Understanding Rack Cabinet
May 29, 2023
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1. Introduction
Rack Cabinets are frequently used in our low-voltage projects, with wall-mounted and floor-standing options available. How to choose the right rack cabinet? We have encountered this question before, where choosing a large one would be wasteful while choosing a small one would be insufficient. To achieve precise selection, one must have a thorough understanding of rack cabinet knowledge. Today's knowledge is crucial.
2. Main Text
Regarding network cabinets, different equipment has strict requirements for cabinet specifications, standards, power capacity, and electrical compatibility. This seemingly inconspicuous cabinet needs to undergo rigorous design in terms of power supply, ventilation, layout, and other aspects when designing data center construction and business planning.
The industry does not have unified standards for the width, depth, and height dimensions of rack cabinets. Insufficient width may result in equipment not fitting, insufficient depth may cause the rear of the equipment to protrude outside the rack cabinet, and inadequate height may lead to insufficient space for equipment installation. Each type of equipment has strict requirements for the rack cabinet. For example, we often see physical parameter descriptions such as a width not less than 600mm, depth not less than 1100mm, height not less than 2000mm, and usable height space not less than 42U.
The power input of the network cabinet should not be less than the total power consumption of the devices inside the cabinet; otherwise, it may pose risks to the customer's power supply system, such as tripping. Therefore, it is necessary to evaluate whether the power consumption requirements are met.
During implementation, the load-bearing capacity of the network cabinet and especially the load-bearing capacity of the data center floor should be considered. Since the entire cabinet is relatively heavy, it is important to avoid posing safety risks to the customer's facility. Thus, an evaluation of the load-bearing capacity of the cabinet and the floor is required.
After adding equipment to the cabinet, the ventilation and heat dissipation in the data center may change. It is necessary to evaluate the heat dissipation capability to prevent device failures caused by excessively high environmental temperatures.
3. Cabinet Standards
When designing cabinets, certain standard specifications need to be followed. The most popular cabinet specifications currently include IEC (International Electrotechnical Commission) 60297-1, 60297-1 standards, EIA-310-D (19-inch cabinet standard), and others. The appearance specification includes requirements such as GB/T4054-1983 visual grade requirements, as well as electromagnetic compatibility standards like CISPR 22(2003), CISPR 24(1998-09+ A1:2001 A2:2003), IEC61000-4-2-X series. Among them, the IEC 60297-1 cabinet standard is the most widely adopted, while the EIA-310-D standard is the American standard.
The most commonly used cabinet in data centersgenerally adopts the requirements of the 19-inch mechanical structure dimensions (IEC 60297-2 specification) and a modular structure for easy expansion and maintenance. The outer surface and rack part of the cabinet is often gray.
In terms of calculating the capacity space of the cabinet, it is generally measured in "U." 1U is equal to 1.75 inches, approximately 44.45mm. U is the height unit defined in the IEC 60297 standard. The weight of an empty cabinet refers to the weight of the cabinet with the front door and rear door.
4. Cabinet Structure and Component Composition
Different standard rack cabinets have slight differences in structure and component composition, but in general, common cabinets consist of a front door, rack, and rear door. Some specialized cabinets may also include PDU, power supplies, cooling systems, management systems, and so on.
5. Working Environment of Cabinets
The working environment of cabinets mainly involves temperature and relative humidity. To ensure that the equipment always operates in good working condition, a certain temperature and humidity level needs to be maintained in the computer room.
The temperature and humidity of the computer room are measured at a height of 1.5m above the ground and 0.4m in front of the equipment. Short-term working conditions refer to continuous operation not exceeding 48 hours and not exceeding 15 days cumulatively in a year.
6. Characteristics of Cabinet Structure
This mainly includes the cabinet material, wiring method, ESD socket, cabinet cooling, cabinet protection, installation scenarios, and cabinet stacking.
Cabinet materials are generally made of high-strength Grade A carbon cold-rolled steel plates and galvanized plates. Internal materials also have certain standards and specifications to follow, such as meeting the fire protection performance requirements of UL (Underwriter Laboratories) standards and complying with RoHS (Restriction of the Use of certain Hazardous Substances) requirements. The fire protection performance of internal materials also complies with UL (Underwriter Laboratories) standards.
The top and bottom of the cabinet have cable holes, supporting both top and bottom cable routing methods.
When performing installation operations on the cabinet, it is necessary to wear an anti-static wrist strap, with one end of the wrist strap plugged into the ESD socket in the middle of the cabinet.
During installation and maintenance operations, it is necessary to wear an anti-static wrist strap, with one end of the wrist strap plugged into the ESD socket on the cabinet. The front and rear doors, as well as the bottom panel of the cabinet, have densely distributed ventilation holes, supporting front-to-back airflow, bottom-to-top airflow, airflow from under the floor, and airflow exiting from the top. This ensures that the cabinet has good heat dissipation performance.
