When one of the two power supplies to a server is lost does it need to be manually 'reset' or will it automatically start working when power is restored. I can find no documentation about this so I would be very grateful if anyone can help me. The servers I am using are Dell Poweredge 2950, 2900 and 2800.

The reason I'm asking is that our servers are currently powered using standard household extension leads and I want to change then for the more reliable PDU's. I would like to be able to do this without having to switch off the servers.