Pressure Independent Control Valves (PICVs)

The body houses the regulator, presetting and control sections. It is made in DZR brass for smaller sizes and cast iron or ductile iron for larger flanged valves.

The diaphragm and spring form the built-in differential pressure control section – the part that makes the valve pressure independent.

A calibrated scale sets maximum flow, usually as a percentage or setting number mapped to flow in the manufacturer’s data. It can often be adjusted with the actuator fitted.

The control element shapes the flow characteristic. Globe-type PICVs use a cone or plug; ball-type PICVs use a characterized ball or disc.

The stem transfers the actuator’s stroke or rotation to the control element. Standard mounting interfaces allow matched actuators to be fitted quickly on site.

Test points allow engineers to measure DP across the valve, confirm it is above the minimum operating DP and support PICV flow measurement or verification during commissioning.

Mechanical PICVs use a diaphragm-and-spring regulator to achieve pressure independence. They are proven, economical and the most widely used type for FCUs and AHUs.

Electronic PICVs measure flow directly with a sensor and adjust valve position electronically to hold the required flow. They offer programmable flow limits, flow data over BMS and very stable control.

Energy valves add supply and return temperature sensors to an electronic PICV. They calculate coil power and delta-T in real time, and can manage delta-T actively – a powerful tool for PICV delta T optimization and energy monitoring.

Globe-type PICVs use a linear stroke and plug or cone. They typically offer excellent control resolution and are common in both small and large sizes.

Ball-type PICVs use a quarter-turn characterized ball or disc with a rotary actuator. They are compact, have good close-off capability and are widely used in HVAC terminal applications.

DN10–DN25 threaded PICVs cover typical FCU and small AHU flows – from a few tens of litres per hour to a few thousand litres per hour, depending on the model. Compact bodies fit easily inside FCU valve packages.

DN32–DN50 PICVs serve medium AHUs, larger cassette units and zone circuits. Threaded and flanged versions are available.

DN65–DN150 and larger flanged PICVs are used on large AHUs, heat exchangers and process circuits with flows running into tens of cubic metres per hour.

Each valve covers a flow range between its minimum and maximum settings. Design flow should fall comfortably inside the range, ideally not at the very bottom where resolution is poorer.

The minimum DP is the pressure needed across the valve for the regulator to work. It often falls in the range of about 15–35 kPa for mechanical PICVs, depending on model and setting. Below this, the valve behaves like a fixed restriction and cannot deliver full design flow.

The maximum DP (often several hundred kPa) is the highest pressure across which the valve still regulates correctly and quietly. It must exceed the highest DP expected at the valve, including low-load conditions near the pump.

Most HVAC PICVs are rated PN16 or PN25. Tall buildings and district cooling networks often need PN25.

Linear characteristics suit many terminal units, while equal percentage characteristics often suit coils where heat output rises non-linearly with flow. Some valves and actuators allow the characteristic to be selected.

Accuracy describes how closely actual flow matches the setting. Hysteresis describes the difference between opening and closing. Low values give stable, repeatable control.

Leakage rate defines how tightly the valve shuts. Close-off pressure is the maximum DP the actuator can close against. Both matter for energy losses and system safety.

PICVs are rated for specific medium temperatures. Most are suitable for chilled water and hot water, and many accept glycol mixtures within stated limits – always confirm the manufacturer’s concentration limit.

Globe-type PICVs have a defined stroke length; ball-type PICVs have a rotation angle. The actuator must match this exactly for full-range control.

Compact, silent and economical, thermoelectric actuators open or close the valve in response to a thermostat. They suit FCUs in hotels, apartments and offices where simple on/off control is acceptable.

A PICV modulating actuator positions the valve proportionally to the control signal, giving smooth, accurate temperature control. It is the standard choice for AHUs and higher-specification FCUs.

Floating actuators receive open and close pulses from the controller. They offer modulating-type control with simple wiring and are common in some FCU controllers.

A PICV digital actuator communicates over BACnet or Modbus, reporting valve position, alarms and – in electronic PICVs – flow data. It simplifies BMS integration and supports advanced optimisation.

Spring return or capacitor-backed actuators drive the valve to a safe position on power loss. They are used where freeze protection or process safety requires it.

