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The OnRak is a compact rear door heat exchanger designed to manage discharge temperatures from the server into the aisle space. In dealing with the heat load at source, the OnRak is highly efficient in floor space and power usage.

Part of the LogiCool range of IT cooling solutions, the OnRak offers an expandable cooling system that can be supplied with an industry standard data rack (42 – 48U) or a mating frame to fit a customer-specific rack. The slim configuration of the OnRak ensures minimal impact into the aisle.

Efficient, Adaptable, Resilient

Enhanced by smart control logic and EC fan technology, the OnRak has an Energy Efficiency Ratio (EER) of more than 100. A means of comparing efficiency, the EER is a ratio of cooling divided by power input. Over a year, an OnRak with an EER of 144 will achieve 88% saving in power input compared with a traditional close control unit with the same capacity (see page 98, Key feature: EC axial fans).

To create an integrated, flexible cooling solution for the data centre, multiple OnRak units can be linked with an Airedale large capacity air cooled chiller using sophisticated AireTronix controls technology. Substantial energy savings are achieved when the OnRak is matched with a free-cooling chiller.

Maximising Uptime

  • n+1 fan configuration
  • ‘Door open’ air flow management
  • ‘Hot swappable’ fan management
  • Easily removable control panel
  • Static transfer switch for instant power supply changeover (option)
  • Uninterrupted power supply (UPS) (option)

Key Technical Data

  • Two product configurations: n (100% air volume); optional n+1 (75% air volume)
  • Cooling capacity: 33kW (n); 28kW (n+1)
  • Variable speed fans for precise cooling between 3 – 33kW
  • EC axial fans for ultimate efficiency: EER of 108 (n); 174 (n+1)
  • Advanced AireTronix control system solutions
  • Flexible water connections maintain cooling when the door is open
  • Self-regulating constant flow control simplifies commissioning
  • Water detection and automatic isolation
  • High efficiency aluminium fin heat exchanger


Key Feature: Simple Connections To Customer-specific Rack


To apply the OnRak to a customer-specific rack with a diff erent width and / or U size, the OnRak can be supplied with an appropriate mating frame which is fitted to the rack cabinet. The OnRak door is then simply dropped onto the frame via lift-off hinges.

Two flexible, stainless steel braided hoses connect the coil to the chilled water supply. The flexibility of the hoses allows the OnRak door to be easily opened for accessing hardware within the server cabinet, without the need to disconnect services or disrupt cooling.

Typical Applications

OnRak Applications

Key Feature: EC Axial Fans For Ultimate Efficiency At Part Load


Since most servers operate at less than 100% capacity, energy costs can be significantly reduced when cooling equipment operates at part load. Since the OnRak has been engineered with very low air flow resistance, it can accommodate latest EC axial fan technology which offers greatly enhanced fan efficiency particularly at part load.

An OnRak with EC fan technology and offering 23kW of cooling uses 0.161kW of power and has an EER of 144. A traditional close control unit delivering same amount of cooling uses 1.3kW of power and has an EER of 17. Over a year, the OnRak in this example will consume 1,410kWhs of power against 11,388kWhs of the close control unit, representing a saving of 88% in power input (see graph right).

Key feature: Pressure Differential Management


By managing pressure at the rear of the server rack, the OnRak controls its fans to ensure they mirror the fans cooling the servers inside the rack
cabinet. The server fans draw air through the servers to the back of the rack where the OnRak’s fans pull the air from the rack and discharge it into the room.

Through active pressure differential control, the OnRak maintains pressure in the rear of the rack within the serverdesign envelope, whilst still ensuring temperature is controlled.

Key Option: n+1 Fan Configuration For Increases Efficiency And Uptime

  • 1U rackmount drawer with either 17” or 19” SAMSUNG LCD
  • Either PS/2 or USB input to the LCD drawer by cable selection
  • Multiple keyboard language selections with either touchpad or trackball
  • Slide rails with fixed positions to prevent drawer movement when typing
  • Multi lingual on screen display menu
  • 12, 24 and 48 volt DC power options

Power Input comparison

AIRETronix controls

The OnRak is equipped with very latest, intelligent Airetronix microprocessor specially developed by Airedale to facilitate automation and optimisation of the system. The fully programmable microprocessor is linked with key components within the cooling system, allowing sophisticated, modulating and self-optimising control for increased energy efficiency.

Tri-Colour LED Status Display

Tri-Colour LED Status Display A tri-colour LED display gives an immediate visual indication of the unit status from a distance, with red denoting critical
status, orange being non-critical and green, all systems functioning. The controller’s door-mounted display features a semi-graphical screen and keypad with optional audible alarm function and allows adjustment of control parameters and viewing of the unit’s operating status.

LED Display

OnRak Controls Management

  • Supply air temperature control
  • Fan speed modulation
  • n & n+1 fan redundancy setup
  • Dew point calculation
  • 2 way valve control
  • ‘Door open’ air flow management
  • Supply / return solenoid valves
  • ‘Hot swappable’ fans
  • Cabinet air pressure
  • Easily removable control panel

Remote Supervision Airedale BMS: Plant Visor Pro

Visor Pro is an intelligent, powerful, latest technology BMS software programme which integrates multi-unit systems managed by intuitive AireTronix controllers and located on one or more sites, into a single, proactive control platform. With the click of a button, information can be pulled back automatically and used for remote monitoring and control including 24/7 alarm indication; time scheduling and adjustment of temperature setpoints for system optimisation and energy efficiency.


The network-capable AireTronix controller can be integrated with a wide range of BMS protocols.


pCOWeb Ethernet Solution

pCOWeb supervisory plug-in cards make communicating with the OnRak purely a matter of logging onto the office Intranet or the web. Based on Ethernet TCP/IP secure technology and SNMP features, pCOWeb requires no proprietary cabling or monitoring software, little or no set-up on site and is pre-programmed with an IP address.

Airedale Controls – Additional Services

Optimised Control System Solution

Optimised Control System

Key feature: Hot swappable fans maintain cooling

Each of the OnRak’s four EC axial fans are ‘hot swappable’ which means that a fan assembly can be removed from the unit whilst it is running and replaced with another fan assembly.

When a fan assembly is unbolted from the OnRak, a micro switch fitted to the main door assembly detects that the fan is being removed and cuts power to the fan. A signal is also sent to the unit’s controller and the OnRak’s other three fans speed up to maintain cooling performance.

Key feature: Integration with a free-cooling chiller, reduces whole life costs*

Free-cooling operates with as little as 1ºC differential between ambient and return fluid temperatures. By dealing with a higher grade heat and subsequent higher processor air off temperatures, a large proportion of the year can be spent in free-cooling mode. In the 24/7 environment of a data centre, a free-cooling chiller will use very little mechanical cooling.

The LogiCool air cooled chiller for example typically saves more than 50%* of the energy consumed by a conventional chiller, by achieving 0-100% free-cooling through integrated, simultaneous mechanical / freecooling.

* Based on Met. Office average ambient figures for London, UK at 16/21ºC, 20% ethylene glycol


Optimised control system solution