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During a recent power fialure our rack mounted UPS failed after 17 minutes( design time 30 minutes). How often should a rack mounted UPS be tested?

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define "failed" ? – Sirex Oct 20 '11 at 11:42

Do you meant that it failed or it ran out of power, because there's a big difference between the two. If it ran out of power than that's due to the load on the UPS. The runtime is based on a particular load and the more you go beyond that load the less runtime you'll have.

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Ask the producer. I would suggest making complte tests every 3 months PLUS after larger changes in the rack (nwe machines, new wiring etc.). Also keep maintenance intervals on batteries.

WHY did it fail? Bad maths (i.e. moer machiens in than originally designed for?)

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We do it once a month or whenever we change something in the rack, but it's really up to you. There is no right or wrong answer here.

Take a few thing in to account here:

  • Can the UPS hold the load?
  • How many times does a power failure occur?
  • What has the producer to say?
  • How important are the servers?
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The UPS we have has a self testing system where it will monthly go thru and do a simple test on the batteries (with automatic notification) I think it has a power out situation for a very small amount of time then sees how much power is drained, then multiplies it out to make sure that it is still good. Beyond that I would say it depends on the SLA which you are trying to reach. I have worked at companies where every 6 months would be fine. I have worked at others where Quarterly was the standard. What is the cost of failure?

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