Redundant Power Supply Qn

Unanswered Question
Apr 10th, 2009

in a 4507 switch, I have 2 units of 4200W working in redundant mode. Each PSU has 2 input of 220V. Call it PSU 1-1, PSU 1-2 for PSU1 and PSU 2-1, PSU 2-2 for PSU 2.

When PSU 2-1 input is faulty (power source and cables are fine, confirm is PSU hardware faulty), the "show power" command indidated that the switch detected different power supplies installed and put the entire PSU 1 in err-disabled more. Causing the PSU to take the load with a total of 2100W available power. The load is around 900W. My question is, why is the switch not using PSU 1 as both the PSU 1-1 and 1-2 source are ok, and it can supply 4200W. Thanks in advance.

I have this problem too.
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Leo Laohoo Fri, 04/10/2009 - 01:13

Not an expert of the 4500 PS stuff but if you get something like

power-supply 2 power-input: AC low

power-supply 2 power-output-fail: failed

Then it means that the 1 or 2 power input or feed is not working.

Make sure that both power cords are providing power to the PS and you should be good to go.

zephyranthes Fri, 04/10/2009 - 07:54

Thanks, but I still dont understand why is the switch making the "good" PSU going into err-disabled mode. I am 100% sure that PSU 1 has 2 x 220V input. But the switch is using the PSU2, only 1 x 220 V input. And it put the PSU 1 into err-disabled mode. Thanks for your time.

glen.grant Fri, 04/10/2009 - 03:29

The way it works is , the one that is err-disable is not the problem .The other one is faulty . If you take out the existing one that is running at 2100 watts it will automatically go over to the other one and it should give you 4200 watts and it will come out of err0disabled by itself . I think its cisco's way of forcing you to replace the faulty PS . The 4200 watt power supplies at least in our installs have been less than stellar reliability wise. A blurb out of a doc.

As with other power supplies, the two power supplies must be of the same type (4200 W AC or 1400 W DC). Otherwise, the right power supply will be put in err-disable state and the left one will be selected. In addition, all the inputs to the chassis must be at the same voltage. In redundant mode, the inputs to the left and right power supplies must be identical. If the left and right power supplies are powered in redundant mode, the power values will be based on the weaker of the two power supplies.

http://www.cisco.com/en/US/docs/switches/lan/catalyst4500/12.2/31sga/configuration/guide/pwr_envr.html

zephyranthes Sun, 04/12/2009 - 20:48

Hi Glenn,

Thanks for your reply. It is happening exactly as you mentioned. I tried searching the bug tool kit but no such info is available. Are there any docs that states this ? Is it the same for all Catalyst switches?

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