The PICV Pressure Independent Control Valve “PICV” is a combined constant flow limiter and full stroke, full authority equal percentage temperature control valve. The PICV is suitable for use in variable and constant temperature systems and may be used as a constant flow limiter in constant volume systems (without an actuator head) or as a true PICV in variable volume MEP supplies systems.
Pressure independent control valves are an automatic temperature control valve and an automatic flow regulating valve packaged inside one valve body. A ball valve with a characterized insert performs as a regular actuated temperature control valve, and a pressure control cartridge offers automatic flow regulation to maintain a constant flow of hot or chilled water regardless of system pressure changes. In many closed-loop HVAC applications, they are sighted to be used. Systems having pressure independent control valves do not need to be balanced and rebalanced during commissioning. They regulate and maintain a constant flow to the coil as water pressure in the system varies with the changing loads. This delivers better comfort, increases energy efficiency, reduces actuator operation and reduces expensive callbacks. PICV valves allow the system to perform better. With the right flow to each coil, boilers and chillers are most efficient.
The purpose of an automatic flow regulating valve is to ensure that each coil has the correct flow at all times and under all load conditions. An HVAC system is in balance when fluid flow through the coil is within plus or minus 10% of the design flow. If the system is not in balance, the unequal distribution of flow will create too much flow in some of the coils and too little flow in others. Coil which is having inadequate flow rates will not condition adequately, coils having surplus flow will not perform efficiently. They will waste energy because the flow will be too high to maximize the amount of energy transferred between the water and the air flowing through the coil increase pumping energy and occupants will complain about hot and cold spots in the building.
Pressure independent control valves integrate dynamic balancing and control functions into a single product. They respond to changes in pressure in order to maintain the desired flow. A rubber diaphragm is incorporated by the differential pressure regulator part of the valve which is moved by pressure differential and a spring. It is exposed to the inlet pressure on one side, and the outlet pressure on the other. As the diaphragm moves, it operates a valve that keeps the pressure drop across the ball valve constant regardless of system pressure changes.