Belimo LM24-SR US - User Manual

The LM Series Direct Coupled Actuator is a compact and powerful device designed for controlling dampers in HVAC systems, specifically VAV units and small zone dampers. It offers a minimum torque of 35 in-lb, suitable for damper areas up to 8 sq-ft. The actuator is designed for direct coupling to the damper operating shaft, eliminating the need for crank arms and linkages, which simplifies installation and reduces labor costs.

Function Description

The LM Series actuators are electronic direct coupled type, meaning they mount directly to the damper operating shaft with a universal V-bolt clamp assembly. They are available in various control types: on-off, floating point, and proportional.

On-off/Floating Point Control (LM24-3, LM24-3-T, LM24-3-5P0-T): These models are designed for on-off and floating point control of dampers. They utilize a Brushless DC motor controlled by an Application Specific Integrated Circuit (ASIC). The ASIC monitors and controls the actuator's rotation and provides a digital rotation sensing (DRS) function to prevent damage in a stall condition. The angle of rotation is mechanically limited to 95°, and the actuator automatically stops when reaching the damper or actuator end position. The LM24-3-5P0-T US model includes a 5 kΩ feedback potentiometer for modulating (floating point) applications.
Proportional Control (LM24-SR, LM24-SR-T, LMC24-SR, LMC24-SR-T): These actuators are used for proportional modulation of dampers in HVAC systems. They respond to a 2 to 10 VDC or 4 to 20 mA input signal (with a 500 Ω resistor). A 2 to 10 VDC feedback signal is provided for position indication or master-slave applications (not available on "-T" versions). The LM24-SR US model offers an electronic angle of rotation adjustment, allowing the rotation to be limited from 20% to 100% while still using the full input signal and feedback control range. The LM24-SR and LMC24-SR models also use a Brushless DC motor with an ASIC for precise control and stall protection.
Multi-Function Technology (LM24-MFT): This actuator is a non-spring return, multi-function proportional damper actuator. It maintains its last position when power is removed. The LM24-MFT US provides 95° of rotation and a position indicator. It synchronizes its mechanical stop with the damper or valve's mechanical stop, using this point as its zero position during normal control operations. The actuator uses a brushless DC motor controlled by an ASIC and a microprocessor, which provides intelligence for constant rotation rate and exact position. The ASIC monitors rotation and provides DRS for stall protection. The position feedback signal is generated without mechanical feedback potentiometers. The LM24-MFT US can be configured with various parameters, including torque, control signal, and feedback, either through pre-set configurations, custom configurations, or using the MFT-Handy® or MFT-Actuate™ PC software.

Usage Features

Direct Coupling: All LM Series actuators are designed for direct coupling to the damper shaft, simplifying installation and reducing the need for additional linkages.
Overload Protection: The actuators are electronically protected against overload throughout their entire rotation range, preventing burn-out and ensuring long service life.
Position Indication: A clear visual pointer (clip-on indicator on non "-T" models) allows for easy checking of the damper position from a distance.
Adjustable Angle of Rotation: Mechanical stops allow for easy adjustment of the angle of rotation up to 95°. For LM24-SR US, electronic angle of rotation adjustment is available, allowing limitation from 20% to 100% while maintaining full input signal and feedback control range.
Manual Override: An easily accessible push-button on the actuator cover disengages the gear train, allowing manual movement of the damper shaft. This feature is useful for pre-tensioning damper blades and testing the installation without power. For tight shut-off, the damper should close with 5° of actuator stroke left.
Direction of Rotation Switch: Most LM actuators (except LM24-3-T US) have a reversing switch labeled "CW-CCW" on the cover, allowing for easy change of control direction. For LM24-3-T US, rotation direction is controlled by wiring to specific terminals.
Consistent Running Time: The actuators offer consistent running time independent of the load, ensuring reliable performance.
Quiet Operation: The actuators operate with a noise level of less than 35 dB (A).
Plenum Rated Cable: Most models come with a 3 ft, 18 GA, UL CL2P plenum rated cable for ease of installation. Screw terminal strips are available on "-T" models for electrical connections.
Control Accuracy and Stability (LM24-SR US): These actuators feature a unique non-symmetrical deadband, responding to an 80 mV signal when not changing direction from the stop position, and a 175 mV signal when reversing direction from the stop position. This design allows for accurate tracking of slight deviations while ignoring minor control signal instability.

Maintenance Features

Maintenance-Free Design: The LM Series actuators are designed to be maintenance-free, contributing to low life-cycle costs.
Overload-Proof: The electronic overload protection means there are no limit switches to adjust or maintain, and the actuator can stall indefinitely without damage.
Easy Troubleshooting: The manual provides a detailed "Startup and Checkout" procedure with expected responses and troubleshooting steps for electrical check-out, helping technicians diagnose and resolve issues efficiently.
Wiring Diagrams: Comprehensive wiring diagrams are provided for various control types (on-off, floating point, proportional) and feedback options, ensuring correct installation and troubleshooting.
Component Testing: Components are tested before assembly, and every product is tested before shipment, ensuring high quality and reliability.
Long Service Life: The actuators are designed for over 30 years of direct coupled actuator operation.
Warranty: Belimo offers a five-year warranty on these actuators, demonstrating confidence in their durability and performance.

Belimo LM24-SR US Specifications

General

Power Supply	24 V AC/DC
Type	Spring Return
Angle of Rotation	90°
Protection Class	IP54
Control Type	Modulating
Control Signal	0...10 V
Output Signal	0...10 V
Rotation	Clockwise/Counter-Clockwise
Mounting	Direct mounting on damper shaft