Re: Dual power supply draw?

michalwd1979 michalwd1979 at
Mon Mar 23 00:51:33 CDT 2009

My experience from PE2850 with single or dual PSUs:

The load on different PSUs is balanced. Each draws more or less the same. However each PSU needs about 40-50W just when it is connected to power line. So on stand-by you need 40-50W more power. With power-on it is a bit worse - efficiency of partially loaded PSU is lower. In my case server with 2 PSUs draws about 80W more power then with 1. Anyway efficiency of the PSU is bad, really.

There should be no problems with separate circuits if the ground wire is connected right. Internally the PSUs are isolated, each has separate PFC circuit and so on.

I've seen somewhere at Dell web page with on-line power calculator. You select server, configuration, ect. and it gives you power consumption. I can not locate it now, sorry.


> If a server has dual power supplies, and each is connected to a
> different power feed, do the PSUs pull from both at the same time, or
> do they pull 100% from one, and then if there's a failure switch to
> the other?
> Also, do you see any other problems with have each power supply on a
> separate circuit?
> I'm looking at both PE1950 and PE2950, and trying to spec out the power needs.
> Thanks
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