The actuator must match the valve’s stroke or rotation, force or torque, control signal, supply voltage and characteristic. Mismatched actuators are a leading cause of PICV control problems – which is why we always supply the PICV actuator as part of a verified combination.

Dezincification-resistant brass is standard for small and medium threaded PICVs, offering good corrosion resistance in treated water systems.

Larger flanged PICVs use cast iron or ductile iron bodies, suited to higher flows and pressure ratings.

• Threaded ends – standard for FCU and small AHU PICVs
• Flanged ends – standard for large AHU and high-flow PICVs
• Grooved ends – available for faster installation in grooved piping systems

A PICV for FCU circuits delivers stable room temperatures in offices, hotels and hospitals, and removes the need for a separate balancing valve at every unit. A PICV for a fan coil unit is typically DN15–DN20 with an on/off or modulating actuator – the most common FCU chilled water PICV arrangement in commercial buildings.

A PICV for AHU cooling coils gives precise supply air temperature control at every load. A pressure independent control valve for an AHU is usually DN25–DN80 or larger with a modulating actuator. For critical spaces, an AHU chilled water PICV with electronic flow measurement or energy valve functionality adds monitoring and delta-T control.

Chilled beams and radiant panels need small, precise flows and stable water temperatures. Small PICVs deliver accurate control and reliable balancing across many zones.

On plate heat exchangers serving secondary circuits, PICVs control primary flow accurately and protect against overflow at low load.

A PICV for a heating coil – on AHU heating coils, reheat coils or fan coil heating circuits – gives the same pressure-independent benefits in hot water systems, provided temperature ratings are confirmed. Across both PICVs for cooling coils and heating coils, the result is stable control and correct flow.

Every PICV needs a minimum DP to regulate. Pump head and DP setpoints must allow for this at the index circuit.

Per point, a PICV costs more than a standard two-way valve. Savings on balancing valves, commissioning time and energy usually offset this over the system’s life.

Small internal passages and regulators are sensitive to construction debris. Strainers, flushing bypasses and good water treatment are essential.

Some mechanical PICVs only allow DP verification rather than direct flow readings. Where measured flow is essential, we recommend models with measurement capability or electronic PICVs.

The wrong actuator can limit stroke, reduce close-off or cause hunting. Matched valve-actuator combinations avoid this risk.

PICVs are selected on design flow. A valve matched to pipe size is often oversized, forcing it to run at a very low setting with poor control resolution. Choose the smallest valve whose flow range covers the design flow with some margin.

Confirm that available DP at the valve stays above the minimum at design flow (critical at the index circuit) and below the maximum at low load (critical near the pump).

The presetting is read from the manufacturer’s table for the design flow. Settings are recorded in a valve schedule so the commissioning team sets every valve correctly.

Match control type (on/off, modulating, floating or communicating), signal, voltage and fail-safe needs to the valve and the BMS controller.

Design flow is calculated from coil capacity and chilled water temperature difference:

Q\\,(l/h) = \frac{P\\,(kW) \times 3600}{4.19 \times \Delta T\\,(K)}

For a 2 TR FCU (about 7.0 kW) with a 5.5 K delta-T, design flow is roughly 1,100 l/h. A small DN15 or DN20 PICV whose range covers about 1,100 l/h at a mid-range setting is typically selected, with an on/off or modulating actuator. The valve is checked to ensure available DP at design flow stays above its minimum.

For a 25 TR AHU cooling coil (about 88 kW) with a 5.5 K delta-T, design flow is roughly 13,700 l/h, or about 13.7 m³/h. A DN50 or DN65 PICV – depending on the model’s flow range – with a modulating actuator is typically selected. Minimum DP is checked against the index circuit, and maximum DP against low-load conditions. Exact selections always follow the chosen manufacturer’s data.

Danfoss offers widely used PICV ranges, including the AB-QM series, with matching actuators for FCU and AHU applications.

Belimo is known for characterized ball PICVs and electronic pressure independent valves, including energy valve solutions with flow and temperature sensing.

IMI Hydronic Engineering provides PICVs and matching actuators for terminal and AHU control, often specified alongside its balancing products.

Siemens PICVs are frequently used in projects with Siemens building automation systems, supported by compatible actuators.

Frese offers PICV ranges for FCU, AHU and larger applications, including flanged sizes.

