Belimo NM24A-SR Modulating Damper Actuator 10 Nm, 2-10 V

Overview

The Belimo NM24A-SR is a 10 Nm modulating rotary actuator for adjusting air dampers in technical building installations. Belimo rates it for damper areas of up to approximately 2 m², which covers most outdoor air, return air, mixing and volume control dampers on air handling units and ductwork. It runs on AC/DC 24 V, follows a 2 to 10 V control signal and returns a 2 to 10 V position signal, so a DDC controller always knows where the blade is. Unlike spring-return types, the actuator simply holds its last position when the supply is removed.

Seven Star LLC supplies the Belimo NM24A-SR on request to HVAC contractors, OEM air handling unit builders and facility maintenance teams in Oman and the GCC, with engineering support in Muscat. It is a frequent choice when an older actuator fails on a large damper and a direct-coupled replacement with analogue control is needed quickly.

Operating Principle

A standard 0 to 10 V output from the controller drives the Belimo NM24A-SR, which uses the 2 to 10 V range as its operating band and moves the damper to the matching angle. The measuring voltage U provides an electrical display of the damper position from 0 to 100 % and can also serve as the control signal for further actuators, a simple way to make several dampers follow one master. Position accuracy is ±5 %, and a full 90° stroke takes 150 seconds at a sound power of 35 dB(A).

Rotation direction is set with a 0/1 switch: at Y = 0 V, switch position 0 gives counterclockwise rotation and position 1 clockwise. The Belimo NM24A-SR is overload protected and needs no limit switches, because it stops automatically when it reaches an end stop. Two adjustable mechanical end stops let the installer limit the angle on either side of the maximum 95° travel, for example to prevent a damper from closing fully against a minimum fresh air requirement.

Engineering Design of the Belimo NM24A-SR

The housing combines an orange top section with a grey base and a direct-coupled universal shaft clamp that accepts round shafts from 8 to 26.7 mm. An anti-rotation device is supplied, and form-fit inserts for square shafts from 8 to 16 mm are listed as accessories. A push-button manual override on the Belimo NM24A-SR disengages the gear train for as long as it is pressed or locked, which allows the damper to be set by hand during commissioning or maintenance. A pluggable mechanical indicator shows the position on the clamp.

Power demand is low: 2 W in operation, 0.4 W at rest and 4 VA for wire sizing, from AC or DC 19.2 to 28.8 V via a 1 m four-core cable. The Belimo NM24A-SR is rated IP54 and NEMA 2 / UL Enclosure Type 2, carries cULus approval to UL 60730-1A and UL 60730-2-14, and is certified to IEC/EN 60730-1 and 60730-2-14. Belimo also lists hygiene testing to VDI 6022 Part 1. The actuator weighs 0.73 kg and is maintenance-free.

Key Features

Specifiers select the Belimo NM24A-SR for large modulating dampers that do not need a fail-safe spring:

• 10 Nm motor torque, suitable for dampers up to about 2 m².
• 2 to 10 V control input with 100 kΩ impedance and 2 to 10 V position feedback.
• Running time of 150 s for 90° with a quiet 35 dB(A) motor.
• Lockable push-button manual override for setting the damper by hand.
• Universal clamp for 8 to 26.7 mm shafts, with form-fit inserts available for square shafts.
• Mechanical end stops on both sides to limit the 95° angle of rotation.
• Direction of rotation selectable with a 0/1 switch.
• Add-on auxiliary switches and feedback potentiometers for extra signals.

Industrial Applications

Air handling units in Gulf buildings work hard for most of the year, and their dampers decide how much hot outside air reaches the cooling coil. The Belimo NM24A-SR is used on outdoor air, return air and exhaust dampers of AHUs in malls, hospitals, hotels, airports and government buildings in Muscat, where economiser and minimum fresh air sequences need a modulating actuator with feedback. It also drives zone and bypass dampers in ductwork, volume control dampers on supply branches, and dampers in industrial ventilation for warehouses, plant rooms and process halls in Sohar and Duqm.

When the BMS needs more than an analogue feedback, Belimo add-ons such as the S1A or S2A auxiliary switches and the P140A, P1000A or P10000A feedback potentiometers mount on the actuator, and the Z-UIC converter accepts a 4 to 20 mA signal. Seven Star LLC supplies the Belimo NM24A-SR together with clamps, crank arms and linkage kits for retrofit and new projects. Room and duct conditions on the same systems are often monitored with the Vaisala HMT330 humidity and temperature transmitter and the Dwyer MSX Magnesense differential pressure transmitter.

Where a damper must close on power loss, the Belimo LF24-SR spring-return actuator is the fail-safe alternative for smaller dampers.

Technical Specifications

The table lists Belimo NM24A-SR data from the Belimo technical data sheet (en-gb, 2023-12-13):

How to Order

For pricing on the Belimo NM24A-SR, tell Seven Star LLC how many units you need, the damper size and shaft dimensions, and any auxiliary switches or linkage parts required. Our team in Muscat will check the selection against the Belimo data sheet, confirm stock and delivery for Oman and the GCC, and send the technical data sheet with the quotation. Variable-speed fans and pumps on the same projects can be controlled with the Schneider Electric Altivar 212 HVAC drive.