AV Racks 101: The Backbone of AV and IT Infrastructure

Racks, enclosures, housings, whatever you call them they are the essential infrastructure component for any installation. They spend their lives behind doors labeled “authorized personnel only” and “danger high voltage.” Or, they remain anonymous behind an unmarked steel door in a dark corner of the basement. They stand side by side, often row after endless row, holding together the electronic components that make our systems function.

Without them, there would be no way to organize hardware, coordinate cabling, structure the signal flow of systems or perform a myriad of other often forgotten, but critical tasks. Racks also provide security, cooling, safety and increase serviceability.

An Introduction

In the A/V world, hardware designed to be placed in a rack is typically labeled as rack mountable, a rack mounted system, or a rack mount chassis. According to the EIA standard EIA-310-D, Cabinets, Racks, Panels, and Associated Equipment, the height of the electronic modules is standardized in multiples of 1.75 inches (44.45 mm) or one rack unit or U (less commonly RU). The industry standard rack cabinet is 42U (6.125 ft.) tall and 19 inches wide to accommodate most AV equipment.

Since the mid-1930’s, the ubiquitous 19-inch rack format has remained constant while the technology that is mounted within it has changed considerably. Typically, a piece of installed equipment has a front panel height 1⁄32 inch (0.031 inches or 0.787 millimeters) less than the allotted number of rack units. Thus, a 1U rack mounted device is not 1.75 inches (44.5 mm) tall, but 1.719 inches (43.7 mm) tall. 2U would be 3.469 inches (88.1 mm) instead of 3.5 inches (88.9 mm). This creates a tiny gap above and below an installed piece of equipment, allowing it to be removed without binding on the adjacent equipment.

The Standard 42U Rack

These simple steel frames often house mission critical AV components, but are habitually overlooked as an essential component of the overall system. As a result, the ordering and configuration of racks is usually left until very late in the project. Given the complex nature of today’s hardware and systems, that methodology is not efficient. Why? Because racks are the basic physical infrastructure of all AV systems and poor choices, or inadequate design, at this point will cause major headaches later on.

Today’s rack designs are made using fully computer controlled manufacturing, laser alignment and automated welding systems that produce a complete rack in one continuous process. This produces products that are identical (very important when there will be dozens of them side by side) and absolutely square, ensuring that all the components will fit properly and the rack itself will be solid and secure, as well as standardized to specific code requirements.

Basic racks are also available in what is commonly referred to as a “flat pack” option, where all the pieces have to be bolted and screwed together onsite. No matter how carefully this assembly process is done, such systems can never be as precisely square and solid as a welded structure, and in many jurisdictions, they will not meet code requirements. If the rack required is quite small (only 6 or so U high) and will only need to hold lightweight equipment, this may be a feasible alternative, but given the minor shipping cost differentials and increased labor costs, you will be far better off purchasing fully welded precision manufactured products.

The Half Height Rack

The second most commonly used rack format is often called the “half-height rack” wall mount design. These are popular in schools, auditoriums, gymnasiums and many hospital facilities. The half-rack designation comes from the fact that these enclosures are usually somewhere between 18 and 24U in height or about ½ the height of the standard 42U rack. These are especially useful for the deployment of smaller scale systems using a compact mixer, one or two modest sized amplifiers and perhaps some source/playback components. Usually supplied with a lockable door, half-racks can be attached easily to almost any wall that will support the weight. Be sure to calculate the actual weight of the fully loaded rack when making this choice.

As with the larger standard AV racks, the smaller products are offered in a variety of sizes, configurations, depths , etc. Today the swing away designs are quite common, allowing for easy and quick access for serving or maintenance.  This style is available from most suppliers.

Three other principal categories for rack systems are designed for hazard areas such as earthquake zones, the racks that are specifically designed for increased half-rack width (that is the front panel of the device, regardless of the number of U high it is, is just under 9.5 inches wide allowing two units to fit side by side in 1 rack slot)  and specific designs used for data, computer, server, router and telecom installs.

