Black Box Explains...NEMA 12 certification.
The National Electrical Manufacturers Association (NEMA) specifies guidelines for cabinet certifications. NEMA 12 cabinets are constructed for indoor use to provide protection against certain contaminants that might come in contact... more/see it nowwith the enclosed equipment. The NEMA 12 designation means a particular cabinet has met the guidelines, which include protection against falling dirt, circulating dust, lint, fibers, and dripping or splashing non-corrosive liquids. Protection against oil and coolant seepage is also a prerequisite for NEMA 12 certification.
Organizations with mission-critical equipment benefit from a NEMA 12 cabinet. Certain environments put equipment at a higher risk than others. For example, equipment in industrial plants is subject to varying degrees of extreme temperature. Even office buildings generate lots of dust and moisture, which is detrimental to equipment. NEMA 12 enclosures help to ensure that your operation suffers from as little downtime as possible. collapse
Black Box Explains…How to keep cabinets cool.
Networking equipment—especially servers—generates a lot of heat in a relatively small area. Today’s servers are smaller and have faster CPUs than ever. Because most of the power used by these... more/see it nowdevices is dissipated into the air as heat, they can really strain the cooling capacity of your data center. The components housed in a medium-sized data center can easily generate enough heat to heat a house in the dead of winter!
So cool you must, because when network components become hot, they're prone to failure and a shortened lifespan.
Damage caused by heat is not always immediately evident as a catastrophic meltdown—signs of heat damage include node crashes and hardware failures that can happen over a period of weeks or even months, leading to chronic downtime.
Computer rooms generally have special equipment such as high-capacity air conditioning and raised-floor cooling systems to meet their high cooling requirements. However, it's also important to ensure that individual cabinets used for network equipment provide adequate ventilation. Even if your data center is cool, the inside of a cabinet may overheat if air distribution is inadequate. Just cranking up the air conditioning is not the solution.
The temperature inside a cabinet is affected by many variables, including door perforations, cabinet size, and the types of components housed within the cabinet.
The most direct way to cool network equipment is to ensure adequate airflow. The goal is to ensure that every server, every router, every switch has the necessary amount of air no matter how high or low it is in the cabinet.
It takes a certain volume of air to cool a device to within its ideal temperature range. Equipment manufacturers provide very little guidance about how to do this; however, there are some very basic methods you can use to maximize the ventilation within your cabinets.
Open it up.
Most major server manufacturers recommend that the front and back cabinet doors have at least 63% open area for airflow. You can achieve this by either removing cabinet doors altogether or by buying cabinets that have perforated doors.
Because most servers, as well as other network devices, are equipped with internal fans, open or perforated doors may be the only ventilation you need as long as your data center has enough air conditioning to dissipate the heat load.
You may also want to choose cabinets with side panels to keep the air within each cabinet from mixing with hot air from an adjacent cabinet.
Don't overload the cabinet by trying to fit in too many servers—75% to 80% of capacity is about right. Leave at least 1U of space between rows of servers for front-to-back ventilation. Maintain at least a 1.5" clearance between equipment and the front and back of the cabinet. And finally, ensure all unused rack space is closed off with blank panels to prevent recirculation of warm air.
Fans and fan placement.
You can increase ventilation even more by installing fans to actively circulate air through cabinets. The most common cabinet fans are top-mounted fan panels that pull air from the bottom of the cabinet or through the doors. For spot cooling, use a fan or fan panel that mounts inside the cabinet.
For very tightly-packed cabinets, choose an enclosure blower—a specialized high-speed fan that mounts in the bottom of the cabinet to pull a column of cool air from the floor across the front of your servers or other equipment. An enclosure blower requires a solid or partially vented front door with adequate space—usually at least 4 inches—between the front of your equipment and the cabinet door for air movement.
When using fans to cool a cabinet, keep in mind that cooling the outside of a component doesn't necessarily cool its inside. The idea is to be sure that the air circulates where your equipment's air intake is. Also, beware of installing fans within the cabinets that work against the small fans in your equipment and overwhelm them.
To ensure that your components are operating within their approved temperature range, it’s important to monitor conditions within your cabinets.
The most direct method to monitor cabinet temperature is to put a thermometer into your cabinet and check it regularly. This simple and inexpensive method can work well for for small installations, but it does have its drawbacks—a cabinet thermometer can’t tell you what the temperature inside individual components is, it can’t raise the alarm if the temperature goes out of range, and it must be checked manually.
Another simple and inexpensive addition to a cabinet is a thermostat that automatically turns on a fan when the cabinet's temperature exceeds a predetermined limit.
Many network devices come with SNMP or IP-addressable internal temperature sensors to tell you what the internal temperature of the component is. This is the preferred temperature monitoring method because these sensors are inside your components where the temperature really counts. Plus you can monitor them from your desktop—they’ll send you an alert if there’s a problem.
