Customer question on "Power Save"

[chuckk281]

David was looking for "Power Save" advice:

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A customer manages power through their PDU and is complaining that the “Power Save” Feature in the OA is causing problems.  I assume the customer is talking about dynamic power capping, but please correct me if im wrong.

Will turning this feature off have a negative impact if they are already managing power by other means?

When changing this feature, is there any need to plan for downtime?  Should this be done during a maintenance window?

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From Monty:

The Onboard Administrator enclosure Dynamic Power Savings feature can be enabled or disabled at any time.  This feature is designed to monitor the power supplies and automatically run those supplies at the highest efficiency by placing one or two pairs of power supplies in standby as the power supply loading decreases and placing pairs of power supplies active as the power supply loading increases.

From Chris:

Yes, the change can be made online.  Some facilities folks can get concerned about Dynamic Power Saver because we’ll take one or two power supplies per circuit and put them in a standby state.  This phase imbalance can be reduced if 3 chassis are on each circuit and the power cables to the single-phase input are wired correctly.  By default, PS #6 and #3 are put in standby, resulting in two power supplies and therefore phases taking the entire load.  If you’re using the 3-phase input module, the same can occur, essentially once power goes into the module we “untwist” the phases.

Hope it makes some sense.

And from Mark:

Also, see page 43 for a wiring example in this doc:

    http://h20000.www2.hp.com/bc/docs/support/SupportManual/c01038153/c01038153.pdf

    The following figure shows an example configuration of three c7000

    enclosures connected to HP S348 (part number AF916A) PDUs. This specific

    wiring configuration is used to ensure that the load is evenly balanced

    across all three phases of the incoming circuit, even with Dynamic Power

    Saver enabled.

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Lots to consider. With high-efficiency power supplies that work best under full load some things are done to try and keep that condition as optimum. Any other comments or questions?