12U 19-inch Data Cabinets

Add together the rack space required by everything you intend to mount: patch panels, switches, shelves, horizontal PDUs, cable managers and any other rack-mounted equipment.

Then consider equipment sitting on shelves. The shelf may occupy 1U at its mounting position, but the equipment resting on its platform may extend through that U and require additional clear space above it.

Finally, leave some room for growth if possible. A cabinet calculation that arrives at exactly 12U for a 12U cabinet is mathematically impeccable and operationally rather optimistic.

Low down where practical.

That isn’t because the bottom of the cabinet possesses some special cooling property. It’s primarily mechanical: keeping heavy equipment lower reduces the height of the combined centre of mass and generally improves stability.

Take the same heavy UPS and move it from the bottom of a freestanding cabinet to the highest available U. The UPS hasn’t changed at all, but you’ve deliberately moved a substantial mass further from the supporting surface and made the whole arrangement less forgiving if it’s disturbed.

The UPS still needs whatever mounting rails or rear support its manufacturer specifies.

No. Plenty of lightweight, shallow rack equipment is designed to hang perfectly happily from its front mounting ears.

Heavier or deeper equipment is a different matter. Some devices require rear support brackets, fixed rails or sliding rails, and the manufacturer's mounting instructions should take precedence.

A shallow patch panel and a deep UPS may both be described as “rack mounted”, but mechanically they’re asking rather different things of the cabinet. Don’t assume the front ears are sufficient simply because the device can initially be persuaded to hang from them.

Where additional support is specified, use it.

The whole lot.

If the cabinet weighs 20kg and you put 50kg of equipment inside it, the wall is supporting approximately 70kg. Describing the equipment as being within a 60kg cabinet rating doesn’t make the cabinet's own 20kg disappear.

And the cabinet rating tells you what the cabinet can carry. It doesn’t certify the brick, block, timber, plasterboard or whatever fixing system sits between the cabinet and the building.

Wall capacity and cabinet capacity are separate questions. Both need satisfactory answers.

Functionally, very little once both are assembled correctly.

The ready-assembled cabinet arrives built, with the door, side panels, mounting profiles, cable-entry covers, locks and bonding components already fitted. The flat-packed version arrives as the same basic cabinet construction in pieces and needs assembling before use.

One practical advantage of the flat-packed version is access. In pieces, it can pass through openings that a fully assembled cabinet may not. A loft hatch is a good example: the finished cabinet might have no realistic chance of getting through it, while the individual panels can be carried up and the cabinet assembled in position.

You’re choosing between factory assembly and doing the assembly yourself, not between two different grades of cabinet.

The flat-pack version hasn’t sacrificed structural integrity for the privilege of fitting into a flatter cardboard box. Once assembled correctly, it’s intended to perform the same job as the ready-assembled version.

The nominal cabinet depth describes the overall depth class of the enclosure — for example 300mm, 450mm, 550mm or 600mm.

The usable internal depth is the space available inside the cabinet after allowing for the front door, rear structure and other parts of the enclosure. It is therefore smaller than the nominal depth.

Approximate usable internal depths are 250mm for a 300mm cabinet, 400mm for a 450mm cabinet, 500mm for a 550mm cabinet and 550mm for a 600mm cabinet.

Usable internal depth should not automatically be treated as suitable equipment depth because connectors, cable bends, rail position and front-door clearance also require space.