There are also cabinet temperature sensors that can alert you over your network. These sensors are often built into another device such as a PDA but only monitor cabinet temperature, not the temperature inside individual devices. However, these sensors can be a valuable addition to your cooling plan, especially for older devices that don't have internal sensors.
The future of cabinet cooling.
Very high-density data centers filled with blade servers present an extreme cooling challenge, causing some IT managers to resort to liquid-cooled cabinets. They’re still fairly new and tend to make IT managers nervous at the prospect of liquids near electronics, but their high efficiency makes it likely that these liquid-cooled systems will become more prevalent.
It’s easy, really.
Keeping your data and server cabinets cool doesn't have to be complicated. Just remember not to overcrowd the cabinets, be sure to provide adequate ventilation, and always monitor conditions within your cabinets.
Black Box Explains...Choosing a cabinet.
Understanding cabinet and rack measurements.
The main component of a cabinet is a set of vertical rails with mounting holes to which you attach your equipment or shelves. When you consider... more/see it nowthe width or height of a cabinet, clarify whether the dimensions are inside or outside.
The first measurement you need to know is the width of the rails. The most common size is 19 inches with hole-to-hole centers measuring 18.3 inches. There are also 23-inch and 24-inch cabinets and racks. Most rackmount equipment is made to fit 19-inch rails but can be adapted for wider rails.
After width, the most important specification is the number of rack units, abbreviated as “U.” It’s a measurement of space available to mount equipment. Because cabinet width is standard, the amount of space is what determines how much equipment you can actually install. Remember, this is an internal measurement of usable space and is smaller than an external measure of the cabinet or rack.
One rack unit (1U) is 1.75 inches of usable space and is usually, but not always, measured vertically. So, for example, a rackmount device that’s 2U high takes up 3.5 inches of rack space. A rack that’s 20U high has 35 inches of usable space.
Choosing the right cabinet.
Here’s a quick checklist of features to keep in mind before you choose a cabinet for servers or other network devices:
• High-volume airflow.
• Adjustable rails.
• Rails with M6 square holes.
• Moisture and dust resistance.
• Air filters.
• Front and/or rear accessibility.
• Locking doors.
• Left- or right-hinging doors.
• Power strips and cable organizers.
• Interior lighting.
• Availability of optional shelves, fans, and casters.
• Cable management rails, space, and knockouts.
• Extra depth to accommodate newer, deeper servers.
Don’t forget to accessorize.
Even if your cabinet is in a climate-controlled room, you may need to add a fan panel to help keep your equipment from overheating. It’s especially important to have ventilation in an enclosed cabinet.
Rackmount power strips mount either vertically or horizontally. Some have widely spaced outlets to accommodate transformer blocks. Some power strips include surge protection.
Mission-critical equipment should be connected to an uninterruptible power supply (UPS). A UPS keeps your equipment from crashing during a brief blackout or brownout and provides you with enough time to shut down everything properly in a more extended power outage.
For accessories that make cabling easier, just take a look at our many cable management products. We have cable management guides, rackmount raceways, horizontal and vertical organizers, cable managers, cable hangers, and much more. collapse
Black Box Explains...Thermocouples
A thermocouple is a device that measures temperature by using the fact that a junction between two different metals produces a varying voltage related to their temperature. Two common types... more/see it nowof thermocouple are Type J and Type K.
Type J thermocouples use iron paired with a nickel-copper alloy. Type J thermocouples may cover a temperature range of up to -40 to +1382° F (-40 to +750°C), and offer high sensitivity.
Type K, the most common type of thermocouple, uses nickel-chromium and nickel-aluminum alloys. Because Type K is an early specification, its characteristics vary widely; individual thermocouples may cover a range of up to -328 to +2462 °F (-200 to +1350 °C).
Black Box Explains…Remote monitoring.
Beyond virus protection.
It has become almost automatic to protect your data center by backing up your servers, installing firewalls and virus protection, and keeping the protection up-to-date.
But what about... more/see it nowmore tangible threats? Do you have hot spots in your racks? If the cooling system shuts down, how will you know when temperatures climb out of control? Are you
alerted to humidity changes or water leaks
that threaten your equipment?
Planning for the unexpected is a critical task because there are more systems performing mission-critical functions than ever before. These systems are often deployed without the proper environmental infrastructure to support them. Equipment density is increasing constantly, which is creating more stress on ventilation and power.
The top three IT risks:
1. Environmental disruption.
The number one cause of downtime for remote locations, environmental problems go beyond fires and floods and affect as much as 30% of a company’s mission-critical infrastructure. Cooling and power are key points of exposure and increase as equipment density does.
2. Unnecessary risk.
When systems are housed in less-than-optimal settings, or are in remote and unsupervised locations, any error causes downtime. Yet, it’s not practical to have someone babysitting the servers.
