Electricians/IT experts: Can you solve this mystery?

November 14, 2012 3:16 PM

My computer cycles off without warning, and it's on a battery pack/surge protector UPS. What gives?

I am in the USA, in a regular two-story office building, on a regular 120V duplex outlet. On this outlet, there is a fluorescent lamp with a 13W ballast, and a UPS/surge protector (APC Back-UPS ES 500). On the UPS, I have a regular desktop PC and two regular 19" LCD monitors. About 0-5 times per week, without any warning or any precipitating factor that I can see (neither I nor my neighbor are bumping the table, the cables, the wall, anything), the UPS will beep and the computer and monitors will turn off, then back on. I lose whatever I had open on the PC; isn't this what a UPS is designed to prevent? Oh, and when this happens, the fluorescent light attached to the other outlet in the duplex is fine; no dim, no surge, nothing. Just carries on brightly.

I have switched out the UPS with another (same model), and it happened again. Then, I switched out the PC (old gateway for new dell), and it happened again. The only thing unchanged at this point is the monitors and the cables attached to them... and the wiring in the wall.

I am not an electrician, but we've called one to check out the building wiring. I'm also relocating desks. In the meantime, I'd appreciate any thoughts for other avenues of investigation. Thanks!

posted by Chris4d to computers & internet (13 answers total)

Subtract the UPS from the equation-- does it happen?
posted by Sunburnt at 3:30 PM on November 14, 2012

Here is a simple test. Make sure that computer and monitor are connected to your UPS and are powered on and running. Disconnect the UPS from the wall. Which of the following happens:

1. The UPS starts beeping, but the computer and monitor run successfully from the UPS for a couple of minutes until the UPS shuts down.
2. The computer and monitor go off as soon as you disconnect the UPS from the wall, possibly with a single squawk from the UPS.

If (2) happens than the problems is either that the load from your PC and monitor exceeds the load capacity or your UPS or the sealed-lead acid battery in your UPS has failed (UPS batteries need to be replaced every two or three years).
posted by RichardP at 3:36 PM on November 14, 2012 [2 favorites]

That used to happen to me. It turned out to be my power supply. But with 2 pcs I got nothing.
posted by Max Power at 3:57 PM on November 14, 2012

In the spirit of process of elimination, have you tried seeing if it happens if you plug the computer into the "surge protection only" receptacles on the UPS?
posted by Dansaman at 4:13 PM on November 14, 2012

Did it ever work? Have you ever tested it? Unplug the UPS during normal operation and see if it will power the load you have attached. it will probably do the exact same thing. If it does, either the battery is bad, or the whole unit is shot.

If it runs, the UPS is still probably bad.

UPS units shouldn't beep when things attached to them turn off.
posted by gjc at 4:57 PM on November 14, 2012

I used to have this exact thing happen to me. There would be some minor power glitch, the UPS would say, "Oh. Hey there, Betelgeuse, let me help you out and take over your power needs for a moment." What the helpful UPS didn't know was that his battery was stone cold dead and as soon as he tried to supply power, the computer would instantly turn off. Replacing the UPS with a simple surge protector solved the problem. Of course, replacing it with a new UPS (or replacing the battery in your existing UPS) would be even better.
posted by Betelgeuse at 5:19 PM on November 14, 2012

What is the UPS model and capacity?
posted by Good Brain at 8:43 PM on November 14, 2012

Download and install RealTemp.

Does your CPU temp get up in the 90^oC's?

You have an overheating problem. Either fans are gunked up and not running or your case is gunked up and not allowing airflow.

Alternatively, I recently upgraded my work laptop's VirtualPC/XP and running almost anything else while that's running fullscreen on a 2nd monitor causes the laptop to blackscreen (due to prolonged 100%+ CPU clockspeed/useage).
posted by porpoise at 9:04 PM on November 14, 2012 [1 favorite]

I also came in to suggest temperature/airflow/fan issue as noted by porpoise.
posted by mikepop at 6:53 AM on November 15, 2012

Your piddly little 300 watt UPS does not have an adequate power rating to supply a PC and two monitors. Get a much gruntier one. 1500VA should be fine.
posted by flabdablet at 7:11 AM on November 15, 2012

OK, so I narrowed it down to this: with the PC and both monitors plugged in to the UPS, unplugging the UPS would cause them to turn off (battery overloaded). With the PC and only one monitor plugged in to the UPS, unplugging the UPS would cause it to beep and switch to battery and keep running. So I still don't know if or why the power from the outlet randomly drops out, but now at least I can be fairly certain that the UPS will keep me running. Thanks everyone for good answers!
posted by Chris4d at 7:29 AM on November 15, 2012

Have you checked the health of the batteries? They need to be replaced from time to time, check with the manufacturer, there is likely an exchange process that you can initiate with them to get new batteries while recycling the old ones.
posted by kuppajava at 8:54 AM on November 15, 2012

now at least I can be fairly certain that the UPS will keep me running

...as long as the PC doesn't happen to be doing something computationally or graphically intensive when or shortly after the power goes down.

A 300 watt UPS really is nowhere near adequate to back a modern desktop workstation. Get a proper one.
posted by flabdablet at 6:07 PM on November 15, 2012