Johnathan Ivey, Senior Vice President Sales & Marketing Atlas Sound / Mitek Communications made the following points regarding both the hazard area racks and the emerging half-width rack configuration.

“While equipment racks are often the last piece added to any installation’s planning and purchasing process, it’s critical to understand that every rack is not produced to the same tolerances and manufacturing standards.”

Ivey explains this becomes especially important, “when different models of what would appear to be the same rack actually include different features that can make or break an installation based on the requirements”.

Increasingly, safety and fire codes are requiring that racks meet much stricter performance and mechanical/structural standards.

Ivey notes that “some cities, counties, or states have different requirements that must be adhered to for a project to be signed off on. One such requirement is a cabinet that features a seismic rating.  Areas like California that frequently endure earthquakes and other seismic activity have requirements that equipment racks must be designed and manufactured to withstand up to a zone 4 level earthquake, which is comparable to Richter magnitude 8.0”

You also need to consider ventilation. Ivey suggests you ensure that any chosen rack “offers a solid design without punched vents to allow for a thermal air flow design that is precisely designed and maintained, ensuring that contaminants or other foreign objects are not introduced into the interior.”

Half Width Racks

Some applications call for an equipment rack, but a full size rack is too big or will not work in the desired install location. For example, classrooms with only one or two pieces of equipment or corner installations where a full size or swing out rack will not fit necessitate an alternative solution.

A number of manufacturers are now offering solutions for unique rack environments. Ivey points out that his company “now offers half width rack units in both on wall mount and in wall mount options that address these scenarios.”

Atlas Sound’s WMA model racks feature another approach, which uses a patent pending fold forward design that allows them to be placed in a corner installation and still allow access to the rear of the product for proper wiring and terminations. Additionally, the back box can be shipped to the install location separately from the rack so that the back box can be placed during construction while loading the rack offsite for installation post construction.

The half rack approach is now standardized with Extron, Middle Atlantic, Atlas (with it’s WMA models) as well as many other manufacturers.

Racks for Big Data, Small Data, IT and Telecommunications

The requirements for rack systems in data centers, for cloud servers, routers, and almost any other IT hardware, as well as other digital telephony are significantly different than requirements for AV equipment.

First and foremost, you will need racks wider than the 19-inch EIA standard formats to accommodate the hardware packages. Secondly, you will need racks that are extra deep to allow for the design and configuration of the various servers, etc.  Third, the planning process for this type of equipment requires considerations for expansion and re-configuration. It is highly likely that the initial design will evolve through several variations before it is built and installed.

Layout Planning:

Will Beene, Rack Systems specialist at Rack Solutions, Inc recommends following a carefully structured planning and design process. He noted “it is essential to determine the room layout for server cabinets and racks before installing any equipment.”

Given the substantial amount of copper, fiber and electrical cable needed for these installs, large or small, Beene suggests that “one of the first things to define is where the network cabling will enter the room. The cabling should come through a single location, typically a wall penetration, and drop into the room.”

Once that location is fixed, you can position the main network rack(s) directly below that point for ease of install and access.

In most large data centers, the racks and cabinets will be arranged in rows. These rows will be designated as hot aisles and cold aisles.  The front of the equipment will face the cold aisles; the rear will face the hot aisles.  Beene says “shallow cabinets that are around 1000mm (37 3/8 Inches) deep can be arranged in a 7 pitch* layout.  Deeper cabinets designed for computing devices that are 1200mm deep will be arranged in an 8 pitch* layout”.

(*Note: The pitch refers to the number of floor tiles from the center of the two cold aisles.)

Security:

When you think of security for your server room, the first thing that comes to mind is the secure cages found in big data centers. However, these secure cages are not always practical for small data center operations like those found in small businesses, churches or educational centers. Rodger Baldwin, executive account manager at Rack Solutions, Inc. suggests the best way to protect valuable data and hardware for these small locations, lies outside the data center itself.

