Centrifugal Fans
Centrifugal fans for duties that must overcome coils, filters and long duct runs: AHU / RTU, data-center CRAH, dust extraction and process ventilation. The LONGWELL centrifugal platform covers backward curved, forward curved and plug-fan (RLM) constructions on AC / DC / EC motors. Final selection is confirmed at the duty point (airflow / static pressure / voltage / control mode) and by project verification.
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Centrifugal Fans — selection guide
Centrifugal Fans: 614 models, impellers Ø108–630 mm, maximum airflow 155–23,896 m³/h, static pressure to 5,401 Pa, EC, AC and DC motors, across 137 series. 525 of them carry a measured P-Q curve and 572 a dimensional drawing.
LONGWELL's centrifugal range is organised by impeller type rather than by application, because the impeller decides the shape of the curve. Backward curved impellers (LWBE3G EC, LWBA AC, LWBD3G DC) hold the high-pressure end and are non-overloading; forward curved multi-vane impellers (LWFE3G EC, LWFA AC, LWFD3G DC) give more airflow per diameter at low pressure; and plug fans are backward curved impellers supplied without a scroll for plenum mounting. The whole family shares the same motor platforms — rotor sizes 92, 102 and 138 on external-rotor motors — so a duty point can usually be met by more than one impeller type, and the selector shows them side by side.
Impeller material follows size: PA66 or PA66-GF up to about Ø225 mm, aluminium alloy from Ø250 mm and galvanised steel for the scroll housings. Supply voltages run from 24 / 48 V DC through 115 / 230 V single-phase to 380 / 400 V three-phase, which is why the same duty can be quoted for a battery-powered unit, a European AHU and a North American rooftop unit.
How to select from this range
- Fix the duty point first: airflow plus the static pressure of the whole system at that airflow, including dirty-filter allowance. Nameplate maximum airflow and maximum pressure are two different points on the curve and are never reached together.
- Above roughly 300 Pa go backward curved; below that a forward curved blower of the same diameter usually moves more air in a smaller housing.
- For AHU plenums and fan walls use plug fans — no scroll, no discharge duct, and EC control as standard.
- Pick the motor platform by duty profile: EC for modulating loads and BMS integration (about 30% lower consumption at part load, confirmed against the load profile), AC for constant duty at lowest first cost, DC for 24 / 48 V equipment.
- Check the curve margin the selector reports: 10–25% is the target, below 8% is flagged.
Where these fans are used
- Air handling units and rooftop units
- Data-center CRAH units and fan walls
- Dust extraction and fume systems
- Fan coil units and compact air conditioners
- Ovens, dryers and process equipment
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 — Centrifugal Fans
How do backward curved, forward curved and plug fans differ in the LONGWELL range?
Backward curved (LWBE3G / LWBA) impellers give the highest static efficiency and a power curve that falls off at high airflow, so the motor cannot overload. Forward curved (LWFE3G / LWFA / LWFD3G) impellers move more air from a given diameter at low pressure but need a scroll housing. Plug fans are backward curved impellers on an inlet cone without a scroll, for mounting inside a plenum.
Which rotor size should I specify — 92, 102 or 138?
The rotor number is the external-rotor motor size. It fixes the available shaft power and therefore the top of the curve for a given impeller: the same Ø355 impeller is offered on 102 and 138 rotors with different maximum pressure. The selector picks the smallest motor that clears your duty point with margin.
Can one duty point be met by more than one centrifugal type?
Often yes. A 3,000 m³/h at 400 Pa duty can be met by a Ø310 backward curved fan, a Ø280 plug fan or a Ø250 dual-inlet forward blower, with different noise, envelope and efficiency. The selector lists all of them; the choice is then about installation format and control.
Are the centrifugal fans available in 115 V for North America?
Yes. The backward curved and forward curved lines include 115 V single-phase versions, and the DC and EC centrifugal lines carry ETL listing (Intertek control no. 5022563) for UL 507 / CSA C22.2 No. 113.