Schneider Electric (Barber Colman) MK-6621 Proportional Control

As a veteran HVACR technician, you know that consistent performance in fluid control relies on the reliability of your actuators. The Schneider Electric MK-6621, formerly under the Barber Colman brand, is a heavy-duty pneumatic valve actuator engineered for precise proportional control of 1-1/2" to 2" VB-7000 series globe valves. Built with a rugged die-cast aluminum housing and a 50-square-inch effective diaphragm area, this unit delivers the necessary force for hot and chilled water applications. The spring return mechanism ensures a fail-safe "stem up" position upon loss of air pressure, protecting your system from uncontrolled flow. Operating on a 8-13 PSI pneumatic range, the MK-6621 features a replaceable neoprene diaphragm and an adjustable start point (±2 psig), allowing you to fine-tune the 1/2-inch nominal stroke to match specific building automation requirements in NEMA Type 1 environments.

• Enhanced Durability: The die-cast aluminum construction stands up to demanding mechanical rooms and industrial HVAC environments.
• Technical Precision: Designed for linear movement with a 50 sq. in. diaphragm to provide consistent torque and positioning accuracy.
• Easy Integration: Standard 1/8" NPT air connection ensures compatibility with existing pneumatic control lines and fittings.
• Maintenance Minded: Features a high-quality, molded neoprene diaphragm that is fully replaceable, extending the service life of the actuator assembly.

What valve series is the MK-6621 compatible with?
This actuator is specifically designed for use with Schneider Electric VB-7xxx series valves, particularly in the 1-1/2" to 2" size range.

Can I adjust the starting pressure of the actuator?
Yes, the MK-6621 features a built-in adjustment nut that allows you to shift the start point by ±2 PSI to synchronize multiple actuators or compensate for line losses.

What is the maximum air pressure this unit can handle?
While the operating spring range is 8 to 13 PSI, the housing and diaphragm are generally rated for a maximum static air pressure of 30 psig.

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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.