Home Forums Strange problem yesterday

Here was a troubling issue. Yesterday, we had a brief partial power outage which shut off only several outlets...including the "main pc." When power was restored, the front desk computer could no longer activate AC unless you signed onto the Adminstrator account.
I really don't like the receptionists/MA to be on an Admin account.

After a few hours with AC tech support, we thought we had it fixed. Then we attempted a final reboot to make sure it would still work after rebooting.

Well, when the pc rebooted (this is the front desk pc) I got a "BLUE SCREEN" that mentioned page map error. Then after 2 seconds, it would reboot. It would continue this routine. Eeeeek!

As I thought how I should have just let the MA use the pc as Administrator, the 2nd Lvl AC Support came on. He eventually said I'd need to re-install Windows. I wanted to hit the roof. Then I remembered about "Restore Points" asked if using a restore point would work. He said "it might."

Found a restore point from 3 days ago. 5-10 minutes later the PC was operating just fine.

Lesson: Restore Points are your Friend.

You probably never lose power in NYC like we do in Florida (like daily!), but get get a power backup for that main computer. For around $50, would save some heartache.

You are right. we had another one today. Something is overloading a circuit in the office.

Make sure backup battery gives true sine wave output. I had backup battery that looked fine until needed. My server is picky about its power.I got new unit and actually pulled plug to test. I sleep easier now.

Pulling the plug to test the backup battery is dangerous. Removing the ground can cause damage to the components. Flip the switch at the breaker.

You should check how many watts you need and get a UPS/AVR combo like this: http://www.amazon.com/CyberPower-CP1500PFCLCD-1500VA-900W-Compatible/dp/B00429N19W.

I just installed it on a DVR and back office computer. Pure sine wave. Gives me 30 minutes run time. Since I only use half that output.

There are better, more expensive ones. That will give you more time. APC is known for their quality commercial UPS's.

Hi Sandeep,

"Pulling the plug to test the backup battery is dangerous. Removing the ground can cause damage to the components. Flip the switch at the breaker."

Please elaborate on this. AC connection is broken before grounding connection is broken. When running on batteries, why is grounding important?

Not trying to give you a hard time, just trying to understand this.

Thanks. Gene

When you unplug a UPS, it's still powered but it has a floating ground. Which can prove to be very dangerous for devices that require grounding and you. Also, pulling the plug does not usually emulate what happens during a power outage.

http://en.wikipedia.org/wiki/Floating_ground

Also check out this article, specifically "Test Under Operating Conditions":
http://www.experts.com/Articles/How-To-Test-Redundant-And-Backup-Control-By-Arthur-Zatarain-PE

Hi Sandeep,

I looked at those references, I'm still a little confused.

I think the most valid point is loss of the neutral interfering with voltage reading. In case of undervoltage or overvoltage, you would need a complete circuit to measure this. But our most common scenario by far is loss of power, the UPS appears to sense this without needing a neutral.

In terms of safety, I'm not sure the floating ground is a concern.

When using commercial AC power, one leg (the neutral or "groundED") connector is physically tied to the earth. This is done at utility poles, and at the circuit breaker panel in your home or office. This is primarily for lightning protection, if overhead power lines get hit, this provides a path for this voltage to get back to the earth with (hopefully) minimal damage to connected cables or equipment.

But another effect of this is that anything connected to the earth has half of the electric circuit completed. This would include metal water pipes, and it would include other electrical equipment that is grounded. So if, say, a computer case were to become electrically energized, and you were on a concrete floor, electricity would have a complete circuit from the computer case, through you, into the ground. Similarly, if you are in your kitchen, and a toaster case became electrically energized, and you touched this toaster while touching a water faucet, the circuit is completed through you.

But a UPS, running through batteries, is a totally isolated system. It is not tied into the earth. So I could be standing on a wet concrete floor, and touch either side of the circuit powered by a UPS, and not be shocked. If one were to ground the UPS, then the circuit would be completed and I would be shocked.

A floating ground is of great concern when commercial AC power is involved.

Please let me know if the above is not accurate.

Thanks. Gene.

Well, I am glad they are known for something good. I have always known them for failures. I would rather use a couple of AAs.

Most systems are not completely isolated. Think about all those network cables. Maybe everything isn't on battery power. While it is unlikely that something may go wrong, UPS are designed with the assumption that the ground is intact. If that ground were to come unplugged and something shorted, the electricity may have to find another course to the ground. Maybe you or something else you like.