Pressure independent control valves (PIV) stabilize variable flow hydronic systems for a lifetime of efficiency and worry-free dynamic balancing. PIVs directly control the water flow required by the coil or a branch and are not affected by pressure fluctuations in the system. The valves are selected based on the flow requirements of the coil or branch, and no Cv calculations are needed. By precisely controlling the flow, the pressure independent valves eliminate the need for balancing valves, thus reducing installation costs. The most significant benefit comes in energy savings by eliminating overflow through the coil or branch. Overflow wastes pumping energy and is the leading cause of low Delta T syndrome in chilled water systems. With Belimo's pressure independent valves, every system performs to its full potential – saving time, money, and other precious resources.
Belimo's PIVs are based on the proven Characterized Control Valve (CCV) technology. The CCV has outperformed globe valves in many tests due to its self-cleaning ability, true equal-percentage valve characteristic, higher leakage class rating, and higher close-off ratings. A PIV is a combination of the CCV technology and a differential pressure regulator. Maintaining constant flow is most important at part-load; for instance, when a fully occupied building becomes partially occupied and the pressure diversity in the building changes, we can maintain design GPM to a coil or branch, unlike a traditional pressure dependent valve.
Advantages of the Pressure Independent Valves
Easy Selection
There is no CV calculation required. If the flow required to a coil is 9 GPM, select a valve with a 9.0 GPM nominal flow. If the exact GPM is not available, select the next larger valve; and the required GPM can be factory set or set in the field.
Hydronic Balancing Simplified
Balancing a system with pressure independent valves installed makes the balancer's job easier. The pressure independent valve is chosen to match the coils design GPM; there is no longer a need to adjust flows at every circuit because PIV dynamically balances to maintain design GPM.
Flexible Commissioning
A building can be commissioned in a phased approach and when future phases come online no rebalancing is required, which also simplifies adding to the system or remodeling later.
One-Piece Installation
The pressure independent valve incorporates the control valve and a flow or pressure monitoring device to ensure constant design flow. Belimo PIV's are offered with a mechanical pressure regulator or an ultrasonic flow sensor to perform a seamless balancing delivery of the coil or branch flow.
Reduces Pumping Costs
PIV assures that each coil or branch depending on its load obtains the required flow and can prevent overflow. The required pump head is substantially lower when the system does not have to over-deliver water which is not needed, eliminating the waste zone and reduces the potential for low delta T syndrome.
Maintains ΔT
Pressure independent valves are designed to operate in full or part load situations. Therefore, the calculated ΔT will lead to the higher efficiency of chillers, condensing boilers, coils, or heat exchangers.
Visualizes Flow
With electronic pressure independent valve, the flow meter communicates the flow information to the Building Management System (BMS).
Prevents Overflow and Underflow
In a plant during morning start-ups, most control valves will drive fully open. In a conventional plant, overflows have been experienced, and less favored terminals do not receive enough flow, which increases the time by which all areas achieve their setpoint. With the PIVs, each terminal receives a proportional flow, and the start-up procedure is parallel.