UPS - single points of failure

Jack Coats jack at coats.org
Fri Dec 1 16:08:03 EST 2006


I worked at a place where we had dual UPS available to all servers.   
We made a box with an AC relay, that stayed pulled in to power single  
power supply equipment.  If the UPS failed to the AC relay, it dropped  
out and connected to the secondary power source (second UPS).

It was a tripple pole double throw AC relay, with about 10A AC rating  
or more per contact.  Put MOVs across all the contacts, and torroids  
on the AC power lines going to the machines as a help.

An easy hack, but a hastle none the less.

When the power failed on the 'primary' there was about a 1 cycle  
(1/60th of a second) or less 'outage'.  Machines with good power  
supplies handle that easily.


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