Pressure independent control valve or PICV innovation came as a result of the continuous problems in HVAC Systems that uses the Conventional Control Valves.
The problem with the conventional control valves is that even after a system is manually balanced, it is only balanced at full flow position.
With variable flow pumps, the flow rates in the distribution pipework fluctuate to match demand. Therefore, the available pressure at individual terminal units varies. This variation in available pressure has the effect of changing the flow rate through the terminal sub-circuit, that is an increase in pressure gives an increased flow rate.

A P I C V is best described as two valves in one: a standard 2-way control valve and a balancing valve.

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