PC Not Booting Until a Different Phase is Used?

2by4 asks: "I run at IT Dept for a small firm, our network room houses production & development servers. Some machines are plugged straight into a strip with no UPS. Here is the Mystery Problem: When the power glitches, the strip machines go down, and some of these machine WILL NOT come up again until I switch them to a new outlet. Once this happens, I can put them back on the original outlet and they will work. Unplugging & replugging on same outlet is not enough. I have seen this on at least 5 machines so far, with independent confirmation. We can narrow the 'fix' to plugging into an outlet of a different phase (there are 3 separate 120v phases powering the room). The symptoms vary from no powerup, to frozen at the BIOS (depends on motherboard make), etc, but consistently, switching to a new phase fixes them. I tried the 'unplug-wait-&-replug' cycle, to no avail. Using a new outlet w/ a different phase is the only solution. Any theories? I assume the new phase is causing something to 'reset', but what? I can provide more details, but I am wondering if anyone has seen this before? I am completely and absolutely stumped. Our power is healthy, lightly loaded, evenly distributed and the power strips are new. I know I should have at least a simple UPS, but this mystery is causing me to lose sleep."

Comments

Check the Neutral To Ground

[getagrip]

We just got a 30 amp circuit installed for a 3kv ups. The UPS once powered up had a "check building wiring" light on the back that came on and stayed on. The cheapy circuit tester indicated that the wiring was fine along with an electrician verifying that all the wiring from the panel to the outlet was correct. One more symptom of this area is that light bulbs blow out much more than normal, although the PCs have not had anything unusual happening.

We had the original electrician who installed the line back out to test. His voltmeter was showing about 20-30V between the neutral and ground. According to code (IANALE), these lines are supposed to be connected at the panel. Apparently without this connection, the two sides coming off the transformer can float in the voltage which may have been responsible for the light bulbs blowing. Once the neutral and ground were connected, the wiring fault light went out on the ups and everthing has since been fine.

SHORT RESPONSE: Have a licensed electrician check out your circuits.

Phase balance?

[redelm]

Three-phase power is kinda screwy and needs to be kept balanced. Is the high-drawer that justifies three-phase running during these restarts? If one leg is overloaded, it can get dragged down and the return path overloaded. Check your neutrals, grounds and voltages.

Drain the Power Supply safely.

[cravey]

I've run into this type of issue several times. The issue is'nt so much moving the plug, it's that the MB maintains power for up to a couple of minutes after the power is lost. If the Power glitched, the MB may be in a non-useable state. The way I solve the problem is this:
1) Unplug the Power supply.
2) Hold down the power button (on the front) for 10 seconds.
3) plug in the power supply
4) Turn on the computer.

I solve this issue with most of my systems by connectiong them to a UPS. Some crash on their own so often that they're not worth a UPS.

Re:Hmm

[Neon Spiral Injector]

My machine at work gets wonky after a power blip. It will not power up until I remove the plug from the wall (or flip the main switch on the PS) and hold the power button on the front of the case. I can actually hear a little squeak from the power supply that lets me know it is ready to go.

Re:As an EE student, my professional opinion is:

[lupinstel]

Actually I believe that it is Gremlins which are typically the cause of machine troubles. I even have a wikipedia link to back it up. http://en.wikipedia.org/wiki/Gremlin

The List

[Ed Almos]

1) As other have pointed out, bad grounding on one or more phases.
2) Bad neutral on one or more phases.
3) Voltage drop on one or more phases.

For the first three get an electrician out, don't mess around with three-phase power.

4) Electrical noise on one or more phases, this may not be caused within your computer room.
5) Equipment connected on different phases affecting each other, for example a printer on phase A and a server on phase B.
6) Borderline power supply in a machine affected by one or more of the above conditions.
7) Faulty power strip(s).
8) Incorrectly wired plug(s) or socket(s).

Ed Almos