We also supply PICVs from brands such as Honeywell, FlowCon, Crane and reputable Indian manufacturers to suit your specifications, budget and delivery schedule. Share your approved make list and we will propose matched valve-actuator options and datasheets.

PICVs must be installed in the marked flow direction, usually on the return side of the coil. Actuator orientation must follow the manufacturer’s limits – many actuators should not hang below the valve.

A strainer upstream of the coil and PICV protects the regulator and control element from debris – one of the most important details for long-term reliability.

Isolation valves allow the PICV to be serviced without draining the system. A flushing bypass lets pipework be cleaned without pushing construction debris through the valve and coil.

Actuators are mounted after flushing where possible, wired to the correct signal type and checked for full stroke.

The presetting dial, test points and actuator need safe access through ceiling panels or FCU access covers.

Chilled water PICVs must be insulated to prevent condensation, with removable jackets or careful detailing that keeps the dial, test points and actuator accessible.

The system is flushed and cleaned with PICVs bypassed or protected, so debris doesn’t block regulators or strainers.

Each valve is preset to its scheduled setting and recorded.

DP is measured at the index circuit PICVs to confirm they are above the minimum operating DP at design conditions – the single most important commissioning check.

Where the valve design allows, flow is verified at representative terminals and all critical AHUs. Electronic PICVs report flow directly.

Every actuator is checked for full stroke, correct direction and response to the control signal.

Command and feedback points are tested end to end with the BMS, confirming each valve responds correctly and reports accurately.

Correct signal types (0–10V, 4–20mA, floating or on/off) and supply voltages are verified to avoid control errors.

Position feedback lets the BMS see how far each valve is open – essential for diagnostics and pump optimisation.

Electronic PICVs and energy valves provide flow, temperature and energy data, supporting metering, delta-T management and fault detection.

Using valve position feedback, the BMS can lower the pump DP setpoint until the most-open valve is nearly fully open. This critical valve reset strategy can deliver large pump energy savings and is one of the best forms of HVAC flow optimization.

Often caused by low available DP, blocked strainers, wrong presetting or an actuator not fully opening. We check each systematically.

If the pump DP setpoint is too low or the index circuit was misjudged, remote PICVs cannot regulate. Raising the setpoint or correcting the critical path restores performance.

Debris from poor flushing blocks regulators. Cleaning, strainer maintenance and improved water treatment solve it.

Causes include wiring faults, wrong signal type, power supply issues or failed actuators. We test signals and replace faulty actuators.

Settings changed during maintenance or set wrongly at commissioning cause overflow or underflow. We re-verify against the schedule.

Hunting usually comes from controller tuning, oversized valves or actuator mismatch rather than the PICV itself. We review tuning and selection together.

Valves near the pump at low load may see DP close to their maximum. Reducing the pump DP setpoint or adding riser DP control resolves it.

Replacing a two-way valve and its balancing valve with one PICV improves control, simplifies the valve set and eliminates rebalancing.

Swapping three-way valves for PICVs converts a constant flow system to variable flow, cutting pump energy and improving delta-T. Bypass lines are closed or reconfigured as part of the upgrade.

Pumps need VFDs and a DP control strategy for variable flow. We check pump curves, minimum flow protection for chillers and available DP at the index circuit.

We replace valves floor by floor or zone by zone, often outside working hours, keeping the building operational throughout.

Small threaded PICVs for FCUs (DN15–DN25) are the most economical and make up most of the quantity on typical projects. Medium PICVs for AHUs (DN32–DN50) cost more, and large flanged PICVs (DN65 and above) are priced significantly higher due to body size and regulator construction.

Mechanical PICVs are the cost-effective standard. Electronic PICVs and energy valves cost considerably more, but add flow measurement, energy data and advanced delta-T control – usually justified on large or critical AHUs.

• On/off thermoelectric actuators – lowest cost
• Modulating 0–10V / 4–20mA actuators – moderate cost
• Communicating BACnet / Modbus actuators – higher cost
• Fail-safe spring return actuators – highest cost

• Number and size of PICVs
• Actuator type and BMS integration
• Strainers, isolation valves, flushing bypasses and FCU valve packages
• Flushing and water treatment scope
• Installation in new build or occupied retrofit
• Commissioning, DP verification and pump optimisation
• Documentation, witness testing and handover requirements
• AMC and lifecycle support