Titus HVAC D21-PS Relay

The Titus HVAC D21-PS Relay is an essential electronic interface designed for commercial VAV terminals and electric duct heaters. As a proportional pull signal relay, this component integrates with patented Titus airflow sensors to modulate heater capacity based on real-time cubic feet per minute (CFM) flux. This HVAC control relay eliminates the binary limitations of standard on-off switches by translating a 0-10 VDC or AC/DC pulse signal into precise thermal output. In VAV applications, the D21-PS ensures that heating elements respond to radiant heat even at low airflow thresholds, preventing high-limit trips while maintaining setpoint accuracy.

For field technicians, the D21-PS terminal unit relay offers flexible installation parameters. The board features accessible jumpers to switch between analog voltage and pulse-width modulation signals. This 24 VAC relay can drive up to four solid-state relays (SSRs), making it a scalable solution for high-kilowatt heating stages. Its built-in logic provides a critical safety layer by initiating a controlled shutdown if airflow drops below minimum operating standards, protecting the heater bank from thermal stress.

• Precise Modulation: Facilitates proportional heating capacity ranging from 0% to 100% based on the 0-10V or pulse input signal.
• Airflow Integration: Works seamlessly with Titus airflow sensors to adjust power based on radiant heat response.
• High-Load Capability: Rated for 24 VAC supply and capable of controlling multiple SSR outputs for complex heating configurations.
• Enhanced Safety: Automatically reduces power or shuts down the heater during low-flow or no-flow conditions to protect system integrity.
• Flexible Input: Supports DC voltage, AC/DC pulses, or simple dry contact on/off adaptation for legacy system compatibility.

How do I switch the input signal type on the D21-PS?
The D21-PS utilizes a standard jumper configuration on the electronic board. By repositioning the jumper according to the silk-screened label, you can toggle between 0-10 VDC analog and AC/DC pulse signal processing.

Can this relay operate without a Titus airflow sensor?
While optimized for Titus terminal units, the D21-PS can function in various proportional control setups; however, it is specifically designed to leverage the patented airflow sensor for optimal capacity modulation and safety interlocks.

What is the maximum number of SSRs this controller can drive?
The Titus D21-PS is engineered to drive a maximum of four solid-state relays. Exceeding this limit may result in signal degradation and inconsistent heating performance.

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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.