ups draw with dual power supply on Intel servers

[Anonymous user]

Hi all,

I have conflicting information on wether you load your UPS to only 50% when you have dual power supplies on an Intel server going into 2 UPS's.
I'm told that the new servers load both power supplies the same and therefore if one fails then the only increased power needed is minor to increase the speed of the fans i.e. each power supply draws .2kw when one fails then the power supply remaining will only draw .21kw.
If the above is correct then it's possible to drive the usage of the UPS's up to 80-90% mark.

Does anybody know the answer?

[BillP]

Hi Steves,

"each power supply draws .2kw when one fails then the power supply remaining will only draw .21kw."

So , if you turn off the first PSU, then the remaining one will draw 210W only, right? Is that promised by the manufacture ( Intel) of the server?

I heard about different servers and scenarios. Please make sure that the specific server will work as you expect.

[Anonymous user]

I have since tested this on a HP Dl380G5 and the measurements are below:

PS1 PS2 PS1 + PS2 Single supply % of original load single supply

0.6 0.75 1.35 1.05 77.78%
0.58 0.73 1.31 1.12 85.50%
0.65 0.75 1.4 1.22 87.14%
Average 83.47%

[BillP · Accepted solution]

Steve: Hopefully your own calculations show that you shouldn't be loading either of the feeds past 50%.

The reason that you are seeing 77 to 87% on a single PS is that there are some "redundancies" lost when you lose a power supply, namely the heat loss/capacitor storage/fan power of the downed PS itself.

If you really wanted to push the razors edge, you could push past 50% per side and rely on the reductions noted above to keep your remaining UPS under 100%. The question then becomes why? 🙂