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Newbie datacenter lesson #3: Racks and 0U PDUs

None of us saw it coming.  I'm still scratching my head about how this is even a problem.

APC rack.  2x Tripplite PDUs (managed, metered).  Mounted in the APC toolless 0U panel at the back of the rack, side-by-side.

As-is, there is no way to remove rear-facing network equipment that mounts using rack ears.  i.e. Physics prevent you from removing said equipment.  I'd have to remove both PDUs to get anything mounted w. rack ears in or out - e.g. if a switch fails...

Maybe you just can't do that - maybe all equipment you want to remove must be mounted from the front.  Did some more looking (to be sure), and both the APC and Tripplite models we can use are pretty much the same physical dimensions.

Unfortunately I wasn't able to meet directly with the datacenter manager (flight was delayed), so we came to the conclusion that our only real solution was to dismantle the rack entirely so we could move the vertical mounting flanges.  Doing so would gain us access to the front cable routing slots.

Much discussion ensued, because that's a big job, and my manager (bless his heart) had a great out of the box idea - can we get shorter PDUs, mount them lower in the accessory channel, and then only mount the network gear up top.

I had gotten so fixated that the 6' zero-U PDUs were the only thing to use that I'd blinded myself to those 3' models on APC's site.  (horizontal PDUs simply won't work because we need minimum 32 outlets - means needs 3x horizontal PDUs, and the 208v splitters only come in 1-2 flavour)

So lo and behold: the APC AP8859NA3 (

208v, 20A, L6-20P.

That, plus the TrippLite splitter (P039-001-2) - it has 1x L6-20P and 2x L6-20R.  So we take a single power circuit, split it between these two PDUs, and then split (as best we can) the power supplies across the PDUs.  Ideally you'd have two power circuits, but here we are.

Once we are done, I'll do another post with pictures to help visualize this.


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