Honeywell VP531C1018 3/4" Pneumatic Terminal Unit Valve

The Honeywell VP531C1018 is a 3/4" pneumatic terminal unit valve with a normally-open, single-seated straight-through design in brass construction with a copper seal. It has NPT connections at both 3/4" inlet and outlet, a 2.6 CV flow rating, and operates on a 2-5 psi actuator spring range, with an optional orange 3-10 psi spring available for different close-off requirements. The valve is temperature rated to 240°F and measures 4-3/16" x 2-7/16" x 3-1/2", suited for commercial VAV boxes and terminal unit HVAC control applications. This valve serves as an OEM replacement for Honeywell VP531A1046 and VP531A1053, compatible with Honeywell pneumatic control systems. Installation requires 1/4" O.D. pneumatic tubing, a bonnet nut wrench, and a copper ring seal (replacement part C7987A if needed). Professional installation is required. Watch for failure symptoms such as a terminal unit not responding to control signal, valve stuck open, improper flow control, or inconsistent zone temperature, which typically indicate valve or actuator issues requiring replacement.