Regardless of the probability, terrorism is
now something each of us must plan for. Your systems can also be brought down from within if the proper security safeguards are not in place.
What’s an environmental
Environmental monitoring products enable you to actively monitor the conditions in your rack, server room, data center, or anywhere else you need to protect critical assets. Conditions
monitored include extreme temperatures, humidity, power spikes and surges, water leaks, smoke,
and chemical materials. With proper environmental monitoring, you’re alerted to any conditions that could have an adverse effect on your mission-critical equipment. These products can also
alert you to potential damage from human error, hacking, or prying fingers.
Environmental monitors consist of three main elements: a base unit, probes or sensors, and
network connectivity and integration. The base units may contain one or more built-in sensors,
as well as ports for hooking up external probes. Additionally, they include an Ethernet port and have software for remote configuration and graphing. This software may also work with
existing network management software,
such as SNMP systems.
An environmental monitoring appliance
displays the values measured by the attached probes, e.g. temperature, humidity, airflow,
status of dry contact, door, motion detector,
and other sensors.
Data collecting and graphing.
Measurements are periodically stored in the internal memory or external storage media and displayed as graphs.
When the measured value exceeds the
predefined threshold, it triggers an alert: a blinking LED on the front panel, an audible alarm, SNMP trap, e-mail, etc. The environmental monitoring appliance can also activate an external alarm
system like a siren or strobe light.
Benefits of environmental monitoring:
Reduced downtime—When things go wrong, you’re the first to know. Minimize downtime by being alerted about conditions that cause damage to servers and other network devices.
Increased profits—Environmental monitoring systems are easy to implement. Also, they help you cut replacement equipment costs and redistribute your workforce more effectively.
Increased employee satisfaction—With built-in notification features like e-mail, SMS, and SNMP traps, a remote monitoring system enables employees to better manage their work.
Envornmental and security monitoring systems can be used for a variety of applications, including:
Data center monitoring
Computer room monitoring
Rackmount industrial equipment
Food and beverage applications
Air conditioner/refrigerants/freezer monitoring
Black Box Explains...Power over Ethernet (PoE).
What is PoE?
The seemingly universal network connection, twisted-pair Ethernet cable, has another role to play, providing electrical power to low-wattage electrical devices. Power over Ethernet (PoE) was ratified by the... more/see it nowInstitute of Electrical and Electronic Engineers (IEEE) in June 2000 as the 802.3af-2003 standard. It defines the specifications for low-level power delivery—roughly 13 watts at 48 VDC—over twisted-pair Ethernet cable to PoE-enabled devices such as IP telephones, wireless access points, Web cameras, and audio speakers.
Recently, the basic 802.3af standard was joined by the IEEE 802.3at PoE standard (also called PoE+ or PoE plus), ratified on September 11, 2009, which supplies up to 25 watts to larger, more power-hungry devices. 802.3at is backwards compatible with 802.3af.
How does PoE work?
The way it works is simple. Ethernet cable that meets CAT5 (or better) standards consists of four twisted pairs of cable, and PoE sends power over these pairs to PoE-enabled devices. In one method, two wire pairs are used to transmit data, and the remaining two pairs are used for power. In the other method, power and data are sent over the same pair.
When the same pair is used for both power and data, the power and data transmissions don’t interfere with each other. Because electricity and data function at opposite ends of the frequency spectrum, they can travel over the same cable. Electricity has a low frequency of 60 Hz or less, and data transmissions have frequencies that can range from 10 million to 100 million Hz.
There are two types of devices involved in PoE configurations: Power Sourcing Equipment (PSE) and Powered Devices (PD).
PSEs, which include end-span and mid-span devices, provide power to PDs over the Ethernet cable. An end-span device is often a PoE-enabled network switch that’s designed to supply power directly to the cable from each port. The setup would look something like this:
End-span device → Ethernet with power
A mid-span device is inserted between a non-PoE device and the network, and it supplies power from that juncture. Here is a rough schematic of that setup:
Non-PoE switch → Ethernet without PoE → Mid-span device → Ethernet with power
Power injectors, a third type of PSE, supply power to a specific point on the network while the other network segments remain without power.
PDs are pieces of equipment like surveillance cameras, sensors, wireless access points, and any other devices that operate on PoE.
PoE applications and benefits.
Use one set of twisted-pair wires for both data and low-wattage appliances.
In addition to the applications noted above, PoE also works well for video surveillance, building management, retail video kiosks, smart signs, vending machines, and retail point-of-information systems.
Save money by eliminating the need to run electrical wiring.
Easily move an appliance with minimal disruption.
If your LAN is protected from power failure by a UPS, the PoE devices connected to your LAN are also protected from power failure.
IEEE 802.3 af
|PoE IEEE 802.3 at
|Power available at powered device
|Maximum power delivered
|Voltage range at powred source
|Voltage range at powred device
|Maximum cable resistance