I'm building a new server room, and have to decide where I'll be locating the power outlets (120V 30AMP locking connectors) that my UPSs will be powered from. In the past I've put the outlets on the back wall, and just run the cords up and over the ladder racking on to the back of the wall. But for this new server room I can't locate the outlets on the back wall. Instead I have to locate them on the racks themselves. I'd always thought that I'd have the electrician run conduit and put the outlets on the top of the racks, but he suggested putting them on the bottom of the rack at the back right at floor level. I see the advantage of this as not having to run power cables up through my cable managers, and thus interfering with any network cable, but the disadvantage is that I'll have long coiled-up 30A power cables jutting out from the back of the racks. Any thoughts? What have you done, and would you do it differently?

  • To clarify: 1) Where are the long coiled-up cables coming from.. The UPSes? 2) Is there anything else around the racks? What's he gonna put the power jacks in... Screw a junction box somewhere? 3) Where are the power lines coming from... do you have a raised floor? – Ward - Reinstate Monica Jul 16 '09 at 0:12
  • 1) coiled-up cables are from the UPSs 2) servers will plug directly into UPSs, no PDUs (yet) 3) power lines (conduit) will be coming from overhead 4) no raised floor :-( – bren Jul 16 '09 at 0:18
  • oh, and yes these are 4 post racks.. – bren Jul 16 '09 at 0:18
  • you might find some ideas here ratemynetworkdiagram.com/toplist.php?ut=10 – Saif Khan Jul 16 '09 at 4:38

If you're talking about 4-post cabinets: I like vertical PDUs inside the sides of the rack. I place them half-way up the height of the rack and coil excess power cords in the side panels. Normally the UPSs are at the bottom of the rack (where they really should be), plugged into mains outlets that are either under the floor or at floor level. The UPSs feed the PDUs, and the PDUs feed the servers and other equipment.

On 2-post racks: I like rack-mounted horizontal power strips staggered throughout the rack. The same is true for the UPSs and electrical receptacles-- they're at the bottom and feed the power strips in the rack. I coil the power cords on one side of the rack in the vertical cable management (and network cables on the other size). Increasing, though, I'm using Neatpatch cable management and have less and less need for vertical cable management.

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The way your question sounds, I'd get the electrician to put your outlets right at floor level roughly in the middle of the rack footprint, put the UPSes a bit above that so that you have room to coil the cords for the UPSes on the ground. Then go with what Evan suggested and mount PDUs in the middle (vertically) of the rack.

In our case, we had a raised floor with the racks in the middle of the room and a 6-foot built-in table right next to the racks, so our electrician ran our lines in raceways along the back of the table.

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  • Ward said pretty much what I was going to say. Your UPSes should be in the bottom of the rack anyway as they'll be the heaviest components. – Karl Katzke Jul 16 '09 at 3:33

If the racks are deep enough, perhaps consider "0 U" vertical PDUs mounted at the back of the cabinet.

With enough space in the back of the rack, these don't interfere too much with data cable management.

Something like this: http://pc.pcconnection.com/1/1/7992-apc-power-distribution-unit-metered-rm-0u-30a-120v-24-5-20-outlets-ap7832.html

Any amount of raised floor helps as well since the electrical conduit can come up under the rack and the PDUs (and slack cord) can be done under a floor tile but it doesn't sound like you have this option.

If none of that is an option, bottom of the rack would be preferable in my opinion to power at the top of the rack.

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I'll second the vertical PDU's. We have used both and the vertical ones are a lot easier in the 4 post racks, otherwise I always have at least one power cable that is too short.

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Typically the best solution to distribute the power throughout a rack is the 0-U PDU's as others have mentioned.

As for the outlets: If you have a raised floor, the outlets can be located beneath the floor panels or come in to the bottom of your rack where your UPS can connect.

If you don't have a raised floor, you can hang the outlets from the ceiling and have them come on to the top of the rack. Most UPSs I've seen come with with at least a 10' or 15' power cord, so it's not hard to run that one cable up to the top of the rack and connect it to the outlet.

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My preference is definitely for vertical but I've also never used anything other than 4 post racks. I also like to get the full length ones. Horizontal outlets always seem to get in the way when you need to make changes to the rack layout, resulting in more work than was planned.

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