Plug Fans (RLM Plenum Fans)
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Plug Fans (RLM Plenum Fans) — selection guide
Plug Fans (RLM Plenum Fans): 111 models, impellers Ø133–630 mm, maximum airflow 267–23,896 m³/h, static pressure to 2,524 Pa, EC motors, across 26 series. 67 of them carry a measured P-Q curve and 69 a dimensional drawing.
Plug fans (RLM plenum fans) are impellers on an inlet cone without a scroll housing, mounted inside the unit plenum so the air discharges freely — the standard format for AHU OEMs and fan-wall (FanGrid) arrays. All 111 models are EC: LWBE3G backward curved impellers from Ø133 to Ø630 mm and LWFE3G forward curved impellers for the compact sizes, on 230 V single-phase up to Ø355 mm and 400 V three-phase above. Impellers are PA6-GF to Ø225 mm and aluminium alloy from Ø250 mm; IP55 on 43 models.
Because there is no scroll, the fan is rated at static pressure and mounting length is short, which is what makes arrays of four to sixteen units possible in the depth of a single large fan.
How to select from this range
- Rate on static pressure — a plug fan does not recover velocity pressure, so compare it with housed blowers on static, not total, pressure.
- For fan walls choose several Ø310–450 mm units rather than one Ø630: redundancy, easier handling and lower noise at the same total airflow.
- Three-phase 400 V from Ø355 mm upward; 230 V single-phase below.
- Allow at least 0.5 × diameter between the inlet cone and the nearest wall or coil.
Where these fans are used
- AHU supply and return sections
- FanGrid / fan-wall arrays
- CRAH and CRAC units
- Retrofit of belt-driven AHU fans
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 — Plug Fans (RLM Plenum Fans)
What is the difference between a plug fan and a free-running fan in the code?
P in the model code (LWBE3G355-188PT) is the plug-fan version with inlet cone and mounting plate; N is the free-running impeller for integration into your own inlet ring. Performance is the same impeller; the P version is delivered ready to bolt into the plenum.
How many plug fans go into a fan wall?
Typically 4–16 units of Ø310–500 mm. Send total airflow, static pressure and the section dimensions and we propose the array with N+1 redundancy.
Can plug fans replace a belt-driven AHU fan?
Yes — that is the most common retrofit. The plug fan sits in the same section, removes belts and bearings maintenance and adds speed control; the 2024 European AHU retrofit used LWBE3G450 units at 8,660 m³/h and 2,000+ Pa with about 30% lower consumption.