Engineering notes
Notes from the works
Long-form answers to the questions that decide a rack order: how tall, how it is cooled, how it is proven in an earthquake.
Every post names the document it draws on and the page it came from. Where we do not have a document, we say so in the post.
The notes
01
42U vs 47U: choosing rack height
What actually fits in the 200 mm between them?
For whoever is signing the rack schedule and has to defend the U count.
02
What 25% cooling savings actually means
Where does the number come from, and when does your site not get it?
For whoever has to put a savings figure in a business case.
03
How a rack passes a seismic test
What does a shake-table test actually do to a cabinet, step by step?
For whoever has been asked for seismic evidence and does not know what good looks like.
Short reads here. Depth in the design guides.
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Rack selection
U count, width and depth, load rating, mesh ratio — how each one is decided.
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Airflow and cooling
Cold aisle, hot aisle, blanking panels, and why mesh ratio matters more than fan speed.
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Cold aisle design
Door type, roof panel, fire linkage, and the heights the row has to fit between.
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Power and grounding
The chain from the room to the rack, the PDU position, and the bonding path.
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Seismic and load
The CAICT report, page by page, plus the static-load evidence behind the rating.
How these notes are written
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01
Every figure is traceable
Each post names its source document and the page number, so you can open the same report and check the number yourself.
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02
No product pitches
If a post would only work as an advertisement, it does not get published here. The design guides carry the specification detail instead.
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03
Limits are stated
Where a test covers one model size, one direction, or one intensity level, the post says so — and says what it does not cover.
If the answer belongs on this page, we will write it. Two fields: your question, and where to send the reply.
