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Centrifugal rectangular duct fans – RL



Basic features

  • Air flow up to 9200m3/h
  • Motor protection IP 54
  • Voltage controllable
  • Integrated thermal protection



Fully controlled, low-pressure centrifugal rectangular duct fans RL are designed to be integrated in square duct ventilation duct system. They can be universally used for complex air-conditioning, from simple venting installations to sophisticated air-handling systems.

RL fans are designed for indoor operation for conveying fresh air free of rough dust, grease, chemical fumes and other impurities.


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Installation and assembly

RL fans are designed to be integrated in ventilation duct system. Fans can be installed in any position and fixed on duct flange with screws.  In case other installation (with free inlet or outlet) installer has to prevent possible injury of rotating impeller.

Allowed temperature range in environment (place of installation) is from -20 °C up to +35 °C, relative humidity up to 90%.

Allowed maximal temperature of transported air is different for each type and is specified in detailed technical description of each fan type and size.

Outdoor applications are possible only if RL fan is protect against outdoor weather conditions (rain, snow and sun shine).  For outdoor applications it is necessary to finish the fans with a protective coating (except labeling) against air humidity and outdoor conditions.

All outdoor installations and non-standard features of transported air must be discussed and confirmed by producer or authorized dealer.

In any case installation it must be done so that there is enough space for access in terminal box and fan motor cup.  If the risk of moisture condensation inside the fan exists, it is better no situate motor (the fan's cup) downwards.

To not increase pressure lost and noise we recommend let approx. 1m long straight duct to the fan's outlet


Detailed description

Dimensional Range

RP fans are manufactured in a range of many sizes according to the standard HVAC channels dimensions. Fan can be equipped with one or three phase motor. Fans differing in the number of motor poles too. The standard dimensional and performance range enables optimize all parameters for air flow up to 9 200m3/h.

Tip: When planning the fan for the required air flow and pressure, the following general rule is applied: the lager fans with higher number of poles reach the required parameters at lower RPM, which results in lower noise and longer service life. Fans with higher number of poles also have lower air velocity in the cross section, which results in lower pressure losses in the duct and accessories, however, at higher investment costs.

Construction and materials

Fan bodies and impellers are made from galvanized steel with Zn layer 275g/m2. Motors are made of aluminum alloys, copper and plastics. All materials are designed in accordance with fan usage, maximum durability and minimal maintenance.


Impeller has forward curved blades and is perfectly statically and dynamically balanced. Proper direction of the impeller rotation must be checked after installation and connection on power supply. Correct direction of rotation is marked on fan body.


RL fans are equipped with energy saving single-phase and three-phase asynchronous motors with an external rotor and a resistance armature. The motors are situated inside the impeller and during operation are optimally cooled by the flowing air. The motors have high quality enclosed ball bearings with permanent lubricating filling enable the fans to reach above 40,000 operating hours without maintenance.

The motor electric protection is IP 54 (only RL40-20-4D and RL50-25-4D has IP44) and insulation class is F. The motor windings are impregnated to provide them with additional protection against moisture.

For motor protection (overheating) are used thermal contacts situated in the motor winding. The thermo-contacts are miniature bimetal switches which after being connected to the protective contactor circuit protect the motor against overheating (damage) due to any reason. Thermal protection by means of thermo-contacts is comprehensive and reliable providing they are correctly connected. This type of protection is essential especially for motor:

  • that are speed controlled by voltage
  • that are operated with excessive switching frequency
  • that are seized
  • that are highly thermally loaded by hot transported air
  • whose cooling has been changed

Therefore, the fan motors cannot be protected by conventional thermal protection ensured by the motor overcurrent protective elements!

Electrical Equipment

Terminal box is placed on fan body and has protection degree IP 54. Single-phase motors are equipped with a starting capacitor which is placed on the fan body too. For wiring diagrams, see detailed information in technical catalogue.



Type of fan Dimensions [mm]
RL40-20-4D 400 200 420 220 440 240 281 501 182 9
RL40-20-4E 400 200 420 220 440 240 281 501 182 9
RL50-25-4D 500 250 520 270 540 290 331 530 198 9
RL50-25-4E 500 250 520 270 540 290 331 530 198 9
RL50-25-6D 500 250 520 270 540 290 331 530 198 9
RL50-30-4D 500 300 520 320 540 340 381 565 209 9
RL50-30-4E 500 300 520 320 540 340 381 565 209 9
RL50-30-6D 500 300 520 320 540 340 381 565 209 9
RL60-30-4D 600 300 620 320 640 340 381 642 234 9
RL60-30-4E 600 300 620 320 640 340 381 642 234 9
RL60-30-6D 600 300 620 320 640 340 381 642 234 9
RL60-35-4D 600 350 620 370 640 390 431 720 258 9
RL60-35-6D 600 350 620 370 640 390 431 720 258 9
RL70-40-4D 700 400 720 420 740 440 481 780 282 9
RL70-40-6D 700 400 720 420 740 440 481 780 282 9
RL80-50-4D 800 500 820 520 840 540 581 885 315 11
RL80-50-6D 800 500 820 520 840 540 581 885 315 11
RL90-50-4D 900 500 930 530 960 560 591 985 350 11
RL90-50-6D 900 500 930 530 960 560 591 985 350 11


The output of all RL fans can be fully controlled by changing the speed. The fan's speed is changed depending on the voltage at the motor terminals.

More stage voltage control (transformer) of single-phase and three-phase RL fans is the most suitable, technically as well as operationally. There is no interference, humming, squeaking or vibration of the motor. For suitable type of controller see detailed information for each fan type and size in tecnhical catalogue.

Motor cannot be controlled by frequency converter.

Thermal contact must be connected in to the protective contactor circuit which manage disconnecting fan from power supply.