In terms of protection, the cabinet design fully considers electromagnetic compatibility issues, making the cabinet have good electromagnetic shielding performance. The ventilation holes on the cabinet's bottom panel are lined with dust-proof nets, ensuring the good dust-proof performance of the cabinet. The design also considers the proper grounding of various components of the cabinet, with a grounding resistance not exceeding 0.1 ohms.
The cabinet supports side-by-side stacking, and the top is connected using cabinet connecting plates, which can achieve secure fixation of the cabinets and effectively utilize the space between cabinets. This is beneficial for customers renting computer rooms as it can effectively save space rental costs.
In some customized or high-end cabinets, a Rack Management Controller (RMC) is often equipped. The RMC can directly manage power modules, fan modules, and small systems.
Power modules are generally divided into AC/DC (compatible with DC/DC) types, providing power to DC devices inside the cabinet. The power modules support hot-swapping and redundant backup. Power management, including monitoring the power status and power capping, is achieved through the RMC module.
PDU (Power Distribution Unit) is divided into DC PDU, three-phase AC PDU, and single-phase AC PDU, providing power distribution for power modules and switches in the cabinet. Below is an illustration of a single-phase PDU.
PDU is used in conjunction with cabinets and is also one of the essential accessories for cabinets. It needs to meet certification requirements such as CE and ROHS, as well as consider whether it meets the input terminal type IEC 309 and output connections IEC 320 C13, and IEC 320 C19 requirements.
A network cabinet is used to combine installation panels, electronic components, plug-ins, junction boxes, devices, mechanical parts, and components into an integrated enclosure. When it comes to cabinets, beginners may have a somewhat vague understanding of the detailed external dimensions of the cabinet.
Let's start by understanding two conversion units: 1 inch = 2.54 centimeters and 1U = 4.445 centimeters.
7. Next, let's understand two basic concepts:
7.1 How to understand the 19" standard cabinet?
First, let's look at a national standard: GB/T19520.1-2007 "Dimensions of mechanical structures for electronic equipment - 482.6 mm (19 in) series." The international standard IEC 60297 is the same. The meaning is that a 19-inch cabinet refers to a cabinet with an internal equipment installation width of 482.6 millimeters.
Therefore, a 19-inch standard cabinet refers to a cabinet with an outer width of 600 millimeters and an inner width of 482.6 millimeters. Otherwise, it is called a non-19-inch standard cabinet.
7.2 How to understand the commonly mentioned 42U cabinet?
42U refers to the internal height of the cabinet. 1U = 44.45 millimeters, so 42U = 42 * 44.45 millimeters = 1866.9 millimeters. It means that the cabinet can accommodate 42 standard units of equipment (although it is not fully loaded). Why is the commonly mentioned 42U cabinet referred to as a height of 2 meters? It is because when adding the outer frame and casters, it reaches a height of approximately 2 meters from the floor to the top. Therefore, the height of nU cabinets can be inferred in the same way.
Generally speaking, the height of cabinets ranges from 4U to 47U. However, certain devices occupy only 1U, but there are no cabinets with a height of 1U, otherwise, it would be laughable.
Understanding these two aspects will help us better understand cabinet knowledge.
The structure of a standard cabinet is relatively simple, mainly consisting of a basic frame, internal support system, comprehensive cabling system, and ventilation system. The external dimensions of a 19-inch standard cabinet have three basic indicators: width, height, and depth. Although the installation width for 19-inch panel equipment is 465.1 millimeters (mounting hole spacing), the physical width of cabinets is generally available in two common sizes: 600 millimeters and 800 millimeters. The height usually ranges from 0.7 meters to 2.4 meters, depending on the number of devices and unified style inside the cabinet. Manufacturers can customize special heights, and the typical heights of finished 19-inch cabinets are 1.6 meters and 2 meters. The depth of the cabinet generally ranges from 400 millimeters to 800 millimeters, depending on the external dimensions of the equipment inside. Manufacturers can also customize products with special depths. The typical depths of finished 19-inch cabinets are 500 millimeters, 600 millimeters, and 800 millimeters.
For 1U, there is usually no specific requirement for depth, but cabinets for server placement are generally set to a depth of 1000 millimeters, while cabinets for network equipment are commonly set to a depth of 800 millimeters.
The equipment panels used in 19-inch standard cabinets are usually made according to the specifications of nU, with 1U commonly used for one device. Some non-standard equipment, most of them can be mounted and secured in a 19-inch chassis using additional adapter brackets. By understanding how many U (standard units) each device requires, one can accurately design the placement of equipment inside the cabinet. However, cabinets should not be fully loaded with devices. Generally, a 42U cabinet is equipped with 10-20U of devices due to heat dissipation and cable management requirements.
8. Now let's focus on understanding server racks and network cabinets.
8.1 Server Racks:
There are specifications for the depth, height, and load capacity of server racks designed specifically for installing 19-inch standard equipment such as servers, UPS systems, monitors, and non-standard devices. The height options include 2.0 meters, 1.8 meters, 1.6 meters, 1.4 meters, 1.2 meters, and 1 meter. Common widths are 600 millimeters and 800 millimeters, while common depths are 600 millimeters, 800 millimeters, 960 millimeters, and 1000 millimeters. Manufacturers can also provide customization based on customer requirements.
