Belimo SM24A-SR modulating damper actuator, 20 Nm, 24 V, 0-10 V, 150 s
- Application: proportional air damper control in HVAC / VAV systems
- Torque: 20 Nm
- Power + control: 24 V AC/DC, 0-10 V (modulating) + 2-10 V feedback
- Running time + IP: 150 s / 95°, IP54
Where SM24A-SR is used
SM24A-SR is the "SR" (stetless / stallless — modulating) version of the SM series. Used where precise damper position from an analogue signal is required: VAV boxes, economiser modulation by CO₂ or outdoor temperature, airflow control by humidity, atmospheric pressure compensation. The 24 V supply is usually drawn from the same BMS controller that delivers the 0-10 V signal.
Compared to SM230A, it offers proportional control (0-10 V instead of on/off) and safe low voltage (24 V instead of 230 V) — allowing longer cable runs without a separate electrical design section.
Technical specifications
| Parameter | Value |
|---|---|
| Code | SM24A-SR |
| Manufacturer / series | Belimo, S series (SR — modulating) |
| Torque | 20 Nm |
| Nominal voltage | AC 24 V, 50/60 Hz / DC 24 V |
| Voltage range | AC 19.2 ... 28.8 V / DC 19.2 ... 28.8 V |
| Power consumption | 2 W (running) / 0.4 W (idle) / 4 VA for wire sizing |
| Control signal | 0-10 V DC (modulating, linear) |
| Position feedback | 2-10 V DC (proportional to angle 0-95°) |
| Input impedance | 100 kΩ |
| Running time | 150 s / 95° |
| Rotation angle | Max. 95° (adjustable mechanical stops) |
| Shaft clamp | 10 ... 20 mm (round or square) |
| Damper area (recommended) | Up to ~4 m² |
| Protection class | IP54 (any mounting position) |
| Ambient temperature | -30 ... +50 °C |
| Connection | Cable 1 m, 4 × 0.75 mm² |
| Overload protection | Stall-torque (no end switches required) |
| Parallel operation | Supported (multiple actuators on one signal) |
When to choose SM24A-SR
- VAV boxes and zonal proportional airflow control (0-10 V is the BMS standard)
- Economiser modulation in AHU systems by CO₂, humidity or temperature delta
- Smoke / atmospheric pressure compensation dampers where pulsing on/off is unsuitable
- Where 230 V is not available at the damper — 24 V from the BMS controller is safer and often connects without separate electrical approval
- Compatibility: fits any damper brand with 10-20 mm shafts; direct shaft mounting; 0-10 V input matches all standard BMS controller outputs (Ouman, Siemens Climatix, Honeywell, Schneider)
B2B delivery and logistics via Amegata.lt
- 24-hour delivery across Lithuania (from our warehouse in Vilnius)
- Competitive B2B pricing — often below market average
- 30-day payment terms for companies (per contract)
- Free technical consultation on actuator sizing and 0-10 V signal integration
Official Belimo catalogue: belimo.com/damper-actuators
Frequently asked questions
What is the difference between SM24A-SR and SM24A?
SM24A is on/off or 3-point; SM24A-SR is proportional 0-10 V with 2-10 V feedback. Torque and mechanics are identical (20 Nm). Pick the SR version for precise airflow control; the plain A version when open/closed is enough.
What transformer size is needed?
Each SM24A-SR needs ~4 VA reserve on the 24 V transformer. In practice, the whole BMS 24 V bus is designed with 30-50 % reserve — sum up controller + sensors + actuators.
Does 0-10 V linearly cover the full 0-95° angle range?
Yes, linearly. 0 V = 0° (closed), 10 V = 95° (max open). The 2-10 V feedback tracks the real angle (2 V = 0°, 10 V = 95°) and can be read directly by a BMS analogue input.
Can several actuators be driven by one signal?
Yes. Multiple SM24A-SR units run in parallel from one 0-10 V source — standard Belimo behaviour. Verify: transformer VA reserve (4 VA × count) and that rotation directions are set consistently so all units move in the same sense.
How is the actuator protected against mechanical overload if the damper jams?
SM24A-SR has stall-torque protection — the actuator stops at any mechanical limit (no end switches needed). If the damper jams, the actuator holds nominal torque without overheating and automatically resumes when the obstruction clears.
