Belimo EFB24-S-N4 Spring Return Damper Actuator 270 in-lb On/Off 24V NEMA 4

The Belimo EFB24-S-N4 is a direct-coupled, spring return damper actuator designed for On/Off, fail-safe control of dampers in commercial HVAC and Building Automation System (BAS) applications. Delivering 270 in-lb (30 Nm) of torque at AC/DC 24V, this actuator features a rugged NEMA 4 / IP66 weatherproof enclosure, making it well-suited for outdoor or wash-down environments where moisture protection is critical.

The EFB24-S-N4 mounts directly to a damper shaft up to 1.05" in diameter using its universal clamp — no crank arm or linkage required. The true spring return mechanism drives the damper to its fail-safe position in under 20 seconds whenever power is lost or interrupted, ensuring reliable life-safety and system-control performance.

Key Features:

• Torque Output: 270 in-lb [30 Nm] — constant torque with and without power applied
• Control Type: On/Off (2-position) via auxiliary contact or manual switch
• Nominal Voltage: AC/DC 24 V (range: AC 19.2–28.8 V / DC 21.6–28.8 V)
• Power Consumption: 9.5 W running / 4.5 W holding; 16 VA transformer sizing
• Spring Return Fail-Safe: Fail-safe runtime under 20 seconds; motor runtime 75 s / 90°
• Enclosure Rating: IP66, NEMA 4X, UL Enclosure Type 4 — suitable for outdoor and wet locations
• Auxiliary Switches: Two built-in 2x SPDT switches for end-position indication, interlock control, or fan start/stop signaling
• Angle of Rotation: 95°, with electronic overload protection throughout full range
• Shaft Compatibility: Accepts round shafts from 1/2" to 1.05" diameter
• Dual-Mount Capable: Two units can be piggybacked on one shaft for up to 540 in-lb combined torque
• Manual Override: 5 mm hex crank (3/16" Allen wrench), supplied with unit
• Electrical Connection: Terminal block(s) inside junction box with knockouts
• Double Insulation: No electrical ground required to meet agency listings
• Operating Temperature: -22°F to 122°F (-30°C to 50°C)
• Housing Material: Die cast aluminum and plastic casing
• Certifications: cULus listed, ISO 9001 manufactured
• Warranty: 5-year manufacturer warranty

The EFB24-S-N4 is shipped pre-set at 5° from full fail-safe to provide automatic compression against damper gaskets for tight shut-off. Wiring accepts 12–26 AWG stranded or solid copper conductors (60°C/75°C rated). When flexible conduit is used, a UL-listed, NEMA 4/4X-rated fitting is required for maintaining the enclosure rating.