Planning a 19-inch rack layout

A rack that looks fine on paper can still be miserable to wire, overheat in its first summer or tip over on a truck ramp. Most of that is decided by the layout, before a single device is mounted.

Rack units and sizing

One rack unit (U) is 1.75 in, or 44.45 mm, of vertical space. "19-inch" is the width of the front panel including its mounting ears (482.6 mm).

• Count the height of every device, then add patch panels, cable managers, blanking panels and power distribution. These add up faster than expected.
• Check depth as well as height. Allow for the deepest device plus its rear connectors and the bend radius of the cables behind it, typically another 100 to 150 mm.
• Leave spare space for future equipment. A rack planned full on day one is over capacity by the first change request.
• For touring racks, check the rail depth of the shock-mounted case itself, not just the rack frame inside it.

Weight distribution

Heavy equipment goes low: UPS units, amplifiers, large power supplies. It keeps the centre of gravity down, which matters for freestanding racks and for road cases pushed up ramps.

• Front ears alone are not designed to carry deep, heavy units. Use rear rails, support brackets or shelves.
• Check the rack's load rating, the castors and, for fixed installs, the floor.
• Freestanding racks need anti-tip feet or fixing, especially if equipment slides out on rails.

Heat and airflow

Almost every watt a device draws ends up as heat in the rack. One watt is 3.412 BTU/h, so a rack drawing 1.5 kW gives off around 5,100 BTU/h, and that heat has to go somewhere.

• Most rack equipment breathes front to back. Keep the whole rack consistent. Side-venting devices, such as some network switches, need space or baffles so they don't draw in their neighbour's exhaust.
• Fit blanking panels in every empty space so hot exhaust can't loop round to the front.
• Leave the vent spaces the manufacturer asks for, commonly 1U above power amplifiers.
• Heat rises, so the top of the rack runs hottest. Heavy amplifiers still belong low for stability, so give them vent space and make sure the rack exhausts at the top or rear.
• A closed rack in a cupboard needs a real air path in and out, usually with fans. A sealed glass door with no vents turns the rack into an oven.

Cable management

• Run mains power down one side of the rack and signal down the other. Where they must cross, cross at right angles. Analogue audio in particular picks up hum from mains running alongside it.
• Put 1U horizontal cable managers (brush or ring panels) next to dense patch panels and switches.
• Use rear lacing bars to take the weight of cables and hold their bend radius. Fibre and 12G-SDI coax are both sensitive to tight bends.
• Leave service loops so a device can slide forward on its rails without being unplugged.
• Label every cable at both ends to match the cable schedule.

Patch panel placement

Patch panels are the part of the rack people touch most, so put them at working height, between waist and eye level. Group them by system:

• Video patching near the router or switcher it feeds.
• Audio patchbays near the console I/O or DSP. Document the normalling next to the panel layout.
• Network patch panels next to the switch, with a cable manager in between and short patch leads.

Power

• Add up the power draw from each device's datasheet and size the PDUs and supply with headroom.
• Split devices with dual power supplies across two PDUs, ideally on separate circuits or one on UPS and one on mains.
• Mount the UPS at the bottom and check its runtime at the real load, not the rated maximum.
• Sequence power so amplifiers come on last and go off first, avoiding thumps through the speakers.
• Use short IEC leads. Metres of spare cable coiled behind the rack block airflow.

A sensible starting order

1. Top: fibre and network patching, network switches.
2. Working height: patch panels and anything handled often, with cable managers between them.
3. Lower middle: processors, routers, converters and playback.
4. Bottom: amplifiers, power distribution and the UPS.

This is a starting point, not a rule. A console shelf, a monitor or a drawer changes things. Start from this order and move equipment only for a reason you can name.

Plan it in Patchify

Patchify's rack builder places equipment from the gear library in 19-inch racks by rack unit, so you can see what fits and how much space is left. Custom patch panels come from the panel designer. The racks sit in the same project as the cable diagram and kit list, and export to PDF with the rest of the documentation.