[G4] APC UPS problem on OS X

[Brooks Graham]

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On Friday, May 16, 2003, at 12:40 PM, josh hough wrote:

> When I test the system by unplugging the UPS,

Here's a lesson I learned the hard way on some *very* expensive Sun 
gear: don't test a UPS by unplugging it from the wall.  (I learned this 
by watching my customer do this - I was an innocent bystander.  No, 
really.)

If you read the manual that came with your UPS, it says (mine did) most 
emphatically *NOT* to test the UPS this way.

The reason for this is that you're lifting the ground along with the 
power.  In a real power outage situation, you'd still have a valid 
ground. If your equipment has a three-prong power cord, then it was 
designed to be grounded.  "Bad Things Happen(tm)" when the ground is 
bypassed.

One example is hard drives - they don't operate in a vacuum, there's 
air in there.  Spinning disc in air creates static electricity which 
normally would be drained via a chassis-to-earth ground.

What I do now is test with a switched outlet strip placed between the 
wall outlet and the UPS.  In the strip that I have, the switch simply 
lifts the hot lead, leaving the ground in place.

HTH


- -
Brooks Graham
brooksgraham at mac.com
http://www.brooksgraham.com/

"Hey, it's Unix - I know this!"
         - From the movie "Jurassic Park"

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