The Zonefirst SPS is a ruggedized dual static pressure switch designed for contractors who need precise modulating control over HVAC bypass dampers. Engineered with two fixed factory settings of 0.2" WC and 0.3" WC, this unit integrates seamlessly with RDM and ZDM dampers to manage bypass air without the need for complex field calibration. Its SPST snap-acting electronic switches ensure a definitive response: the damper powers open above 0.3" WC and starts to close once pressure drops below 0.2" WC, preventing excessive static in zoned duct systems and protecting the blower motor from unnecessary backpressure and noise. For optimal performance, the static pressure sensor must be installed with its diaphragms in a vertical orientation, ideally positioned downstream of the bypass damper and before the furthest zone branch to maintain constant air volume across the entire residential or light commercial plenum. Key Benefit List: Factory Calibrated Dual Setpoints: Pre-set at 0.2" WC and 0.3" WC for immediate, reliable modulating bypass control without manual adjustment. High-Efficiency Dampening: Actively maintains system static below 0.3" WC, significantly reducing duct noise and improving airflow management. Contractor-Grade Durability: Features 28VA pilot duty at 24VAC and robust pressure-sensitive diaphragms built for long-term cycling in high-demand zoned systems. Direct Sensing Logic: Provides a simplified static pressure regulation solution compared to variable speed motor tuning or complicated barometric dampers. Common Questions: How do I wire the Zonefirst SPS to a modulating damper? The SPS uses SPST contacts to signal the motor. Typically, it is wired to a 24VAC transformer so that it powers the damper open when high-side pressure exceeds the 0.3" WC threshold and closes it when the pressure falls below 0.2" WC. Does the mounting orientation of the SPS matter? Yes, for the pressure-sensitive diaphragms to trip accurately at their factory settings, the unit must be mounted vertically. This prevents gravitational force from creating a bias in the switch sensitivity. Where should the sampling tube be installed? The sampling probe should be inserted into the main supply air plenum, approximately 3 feet from the air handler and definitely downstream of the bypass damper but before the first zone damper to ensure total system pressure is correctly monitored. 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.
