C6509-E heat dissipation

Unanswered Question
Sep 10th, 2009


I am trying to figure out what is heat dissipation of a C6509-E configured as follows:

1 x WS-C6509-E-FAN

1 x VS-S720-10G-3C

1 x VS-F6K-PFC3C

8 x WS-X6748-GE-TX

8 x WS-F6700-DFC3C

2 x WS-CAC-6000W

I have tried two ways: 1) the power calculator and 2) manual calculation using the C6500 installation guide.

1) The power calculator says 13630 BTU/h

2) Manual calculation says:


per unit Units BTU/h

WS-C6509-E-FAN 896.44 1 896.44

VS-S720-10G-3C 1443.26 1 1443.26

VS-F6K-PFC3C 340.65 1 340.65

WS-F6700-DFC3C 295.82 8 2366.56

WS-X6748-GE-TX 1255.01 8 10040.08

TOTAL 15086.99 BTU/h

The there should be also the two PS in the picture, and the new total should be:


per unit Units BTU/h

WS-CAC-6000W 23812.00 2 47624.00

TOTAL 62710.99 BTU/h

Well, 62711 BTU/h looks quite a bit too much and I think that the heat dissipation of the power supply should't be considered in the calculation.

If so, why?

Isn't it an item that takes power from the grid and that generates heat according to its efficiency as the other modules?

I am puzzled, can anyone help me?


I have this problem too.
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Giuseppe Larosa Sun, 09/13/2009 - 14:12

Hello Andrea,

two notes

power heat dissipation of PFC3C is already taken in account in supervisor one if you look at the table it says with a PFC3C and an MSFC3.

fan-tray has two ways of working slower mode uses only 641 BTU/h.

fastest mode should be triggered by the presence of 10GE linecards in the chassis that I don't see in your current module list.

another note is about the power supplies: each of them require two AC power cords to work at 6000W otherwise they operate at 2900W.

These PS are oversized for the current needs of your chassis but I guess you are planning to add modules in the future.

About the power supplies: for AC 6000W system power usage is rated at 7034 W.

The difference should be the power dissipated on the PS itself.

Hope to help


sajid_m123 Tue, 08/21/2012 - 15:25


Does it mean that we will not calculate the BTU provided for the power supply in the data sheet?


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