A comms cabinet is a standard 19-inch enclosure that holds your patch panels, switches and recorders. Height is measured in rack units (U) and is easy to get right. Depth is measured in millimetres and is the decision people get wrong — because a cabinet that is too shallow cannot be fixed once it is on the wall.
We sell a lot of 4U and 6U wall cabinets across the counter on Villa Road. We also hear a lot of “the switch won't fit with the door shut”. This is how to avoid that call.
1. What U actually means
One rack unit — 1U — is 44.45 mm of vertical mounting height. Every rack-mount device is designed in whole multiples of it. A 24-port patch panel is 1U. A 48-port panel is 2U. A small network switch is usually 1U.
The mounting width is fixed at 19 inches, which is why anything rack-mount fits any rack. Height and depth are the only variables you choose.
2. Sizing the height — add a U for air
Count the devices, total the U, then add space you are not going to fill on day one. Two reasons, and the second one surprises people:
- Growth. Another switch, a recorder, a small UPS, a second patch panel when the extension goes up.
- Cable management. A patch panel bolted directly above a switch leaves the leads nowhere to turn. They bend hard against the ports, the face becomes an unreadable wall of cable, and you can no longer trace anything.
Leave a U between the panel and the switch. It is the cheapest decision in the whole install and the one you thank yourself for in three years.
Trade Tip: Total your kit in U, then go up one cabinet size. A 4U of equipment in a 4U cabinet is a cabinet you cannot work in — no room for fingers, no room for leads to loop, and the door will not shut on a fat patch lead. A 6U costs a little more and stays workable for a decade.
The Adastra 953.504UK is a 19-inch 4U cabinet, 450 mm deep, cold-rolled steel with a glass door — the standard answer for a small office or retail unit running a patch panel and a switch.
3. Depth — the measurement that catches people out
This is the one. Height you can eyeball. Depth you have to check against the deepest thing going in.
A patch panel is shallow — it barely projects behind the mounting rails. A network switch is deeper. A recorder is deeper still. And behind whatever you fit, you need room for:
- The power lead and its plug, which does not bend at 90 degrees;
- Patch leads looping out of the rear of the panel;
- Enough air for the equipment to actually breathe.
A 450 mm cabinet suits a patch panel and a typical switch comfortably. Put a deeper recorder in it and you will be closing the door onto a power lead.
Trade Tip: Measure the deepest device you own, then add 100 mm for cables and plugs. That number is your minimum cabinet depth — not the device depth, and definitely not the depth of the shallowest thing you are fitting. We cannot make a 450 mm cabinet deeper once it is screwed to a wall.
4. Wall or floor?
For most small installations, wall-mounted is right: it keeps the kit off the floor, out of the way of mops and feet, and at a height where you can see the ports without kneeling.
Mount it at roughly head height so the patch panel is at eye level, and check what is behind the plasterboard before you commit. A loaded cabinet is heavy and gets heavier every time somebody adds a switch.
The SFX 6U is a 600 × 450 mm wall cabinet with a lockable glass door — the extra 2U over a 4U giving you the working room described above. Where you need to lay something flat rather than rack-mount it, the All-Rack SHELF550800 is a 19-inch fixed shelf, 550 mm deep, black steel, rated 90 kg.
5. Ventilation and locking
Ventilation. Switches and recorders make heat, and a sealed box in a cupboard concentrates it. Glass doors look tidy but do not breathe — so keep the cabinet out of airing cupboards and off south-facing walls in a conservatory, and leave clearance above and below.
Locking. A lockable door is not about defeating a determined thief; it is about stopping casual interference. In a shop, a school or a shared office, the ability to unplug something is the vulnerability, and a key removes it.
Summary: choosing a comms cabinet
| Decision | Answer |
|---|---|
| Width | 19 inch — fixed, no decision to make |
| Height | Total your kit in U, then go up one size |
| Cable management | Leave a spare U between panel and switch |
| Depth | Deepest device + 100 mm. The one you cannot fix later |
| Mounting | Wall at head height for small installs; check the substrate |
| Ventilation | Clearance above and below; avoid enclosed warm spaces |
| Security | Lockable door to stop casual unplugging |
Expert Help in the West Midlands
Villa Road, Birmingham, since 1975. Tell us what is going in the cabinet — the panel, the switch, anything else — and we will tell you the U height and the depth you need before you buy, rather than after you have drilled the wall.
Browse our data and communication range for panels, modules and faceplates, or read our comparison of Cat5e and Cat6 if the cabling is still undecided.
Frequently asked questions
What size comms cabinet do I need?
Add up your equipment in rack units, then go up one cabinet size. A patch panel and a switch fit a 4U comfortably; 6U gives you working room and space to grow.
How deep should a comms cabinet be?
Measure the deepest device you are fitting and add around 100 mm for power leads, plugs and rear cabling. 450 mm suits a patch panel and a typical switch; deeper recorders need more.
Can I mount a comms cabinet in a cupboard?
You can, but watch the heat. Switches and recorders warm up, glass doors do not ventilate, and an enclosed cupboard concentrates it. Leave clearance above and below, and avoid warm enclosed spaces.