Valve & System Inputs
Results
Required Cv
—
GPM / √psi
Valve Authority β
—
ΔPv / ΔPsys
Flow @ 50% Lift
—
GPM
Flow @ 25% Lift
—
GPM (min controllable)
Flow Characteristic Curve (Inherent)
Equal-percentage valves maintain a constant percentage change in flow per unit change in lift — ideal for HVAC coil control where system resistance varies with flow. Linear valves best suit fixed-ΔP applications like bypass lines.
Characteristic Selection Guide
| Characteristic | Best Application | Installed Behavior | Authority Needed |
|---|---|---|---|
| Equal Percentage | Cooling/heating coils, most HVAC | Becomes more linear in system — improves controllability | β ≥ 0.25 |
| Linear | Mixing valves, bypass valves, fixed ΔP | Becomes quick-opening if authority low | β ≥ 0.50 |
| Quick Opening | On/off service, safety valves | Most flow near closed position | N/A (on/off) |