Posted on 2006-03-21
Last Modified: 2011-10-03
Hi All,

Here is the setup:

1 x APC UPS with SNMP Network Management Card installed.
3 x Windows 2003 Servers with Powerchute Software installed.

Powerchute has been installed and configured on the Windows 2003 Servers. It is installed and can talk to the UPS. The servers are set to start shutting down after 2 minutes.

I test the above setup by pulling the power cord from the UPS to simulate power failure. The servers all start shutting down after 2 minutes as expected. I wait for all of the servers to finish shutting down. I plug the power cable back into the UPS. The UPS goes back onto mains power, but the servers do not switch back on automatically. How can they be set to turn back on?

I have considered the BIOS settings such as "last state" etc, but in the above scenario, the servers never lost power (because the UPS never ran out of battery). Believe it or not, the above scenario is quite common in our area of late. That is, the power goes out long enough for the servers to shutdown, but not for the UPS to turn off.

Any help would be most appreciated!

Question by:PeteJH
    LVL 16

    Accepted Solution

    The server *powering up* again when mains is restored is a BIOS setting on the server, not a config of teh UPS or the UPS monitoring software. Look for "Power Recovery" or similar in the BIOS.

    Remember, once the server has shut down, it isn't running any software, so no software or setting in Windows can take any effect.


    Author Comment

    Thanks for the response.

    I understand what you are saying, but I was wondering if the BIOS settings apply, because in my scenario the server never loses mains power. The UPS loses mains power for a brief period of time (eg 5 minutes) and is able to keep providing power to the server via battery backup the whole time the mains power was down. However the outage occured, PowerChute on the servers communicated with the UPS and commenced shutdown of the servers.....

    LVL 4

    Assisted Solution

    From memory there is a setting in the powerchute software as to whether the server repowers. You can say only power back on when the UPS reaches 50% of charge for instance - ths prevents the power from coming back on when the UPS is at 5% charge you then get another power failure and not enough UPS charge for a clean power down. When I worked with these devices we never had to worry about server bios settings - because its a UPS shutdown the server seems to know to come back up. The other option is to say to the servers to wait X minutes before powering up - an important thing to consider is to stagger the time between the servers powering up. If you switch all your servers on at once you can trip the circuit breakers for power due to the unexpected surge in demand.
    Hope this helps
    LVL 11

    Assisted Solution

    Shouldn't that UPS be able to send a  "wake-up-on-lan" signal to the servers?
    LVL 3

    Assisted Solution

    "Shouldn't that UPS be able to send a  "wake-up-on-lan" signal to the servers?"

    That is a good point. I wonder if the servers are set to FULLY power down instead of "wake-up-on-lan" signals from the SNMP card. This seems like a server power configuration setting issue, or a misconfiguration of the PowerChute software. I'm no expert, just some thoughts.
    LVL 3

    Assisted Solution

    I don't think the UPS can send WOL packets, it would have to know the MAC address of every computer. I'd try sth more hardware like:
    1 Relay (110 or 230V AC coil rating, depends on area). The coil is attached to the net supply before the ups. With its closing switch, the relay should send a PC's +5Vstandby thru the normally closed switch of a second relay and further thru a third relay's coil (5V rated, small signal relay). This third relay "presses" the power button with it's closing switch contact by wiring it in parallel to the switch in the case. The coil of the second relay (also small 5V signal relay) is attached to "normal" +5V in the PC.
    The thing works as follows:

    The power grid comes back and makes the first relay close it's switch.
    If the PC is off, the second relay's switch is closed and +5Vstandby is applied to the third relay and presses the power button in order to activate the PC.
    As soon as the power supply comes up, the second relay switches off the relay that "presses the button" This second relay also prevents the button to be pressed, when the line comes back even before the server has been shut down. Otherwise, the server would be shut down *because* the power came back online.
    But even this solution is not perfect: What if the power came back while the pc would be shut down ?

    I don't think that there is a good solution in sight.
    LVL 3

    Expert Comment

    There is a solution:
    See this site:
    If you connect Pin14 (PS-ON) with ground, then your PC is always on, regardless of BIOS command.

    But this is not what you want. Because if you'd do that, you PC would shut down when the power failed and reboot and then crash as soon as the UPS runs out of battery.

    Instead you make the PS-ON to ground connection thru a relay (110/120V or 220-240V AC, depending on area) driven by mains power *before* the UPS.

    As long as the power grid is up, this relay forces the computer to be on, even if it was just shut down. If main comes back on, the computer is restarted ASAP or forced to restart instead of reboot. This means as soon as the Power is restored enogh to make the Servers power supply work.
    Sole problem: You can't turn your computers off any more except by pulling the plug (or switching that little swich in some power supplies). But why'd you want to turn it off anyway ? You talked on making it run :-)

    Sorry, neither of my solutions is software based.

    Take care when working with mains power. Alas, it's not *that* dangerous, but maybe dangerous enogh to kill you if you make a mistake.

    For the relay see that your relay is capable of working with 100% duty ratio.

    You might also use some transformer (maybe a scavenged "wall wart") to drive a low voltage relay. This is maybe much safer to use. The transformer of course is then to be attached "before" the UPS.

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