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Belimo: Spring Return Fail-Safe, On/Off Damper Control Actuator, 24 VAC/DC W/ Aux Switch - EFB24-S

Quantity: 1


The EF actuator utilizes rugged components in a pressure cast aluminum housing for added strength and reliability. It offers a high torque output of 270 in-lbs and a NEMA 4 option to meet tough environmental conditions found in many HVAC applications.

The EF actuator was developed to satisfy high torque applications with a single actuator. The EF can take the place of two classic AF actuators in a piggy-back mounted application; simplifying wiring and mounting requirements while reducing material and installation costs. The NEMA 4 protection feature allows complete access to change the direction of rotation and allows locking or manually overriding the actuator. The EF provides a cost effective and flexible solution that will deliver years of dependable performance over a wide range of operating conditions.

For On/Off, fail-safe control of dampers in HVAC systems. Actuator sizing should be done in accordance with the damper manufacturer’s specifications. Control is On/Off from an auxiliary contact or a manual switch. The actuator is mounted directly to a damper shaft up to 1.05” in diameter by means of its universal clamp. A crank arm and several mounting brackets are available for applications where the actuator cannot be direct coupled to the damper shaft. Maximum of two EF’s can be piggybacked for torque loads of up to 540 in-lbs. Minimum 3/4” diameter shaft and parallel wiring.

The EF..24-S series actuators provide true spring return operation for reliable failsafe application and positive close off on air tight dampers. The spring return system provides constant torque to the damper with, and without, power applied to the actuator. The EF..24-S series provides 95° of rotation and is provided with a graduated position indicator showing 0° to 95°. The actuator may be stalled anywhere in its normal rotation without the need of mechanical end switches. The EF..24-S versions are provided with two built-in auxiliary switches. These SPDT switches are provided for safety interfacing or signaling, for example, for fan start-up. The switching function at the fail-safe position is fixed at +10°, the other switch function is adjustable between +10° to +85°. The EF..24-S actuator is shipped at +5° (5° from full fail-safe) to provide automatic compression against damper gaskets for tight shut-off.

Installation Note: Use flexible metal conduit. Push the UL listed conduit fitting device over the actuator’s cable to butt against the enclosure. Screw in conduit connector. Jacket the actuator’s input wiring with UL listed flexible conduit. Properly terminate the conduit in a suitable junction box


Actuator Type:

Two Position

Fail Safe Mode:

Spring Return

Power Supply:

24 VDC, +20% / -10%

24 VAC +/- 20%


270 lb-in

Running Time:

75 Seconds

< 60 sec @ -22°F (spring)

20 sec @ -4°F to 122°F (spring)

Power Consumption:

9.5W (running)

4.5 W (holding)

VA Rating:


Ambient Temperature:

-22°F to +122°F

Control Input Values:


Auxiliary Switch:


Manual Override:


Direction of Rotation:

Reversible w/ cw/ccw mounting

Product Datasheet

Part Number EFB24-S
Weight (KG) 5.500000
Packing Unit 1 Piece
Product Availability In Stock
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