated from the backplane 
in order to have 15.4 W at the switch port. 17.3 W comes from the WS-X4248-RJ45V DC-DC 
converter’s efficiency (89%).

 lists the site-planning activities that you should complete before you install a Catalyst 4500 

E-series switch. Completing each activity helps to ensure a successful switch installation.

1 - Catalyst 4506-E 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

1 - Catalyst 4506-E with fans 

50 W

1 - Supervisor Engine IV

145 W

1 - WS-X4248-RJ45V with no phones

72 W

1 - IEEE class 3 device

17.3 W

                                 total output power  284 W

Total heat dissipated by system = (284/.75) * 3.415 = 1293 BTUs/hr