the client bought a ups recently and it failed.

The power went off the clients critical supplies and caused a lot of damage.no one knows why. the ups has an alarm built in to it but it is situated in the main switch room where no one can hear it.

during the time of the incident, the normal supply did not fail.

any ideas?

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keithredpath

Soeone doing testing on it and wasnt aware of the ups?

"Topic Summary: what has went wrong"

Sounds like the UPS went wrong! After a couple of failures recently of new simple switches that fail to do so... the failure of something a tad more complex like a UPS is no surprise to me.....

The failure could be for many reasons.

The UPS may have been selected wrongly for the duty and installation topography. What is the critical supplies load, is it IT equipment, how many kW, power factor of load. Is the UPS a static (battery) type, or a rotary type.

It appears an unusual fault because nearly all UPS systems I have met fail to internal Mains by-pass without interuption of the critical supplies.

Can you indicate what the design criteria was applied to the resilient electrical supply system (N+1 maybe)and what design criteria were used to select the UPS.

I will get more info next week.

the ups supplies it equipment.

it is rated 4.5 kva

the neon indicators on the ups spur units went out indicating a loss of power but the mains supply was ok.

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keithredpath

Caught out with a problem like that some time ago, organised a switch down at a large store, all the checkouts were on the ups system. Inspection was before the store opened for business. Switch off all switchgear for internal check and size of fuse links, overheating etc. On switch on unknown to the experienced tester, a 32amp HRC mains fuse had blown in the switch-fuse for supply to UPS panel. The battery supply lasted about an hour operating the cash registers then crash. In addition, trouble. Well you should check if the red or green lights were on the UPS, but you have to learn the lesson the hard way do you not.
I think myself Keith that with a mains outage blackout, on restoration it is a slightly softer start than would be if you suddenly turn on and off a supply main switch with the power on ,the inrush current could blow a fuse, so maybe you should look at that (as what happened in the above case ).

http://www.sinetech.co.za/powe...verload%20capacity.pdf