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A Rack Unit is abbreviated as U. One Rack Unit (1U) is equal to 1.75" (4.44 cm).

Why racks?
There are several things you should consider when choosing a rack.

What kind of equipment will you be putting in it? If you need frequent access to all sides of the equipment, an open rack is more convenient than a cabinet. If your equipment needs ventilation, a rack poses no air circulation limitations. And don’t neglect aesthetics. Will customers or clients see your installation? A rack with cable management looks much neater.

Finally, consider security. Because a rack is open, you need to take steps to secure your equipment. Set up your rack in a locked room so prying fingers can’t access your network equipment.

Racks come in various sizes and installation styles. Some are freestanding; some are designed to be wallmounted. Some can be a combination of both styles, sitting on the floor but attaching to the wall for more stability.

Understanding rack measurements.
The main component of a rack is a set of vertical rails with mounting holes to which you attach your equipment or shelves.

The first measurement you need to know is the width between the two rails. It’s commonly given in inches, measured from one mounting hole to the corresponding hole on the opposing rail. The most common rail width is 19"; 23" rails and racks are also available. Most rackmount equipment is designed to fit 19" rails but can be adapted for wider racks.

The next important specification is the number of rack units, which is abbreviated as “U.” This is a measurement of the vertical space available on the rails. Cabinets and racks and rackmount equipment are all measured in rack units. One rack unit (1U) is equal to 1.75" of usable vertical space. So, for example, a device that’s 2U high takes up 3.5" of rack space. A rack that’s 20U high has 35" of usable space.

Because the widths are standard, the amount of vertical space is what determines how much equipment you can actually install. Remember this measurement of usable vertical space is smaller than the external height of the rack.

Getting power to your equipment.
Unless you want to have a tangle of extension cords, you’ll need to get one or more power strips for your rack. Consider which kind would be best for your installation. Rackmount power strips come in versions that mount either vertically or horizontally. Some have outlets that are spaced widely to accommodate transformer blocks—a useful feature if most of your equipment uses bulky power transformers.

Surge protection is another important issue. Some power strips have built-in surge protection; some don’t. With the money you have invested in rackmount equipment, you’ll certainly want to make sure it’s protected.

Any mission-critical equipment should also be connected to an uninterruptible power supply (UPS). A UPS prevents your equipment from crashing during a brief blackout or brownout and allows enough time to shut everything down properly in the event of an extended power outage. Choose a rackmount UPS for the most critical equipment or plug the whole rack into a standalone UPS.

Managing cables.
Your equipment may look very tidy when it’s all mounted. But unless you’re very careful with your cables, you can create a tangle you’ll never be able to unravel.

Plotting your connections in advance helps you to decide the most efficient way to organize the cables. Knowing where the connections are tells you whether it’s better to run cables horizontally or vertically. Most network problems are in the cabling, so if you let your cables get away from you now, you’re sure to pay for it down the road.

There are many cable management accessories that can simplify your racks.

After you choose your rack, consider how you’ll set it up and what accessories you might need.

Your rack may need to be secured. A typical rack has about a 15"-deep base, providing some stability, but not enough to prevent the rack from tipping if heavy objects are mounted on it. To solve this problem, most rack bases can be bolted to the floor.

You also need to decide how to accommodate standalone equipment, which is not actually rackmounted or bolted to the rack. You can place small devices on a cantilevered shelf such as the RM001, however, you should place heavier items such as monitors on a center-weight shelf such as the RM377.

Small extras, such as Patch Panel Hinge Kits, can make your job easier. These hinges enable you to access the back of a patch panel simply by swinging it out from the rack. They’re particularly useful for racks in hard-to-reach areas.

If you need to mount both 19" and 23" equipment in the same rack, use a 23" rack with 23"-to-19" Rackmount Adapters to fit the 19" devices.

For a neater appearance, you can cover unused spaces in a rack with Filler Panels.

Cable management is also an important consideration. Our Horizontal and Vertical Cable Managers help you to route cables along the sides of racks, between racks, and to the rackmounted equipment.