Blog Details

What Is Kp in Control Valves — and Why It’s the Hidden Hero of Stability?

October 13, 2025

In Building Automation, we often talk about Cv (Flow Capacity) and sometimes Fp (Piping Correction). But there’s a third term that defines how well your valve actually performs in real life — Kp, or Valve Authority.

🔹What Is Kp?
Kp represents the ratio of the pressure drop across the control valve to the total pressure drop of the entire circuit. It tells us how much control influence the valve truly has over the system.

🔹Why Kp Matters ?
When Kp is too low (<0.2) => The valve becomes powerless — the system hunts, overshoots, and temperature control becomes unstable.
When Kp is ideal (0.3–0.5) =>You get smooth modulation, stable coil ΔT, and efficient chiller operation.
When Kp is too high (>0.6) => You waste pump energy — too much pressure drop across the valve with no added benefit.

🔹Tip
During design or commissioning, don’t just select valves based on Cv.
Check how much pressure is dropping across your control valve at design flow. Rebalance your circuit or adjust pump head so that the valve’s Kp sits between 0.3 and 0.5 — that’s the sweet spot for comfort and efficiency.

🔹Engineer’s Mindset
“The smartest valve isn’t the one that fits the line size — it’s the one that fits the control logic.” Let’s keep building systems that don’t just run — but run in harmony.

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