Siemens Building Technology 331-2905 Actuator

The Siemens Building Technology 331-2905 is a professional-grade No. 4 Pneumatic Damper Actuator engineered for the gradual or positive control of outdoor air, return air, and exhaust dampers. As a veteran-preferred HVAC pneumatic actuator, this unit features a rugged all-metal body and a 4-inch stroke designed for longevity in demanding ventilating systems and terminal units like unit ventilators and mixing boxes. This model is equipped with an integral pivot mount and has a nominal spring range of 3 to 13 psi, making it essential for sequencing HVAC controls where precise pressure response is required.

Utilizing a high-performance, ozone-resistant EPDM rubber rolling diaphragm, the 331-2905 ensures consistent effective diaphragm area throughout its entire stroke. Contractors typically select this Siemens pneumatic piston actuator for applications requiring reliable mechanical damper linkage movement and mid-range thrust. The air connection is a standard 1/8-inch NPT internal thread, compatible with 1/4-inch OD tubing via the included dual barb elbow fitting. For technicians performing HVAC damper repair or upgrades, this actuator provides a field-proven solution for commercial air handler maintenance and static pressure control.

• Industrial Durability: Robust metal construction and steel housing withstand the rigors of commercial mechanical rooms.
• Precision Sequencing: The 3-13 psi spring range allows for accurate multi-device staging in pneumatic control loops.
• Serviceable Design: Features a replaceable EPDM diaphragm to extend the service life of the damper motor.
• Versatile Mounting: Integral pivot mount design reduces side-loading on the shaft, preventing premature wear on damper hardware.
• Safety Rated: UL recognized for use in fire and smoke leakage-rated dampers, ensuring compliance with building codes.

What is the maximum air pressure for the Siemens 331-2905?
This actuator is rated for a maximum operating pressure of 30 psig, though it operates within a 3-13 psi control signal range.

Can this actuator be used for both normally open and normally closed dampers?
Yes, by adjusting the mounting position and linkage connection on the damper shaft, you can configure the travel for either standard fail-safe orientation.

Is the diaphragm replaceable in the field?
Absolutely. The ozone-resistant rolling diaphragm is designed for field replacement, allowing technicians to restore performance without replacing the entire pneumatic drive.

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Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.