A damper actuator is a small device with an outsized impact on comfort, energy use, and system stability. Specified correctly, it holds airflow and static pressure where you want them. Specified wrong, it hunts, stalls, or never reaches the setpoint. This guide covers the three decisions that matter most: torque, control signal, and feedback.
1. Torque: match the damper, not the catalogue
Torque (measured in N·m) is the rotational force the actuator can apply to the damper shaft. Undersize it and the blade won’t seat or hold against duct pressure; oversize it and you waste cost and current. A practical rule:
Required torque ≈ blade area (m²) × differential pressure (Pa) × safety factor (1.5–2) ÷ shaft lever arm
In practice, for typical VAV and mixing-box dampers in commercial buildings, 2–10 N·m covers most jobs; large outdoor-air or fire/smoke dampers often need 20 N·m and up. Always check the damper manufacturer’s published torque requirement first.
2. Control signal: how the actuator “thinks”
The control signal determines how precisely the actuator can position the damper:
| Signal | Behavior | Best for |
|---|---|---|
| On/Off (2-position) | Opens or closes fully | Simple exhaust, isolation |
| Floating | Motor up/down on pulse | Legacy BMS, low cost |
| 0–10 V / 4–20 mA | Proportional (modulating) | VAV, pressure control |
| BACnet / Modbus | Communicating, addressable | Modern BMS, diagnostics |
For any application that controls how much air rather than whether air flows, choose a modulating signal (0–10 V or 4–20 mA). For new BMS-integrated projects, a communicating actuator pays back through commissioning speed and remote diagnostics.
3. Feedback: proving the position
Feedback tells the controller where the damper actually is. Options include a potentiometer, a 0–10 V or 4–20 mA position signal, or a built-in beacon/switch. If your sequence of operation depends on knowing damper position (most VAV and economizer loops do), insist on analog feedback rather than a simple end-switch.
Power, environment, and fail-safe
- Supply: 24 V AC/DC is standard for building automation; 230 V suits standalone or retrofit where a 24 V supply isn’t available.
- Enclosure: Match the IP rating to the location — IP54 for most indoor duct mounts, higher for outdoor or wash-down areas.
- Fail-safe: A spring-return model drives the damper to a safe position on power loss — essential for fire/smoke and critical ventilation.
Modulating vs 2-position: the one-line rule
If the control loop cares about a value (CFM, Pa, °C), use modulating. If it only cares about open vs closed, 2-position is fine. Choosing modulating everywhere “just in case” adds cost with no benefit; choosing 2-position where precision is needed guarantees a callback.
DNARENS stocks on/off, floating, 0–10 V, and BACnet/Modbus damper actuators across the 2–40 N·m range, with IP54+ enclosures and spring-return options.
Need Help Specifying or Sourcing?
Tell us your system type, required quantity and target market — our engineers reply within 24 hours with matched models and a quotation.
Back to Blog
