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Adding 2nd P/S to 4000m causes reboot

Jim Smith_19
Occasional Advisor

Adding 2nd P/S to 4000m causes reboot

I installed a 2nd power supply in order to migrate a 4000m to a UPS outlet. When the new P/S had AC applied to it, the switch rebooted. No other action caused this to happen, including subsequent P/S removal or removing AC from either P/S. I couldn't find any references in the knowledgebase. Anyone else seen this?
Building better networks since 1981
5 REPLIES
Rich S
Honored Contributor

Re: Adding 2nd P/S to 4000m causes reboot

One of 2 things is happening here... your P/S is overloading the application and/or the voltages or polarity don't match. Any of these cases would cause a reboot. Its a safety in a lot of the newer switches to prevent damage.


I do not know your depth of electronics, but if you add a diode in line of both supplies it will act as a filter and reduce the current slightly. It will also prevent a "backup" in the voltage. I usually add a simple diode in line with the positive lines of both supplies. You can buy the diode at you local electronic store.

Hope that wasn't too much info.



Rich
Jim Smith_19
Occasional Advisor

Re: Adding 2nd P/S to 4000m causes reboot

>> One of 2 things is happening here... your P/S is overloading the application and/or the voltages or polarity don't match...if you add a diode in line of both supplies it will act as a filter and reduce the current slightly. It will also prevent a "backup" in the voltage... <<

This sounds like a reference to DC power supplies. I have conventional A/C, so I don't think the diodes would help. However, one source was general "house power" and the other was from an Avaya-supplied UPS. It's possible that hot/neutral are reversed on one of the outlets, or that the UPS is out of phase. This sounds like something that might cause the safety feature you described. Thanks for the idea - I will test the two sources for any differences. Thanks!
Building better networks since 1981
Rich S
Honored Contributor

Re: Adding 2nd P/S to 4000m causes reboot

Most Power Supplies are set for current overload.... so when you hook up 2 in tandom, you trip the safety built in the PS.

You could check the current if you have a DVOM but my guess is you are overloading the circuit. Check the specs.


Rich
Jim Smith_19
Occasional Advisor

Re: Adding 2nd P/S to 4000m causes reboot

Rich,
These are hot-plug redundant AC power supplies built into the 4000m. I can't fathom why powering the 2nd one up would cause a current overload in the switch. As to the supply circuit, this is a standard NEMA 20-amp circuit with very little load on it (terminal and modem). An overcurrent on the circuit would trip a breaker - this did not occur. The only anomoly was that the switch rebooted when the 2nd power supply was powered up. I will check the hot/neutral on both circuits. My earlier theory on an out-of-phase condition is very unlikely to cause a problem as the individual power supplies simply supply DC voltages on a common buss inside the switch.

If the hot/neutral and voltage levels are OK, I'm putting this down to a glitch. Just wondered if anyone had seen a aimilar problem related to code version/bug/etc. Thanks again!
Building better networks since 1981
Rich S
Honored Contributor

Re: Adding 2nd P/S to 4000m causes reboot

Hi Jim,

Then maybe one of them is flawed.... the reboot is a protection that even Windows uses to keep damage away from the OS. Check the technical specs of the units and you might just find the same thing. From there you can work backwards to find out exactly what is causing the problem. Again, one of them may have an interupt problem that is triggering the IPL.

You will have to forgive me, sometimes my logic in my head is not always how I explain things out in words to the point where I can convey the whole process I am thinking.

Let me know what you find.

Rich