UPS & Power Supplies

Unanswered Question
Oct 25th, 2007

In order to properly size a UPS to a multi-slotted switch, such as a Cisco 4506:

1. Do the switch's power supplies, modules and fan unit of the switch draw power from the UPS?


2. Do the modules and fan unit draw power only from the switch's power supplies and therefore a switch's power supply is selected based on the modules and fans installed...and then the UPS is seleted based on the switch's power supply?

I have this problem too.
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bwilmoth Wed, 10/31/2007 - 08:53

The size of a UPS is determined by time x power consumed. Knowing the power requirements is useful for planning the power distribution system needed to support the switches. You should consider the heat dissipation specifications when estimating the air-conditioning requirements for an installation.

Joseph W. Doherty Wed, 10/31/2007 - 18:48

To properly size a UPS, you need to know the total load created by all the powered modules in the chassis, i.e. how many AC amps are being used. Once you know the drawn amps, then you will need to decide how long you're want to run the chassis off the UPS.

If you have a logon account with Cisco, you can run the power calculator to obtain the power draw for your chassis devices.


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