P/T port P/T port 100% CQB24-SR inlet — P₁ intermediate — P₂ outlet — P₃ differential pressure regulator regulator cap P₂ acts on the diaphragm P₃ + regulator spring push back regulator shaft P₃ sensing passage ball with profile — equal percentage the spring sets P₂ − P₃only while the regulator can still throttle P₁ − P₃ is what you measure at the P/T ports

Valve, setting, and system pressures

Drives P₁ from 0 to 90 psig with P₃ and the demand held.
Nominal size / connection½", NPT or press fit
Max flow at no clip4.3 gpm
Clip setting selected4.3 gpm, 75 s runtime
Differential pressure range5…50 psid published
Close-off pressure200 psid published
Body pressure rating360 psi NPT / 250 psi press fit
Flow control tolerance±5% published
Controllable flow range75° of ball rotation
Leakage0%

Where the pressure goes

Flow through the valve4.30gpm
Across the ball (P₂ − P₃)2.9psid inferred
Across the regulator (P₁ − P₂)22.1psid
Measured at the P/T ports (P₁ − P₃)25.0psid
Regulating.

Why the chart is plotted against ΔP. The valve only ever sees the difference, so the curve is fixed and both pressures just slide the marker along it. Raise P₃ far enough and you starve the valve without touching the pump — the usual culprit is a return main that isn't where the design assumed, or a riser ΔP control valve set for a different floor.

Published vs. inferred. The 5…50 psid range, 200 psid close-off, ±5% tolerance, equal-percentage characteristic, and every clip-position flow value come straight from the ZoneTight documentation. Belimo does not publish the regulator's internal setpoint, so the split of that 5 psid minimum into 2.9 psid held across the ball and 2.1 psid lost through the wide-open regulator is my own apportionment — it sums to the published minimum and behaves correctly, but don't quote the two halves. The equal-percentage curve uses an assumed 15:1 rangeability; Belimo publishes the characteristic, not the rangeability.

For pump head. Belimo publishes a 5…50 psid band for pressure independence; that is the manufacturer's published range, not design guidance or a substitute for PE judgment. Belimo is explicit that circuit setters and automatic flow limiters must not be used with a PIQCV — if any exist they must be locked fully open. Install on the return side of the coil, flow arrow forward; backwards can damage the diaphragm or regulator. Re-run the actuator adaption routine any time the clip position changes.

Data from Belimo Tech.Doc 04.2025. Not affiliated with or endorsed by Belimo. Belimo and related marks are trademarks of their owners. Verify against manufacturer documentation.