A Server Rack Guide : Selecting The Right Server Racks and Data Cabinets

In any IT environment, server rack and cabinet choices are fundamental to the overall physical layout, hardware reliability and uptime. The choice of rack type, cabinet dimensions, power distribution, and cooling approach all have direct consequences for airflow management, IT hardware, uptime, working life, and the ability to scale infrastructure over time. A correctly specified server rack installation reduces the risk of equipment overheating, maintains efficient cable and power management, and provides the physical security and access controls required by regulated environments.

Server Rack Types, Sizing, Power, Cooling and Compliance

Server Room Environments supplies a complete range of server racks and data cabinets from 4U to 48U, including standard and bespoke enclosures, open-frame racks, wall-mounted cabinets, air-conditioned racks. Available brands include APC by Schneider, Eaton, Legrand, Panduit, Prism, Rittal, Tripp Lite and Vertiv, alongside SRE’s own-brand cabinets manufactured in the UK. This guide covers the key specification decisions for any server rack project, whether specifying a new server room from the ground up or refreshing an existing installation.

What Is A Server Rack?

A server rack or cabinet is a standardised metal enclosure designed to house IT equipment in a structured, vertically stacked format. The 19-inch mounting rail standard, which defines the width of rack-mounted equipment, has been in place for decades and allows hardware from different manufacturers to be installed in the same enclosure without custom fabrication or modification.

Beyond providing physical housing, a rack directly influences how heat moves through the equipment, how power is distributed to each device, how cables are routed and managed, and how quickly engineers can locate and address faults. In a properly specified installation, the rack is an integral part of the room’s overall thermal and power management strategy, not simply a container for hardware.

For IT managers and infrastructure leads, rack selection also has consequences for compliance and physical security. ISO 27001 includes controls relating to physical access to IT equipment, and organisations in regulated sectors, including healthcare, financial services and the public sector, are generally required to demonstrate that access to IT infrastructure is controlled, logged and auditable.

Server Rack Types

The right rack type depends on the data environment, security requirements, cooling approach and rack density; the number of racks required for the installation. The main types are summarised in the table below.

Open-Frame Racks

Open-frame racks, available in two-post and four-post configurations, provide unrestricted access and excellent natural airflow. The absence of side panels and doors makes them practical for controlled telecom applications where physical security is managed at the room or facility level rather than at the individual rack level. Two-post open frames are commonly used for patch panels and lighter networking equipment; four-post frames provide the structural support required for full-depth servers and storage arrays.

Open-frame racks are generally lower in cost than equivalent enclosed cabinets and easier to work in during installation and maintenance. They are not appropriate where physical access control at the rack level is a security or compliance requirement.

Enclosed Server Cabinets for Server Rooms and Data Centres

These cabinets are typically available from 12U to 48U or more, and with side panels and lockable front and rear doors. They are the most commonly used in data centres, server rooms and comms rooms. The cabinets can be installed with key-lock doors, combination-lock doors, or RFID door handles with access control. The cabinets can be installed with front and rear cable management. Blanking panels are used to support an effective airflow strategy. The blanking panels fit to the front server cabinet pillars. Effective cooling also requires the doors and side panels to be fitted.

Server cabinet doors can be glass (commonly used for a front door), mesh, perforated or steel. Server manufacturers typically want a minimum door performance factor of 60% or more to ensure adequate front-to-rear airflow through the cabinet. For high-density deployments, perforated front and rear doors combined with blanking panels in unpopulated rack U-spaces are essential. These help maintain airflow from the front to the rear and the mixing of cool and warm exhaust air, helping maintain inlet temperatures.

Server Room Environments supplies enclosed cabinets in standard widths of 600mm and 800mm, with depths from 600mm to 1200mm. The wider 800mm cabinet provides greater access for cabling, but care must be taken with logistics planning, as it is wider than most typical doorways. Assembly on-site from flat-pack kits may be required. Most racks are available in black or grey paint finishes. A wider set of custom colours may be available for large-quantity runs.

Wall-Mount Cabinets

Wall-mount data cabinets are sometimes referred to as data cabinets and are typically used to house smaller quantities of IT equipment, including routers and hubs, patch panels, small switches and UPS systems. They may range from 4U to 22U, have a shorter depth than a floor-standing cabinet, between 400 and 600mm. Wall-mount enclosures are not designed for high-density server deployments and should not be used where heat loads or equipment weight exceed the specified limits for wall-mounted installation.

Air-Conditioned Racks

Air-conditioned racks integrate self-contained cooling directly into the cabinet enclosure. The side-mounted air conditioner maintains an internal cabinet temperature of 25degC upto an external temperatue of 30degC. This makes them suitable for buildings where a dedicated server room is not available.

