Discharge positions of centrifugal fans (LG & RD)
Centrifugal fans are available in various discharge positions, depending on the required airflow direction within your installation. These positions are indicated by the abbreviations RD (right-hand discharge) and LG (left-hand discharge), followed by an angle in degrees that shows the orientation of the discharge opening relative to the motor shaft.
Selecting the correct discharge position prevents unnecessary duct bends, reduces pressure losses, and increases the overall efficiency of your system.
What do RD and LG mean in fans?
The discharge position of a centrifugal fan is determined by viewing the fan from the drive side. The following applies:
- RD (Right-hand discharge): The airflow exits in a clockwise direction.
- LG (Left-hand discharge): The airflow exits in a counterclockwise direction.
The angle (0° to 315°) indicates the exact orientation of the discharge opening relative to the motor shaft, in 45° increments.
Overview of discharge positions
The diagram below shows the discharge directions (LG and RD) of centrifugal fans. This visual is often used when specifying fan configurations. In the table below, you will find the corresponding descriptions.
Intermediate positions (e.g., RD 45, RD 135, LG 225, etc.) are chosen when precise duct alignment is required.
| Abbreviation | Description |
|---|---|
| RD 0 | Clockwise rotation, discharge straight up |
| RD 90 | Clockwise rotation, discharge to the right |
| RD 180 | Clockwise rotation, discharge downward |
| RD 270 | Clockwise rotation, discharge to the left |
| LG 0 | Counterclockwise rotation, discharge straight up |
| LG 90 | Counterclockwise rotation, discharge to the left |
| LG 180 | Counterclockwise rotation, discharge downward |
| LG 270 | Counterclockwise rotation, discharge to the right |
When to choose which discharge position?
The selection of a specific discharge position depends on:
- The required airflow direction in the ductwork.
- Limited space or obstacles around the fan.
- Placement of other components (filters, silencers, etc.).
- Technical requirements such as maintenance access and vibration behavior.
For new installations, it’s worth considering the optimal discharge position already in the design phase. This prevents costly modifications later on.
For more technical specifications about our centrifugal fans, please visit the respective product pages. We’re happy to help you select the correct solution.
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Frequently asked questions about discharge positions of centrifugal fans
What is the difference between RD and LG in fans?
RD stands for right-hand discharge (clockwise), LG stands for left-hand discharge (counterclockwise). It refers to the airflow direction relative to the motor.
How do I determine the correct discharge position?
View the fan from the drive side and determine which way the airflow needs to go, aligning it with your ductwork design.
Are all discharge positions available as standard?
Most positions are standard or available with short lead times. Non-standard positions can be manufactured to customer specifications.
Can I change the discharge position afterwards?
For some fan models this is possible, but not for all. Contact us for advice if you require flexibility in discharge orientation.