Siemens OpenAir GCA Series

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Overview

The OpenAir GCA Series Spring Return 160 lb-in Electronic Damper Actuator is engineered for precise control of building HVAC dampers, suitable for both constant and variable air volume installations. This actuator is particularly well-suited for applications involving return air, mixed air, exhaust, and face and bypass dampers that require up to 160 lb-in (18 Nm) of torque. A key design feature is its bi-directional fail-safe spring return, ensuring that the damper automatically returns to a predetermined safe position in the event of a power failure, thereby enhancing safety and system integrity.

At its core, the GCA actuator utilizes brushless DC motor technology, which provides robust performance and includes integrated stall protection to prevent damage under load. This motor design contributes to the actuator's reliability and extended operational life. The device incorporates a patented self-centering shaft coupling, simplifying installation and ensuring a secure, aligned connection to the damper shaft. This feature is particularly beneficial for maintaining optimal damper performance and reducing wear over time.

For operational flexibility, the actuator includes a manual override function, allowing for temporary manual positioning of the damper when power is absent or for commissioning purposes. The angular rotation of the actuator is adjustable between 0 and 90 degrees, with five-degree intervals, enabling precise customization of the damper's travel range to match specific application requirements. To limit the range of shaft movement, users can remove the locking clip and self-adjusting shaft adapter, rotate the damper blade shaft to its failed position, adjust the shaft coupling to the desired position, and then refasten it with the locking clip.

The GCA series offers various control options to integrate seamlessly into different building management systems. Modulating models (GCA15x and GCA16x) accept a continuous 0 to 10 Vdc or 2 to 10 Vdc signal from a controller, allowing for proportional control of the damper's angle of rotation. These models also provide a 0 to 10 Vdc or 2 to 10 Vdc position feedback output signal, enabling monitoring of the damper's position. Floating control models (GCA13x) respond to a 24 Vac/dc signal to rotate the actuator coupling clockwise or counterclockwise, holding its position when no control voltage is applied. Two-position control models (GCA12x and GCA22x) simply move the actuator coupling to the open position (90 degrees) when power is applied.

Certain models, such as the GCA163 and GCA164, feature control signal adjustment capabilities. The offset (start point) can be adjusted between 0 to 5 Vdc, and the span can be adjusted between 2 to 30 Vdc, providing fine-tuning for the control signal to match the desired damper response. This allows for precise calibration of the actuator's operational range.

For enhanced functionality, some GCA models are equipped with dual auxiliary switches (GCAxx4 and GCAxx6). These switches can be independently adjusted to trigger at specific points within the actuator's 0 to 90-degree rotary range, with five-degree intervals and a 2-degree switching hysteresis. This allows for the integration of additional control logic or status indications within the HVAC system. It is crucial to note that only AC-line voltage from the same phase or UL-Class 2 voltage should be applied to the switching outputs of both auxiliary switches; mixed operation is not permissible.

The actuator is shipped from the factory with a 5-degree preload, which facilitates tight close-off of the damper in power-fail-close applications, ensuring minimal air leakage when the system is de-energized. A mounting bracket is included with the actuator, and the shaft adapter and mounting parts are shipped in a separate container. The shaft adapter and position indicator can be mounted on either side of the actuator, offering flexibility in installation based on the actuator's orientation and shaft length. The minimum damper drive shaft length required is 3/4-inch (20 mm).

The GCA series also supports tandem applications for controlling larger dampers or multiple dampers simultaneously. Tandem mounting brackets, such as ASK73.1 and ASK73.2U, allow two GCA actuators to directly drive a single damper shaft. For modulating control, GCA15x series actuators can be configured in a Master/Slave mode, enabling up to four actuators to operate a single damper shaft. This configuration requires specific DIP switch settings to designate one actuator as the Master and the others as Slaves, with appropriate wiring for power and control signals.

The self-adapt feature, available on GCA15x models, allows the actuator to calibrate its rotation limits if the mechanical angle of rotation is restricted. When this feature is turned on, the actuator undergoes a three-minute calibration cycle to adjust to the actual rotation limits of the system, redefining the 0% to 100% range for the actuator logic. However, the position output signal (U) remains proportional to the full 0 to 90-degree range, regardless of the self-adapt function.

Maintenance of the GCA actuator is designed to be straightforward. The robust construction and brushless DC motor minimize the need for frequent servicing. In the event of an inoperative actuator, the unit should be replaced rather than opened, as opening the actuator is not recommended. Troubleshooting guidelines include checking wire connections, verifying offset and span settings, using a digital multimeter to confirm operating voltage, and inspecting the damper for blockages. If a blockage is found, it should be removed, and the actuator power cycled to resume normal operation.

Various accessories are available to enhance the versatility and installation options of the GCA actuators. These include floor mount kits (ASK71.1U) for in-air stream applications, frame mount kits (ASK71.2U) for direct mounting to damper frames, and crank arm kits (ASK71.3, ASK71.4) for converting angular rotation into linear stroke or driving auxiliary linear mechanisms. Weather shields (ASK75.1U for NEMA 3R and ASK75.7U for NEMA 4X) are available for outdoor installations, providing protection against environmental elements. Heater/weather shield assemblies (985-106) offer protection down to -58°F (-50°C). A 499 Ohm Resistor Assembly Kit (985-124) is available for converting 4 to 20 mA controller output signals to 2 to 10 Vdc actuator signals. Service parts such as position indicators, standard shaft adapters, anti-rotation brackets, and conduit adapters are also available.