Server Room Environments supplies air-conditioned rack enclosures in 27U and 42U configurations with single-phase 1.5kW or 3-phase 2.5kW cooling units and IP54 ingress protection ratings, allowing deployment in locations outside a controlled server room environment. These enclosures are commonly used in manufacturing facilities, production environments and remote locations where ambient conditions would otherwise preclude the installation of sensitive IT equipment.

Acoustic or Soundproof Racks

This type of server cabinet is designed to reduce noise levels by approximately 95%. This is achieved by using sound insualting foam within the cabinet design and super silent cooling fans. The fans are AC powered and require a suitable uninterruptible AC power source.

Outdoor Enclosures

This type of cabinet is used in outdoor spacea including roadside applications. The cabinet is designed with 19inch profiles, cooling and heating options to provide a safe and secure cabinet for IT related loads.

Rack Units, Dimensions and Load Capacity

Every piece of rack-mounted equipment is measured in rack units (U), where 1U equals 44.45mm of vertical space. A 1U server occupies a single rack unit; a large storage array may require 4U or more. Understanding the U-height of all current and planned equipment is a prerequisite before committing to a rack height.

Standard srack dimensions are summarised in the table below:

Load capacity is a critical specification that is frequently underestimated during planning. Static load ratings indicate the maximum weight the rack can bear when stationary; dynamic ratings apply when the rack is being moved. A fully populated 42U cabinet with dense servers, a rack-mount UPS and cable management can exceed 500kg. Floor loading should be verified at the same time, particularly in older buildings and upper-floor installations where construction constraints may apply.

How large a rack will you need? It is important to allow at least 20% free rack space for future expansion from day one. This can also help to improve airflow, especially in highly populated racks and avoid the thermal risks and hotspots associated with heavily populated racks.

Server Rack Power Distribution

Power distribution within a server rack starts with selecting the appropriate PDU (power distribution unit) based on the load characteristics, including socket outlet types (C13, C19), number required, power supply (single- or 3-phase), and required PDU features.

Basic PDUs provide multiple outlet sockets from a single input supply and are suitable for non-critical applications where per-branch or outlet monitoring is not required. Intelligent PDUs add per-outlet power monitoring, remote on/off switching, load reporting and integration with environmental monitoring systems, providing the data needed for capacity planning and fault diagnosis.

For critical environments, dual-corded equipment fed from separate PDUs on independent A and B power circuits provides resilience at the rack level. This architecture, combined with a dual-input UPS system or dual UPS feeds from separate units, eliminates the rack power path as a single point of failure. Rack-mount UPS systems from 500VA to 20kVA are available from Server Room Environments for installations that require battery backup within the cabinet itself.

PDU socket types should be confirmed against the equipment being installed. The most common connectors in UK server room environments are IEC C13 (for standard 1U servers and networking equipment) and IEC C19 (for higher-current devices including high-density servers and storage arrays). Mixing socket types on a single PDU is possible and avoids the need for adapters, but the PDU specification must be confirmed against the actual devices being powered.

Rack Cooling and Airflow Management

Rack-level cooling is directly interconnected with the room-level cooling strategy and airflow management. IT equipment is designed to draw cool air in through the front of the rack and exhaust hot air from the rear. Maintaining this front-to-rear airflow direction consistently across all equipment in a rack is a basic requirement for effective thermal management.

Blanking panels should be installed in every unused rack unit space. These inexpensive fillers, available in 1U and 2U configurations, prevent hot exhaust air from recirculating to the front of the rack through unfilled U-spaces, a phenomenon that can increase inlet temperatures even in a well-cooled room. Blanking panels are among the lowest-cost, highest-impact interventions available in any server room installation.

For high-density racks exceeding 10kW per cabinet, room-level precision air conditioning may be insufficient to prevent localised hot spots. In-row cooling units positioned within the server row, rear-door heat exchangers fitted to individual cabinets, and overhead cooling units are all options for delivering cooling closer to the heat source. These approaches integrate with hot- and cold-aisle containment installations, which Server Room Environments designs and installs as part of complete data centre cooling projects.

Fan trays can be fitted within rack cabinets to supplement passive airflow where required. These can be mounted at the top, rear or sides of the cabinet and are available in AC and DC configurations. Bespoke fan tray designs are available through SRE for non-standard cabinet dimensions or specific airflow requirements.

Cable Management

Structured cable management is important in server racks. Cable population directly affects airflow performance, fault-finding speed, and the safety of equipment changes. Unmanaged cabling restricts airflow through the cabinet, obscures equipment status indicators, and increases the risk of accidental disconnection during maintenance.

