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UPS works in one office but not another.

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Actually, I find it hard to explain why the UPS works in the first office.

Most UPS systems will not switch over to battery if you simply pull the plug. As part of safety circuits, they require at least the AC ground if not the AC neutral connection on the input in order to turn on the output with battery power.

Instead of just pulling the plug to test the UPS, plug it into an outlet strip and then switch off the outlet strip.

Since most outlet strips only break the hot side connection when you turn them off, the ground and neutral connections are still present and the UPS should switch over to battery.

About the only thing that would explain why the UPS works as described in the one office is that you must have an extra ground connection to the PC chassis. Perhaps fully shielded Ethernet cable that is grounded back at the switch or server.