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In our data center we are going to be moving all of our dual power supplied IBM servers (auto sensing 110/220) from an outdated 110 system of dumb power strips to an updated in rack 0u 220 monitored PDUs.

In order to do this we will either need to power down each server one by one to move both power supplies from the 110 plugs to the 220 plugs or move each psu at a time which means having half in 110 and half in 220 for a few seconds while we move the wires. Has anyone ever done this? I have read on a couple data center blogs that it's not a problem, found a support thread on HP about their servers saying it's not a problem, but still want to ask if anyone else has done it. Being able to use different voltages will reduce the time needed for the conversion from a year to instead several months as down time for every single system will not be required.

Again, these servers have dual, some quad, independent hot swappable power supplies that auto sense the incoming voltage and adapt accordingly.

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POWER IT DOWN DUDE!!!

Seriously don't even think of running them separately, first of all their phases will be out no matter what you do - basically that's the same as crossing the streams - not advised.

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Output may be DC but input's not yet they'll share a common earth, therefore phase-shifts create spikes >220v - electrics-geek-ahoy! –  Chopper3 Jun 16 '11 at 15:30
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earth may in general by a universal common but it can be heavily affected 'in-box', I'm not kidding, don't mix two phases, three is fine as they're 120 degrees out of sync - hence the whole need for three phase, there's no such thing as two phase. You have to be very careful with not mixing PDU phases, people die. –  Chopper3 Jun 16 '11 at 15:36
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How about this Jason, try it with a multimeter attached to the server chassis. –  Chopper3 Jun 16 '11 at 15:46
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@Jason - Chopper3 is correct here. I speak from having had the experience of watching someone go stiff when a chassis went hot. You CAN do what you're suggesting and probably get away with it, but it's a BAD IDEA, potentially a lethal one. Take the outage window on the hardware rather than risk taking one on yourself. –  voretaq7 Jun 16 '11 at 15:51
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ad-hominium - sounds like a new element. –  mfinni Jun 16 '11 at 16:54
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