I am suppose to teach a class on why you should use AC power or DC power for your network... the main issue I am having is I have no idea why you should use DC power for your network... I have seen the distance argument, but I don't think that really applies here as most of the gear is in a very small room. I know there must be a reason as they have DC power supplies for all the equipment.

It doesn't seem to be anything they have papers written on either

Any ideas?

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I've only ever seen DC used as a redundant, secondary power source. Primary power is always AC in my experience.

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I'm no power guru but I had always been told that DC was more consistent and cleaner than AC. We see a lot of DC in telco environments.

I skimmed through this paper a bit. Looks to be a good read on it.
http://www.apcmedia.com/salestools/SADE ... _R6_EN.pdf

This. For some reason I have been interested in the AC vs DC power in the DC for a few years. Honestly its going both ways. I read WPs from companies that clam AC is more efficient and reduces ROI and then I will read something else a few months later stating the reverse.

Myself I love DC. racking and cabling is a ton cleaner and compact in the rack.

Dig around in http://www.techtarget.com/ and http://www.datacenterknowledge.com/. Im thinking these are the two Im seeing the most WPs from.

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Thank you
The other one supported me in the "DC... that's dumb" stance I have... but we use DC so I assume I shouldn't teach the class on why what we do is a bad idea

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Thanks, I think that should be enough for my class on site design... assuming my assumption on what our sites look like is correct

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Ahh poop... I think I am getting up and teaching about a holy war and pooping on both sides since we use AC in some places and DC in others

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Haha I'm all for knowing less about the power. Seems I have to know more about it the higher up the tech chain I get.

A few things about DC vs AC. (thinking mainly about -48Vdc and not fancypants Facebook stuff)

UPS are not needed. You can run your load directly from battery without needing an inverter. You just need a rectifier to convert from an AC input & charge batteries. Same idea as double conversion UPS, but skip the conversion back to AC, therefore more efficient, and more efficient use of the stored energy.

-48V is still considered low voltage, so it's not subject to the regulation that is required for typical AC installs.

You can feed a DC bus from multiple sources and not have to worry about synchronization.

Fewer components to fail in equipment (no need to do AC-DC conversion inside your gear)

DC cabling takes a lot longer than just plugging something in using an IEC connector.

DC cabling requires larger conductors. Add distance and get even larger conductors. You want your equipment close to your source. This often means that your batteries will be in the same fire suppression zone as your other equipment, which can be bad when a cell develops a dead short.

You probably don't want to coil the excess slack on your DC cables.

good points! Some I have not heard before.

Thanks for sharing.

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nice thanks

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Thanks!

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