Free Cooling Unit – System Infra Solutions

Free Cooling Unit

Cooling Solutions for Telecom industry without Compressor.

Free Cooling Unit is Cooling solution that uses the ambient air to cool the Electronics and Electrical system inside a shelter.

The electronic Microprocessor based controller allows free cooling and emergency cooling by sensing room and ambient temperature.

Free Cooling Unit – Benefits:

  • Excellent Power savings
  • Faster ROI
  • Reduces AC running time increasing appliance life.
  • Eco friendly
  • No need of Generators since the fan runs with 48 V
  • Low maintenance
  • A sturdy cooling solution for emergency and ordinary cooling
  • Less maintenance

How does a Free Cooling Unit Works


  • FCU – (Free Cooling Unit) is equipped with Microprocessor based control unit to precisely control the operation of the Cooling Unit, Air-conditioners and Generator of a Telecom site. Suitable temperature sensors and intelligent interface with the Air conditioning equipment, Generator ensures these are Switched ON when absolutely necessary to minimize power consumption.
  • When the ambient temperature is >2-4 °C lower than inside, the heat load inside the shelter is transferred outside through mass transfer between air inside and outside. Free cooling results in reducing the operating time of air conditioner (AC), lengthening the life of AC and saving the energy.
  • Gravity louvers restrict outside air contact when not in use.
  • Air filters provide clean air.
  • -48V DC operated variable speed control fans to optimize the usage.

Free Cooling Unit – Salient Features

  • Electronic Clean Room Environment
  • Energy savings up to 80% with free cooling
  • Emergency cooling
  • Monitors indoor shelter & outdoor air temperature
  • Speed Controlled DC Fans to maintain set temperature
  • Generator & Air-conditioner control
  • Microprocessor controlled system for automated and optimized operation
  • Light Weight and easy transportation
  • Sturdy design
  • Gravity Louvers to block outside air contact, when not in use
  • Specially designed air-filters to provide clean air

Technical Specification for FCU

1 CAPACITY 4 KW , ΔΤ = 5 ° C
3 SHELTER SET TEMP 20 ° C to 35 ° C ( Default Value 30° C )
5 CASING MATERIAL GI Powder Coated, 1.2 mm for main Box, 1.6 mm for motor support, 1.0 mm for flange.
6 DIMENSION 615 x 615 x 420 mm ( L x B x H ) Approx.
7 FAN 48 V DC EC Centrifugal Fan backward curved with inlet cone step less variable speed controllable from controller.

EBM PAPST – Model- R3G-4000 AD20-30

8 FILTER Washable wave type HDPE 600 x 600 x 75 mm with metal frame, efficiency 90%down to 10 mi-cron. /Back removable from outside housed at the bottom.
9 AIR SUCTION Bottom of unit GI Powder Coated mesh.
10 AIR DISCHARGE From front open able in shelter.
11 GRAVITY DAMPER Two piece assembly with gravity louvers for an opening of 400mm X400mm with GI powder coated frame 60mm THICK and aluminum blades. Internal assembly to be fitted from inside and external assembly to be fitted from outside to meet rain protection.
12 Inlet Ring Inlet ring of diameter recommended by fan manufacturer punched on the partition sheet.
13 CONTROLLER This controller allows Free Cooling and Emergency Cooling based on room as well as ambient temperatures.

Tools required for installation

  1. Star Screw Driver kit
  2. Sealant gun
  3. Spanners of 16/17 and 18/19 each one number
  4. Screw driver kit
  5. Tester
  6. Jig saw cutter

Packing list

  1. FCU Sheet metal assembly
  2. Accessories box
  3. Exhaust assembly (internal 1 no)
  4. Exhaust assembly (external 1 no)
  5. Silicone Sealant with cap (1 no)
  6. Bolt, Nuts & washers (6 nos)
  7. Screws ( 10 nos)
  8. Controller ( RH Sensor, Ambient Temp Sensor, Room Temp Sensor)
  9. Cables ( 2 Core -1.5Sqmm -1 Nos, 4 Core -2.5Sqmm -1 no)
  10. Tie clips & cable sticks (10 nos)
  11. Flexible hose (1 no)

Installation Procedure:

Step – 1

  1. Open the packing box and check all the accessories as per the list.
  1. Cut the panel to the required size (563mm W X 232mm H) as shown in the drawing below.
  1. Lift the unit and fix in the cut out and insert the bolts from outside and fix washers from inside and tighten the nuts as shown in the picture. Also drill a small hole diagonally right top corner for taking the cable into the room.
  2. Apply sealant around the mouth of the discharge grill to avoid leakage of air.
  3. Cut the panel to the required size ( 395mm W X 385mm H) as shown in the drawing where the exhaust is to be located. Fix the internal and external exhaust assembly by using screws.

Drawings & wiring diagrams

Fix the controller and connect the FCU and Air-conditioners through the controllers as per the drawing.


  1. A detailed user manual for the controller is available in each box. Please follow the Instructions carefully.
  1. All specifications subject to change without any prior notice due to continuous R & D


This controller allows Free Cooling and Emergency Cooling based on room as well as ambient temperatures.

Features of Controller

  1. Power supply 48 VDC
  1. Analog Inputs: 4

1) Room Temperature sensor

2) Ambient Temperature sensor

3) Indoor Humidity Sensor

4) Input Supply DC voltage sensing

  1. Analog outputs: 2

0-10 V DC Fan1 Control Voltage

0-10 V DC Fan2 Control Voltage

  1. Digital Inputs:

1) AC1 Alarm Input

2) AC2 Alarm Input

3) AC1 voltage input

4) AC2 voltage input

  1. Digital Outputs:

1) Damper Forward and Reverse (Damper 48 V operated)

2) Relay for Compressor1

3) Relay for Compressor2

4) Alarm Relay (All Sensor Fails, Very High Temp, DC voltage Fail)

5) FC/EFC ON Alarm

  1. User Interface

Display: 4 Digit Display and 5 LEDs for indication.

2 digits for Room Temperature /Room RH

2 digits for Ambient Temperature

Keypad: 5 keys (PRG, UP, DOWN, RH, SET).



  1. The controller will measure the run hours of FCU.
  2. Temperatures shown above are default values. Controller shall have the provision to change the same through key pad at site.
  3. Controller shall ensure AC off when Free cooling is ON & vice versa
  4. The Controller shall have green LEDs for power, Fan & red LEDs for alarm. One Potential free contact for remote alarm shall be provided.


  1. Making suitable cutouts in the shelter for inlet unit & outlet air unit shall be the firm’s responsibility.
  2. Inlet unit FCU shall be installed as low as possible at a position which allows proper air circulation in the shelter and there is no hindrance for suction of fresh air.
  3. Out let unit should be installed diagonally opposite to the free cooling box above door height as far as possible. This should be adequately sealed to prevent any leakage of cool air when AC is on.
  4. The firm shall be responsible for installation, testing & commissioning of FCU on turnkey basis.

All installation materials (nuts ,bolts etc ), power cables, 10 A DP MCB with box suitable for 48 V DC, Interconnecting cables between controller & existing AC controller, connectors and all other accessories shall be supplied by the FCU firm at its own cost..