How to Design an AV Rack Elevation

What is a rack elevation?

A rack elevation maps every device in a rack to a numbered rack space, drawn to RU scale, front and rear. It's the build sheet the shop works from, the service map a stranger uses two years later, and the document that proves, before anyone lifts a screwdriver, that twelve rack units of gear actually fit in a twelve-unit case.

It answers a different question than the wiring drawing: the signal-flow diagram says what feeds what; the elevation says where each box physically bolts in. You need both, and they need to agree on the device list.

Get the RU math right first

One rack unit (1U) is 1.75 inches / 44.45 mm of vertical rail space, and every rackmount device is a whole multiple of it, 1U switches, 2U UPSs, 4U amps. The math is trivial; the trap is the difference between nominal and usable space. A "12U case" offers 12U of rail, but blanks, vents, drawers, and future expansion all spend from the same budget as the electronics.

Power block: UPS (2U) + PDU/sequencer (1U) = 3U
Electronics: network switch (1U) + audio DSP (1U) + streaming encoder (1U) + wireless RX (1U) = 4U
Access: rack drawer (2U) + patch/I-O panel (1U) = 3U
Thermal gaps: 2 × 1U vented blank = 2U
Total: 3U + 4U + 3U + 2U = 12U used of 12U nominal

Do this arithmetic for every rack before any layout work, the rack units and equipment guide covers how RU heights are counted when datasheets get creative.

The layout order that keeps racks buildable

Place gear in this order and most rack-design arguments settle themselves:

1. Heaviest gear lowest. UPSs and amplifiers go to the bottom of the rack, weight down low is what keeps a loaded rack stable on a ramp.
2. Power distribution next, near where power enters the case. The PDU or sequencer sits close to the inlet so the feeder run inside the rack stays short and obvious.
3. Hot gear gets breathing room. Devices that run warm all show get placed with venting in mind, a vented blank above a hot box is the cheapest cooling you will ever buy.
4. User-facing gear at eye and hand height. The devices someone touches during a show, mixers, monitors, anything with a front-panel workflow, land where a standing tech can see and reach them.
5. Patch panels and I/O where hands go. Show-site connections belong at the top or wherever the case opens naturally, so nobody patches blind behind a dolly board.
6. Spend 1U on gaps deliberately. Empty units are thermal spacing today and expansion space next year, draw them into the elevation as real line items, not leftovers.

Weight and balance for racks that travel

A mobile rack is a road case that happens to contain electronics, and it gets handled like one, tipped on ramps, rolled over cable ramps, slid on and off lift gates. Common field practice is to keep the center of gravity as low as practical: heavy amps and UPSs at the bottom, light processing up top. A top-heavy rack is a tip hazard for the crew and a warranty claim for the gear.

Think in thermal zones, not individual fans

Heat rises inside a closed case, so a rack is a vertical stack of thermal zones: each device's exhaust becomes the environment of whatever sits above it. Two placement conflicts to catch at the drawing stage rather than on site:

• Front-to-back vs. side-vented gear. Most IT-style gear breathes front to back; plenty of AV gear vents out the sides. A side-vented device in a narrow enclosed rack can starve with its fans running, check each unit's airflow direction against the case, per its documentation.
• Recirculation. Open rack spaces let hot exhaust curl around and re-enter intakes. Blanking panels over unused spaces are common practice for exactly this reason, they force air through the gear instead of around it.

At the elevation stage this is concept-level planning: stack the sustained-heat devices apart, give them vented space, and mark airflow direction on the drawing so the build tech sees the intent.

Plan power inside the rack like a circuit, not an afterthought

• PDU placement and loading. Note which devices feed from which PDU outlets on the drawing, it turns "why is the switch dark" from an investigation into a glance.
• Service loops. Leave enough slack behind each device that it can slide forward for service without unplugging half the rack.
• Dress power and signal separately. Running power down one side of the rack and signal down the other is long-standing practice, it reduces the chance of interference problems and, just as valuable, makes the loom legible to the next tech.
• Label both ends of every internal cable. Inside the case counts as documentation territory too, the same ID scheme as the cable schedule.

Why the rear elevation matters more than the front

The front elevation is the one that looks good in the proposal. The rear elevation is the one that catches problems, because the rear is where the build actually happens:

• Depth conflicts. Device depth plus connectors plus cable-bend radius has to fit inside the usable case depth, the datasheet depth of the box is never the whole story once a stiff cable is hanging off it.
• Connector clearance. Rear-panel connectors that land against a case lid, a rear rail, or another device's loom show up on the rear drawing and nowhere else.
• Reachability. Can a hand actually get to the PDU outlets, the switch ports, the DSP's reset button with everything installed? The rear view answers it before the build does.

If you only draw one view, draw the rear, the build tech will thank you. Better: draw both from the same data so they can't drift apart, which is exactly what the front and rear views guide walks through.

Worked example, a 12U mobile production rack

Here's the 12U rack from the RU budget above, laid out with the rules applied, heaviest low, power block isolated, hot gear vented, hands-on gear up top. RU 1 is the bottom of the rack:

Two details worth copying: the vented blanks are drawn as real rows (so nobody "borrows" them at build time), and the switch's power entry is flagged as variable, PoE loads change the math, which is why PoE budget planning is its own exercise.

Document internal connections as their own layer

A production rack contains a whole wiring system that never leaves the case: patch panel to devices, PDU to devices, switch to everything. Document it as its own layer, separate from show-site cabling, the internal wiring is built once in the shop and should never be re-derived on site. Keeping the layers separate is what lets a site tech re-patch the panel all day without ever wondering whether they broke something inside. The rack internal connections guide covers how this layer is drawn and maintained.

Drawing it in WireFlow

WireFlow's rack builder does the mechanical parts of everything above: RU-accurate placement, front and rear views generated from the same data, internal patch documentation as its own layer, and install-ready PDF exports. Because the rack lives next to the signal-flow diagram in the same project, the elevation, gear list, and cable schedule ship together in one tech pack instead of three separately aging documents.

Frequently asked questions

What's the difference between a rack elevation and a rack layout?

In practice the terms get used interchangeably. "Elevation" usually implies the RU-accurate, to-scale drawing, front and rear views with numbered rack spaces, while "layout" sometimes means the earlier, rougher pass of deciding what goes in which rack. The deliverable that matters is the RU-accurate elevation, because it's the one the shop can actually build from.

How much empty space should I leave in a rack?

There's no fixed rule, it depends on heat, budget, and how likely the system is to grow. Common practice is to draw deliberate vented gaps above sustained-heat devices and keep at least some RU free for expansion. A rack designed to exactly 100% capacity is a rack that gets rebuilt the first time anything is added.

Do I need a rear elevation for a small rack?

If anything in the rack has meaningful depth, rear connectors, or internal cabling, yes. Depth conflicts, connector clearance, and cable-bend problems only show up in the rear view, and they're just as expensive in a 6U lunchbox rack as in a 45U install rack.

Where should the UPS go in a rack?

At the bottom, essentially always. It's typically the heaviest single device, and keeping that mass low keeps the rack's center of gravity down, which matters most for mobile racks that ride trucks and roll down ramps. Placing it low also keeps it close to where power enters the case.

How do I know if my gear will fit the rack depth?

Compare each device's datasheet depth plus an allowance for rear connectors and cable-bend radius against the case's usable depth between rails and lid. The devices that surprise you are the ones with stiff cabling or bulky rear connectors, which is exactly the check the rear elevation exists to force.

Build your rack elevation in WireFlow

Drag gear into front and rear rack views, document internal patching, and export install-ready PDFs.

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