Overview
The Belimo S1A Auxiliary Switch is a compact add-on designed for use with Belimo damper and rotary actuators. It provides accurate position feedback or triggers external devices when a damper reaches a specific angle. Featuring a single SPDT contact, the switching point is adjustable across the full actuator rotation range (0–100%). This makes the S1A a flexible accessory for building automation systems and control applications.
Key Features
Single SPDT contact (changeover switch)
Adjustable switching point over full actuator travel (0–100%)
Switching capacity: 1 mA up to 3 A (0.5 A inductive) at AC up to 250 V
DC switching range: 5 V to 110 V
Factory-wired 3 ft (1 m) cable, 3 × 0.75 mm²
IP54 / NEMA 2 enclosure protection
Operating temperature: –22 °F to 122 °F (–30 °C to +50 °C)
Compact, robust, and maintenance-free design
Technical Specifications
| Parameter | Value |
|---|---|
| Switch Type | 1 × SPDT |
| Switching Range | Adjustable 0–100% of actuator rotation |
| Switching Capacity | 1 mA … 3 A (0.5 A inductive), AC up to 250 V |
| DC Rating | 5 V … 110 V |
| Cable Connection | 3 ft / 1 m, 3 × 0.75 mm² |
| Protection Class | IP54 (NEMA 2), UL Enclosure Type 2 |
| Operating Temperature | –22 °F to 122 °F (–30 °C to +50 °C) |
| Storage Temperature | –40 °F to 176 °F (–40 °C to +80 °C) |
| Weight | ~0.21 kg |
Applications
Position Feedback: Provides a signal to building automation systems when an actuator reaches a specific position.
Interlocks: Activates external devices such as fans or pumps based on damper position.
Retrofit Use: Adds auxiliary switching capability to existing Belimo actuators.
Safety & Monitoring: Offers redundancy or secondary confirmation of actuator position.
Installation & Mounting
Disconnect power before installation.
Remove the actuator position indicator if present.
Engage manual override and rotate actuator to a reference position.
Mount the S1A directly onto the actuator using the built-in guide grooves.
Adjust the switch setting dial to the desired switching point (0–100%).
Connect the wiring to terminals S1, S2, and S3 based on control requirements.
Restore power and test the switch operation.
Benefits
Full-range adjustable switching point for maximum flexibility.
Provides reliable, consistent position feedback.
Easy installation on compatible Belimo actuators.
Compact accessory that adds functionality without replacing actuators.
Increases control accuracy in HVAC and building automation systems.
Ordering Information
Model: Belimo S1A
Type: Auxiliary Switch / Actuator Accessory
Contacts: 1 × SPDT
Category: Damper and Rotary Actuator Accessories






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