He says, “Perhaps the easiest, and often overlooked, option is securing the server room externally. You can do this by adding a Badge Reader or Push Button Security panel to the server room’s main access point. Most of these security devices store information, including a time and date stamp, so you can manage who has been coming and going from the server room.”

Most rack manufactures offer some level of security options for their cabinets. These options range from multi-tumbler keyed locks to biometric scanners. Manufacturers also typically offer the standard front and rear locking door with keyed entry for your purchased racks. If space is limited, you may also want to consider a colocation cabinet, which provides a secure, self-contained means for different organizations to share a single cabinet, minimizing the amount of unused space in the cabinets.

A 16 U cabinet offers an even smaller option for storage space and is especially convenient for organizations that may not have a designated data center. This compact option also offers front and rear lockable doors and secure cabinet side panels.

Cable Management

Cable Management refers to an important step during the installation of equipment – providing the means to secure power, data, and other cables. The purpose of cable management is to support the cables while being routed throughout the building, within the cabinets and when connected to the equipment.  Good cable management also makes subsequent cable maintenance and troubleshooting easier.

“Unfortunately cable management is often overlooked, as evident by the many instances of ‘cable spaghetti’ seen in IT organizations of all sizes. But cable routing is not as difficult as it seems.”

According to Baldwin there are easy and inexpensive methods to assure good cable management.

Most data center cabinets include cable management bars in the back of the cabinets. These vertical bars provide a simple method to route, fasten and organize the cables. However, these vertical bars can be naively overlooked if the installer opts to leave the cables unsecured.

“A great and inexpensive method for nicely and easily securing these cables is to use Velcro straps in place of cable ties,” suggests Baldwin.

A Velcro cinch strap can be purchased for just a few dollars. Most vertical wire management bars have cutouts that are ideal for integrating Velcro to secure the cabling within a rack.

Another common issue with cabling is routing the cables from a cabinet to the ceiling or the wall. This can be done by utilizing a cable trough or a ladder rack. These are essentially trays that hang from the ceiling or attach to the rack and to the wall. The cables will lay nicely in the tray and route to the desired location. The ladder racks or troughs are also widely available and cost effective to use.

As Baldwin explains, “cable routing is not as intimidating as it looks. With a little extra time and attention to detail, you can add a professional look to the cable management of your server room with little added expense.”

This will make all future expansion, servicing and maintenance much easier and less troublesome.

Planning for the future – New Trends

Racks and cabinets for both small office IT departments and large data centers are evolving.  Cable mounting options and cabinet door open air space continue to advance. Therefore, there are several features that IT departments should look for when purchasing new data center racks and cabinets, notes Baldwin. “The most important features include size of the cabinet/rack and airflow and the height, depth and width of the racks.”

Data Centers and related IT infrastructure, as well as Telco infrastructure installs, need to have a long term strategic approach when adding servers and other equipment to a data center facility to minimize future hardware expenses.

Therefore, Whit Wilson, Senior Mechanical Engineer at Rack Solutions, recommends avoiding using 2 post racks.  “Although the initial purchase cost for a two post rack is less expensive than a traditional data center cabinet, the 2 post racks don’t provide the same capability for continued expansion as do 4 post cabinets.”

Airflow capability of a rack/cabinet is also a key factor to take into consideration. The cabinets should always meet or exceed the cooling requirements of the equipment being installed. It is important that the cabinet has good ventilation in the front and back in order to draw cold air in and discharge hot air out the back in a hot / cold aisle set up.

As the market turns to cloud based data centers, there is more of a need for these cabinets to accommodate the growing size of servers as well as the need for extra cable management space.  When selecting the cabinet, make sure the cable management allows for future expansion. Baldwin advises to choose sizes that have plenty of excess capacity to allow for additional cables in the future.

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