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Fan Safety Alarm Circuits

Fan Safety Alarm Circuits

Air Handling Units and HVAC control systems are intricate, comprising various safety devices to monitor different aspects of the system. These safety devices include a high static pressure limit for supply ductwork, a low-temperature limit (freezestat) for the cooling coil, a Supply Air smoke detector for smoke detection within the air handler, and a building fire alarm status monitor.

In the event any of these safety devices are triggered, several actions are required for fan safety. Specifically, the fan must cease operation, the outside air damper should close, and the chill water valve must open. Achieving this can be done in multiple ways, such as running multiple cables to the safety devices or using multiple double pole double throw relays connected in series with the fan damper and valve control commands.

However, relay logic can be challenging to install and troubleshoot. To simplify this process and reduce the number of wires required, the RIB fan safety shutdown product series features logic boards. These boards not only standardize the wiring of safety devices in control systems but also provide indicator lights for easy troubleshooting in case of system-related issues.

These logic boards offer inputs for connecting safety devices and outputs that connect to the controller, indicating which device has been triggered to the Building Automation Systems. Additionally, they offer extra outputs to return valve and damper actuators to a default position, safeguarding equipment and buildings from further damage.