[ale] OT: question about replacing batteries in a APC UPS

[James P. Kinney III]

Mike: Great instructions. An easier method is to test with on of the $13
at Home Depot outlet testers. It has 3 lights that indicate all good,
open ground, open common, reversed polarity (hot swapped with common) or
fatal nightmare of hot swapped with ground (this will KILL a UPS). It
can't test the ground to cold water pipe path though so keep that test
around.

On Wed, 2005-12-21 at 10:30 -0500, Mike Harrison wrote:
> Courtney asked:
> > What and how do the testers reveal ?
> 
>   Disclaimer: This is potentially dangerous, don't touch anything metal, 
>   don't wear shoes with metal tacks in the heels.. don't.. (it's a long list)
> 
> 
>   Good question. Set to AC Volts, (Alternating Current) you can test an 
>   outlet as follows:
>        
>      The outlet should have 3 plugs.. 2 slots, one larger than the other
>      and a round hole:
> 
>              [ |
>               o      
>      The larger slot on the left is 'neutral' the smaller one on the right
>      is 'line' or 'hot' and the small circle is 'ground'. 
> 
>      In a perfect world. 'hot' has a sine wave of approximately 117 volts 
>      calculated as a 'root mean square' average of alternating electrical
>      potential. You want to make sure it's there, and that 'neutral' is 
>      at 0 volts, as is ground.
> 
>      So with your el-cheapo voltmeter, stick the probe tip black lead in 
>      the 'neutral' and the red lead into 'hot'. You should get 110 to 120 volts AC.
>      
>      Then move the red lead into 'ground'. You should get 0 volts. Maybe 0.5volts. 
>      but it should be 0. Ground and neutral (in most systems) tie into the 
>      same place back at the breaker panel.. they should have the same 
>      potential. 
> 
>      Then move the black lead to 'hot'. You should get 117 volts. If not, 
>      your ground is open, not grounded. Very common problem in houses. 
>      The purpose of the ground wire is safety. The metal chassis of a 
>      device uses the ground wire as a redundant path back to the breaker 
>      box. If there is 'leakage' via EMF from high voltage electronics
>      or transformers or.. (lots of things), it should drain down the
>      ground wire. If it is 'open', a shock potential from the device may 
>      exist. Grounds are also a catastrophic failure protection means. 
>      If a power supply 'melts down' and shorts to ground, the current 
>      should travel back to the break panel at close to 0 volts, and if the
>      current level is high enough, allow the breaker to trip. 
> 
>      Last test: paranoid mode. If you have something that is grounded 
>      handy, like a metal copper pipe that goes into the earth, large metal 
>      structural supports.. etc..  - Measure between it and the Ground and 
>      Neutral and make sure it's 0 volts or really really close to it. (.5volt?)
>      and measure between the natural earth ground and 'hot' you should get 
>      110-120 volts.
> 
> So.. If all is good, you have a properly wired electrical outlet, there is 
> one good 'idiot check' you can make on your UPS:
> 
>      Set your meter to Ohms. A measure of electrical resistance. 
> 
>      With your UPS unplugged, put the black lead on the round pin. 
>      then put the red volt meter lead on any metal on the case. 
>      It should be under 1 ohm. Now move the red lead to the round
>      plug hole on the outlets. Same thing. 1ohm or less. 
> 
>      On some UPS's you MAY be able to do this with 'hot' and 'neutral' on
>      the outlet to the cord plug end for hot and neutral, depends
>      if it's using a relay for power pass through and what it's position
>      is when 'off'. 
> 
> Plug your UPS in and turn it on. Repeat the first set of steps for the 
> outlets on the UPS.
> 
> Last test. turn off the power to the UPS, but keep it plugged in (so 
> ground is still attached) so that the UPS is running on batteries. 
> It may work better if something is plugged in and running off the UPS
> as many of them require a load. Then do the tests again. You will get 
> something approximating 110-140 volts from neutral to line on the UPS, it 
> depends on the quality of the site wave your UPS generates. It may read 
> high if there is no load or a very small one, and/or it produces a squarer 
> waveform than normal line power.
> 
> ----------------
> 
> Honest disclaimer: I've done these tests and more.. but I usually 
> just plug them in and see if they work. :)  - I did check out the wiring in my house
> when I bought it for proper polarity of the pins, and good grounds.. 
> and again when I put in the generator and UPS's.. but I'm insane.
> 
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-- 
James P. Kinney III          \Changing the mobile computing world/
CEO & Director of Engineering \          one Linux user         /
Local Net Solutions,LLC        \           at a time.          /
770-493-8244                    \.___________________________./
http://www.localnetsolutions.com

GPG ID: 829C6CA7 James P. Kinney III (M.S. Physics)
<jkinney at localnetsolutions.com>
Fingerprint = 3C9E 6366 54FC A3FE BA4D 0659 6190 ADC3 829C 6CA7
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