Schneider Electric (Barber Colman) 21-038 Restrictor Tee

For field technicians maintaining legacy pneumatic controls, the Schneider Electric (Barber Colman) 21-038 Restrictor Tee is a critical component for ensuring precise signal air delivery. This pneumatic restrictor tee features a precision-machined .007 orifice, specifically calibrated to provide a constant bleed of 1.0 SCFH (standard cubic feet per hour) at a 20 PSIG nominal supply pressure. Designed for seamless integration with one-pipe thermostats and pneumatic transmitters, this red-coded fitting allows for the essential airflow required to operate single-line branch circuits. The 1/4" barbed connections ensure a secure, leak-free grip on either polyethylene or polyurethane tubing, preventing the pressure drops that lead to calibration drift in sensitive HVACR control loops. Whether you are performing a retro-fit or a necessary repair, using this HVAC pneumatic fitting ensures the branch pressure remains stable, allowing the thermostat to modulate the control valve or actuator accurately across the full throttling range.

Key Benefits

• Precise Flow Calibration: Fixed .007 orifice provides a consistent 1.0 SCFH bleed rate for accurate one-pipe control.
• Universal Compatibility: Direct replacement for Barber Colman, TAC, and most standard pneumatic systems using 1/4" tubing.
• High-Visibility Identification: Color-coded red for instant identification of the 1.0 SCFH flow rating during field service.
• Durable Barbed Interface: Engineered for a tight mechanical seal with poly tubing to eliminate parasitic air leaks.

Common Questions

What is the purpose of the 1.0 SCFH rating in a one-pipe system?
In a one-pipe pneumatic circuit, the 21-038 provides a constant pilot air supply. The thermostat then bleeds this air to modulate the branch line pressure, which is impossible without a calibrated restrictor tee.

Can the 21-038 be used with third-party pneumatic transmitters?
Yes, as long as the transmitter requires a 1.0 SCFH restrictor for proper signal generation and the system utilizes 1/4" O.D. tubing.

Why is the 0.007 orifice size significant for HVACR contractors?
The .007 orifice ensures that the air volume is restricted enough to allow the thermostat to maintain control over the branch pressure without overwhelming the system's air compressor capacity.

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.