Optional accessories:
Fixed Cable trays, casters, sliding trays, cable management rings, horizontal brackets, horizontal cable management racks,vertical cable management racks, L brackets, blank panels, and others.
The main frame, front and rear doors, and side doors can be quickly assembled and disassembled.
Fixed trays:
Used to install various devices, available in different sizes and suitable for a wide range of applications. They include standard 19-inch trays and non-standard fixed trays.
The basic configurations of fixed trays have depths of 440 millimeters, 480 millimeters, 580 millimeters, 620 millimeters, and other specifications.
The load capacity of fixed trays ranges from 50 kilograms to 200 kilograms.
Sliding trays:
Used to install keyboards and other devices, allowing for convenient sliding in and out. Standard 19-inch sliding trays can be used with any 19-inch standard server rack.
The basic configurations of sliding trays have depths of 400 millimeters and 480 millimeters.
The load capacity of sliding trays is no less than 50 kilograms.
Power Distribution Units (PDUs) for server racks:
Optional power sockets are suitable for any standard power plug. They can be flexibly installed using a 19-inch mounting bracket.
Specifications include 6-port, 8-port, 16-port, 21-port, and other options.
Cable Management Rack:
A 19-inch standard cable management rack can be used with any type of standard server rack. The 12-hole cable management rack works best with 12-port, 24-port, and 48-port patch panels.
Cable Management Rings:
They are easy to install and remove, and the number and position of rings can be adjusted as needed.
L Brackets:
L brackets can be used in conjunction with server racks to install 19-inch standard equipment, especially heavy 19-inch devices such as rack-mounted servers.
Blank Panels:
Blank panels are used to cover unused spaces inside 19-inch standard server racks. They come in various sizes, including 1U, 2U, and so on.
Installation Nuts (Square Nuts):
They can be used with any TOPER series server rack for installing all equipment and most of the rack accessories.
Keyboard Tray:
Used to install standard computer keyboards, compatible with keyboards of all sizes available in the market. It can be folded 90 degrees. The keyboard tray must be used in conjunction with a sliding tray.
Fan Tray:
Installed on the top of the server rack, it allows the fan speed to be adjusted based on the ambient and equipment temperatures, effectively reducing the noise in the server room.
Variable speed options: Manual, step-less speed control.
Full-Mesh Front Door:
The front door of the server rack consists entirely of Ø3 round holes, improving the rack's heat dissipation performance.
Full-Mesh Rear Door:
The rear door of the server rack consists entirely of Ø3 round holes, improving the rack's heat dissipation performance.
8.2 Network Cabinet:
The network cabinet is mainly used for cabling projects and is used to store routers,switches, monitors, patch panels, and other equipment. It is widely used in engineering projects.
On the right rear side of the network cabinet, there are usually two 100mm-wide iron plates. Each plate has 5x100mm waist-shaped holes spaced 10mm apart vertically. The length of the iron plates is generally determined by the distance between the top and bottom plates of the cabinet. At the same time, a similarly sized iron plate is installed on the left rear side.
On the left rear side of the network cabinet, there is usually a fully enclosed metal power strip that extends from the bottom to the top of the cabinet. The topmost socket of the power strip is specifically designed for fans. The purpose of vertically installing the fully enclosed metal power strip is to avoid power interference with horizontal twisted pair cables.
In the middle section of the network cabinet, a grounding copper strip is vertically installed from the bottom to the top, and there is an M6 coarse thread screw hole every 2U distance on the copper strip. This is done to facilitate the grounding of nearby patch panels. The bottom screw hole of the copper strip can be used to lead out the grounding wire of the cabinet.
The rear of the network cabinet generally has a rectangular inlet hole of 300x200mm, which is wrapped with rubber. The purpose of this is to avoid damaging the cables. About 90mm above the hole, a partition is usually installed to improve the overall aesthetics of the cabinet.
The network cabinet should have excellent technical performance. To ensure that the cabinet has excellent electromagnetic isolation, grounding, noise isolation, ventilation, and heat dissipation performance, the construction of the network cabinet should be based on the electrical and mechanical performance of the equipment and the needs of the operating environment, and necessary physical and chemical design should be carried out. In addition, to ensure the stable and reliable operation of the equipment, the network cabinet should have properties such as impact resistance, vibration resistance, dust resistance, moisture resistance, corrosion resistance, and radiation resistance. The network cabinet should have good usability and safety protection devices, facilitating operation, installation, and maintenance, and ensuring the safety of the operator. The network cabinet should be conducive to production, installation, adjustment, packaging, and transportation. The network cabinet should meet the requirements of standardization, specification, and serialization. The design of the cabinet should be aesthetically pleasing, and practical, and have coordinated colors.
