Control valves are essential components of modern HVAC systems. They regulate fluid flow to
match real-time heating or cooling demand, ensuring consistent comfort and energy efficiency
across buildings. By modulating how much fluid passes through coils and circuits, these valves
maintain stable temperatures while minimizing wasted energy.
Manufacturers like Belimo and Siral have advanced control valve technology, integrating
sensors, cloud connectivity, and pressure-independent designs that go far beyond simple on/off
functionality. Understanding how control valves operate, the types available, and how to select
them is essential for engineers and facility professionals focused on performance, reliability, and
sustainability.
What Is a Control Valve?
A control valve regulates the flow or direction of a fluid within an HVAC system. It serves as
the final control element in a control loop, typically driven by an electronic actuator receiving
signals from a Building Management System (BMS).
Depending on the control signal, the valve may open, close, or modulate to maintain the desired
flow or temperature setpoint. Proper valve function ensures efficient energy transfer, occupant
comfort, and optimized system performance across hydronic and air systems.
How Do Control Valves Work
Control valves respond to signals—usually electrical (analog or digital) in modern systems,
though older designs may use pneumatic control.
The actuator receives this signal and moves the valve to adjust flow. By changing the valve
opening, it varies the flow rate to maintain the target temperature or pressure.
A valve’s flow capacity is represented by its flow coefficient (Cv)—the number of gallons per
minute (GPM) that flow through the valve at a 1 psi pressure drop. Cv helps engineers select the
correct valve size for each system application.
Types of Control Valves
Control valves come in several forms, each suited to different performance requirements:
| Valve Type | Description | Common Applications |
| Globe Valve | Linear-motion design for precise throttling control. | Systems requiring fine modulation or high accuracy. |
| Characterized Ball Valve | Quarter-turn ball valve with internal flow characterization for precise modulation and tight shutoff. | Variable flow systems, coils, or zones requiring zero leakage. |
| Butterfly Valve | Compact, quarter-turn valve ideal for large pipe sizes and high-flow systems. | Chilled water mains, condenser water loops. |
| Pressure-Independent Control Valve (PICV) | Maintains constant flow regardless of pressure fluctuations. Available in mechanical or electronic versions. | Variable flow systems, energy-efficient designs. |
Siral Control Valve Portfolio
Siral offers a comprehensive range of valves designed for precision, flexibility, and durability
across commercial HVAC applications:
Characterized Control Valves for Water (CVW):
Combine the tight shutoff of a ball valve with the precision of a globe valve. Internal
characterization discs create predictable flow curves ideal for variable-flow hydronic
systems.
o High-temperature versions (CVS) serve steam and hot water applications.
o 3-way CVW valves handle both mixing and diverting functions, providing zero
leakage on all ports.
Pressure-Independent Valves:
o PI-1: Mechanical pressure-independent valve.
o PI-2: Electronic version with IoT integration, cloud connectivity, flow and
power monitoring, and ΔT management.
These eliminate the need for balancing valves while maintaining precise flow
under varying pressure conditions.
Ball Valves:
Available in two-way and three-way configurations for both standard and high-
temperature applications.
Butterfly Valves:
Compact, lightweight design for large-diameter and high-flow systems. Options
available for on/off or modulating operation.
Modular Six-Way Valves:
Designed for four-pipe systems (chilled beams, fan coils, radiant ceilings). A single
actuator controls both heating and cooling circuits—replacing multiple traditional
valves.
Siral’s 6-Way CVW offers:
o Equal percentage characterization discs
o Double the industry Cv values
o Functionality as both a changeover and control valve
All Siral valves are compatible with modulating, 2-position, and floating-point control signals
for seamless integration into DDC systems.
How to Select a Control Valve
Pressure-Dependent Valves:
Select based on the required Cv value (flow coefficient), calculated using system flow
and pressure drop.
Pressure-Independent Valves:
Select by matching the valve’s rated GPM to the coil’s design flow rate—no Cv
calculation required.
Actuator Selection:
Choose based on the control signal type (e.g., 0–10 VDC, floating, or On/Off) and
determine whether fail-safe operation is required in the event of a power loss.
Siral provides a valve sizing tool to ensure correct selection and configuration for any project.
Solving and Building Together
Control valves are vital to achieving energy efficiency and performance in HVAC systems. Siral
continues to develop innovative products—such as the upcoming Smart Pressure-Independent
Valve with built-in analytics—that simplify system design, improve control accuracy, and reduce
long-term operating costs.
Whether you need a CVW for precise modulation or a cloud-connected PICV for intelligent
system control, Siral delivers reliable solutions that enhance comfort, efficiency, and
sustainability.