Valve Inputs
Results
Required Cv
—
GPM / √psi
Recommended Cv
—
1.3–1.5× required
Valve Authority
—
ΔPvalve / ΔPsys
Suggested Size
—
nominal pipe size
Standard Balancing Valve Cv Range
| Pipe Size | Min Cv | Max Cv | Typical Max Flow (GPM @ 2 psi) | Match |
|---|---|---|---|---|
| ½" | 0.3 | 4.0 | 5.7 | |
| ¾" | 0.5 | 6.3 | 8.9 | |
| 1" | 1.0 | 10.0 | 14.1 | |
| 1¼" | 2.0 | 16.0 | 22.6 | |
| 1½" | 4.0 | 25.0 | 35.4 | |
| 2" | 6.3 | 40.0 | 56.6 | |
| 2½" | 10.0 | 63.0 | 89.1 | |
| 3" | 16.0 | 100.0 | 141.4 | |
| 4" | 40.0 | 160.0 | 226.3 |
Select a valve whose Cv range brackets the required Cv with the recommended setpoint at 60–80% open. Valve Cv at full open should be 1.3–1.5× required Cv for adequate rangeability.
Valve Authority Reference
| Authority (β) | Control Quality | Recommendation |
|---|---|---|
| β ≥ 0.50 | Excellent | Ideal for critical control loops |
| 0.25 ≤ β < 0.50 | Acceptable | Satisfactory for most applications |
| β < 0.25 | Poor | Valve has insufficient authority — increase ΔP or reduce system ΔP |
Valve Authority β = ΔPvalve / ΔPsystem — When authority is low, a small valve movement causes a large flow change, making the system difficult to balance and control accurately.