I have already explained what a rack cabinet is when presenting the 10” rack cabinet system. Let me just briefly remind you that it is a standardised system for mounting devices in telecommunication and server cabinets. As it is standardised, it allows you to install equipment (in rack cabinets) from various suppliers in a cabinet from another supplier. Currently it is available in three variants that differ in the spacing of rack cabinet rails: 10, 19 or 21 inches. The 19” rack cabinet system is the most popular one used in most installations, so I will describe it in this article.

Why is the 19” rack cabinet the most popular and not the 10” or 21” systems? The answer seems to be a bit of gobbledygook. That spacing is the most popular because most network devices, including servers, are supplied in 19” housings. The 21” size is used almost only by operator-class telecommunication devices, and 10” by small switches in home systems. It turns out that the popular 19” format is just the most versatile size. This is why the range of rack cabinets having rails with that spacing is the most extensive. It starts from small wallmounted 4U rack cabinets and ends with huge 47U rack cabinets.

As I mentioned above, the range of 19” rack cabinets is very extensive, the rack cabinets differ by many parameters, and additionally Start.LAN offers rack cabinets not provided by most manufacturers. So I will try to group and characterise the rack cabinets.

RACK ‘CAPACITY’

The U value composing a rack cabinet name refers to the option to install devices with a specific (overall) height. Each rack cabinet component (a device, patch panel or even a cable organizer) is marked by its height given in U units. They are normally full units (1U, 2U, 4U), but it may sometimes be 0.5 U for patch panels. One U equals 1 ¾ inches (4.445cm) but, as I have mentioned, it is not very important, as the value is standardised: U just means ‘unit’.

HEIGHT X WIDTH X DEPTH: OVERALL DIMENSIONS

The overall dimensions inform us about the rack cabinet’s external dimensions, so what is the minimum space it will take. Obviously, a rack cabinet should not be pushed anywhere by force, as we must ensure an appropriate ventilation.

We should also note that the overall depth does not stand for the maximum depth of the equipment we can install! This is a frequent mistake made by novice installers or administrators.

The installation space in a rack cabinet is adequately smaller; the rack cabinet rails are properly moved, both at the front and rear, to allow you to lay the cable as well as to easily open and close the door. The installation depth can be found in the rack cabinet specifications.

SUSPENDED-AND-STANDING RACKS... AND A DEPARTURE FROM THAT CLASSIFICATION

Normally the smallest rack cabinets (4–22U) are wallmounted on a wall, and the floor-standing rack cabinets range from 18 to 47U. The floor-standing rack cabinets have both transport wheels and levelling feet, and the wallmounted rack cabinets have a dedicated hanger attached to the wall. The product range of Start.Lan is unique here, as we offer wallmounted-and-floor-standing 9U and 12U rack cabinets. In practice, they are wallmounted rack cabinets with the option to install wheels or feet. This will allow you to place the rack cabinets for example under a desk or in low alcoves. The rack cabinet is delivered as a wallmounted system, and a set of wheels or feet is available as an accessory.

DOOR

The wallmounted rack cabinets are provided only with a front door. Their rear surface is pressed against the wall, so it is closed by a fixed metal cover. The floor-standing rack cabinets are fitted with front and back doors. They are offered in the following sets:

  1. Glass front door + full steel back door
  2. Perforated single-leaf front door and double-leaf back door

LOAD CAPACITY

This parameter tells us the total weight of the equipment that can be installed in the rack cabinet. We should note that the parameter refers to equipment mounted to the rack cabinet rails at four points. Heavy equipment, such as UPS or servers, cannot be mounted at two points, as such load is not considered in the rack cabinet design. If there are no original mounting rails, you should buy universal supporting rails for heavy equipment.
When installing devices in a rack cabinet, the principal rule is to mount heavy devices possibly low (this particularly applies to UPSs) so that the centre of gravity in the filled rack cabinet is located as low as possible. This considerably improves stability when the rack cabinet is rolled or during maintenance works that require any device to be moved out.

WHICH RACK IS GOOD FOR WHICH APPLICATION?

A rack cabinet must above all be chosen for its capacity counted in U (including a reserve) and installation depth. Another thing is to ensure an adequate ventilation for the devices installed. If the rack cabinet is not located in a dedicated room, it may also be important to provide at least a basic dust protection.In practice:

  • Wallmounted rack cabinets are used for monitoring systems, small networks and intermediate points in cabling distribution.
  • Floor-standing rack cabinets of up to 800mm are used as telecommunication cabinets that concentrate the cabling in central or intermediate points. Normally the rack cabinets of this type are provided with a glazed front door.
  • Floor-standing rack cabinets of up to 1000–1200mm in depth are used as server cabinets in server rooms and data centres. They usually have a perforated door to ensure an appropriate ventilation for the servers.

EXAMPLE DESIGN OF EQUIPMENT IN 19” 42U RACK FOR A SERVER ROOM IN A SMALL ENTERPRISE (UP TO 48 PORTS, INCLUDING A MONITORING SYSTEM)

List of equipment
ManufacturerName
Mounting method
U height
START.LANSTLPDU08-F-H1U-1.8 power strip
rack 19"
1U
 Fibre optic distribution frame
rack 19"
1U
 ISP modem
rack 19"
1U
ZyxelZyWall 310 router
rack 19"
1U
TP-LINKManageable T2600G-28TS switch
rack 19"
1U
START.LANSTLCA-CM1 cable organizer
rack 19"
1U
START.LANPatchpanel 24P STLPP24UC5E-F
rack 19"
1U
START.LANPatchpanel 24P STLPP24UC5E-F
rack 19"
1U
START.LANSTLCA-CM1 cable organizer
rack 19"
1U
TP-LINKManageable POE T2600G-28MPS switch
rack 19"
1U
ThecusNAS N4910U-R server
rack 19"
1U
START.LANKVM STLCON1908 console
rack 19"
1U
 SERVER 2
rack 19"
2U
8levelNVR NVRHD-1HDD-9CH recorder
free-floor-standing
1U
TP-LINKWiFi AC500 controller
rack 19"
1U
 SERVER 1
rack 19"
2U
 Phone patch panel
rack 19"
1U
START.LANSTLCA-CM1 cable organizer
rack 19"
1U
 Telephone exchange
rack 19"
3U
START.LANSTLPDU08-F-H1U-1.8 power strip
rack 19"
1U
 UPS
rack 19"
2U