Horizontal cable managers mounted between rack units provide a dedicated routing path for patch cables at each cabinet level. Vertical cable managers fitted to the sides of the rack handle power cables, longer fibre runs and trunk cables between equipment at different heights. Both horizontal and vertical cable management should be specified as part of the initial rack design, not added retrospectively once the cabinet is populated.

Consistent labelling of cables, at both the device and patch panel ends, helps to reduce fault-finding time and is a practical requirement in any environment where multiple engineers or contractors will work in the rack over the rack’s operational life. Colour-coded patch cables are a widely used convention for distinguishing between networks, VLANs or service types within a single cabinet.

Rack Layout and Population

It is important to plan where each item will be placed within a server cabinet. Each will have its own heat output and cabling requirements (front or rear), as well as inspection or maintenance requirements. High-density servers and storage arrays, which generate the most heat and add the most weight, should be positioned in the middle of the rack where airflow is most consistent, and the centre of gravity is most stable. Networking equipment and patch panels are typically mounted near the top of a cabinet where they are more easily accessible and generate relatively little heat. Rack-mount UPS units are generally installed at the bottom of the cabinet to maintain a low centre of gravity, which is particularly important for taller cabinets. If rack-mounted fire suppression is installed, it will be placed at the top 2U of the server cabinet, leaving at least 2U before the next device. This is because the fire solution will discharge with force downwards when activated.

All equipment should be installed with front-to-rear airflow orientation. Installing equipment in mixed airflow orientations within the same cabinet, some drawing air from the front and exhausting to the rear, others drawing from the rear and exhausting forward, creates thermal conflict that cooling systems cannot fully compensate for and that will result in elevated operating temperatures for some equipment.

It can be useful to maintain a rack-populated diagram in a spreadsheet or within a suitable program such as a DCIM (Data Centre Infrastructure Management) platform or environmental monitoring package, such as Quicklime from AKCP, which includes the facility for rack maps. Each time changes to the rack population are made, the maps should also be updated to maintain an accurate record of what is installed in each rack, the power draw of each device, and the distribution of weight and heat load across the cabinet, information that is essential for capacity planning and for engineers responding to faults.

Compliance, Physical Security and Electrical Safety

Rack infrastructure is subject to a range of compliance, safety and security requirements that vary by sector and the nature of the data being processed.

Physical security is a baseline requirement for most organisations. Enclosed racks with key-locked or combination-locked front and rear doors are the minimum for IT hardware handling sensitive or personally identifiable data. For higher-security deployments, individually alarmed rack doors, electronic access control with audit logging, and CCTV coverage of the rack environment may be required. ISO 27001, which Server Room Environments holds certification to, includes controls that relate directly to physical access to IT equipment and its management.

Electrical installations within any building must comply with BS 7671:2018 (18th Edition), the UK wiring regulations, which apply to data centres, server rooms, and comms rooms. The regulations stipulate the requirements for earthing and bonding, circuit protection, cable segregation between power and data cabling, and the labelling of distribution circuits. This is relevant for server cabinet installations with power distribution units (PDUs) and critical power protection infrastructure, including uninterruptible power supplies. Hardwired connections must be carried out by qualified electricians, and periodic inspection and testing of the electrical installation are required to maintain regulatory compliance. Plug-and-socket connections, installed by a suitably qualified electrician, can be ‘plug-and-play’ for the local IT team.

For more information on BS 7671:2018 (the 18th Edition, Amendment 4), see: https://shop.theiet.org/product-category/electrical-regulations

Seismic and structural considerations apply where racks are tall, fully loaded, or installed on raised access floors. Anti-tip restraints and floor anchoring should be standard practice for floor-standing cabinets above a specified height or weight. Raised access floor tiles beneath heavily loaded racks should be rated for the imposed static and dynamic loads, with spreader plates used where tile capacity is a limiting factor.

Server Room Environments holds ISO 9001, ISO 27001, and SafeContractor certifications and works with clients across the UK in regulated sectors, including healthcare, financial services, and the public sector, to ensure rack infrastructure meets operational, compliance, and audit requirements from installation onward.

Summary

Server Room Environments supplies a complete range of rack enclosures and accessories for server rooms and data centres of all sizes, from 4U wall-mount cabinets for edge and branch locations through to bespoke 47U floor-standing enclosures for high-density data centre environments. Rack supply is supported by design, installation and commissioning services, with nationwide engineering coverage and manufacturer-certified technical support across all major rack brands.

For new installations, Server Room Environments provides free site surveys covering rack specification, floor loading, power distribution, airflow management and containment design, guaranteeing that the physical infrastructure is correctly sized and specified for current requirements and planned growth. For existing installations, rack audits and infrastructure reviews are available to identify thermal risks, power capacity constraints and cable management improvements.

For more information on server rack supply and installation, or to arrange a free site survey, please contact our Projects Team.