The Belimo GM24S.28 is a high-torque non-spring-return damper actuator delivering 360 in-lb [40 Nm] of torque with on/off (two-position) control on AC/DC 24 V power. It direct-couples to round or square damper shafts up to 1.05 in. with a universal clamp and holds its last position on loss of power (non-fail-safe, no spring return), making it a Belimo GM-Series actuator for large commercial HVAC dampers. A faster 35-second run time speeds damper response. Two built-in SPDT auxiliary switches signal damper position or interlock equipment.
Specifications sourced from the official Belimo GM24S.28 technical data sheet (rev 2026-05-08).
Overview
Belimo GM-Series actuators are high-torque non-spring-return drives for the largest commercial HVAC control dampers — they position the damper under power and hold the last commanded position when power is removed (there is no spring-return fail-safe). The GM24S.28 produces 360 in-lb [40 Nm] and mounts directly to round or square damper shafts up to 1.05 in. with its universal clamp (a crank arm and brackets are available for jackshaft and linkage applications); manual positioning uses an external push button. This unit uses a faster 35-second motor for quicker damper response. Two-position on/off control positions the damper from a controller, relay or switch.
Best for
- Large, high-torque commercial HVAC dampers (360 in-lb)
- Non-spring-return applications (no fail-safe required)
- Big outdoor-air, mixing-box and industrial dampers
- Faster (35-second) damper actuation
- End-position signaling or interlock (2x SPDT)
Key Features
High 360 in-lb Torque
Belimo's largest non-spring-return class — drives big commercial and industrial dampers, direct-coupling to round or square damper shafts up to 1.05 in..
Non-Spring-Return Design
Holds the last commanded position when power is removed (non-fail-safe). Lower cost and power draw than a spring-return where fail-safe is not required.
On/Off Control
Accepts two-position on/off control from a controller, relay or switch.
Fast 35-Second Run Time
A faster motor drives 90° in about 35 seconds for quicker damper response.
Push-Button Manual Override
An external push button declutches the gear train so you can position the damper by hand for setup or service.
Two SPDT Aux Switches
Two built-in SPDT auxiliary switches (1 mA-3 A) signal damper end position or interlock other equipment.
Technical Specifications
| Parameter | Specification |
|---|---|
| Manufacturer | Belimo |
| Part Number | GM24S.28 |
| Actuator Type | Non-Spring-Return (Non Fail-Safe) Damper Actuator |
| Nominal Voltage | AC/DC 24 V |
| Nominal Frequency | 50/60 Hz |
| Power Consumption (Running) | 4 W |
| Transformer Sizing | 8 VA |
| Torque | 360 in-lb [40 Nm] (minimum) |
| Control Signal | On/Off (two-position) |
| Shaft Range | Up to 1.05 in. [26.7 mm] via universal clamp; crank arm available |
| Angle of Rotation | 95° (adjustable mechanical stops) |
| Running Time (Motor) | 35 s / 90° |
| Behavior on Power Loss | Holds last position (non-spring-return) |
| Auxiliary Switches | 2x SPDT, 1 mA-3 A (0.5 A inductive), DC 5 V-AC 250 V |
| Manual Override | External push button (self-locking gear) |
| Direction of Motion | Selectable with 0/1 switch |
| Electrical Connection | 18 AWG plenum cable, 3 ft [1 m], 1/2" NPT connector |
| Overload Protection | Electronic, full 0-95° rotation |
| Electrical Protection | Double insulated (Class 2) |
| Enclosure Rating | NEMA 2 / UL Type 2 |
| Ambient Temperature | -22 to 122°F [-30 to 50°C] |
| Agency Listing | cULus (UL60730-1A/-2-14, CAN/CSA) |
| Quality Standard | ISO 9001 |
| Plenum Rated | UL 2043 (suitable for air plenums) |
| Weight | 3.5 lb [1.6 kg] |
| Warranty | 5 Years |
Documentation
Related Products
Accessories & Mounting
Common Belimo accessories for mounting, linkage, signaling and powering the GM24S.28, drawn from the actuator datasheet. All are stocked by ZOT Supply as an authorized Belimo distributor.
Mounting & Linkage
Electrical Add-Ons
Frequently Asked Questions
What is the Belimo GM24S.28?
The Belimo GM24S.28 is a high-torque non-spring-return (non-fail-safe) damper actuator for large commercial HVAC. It produces 360 in-lb [40 Nm] of torque, uses on/off (two-position) control on AC/DC 24 V power, and holds its last position on loss of power. Its housing is rated NEMA 2.
Is the GM24S.28 a spring-return (fail-safe) actuator?
No. The GM24S.28 is non-spring-return: on power loss it holds its last position rather than driving to a fail-safe position. For fail-safe operation choose a spring-return Belimo actuator (such as the EF-Series) instead.
How much torque does the GM24S.28 provide?
It delivers 360 in-lb [40 Nm] of torque — Belimo's largest non-spring-return class, sized for big commercial and industrial dampers.
What shaft sizes does the GM24S.28 fit?
It direct-couples to round or square damper shafts up to 1.05 in. using its universal clamp (K-GM20). For jackshafts or off-shaft mounting, a crank arm and brackets (ZG-JSA-1, ZG-GMA) are available.
What control signal does the GM24S.28 use?
It uses on/off (two-position) control. Two-position on/off control is driven from a controller, relay or switch.
What is the running time of the GM24S.28?
This unit uses a faster motor with about a 35-second running time for 90 degrees of travel — quicker than the standard 150-second GM actuator.
Does the GM24S.28 have auxiliary switches?
Yes. It has two built-in SPDT auxiliary switches (rated 1 mA to 3 A) for end-position signaling or interlocking other equipment.
Is GM24S.28 a current Belimo part number?
The GM24S.28 uses Belimo's legacy GM type-reference numbering. It remains available and is functionally a 360 in-lb non-spring-return GM actuator; ZOT Supply can help cross-reference it to the current GMB/GMX equivalent if needed.
How do you manually position the GM24S.28?
Press the external manual-override push button to declutch the gear train, then turn the damper by hand for setup or service.
Is the Belimo GM24S.28 available from an authorized Belimo distributor?
Yes. ZOT Supply is an authorized Belimo distributor and carries the GM24S.28. Every unit ships factory new with Belimo's full 5-year warranty and application support.
- Actuator Type:
- Non-Spring-Return
- Torque:
- 360 in-lb
- Control Signal:
- On/Off
- Voltage:
- 24 VAC/DC
- Auxiliary Switch:
- 2x SPDT
- Enclosure:
- NEMA 2
- Series:
- GMB
