Design guide · 04

Power & Grounding

Two things decide whether a rack row is buildable: where the power comes in, and how the bonding path is proven. This guide walks that chain and shows the measured values from the third-party reports on our own cabinets.

Our scope on this page: the distribution cabinet, the rack-level feed provision, and the bonding path. Utility intake, UPS and generation are outside it, and the diagram says so.

The chain as it is actually owned. A blank rectangle is not ours to draw: the busway, the PDUs and the UPS are third-party equipment that lands on a provision we leave.

Layers

From the utility intake to the rack: the interface to settle on each layer.

Layer map
Layer	What it is	Interface to define before order	In our scope
1 · Utility intake	Incoming supply from the site transformer	Capacity, voltage, single or dual feed	No: facility
2 · LV switchboard	Main low-voltage distribution for the hall	Fault level, breaker type, metering point	No: facility
3 · UPS	Ride-through for the IT load	Whole hall or one row; autonomy target	No: partner brand
4 · Precision column-header cabinet	Row-level distribution cabinet, fed from the UPS	Feed arrangement, outgoing ways and ratings, metering provisions	Yes: we build the cabinet body
5 · Row-level cable route	How the feed reaches the rack positions	Route (overhead or underfloor), tray or ladder, data segregation	Provision only: you design the route
6 · Busway provision	Space and mounting provision for an intelligent busway, if used	Busway-fed or cable-fed; vendor and its mounting standard	Provision only: third-party busway
7 · Rack-level feed	The final run into each cabinet	Top or bottom entry; PDU or terminal block	Yes: provision in the cabinet
8 · PDU position	Where a vertical PDU mounts inside the cabinet	PDU height, mounting standard, metered or switched	Provision only: position and fixing points
9 · Vertical cable management	Vertical duct carrying feed and data cabling inside the cabinet	PDU fixing inside the duct; power and data separation	Yes: mounting holes for common PDU models
10 · Bonding of the cabinet	Puts frame, front door and rear door at the same potential	Bonding conductor size; dedicated strap or through the hinge	Yes: multi-point, front door, rear door, frame
11 · Earth bar and the run to the room earth	Cabinet earthing lead-out and its connection to the room grid	Earthing conductor size and route; room arrangement	Yes for the earthing point; room run is yours
12 · Verification	How the bonding is proven and recorded	Whether you require a measured value at handover	Yes: measured values in the reports below

Provision

What we leave, and what you fit.

Cabinet plan. The vertical ducts and the busway channel are positions, not parts: the dashed band is left empty on purpose.

ProvisionProvision for an intelligent busway and for PDUs is built into the cabinet and the rack: position, fixing points and cable route.

Third partyThe busway itself and the PDUs are third-party equipment: not supplied by us, not integrated by us, not shipped with the cabinet.

IntegrationWe support integration of third-party busway and PDUs: our provision follows a documented fixing standard, so your vendor's equipment lands on it.

AskIf your design uses a busway, send the vendor's mounting drawing with your enquiry; we will confirm the provision against it.

150 mm Width of the vertical cable duct, full cabinet height

1.12 mm Measured duct material thickness (requirement: not less than 1.0 mm)

Top & bottom Both entries provided; the roof panel carries the top cable tray, keeping power and data apart

Send us your single-line diagram

Bonding

How the bonded parts meet at the earthing point.

The bonding path. Front door, rear door and frame are each bonded; the three paths meet at the earthing point inside the cabinet before the lead-out leaves for the room earth. Doors are bonded deliberately, not through the hinge: a moving contact is not a bonding path.

01Frame bonding first: establish the earthing point before anything is fitted to the frame.
02Bond every removable panel that carries equipment or closes the EMC envelope: front and rear doors.
03Bond through a conducting surface: masked, plated or toothed. Powder coat is an insulator; a bonding point on top of it is a drawing error.
04Measure at the earthing lead-out, not at the door. Record the value; the reports on this page do exactly that.

Measurement

What the reports measured, and where to find the line.

1 mΩ Measured DC bonding resistance at the earthing lead-out; requirement not more than 10 mΩ Third-party inspection report, page 2

1.5 mΩ Measured earthing resistance, cold aisle containment; requirement not more than 10 mΩ Third-party inspection report, page 4

Front · Rear · Frame Three bonding paths, multi-point, on every cabinet Design feature, server rack range

Both are third-party inspection reports, and both are on this page: the requirement and measured columns can be read against each other without leaving it.

Drawing review

Questions to ask any supplier, including us.

01Ask which standard the cabinet was type-tested against, and for the report number.
02Ask for the measured DC bonding resistance at the earthing lead-out, not a target.
03Ask whether both doors are bonded, or only the frame.
04Ask how the bonding point gets through the coating: masked, plated or toothed.
05Ask where the earthing point is, and how the room conductor lands on it.
06Ask for the cabinet outline as a drawing, not a photograph, before fixing the row pitch.
07Ask for the duct width and whether your PDU will fix inside it.
08Ask whether power and data are separated along the top route.
09Ask explicitly: is the busway supplied, or is there a provision? Get it in writing.
10Ask for the fixing standard of the busway provision, and check your vendor's drawing against it.
11Ask for the single-line diagram of the cabinet you are quoted.

A single-line diagram and a row pitch is enough for us to come back with the cabinet arrangement and the rack-level provision.

If something in your diagram is outside what we build, we will say which part it is.

Send us your single-line diagram

Next: Seismic & Load Power distribution