Siemens Building Technology 257-02002B 1/2" NPT Female Union Normally Closed Pneumatic Valve 0.63 Cv

The Siemens Building Technology 257-02002B is a 1/2-inch female x female (union) normally closed pneumatic control valve designed for commercial HVAC and building automation systems. With a flow coefficient (Cv) of 0.63, this compact valve is well-suited for precise hydronic flow control in heating, cooling, and heat exchanger applications.

The valve features a 2-inch pneumatic actuator with a 3–8 PSI spring range, providing reliable fail-safe normally closed operation on loss of air signal. The brass body construction offers excellent corrosion resistance and durability in hydronic piping systems.

Key Features:

• Connection Size: 1/2-inch Female x Female (Union) NPT
• Valve Action: Normally Closed (NC) — closes on loss of pneumatic signal
• Flow Coefficient: Cv = 0.63
• Actuator Size: 2-inch pneumatic diaphragm actuator
• Spring Range: 3–8 PSI
• Body Material: Brass
• Designed for commercial HVAC hydronic system control
• Compatible with standard pneumatic building automation control systems

This Siemens pneumatic valve assembly is a reliable choice for zone control, coil control, and other building automation applications requiring precise, fail-safe flow regulation in a compact 1/2-inch package.