c7000 blade Chasis single phase -vs- 3 phase

[Benjamin Boone]

We are having some internal debate over whether to order a single phase or three phase c7000 enclosure.

We already have 3 phase power at the rack with a PDU that breaks each phase into single phase sets of plugs. Page 43 of this design document:
http://h20000.www2.hp.com/bc/docs/support/SupportManual/c01038153/c01038153.pdf
mentions a PDU with 3 phase inputs, and 3 sets of "single phase" output plugs. It suggests the load should be balanced across the phases.

If we already have an equivalent PDU in place, is there any efficiency to be gained by ordering a c7000 with 3 phase inputs and having our rack rewired?

Since both single phase and 3 phase versions of the enclosure use the same power supplies, doesn't the 3 phase version of the enclosure essentially do what the PDU does?

Thanks,
Benjamin

[JKytsi]

Since both single phase and 3 phase versions of the enclosure use the same power supplies, doesn't the 3 phase version of the enclosure essentially do what the PDU does?

Yes it does. We are using only 3 phase versions (less cables / cheaper).

[Adrian Clint · Accepted solution]

Ben,

There is an advantage to using the 3 Phase PDUs... if you have many enclosures/racks you can balance the phases and reduce power consumption.

If you put too much equipment on a single phase then you can unbalance the phases which is not best for power efficiency at your supply of power.

So what you do is.
1st enclosure
PSU 1 & 4, - Red Phase
PSU 2 & 5, - Blue Phase
PSU 3 & 6, - Green Phase

2nd enclosure
PSU 1 & 4, - Green Phase
PSU 2 & 5, - Red Phase
PSU 3 & 6, - Blue Phase

2nd enclosure
PSU 1 & 4, - Blue Phase
PSU 2 & 5, - Green Phase
PSU 3 & 6, - Red Phase

doing this ensures that if you select dynamic power in the OA then you spread the power consumed across all phases.

Using the 3-phase enclosures would mean that the power is not balanced, as its fixed which PSUs connect to which phase.

[JKytsi]

But when You think about the price of the PDU ....

[Benjamin Boone]

All, thanks for your replies.

Adrian mentions the 3-phase c7000 has a fixed configuration in how the PSU's are connected.

Would like to know if there is a schematic or specs of the 3-phase chassis AC unit . .. how are the PSU's connected to the phases of a 3-phase feed?

Thanks,

Benjamin

[Adrian Clint]

Ben,

On the 3-phase enclosure
PSUs 1 & 4 connected to one phase
PSUs 2 & 5 to another
PSUs 3 & 6 to another

For one customer we supplied 7 blade enclosures from six 3-phase PDUs. The total power was with the rated amount for the 32A connector...
3 on 2, 3 on 2 and 2 on 2
Use the blade power sizer to check for your environment
http://h71019.www7.hp.com/ActiveAnswers/cache/347628-0-0-0-121.html

See the HP picture attached. See how each coloured phase (White, Light Grey or Dark Grey on this PDU) is spread between PDUs in different positions. eg not all White go to PDU positions 1 & 4.
This pic is from the c7000 cbt.

[Benjamin Boone]

Thanks for the latest reply. I'm still more curious about how the c7000 3-phase power unit connects to the power supplies.

Does the 1st power cord connect to PSUs 1, 2, and 3; and the 2nd power cord connect to PSUs 4, 5, and 6?

If I have 2 3-phase circuits and want fault tolerance across the circuits, how does the 3-phase enclosure handle this? Say I lose 3-phase circuit 1, which PSU's still have power with a 3-phase enclosure?

Thanks,

Benjamin

[karim h]

This is a little off topic but have you considered using DC power? Your datacenter has to be equipped to deliver it in it's native form but there is new research to suggest that it can be up to 20% more efficient...

[Adrian Clint]

Ben,

On the 3-phase enclosure you have two cables exiting the enclosure with 3-phase connectors. The cable on the left connects to the left three PSUs and the one on the right .... the right.

That covers you for the loss of a cable.

See the picture