Three phase is more efficient than single phase.  You may save on electric
bills but I am not sure.  Also, I think if you take a short power hit on a
single phase unit (without battery backup), you have a higher chance of the
box going down than if you were to take a hit on a 3 phase powered unit.  

Here is a link that talks about efficiency
http://www.windstuffnow.com/main/3_phase_basics.htm

> -----Original Message-----
> From: The IBM z/VM Operating System [mailto:[email protected]] On
> Behalf Of Brian Nielsen
> Sent: Friday, May 01, 2009 11:42 AM
> To: [email protected]
> Subject: z890 power: 3 phase vs 1 phase?
> 
> We're looking at power options for a z890 in a backup datacenter.  The
> Installation and Planning manual says that the z890 can run off either
> single phase or three phase power.  The site cost for a three phase
> supply
> is more than the cost for a single phase supply.  I understand what
> single
> and three phase power are (thanks Google), I just don't understand, and
> havn't been able to find, what the trade-offs/compromises are other
> than
> the cost.  This leaves me unable to evaluate the cost benefit of 3
> phase
> vs 1 phase, and hence make a recommendation.  Any help would be
> appreciated.  Reference to source material would be great.
> 
> Brian Nielsen

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