esx servers and 3 phase power

[pauliew1978]

Dear all,

Firstly apologies for posting this here but a.) i couldnt find a forum for off topic bits and b.) I know you guys are a wealth of knowledge!

At my company we have just installed three phase power. It is coming from a huge ups downstairs up to the server room. At the moment all the servers are connect on to the mains (via small ups's). We have pdu's now on the rack that are connected to the three phases. What i want to know is can i connect an hp dl380 with 2 redundant power supplies to 2 different phases of power through the pdu's

thanks,

Paul

[weinstein5]

I believe you can but this question is better aimed at HP since they need to support that in a dl380 - the type of power feeding the server running ESX does not matter -

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[chrisfmss]

Yes you can. Your PSU is converting AC current to DC current witch has no phase. You can also run 1 PSU with 110 V and the other one with 208 V.

[Leafy911]

Hi Paul

I DON'T think this is such a good idea from a safety point of view. From a UK based perspective if you connect your host to 2 different electrical phases this means that you would have up to 415 volts in your chassis/cabinet. Should anything go wrong electrically then I would not like to be standing near by.

I believe this might be upto 208 Volts in the US which might be more acceptable to survive from in an incident.

Regards

Leafy911

(Dont forget you recieve points when you award points)

[chrisfmss]

Don't be fear of that. With 3 phase power, you need to balance load between each phase. PSU are 1 phase only, it convert AC to DC, DC current has no phase because is linear. If you look for 3 phase PDU, look at HP http://h18004.www1.hp.com/products/servers/proliantstorage/power-protection/power-distribution/power...

[pauliew1978]

Hi Guys

thanks for your replies. I have spoken to HP and they said yes it is fine but they can't give me a document stating it. We have the 3 phases. Each phase goes into a pdu. From the pdu then into the redundant power supply of the server. pdu1 (phase1) into power supply1 and pdu2 (phase2) into power supply 2. I am in the uk btw

you would have thought there would be a definitive answer somehwere on the web or with HP!!!

surely someone out there in the uk nows the answer to this

[Leafy911]

In all the datacenters I have worked in you never mix the phases. Of course if you have a power conditioning unit such as a 3 phase capable PDU then thats ok. Keep in mind that you are still initially feeding the rack with 415 Volts from the input side of the PDU. I have used static transfer switches in the past which have been mounted under floor with 20 A commando connectors; these in turn then fed in rack PDUs.

Regards

Leafy911

(Dont forget you recieve points when you award points)

[JoJoGabor]

I was always told that this was dangerous due to the high voltage difference, but then HP Blade chassis can be configured with 3-phase power without any safety issues.