Backward Curved Centrifugal Fans
Backward curved impellers give the best efficiency in the high static pressure region, suited to AHU, RTU, CRAH units and the clean side of dust collectors. The third-generation LWBE3G platform uses a bionic blade profile, covering impellers Ø190–710 mm and static pressures up to about 1,800 Pa. Final selection is confirmed at the duty point (airflow / static pressure / voltage / control mode) and by project verification.
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Backward Curved Centrifugal Fans — selection guide
Backward Curved Centrifugal Fans: 314 models, impellers Ø133–630 mm, maximum airflow 225–23,896 m³/h, static pressure to 2,523 Pa, AC, EC and DC motors, across 69 series. 310 of them carry a measured P-Q curve and 314 a dimensional drawing.
Backward curved centrifugal fans are the largest line in the catalogue: 314 models from Ø133 to Ø630 mm on three motor platforms — LWBE3G EC (144 models, bionic blade profile, 0–10 V / PWM), LWBA AC (144 models, 2- and 4-pole external rotor) and LWBD3G DC (26 models, 24 / 48 V). Impellers are PA66 or PA66-GF up to Ø225 mm and aluminium alloy from Ø250 mm; the housing options are free-running (no scroll), scroll housing or plug-fan inlet cone.
This is the impeller for high static pressure: the curve stays steep to 1,000–2,500 Pa on the larger sizes, the power curve is non-overloading, and static efficiency is the highest in the catalogue. LWBE3G450 and LWBE3G560 are the sizes used in 2024 European AHU retrofits at 8,660 m³/h and 2,000+ Pa.
How to select from this range
- Select on static pressure at the duty airflow; backward curved fans lose little airflow as the filter loads, so the margin can be at the low end of the 10–25% band.
- PA66 impellers up to Ø225 mm keep weight and cost down; specify aluminium (standard from Ø250 mm) for higher tip speeds and temperature.
- Rotor 72 / 92 / 102 sets the motor power for a given impeller: the selector picks the smallest that clears the point.
- Choose EC (LWBE3G) for modulating AHU and CRAH duty, AC (LWBA) for constant duty, DC (LWBD3G) for 24 / 48 V equipment.
Where these fans are used
- AHU and RTU supply / return
- CRAH units and fan walls
- Clean side of dust collectors
- Fan filter units and air purifiers
- Heat-recovery ventilation units
Every figure above is measured on our own test rigs per AMCA 210 / ISO 5801 methods — see the test labs and certificates. Final selection is confirmed at the duty point and by project validation.
FAQ — Backward Curved Centrifugal Fans
What does LWBE3G355-188NT-29 mean?
LWBE3G = third-generation EC backward curved, 355 = impeller diameter in mm, 188 = rotor / motor size, N = free-running (P = plug fan, S = scroll), T = three-phase (S = single-phase), 29 = version. The same impeller is offered on several rotor sizes.
Backward curved or forward curved for my AHU?
Backward curved above about 300 Pa or wherever the resistance may drop (non-overloading); forward curved for compact, low-pressure units. Enter the duty point and the selector shows both with margin and power.
Which sizes are available in 115 V?
Ø133–355 mm on the AC and EC platforms include 115 V versions (32 models); larger sizes are 230 V or 380 / 400 V.
Is the LWBE3G a drop-in for other EC backward curved fans?
The LWBE3G560 is dimensioned 1:1 to the common Ø560 mm EC plug-fan format and delivers 16,039 m³/h; other sizes follow the same standard inlet-cone and mounting dimensions. Confirm with the drawing on the model page.