Schneider Electric (Barber Colman) MK-6821 Proportional Control

The Schneider Electric (Barber Colman) MK-6821 Proportional Control is a rugged 50 square inch pneumatic valve actuator engineered for precise linear movement in commercial HVAC systems. This spring return actuator operates on a 8-13 PSI pneumatic signal range, providing reliable fail-safe positioning during pressure loss. Encased in a durable Nema 1 enclosure, it features a 1/8" NPT air connection and a 1" nominal stroke, making it a standard choice for heavy-duty valve modulation. The MK-6821 serves as the professional direct replacement for MK-6721 and MK-6821-701 models, ensuring seamless integration into existing proportional control pneumatic loops. For field technicians, this unit offers the high-torque performance required for accurate steam and water flow regulation. When calculating pneumatic actuator sizing, the 50 sq. in. effective area provides the necessary force to overcome high close-off pressures in demanding mechanical rooms.

Technical Benefits

• Precise Modulation: Responds to 8-13 PSI signals for accurate valve throttling and stable building automation performance.
• Fail-Safe Operation: Mechanical spring return ensures the valve moves to a predetermined position upon loss of control air.
• Robust Construction: Built with a 50 square inch diaphragm and Nema 1 enclosure to withstand industrial mechanical environments.
• Direct Retrofit Compatibility: Engineered to replace legacy MK-6721 and MK-6821-701 units without extensive piping modifications.

Common Questions

What is the effective diaphragm area of the MK-6821?
This model features a 50 square inch effective diaphragm area, providing the force required for a 1-inch nominal stroke.

What air pressure range does this actuator require for proportional control?
The unit is calibrated for an 8 to 13 PSI spring range, allowing for smooth linear modulation based on pneumatic signal pressure.

Can this actuator replace the older Barber Colman MK-6721?
Yes, the MK-6821 is the specified direct replacement for the MK-6721 and the MK-6821-701 series.

This item is not eligible for free shipping.

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.