Johnson Controls T-4756-205 Thermostat

The Johnson Controls T-4756-205 is a professional-grade horizontal pneumatic thermostat designed for high-volume dual-temperature control in commercial pneumatic HVAC systems. Engineered for heating-cooling changeover applications, this unit operates with a 15 psig reverse acting signal for heating and a 20 psig direct acting signal for cooling. The high-volume output relay ensures rapid response times and consistent pressure delivery to terminal units, such as vAV boxes and damper actuators. Utilizing a sensitive bimetal element, the T-4756-205 dual temperature thermostat provides precise setpoint maintenance across a standard 55°F to 85°F range. This pneumatic room thermostat is a reliable replacement for older T-4000 series models, offering a robust solution for maintaining air balance and thermal comfort. Its dual-pressure design necessitates a clean, dry air supply to prevent orifice fouling, making it essential for contractors to verify pneumatic control system calibration during installation to ensure optimal sensitivity and branch line pressure accuracy.

• Dual Temperature Versatility: Seamlessly switches between heating and cooling stages based on supply pressure adjustments.
• High-Volume Output: Integrated relay pilot allows for faster actuation of pneumatic components compared to standard bleed-style stats.
• Horizontal Orientation: Designed specifically for horizontal mounting to match existing wall boxes and architectural layouts.
• Pneumatic Reliability: Minimal moving parts ensure long-term stability in mechanical environments without the need for electrical wiring.

• What is the difference between direct and reverse acting in this model? In this setup, 20 psig supply pressure puts the unit in direct acting mode for cooling, while 15 psig supply pressure shifts it to reverse acting for heating control.
• Can this unit replace a single-temperature T-4002? No, this is a changeover thermostat meant for systems that modulate supply pressure to determine the mode of operation.
• How do you calibrate the setpoint? Calibration requires a 0-30 psi gauge on the branch line; adjustments are made via the internal setpoint dial to match the actual ambient temperature to the branch output.

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.