APPLICATION GUIDE Valve Basics for Hydronic Flow Optimization usa.siemens.
Choose the right valve for the best hydronic system performance This guide will help you understand the mechanics of valves, how they work and some basics on how to size and select the right valve.
Valve components 1 An HVAC valve assembly has two major components: the valve body and the valve actuator. Actuator The actuator is the “engine” that powers the valve. The valve actuator is responsible for receiving a control signal, and moving the components in the valve body to the position required by the controller. Valve The valve body is the outer housing and components through which the fluid we control will flow.
Valve components Ball Valve Ball = trim component that varies the area of the flow within the valve body. Ball seals = outside, on either side of the ball, to prevent leakage. Flow characterizer,or integral flow insert = provides ball valves with their equal percentage flow characteristic. Universal actuator mounting bracket Stem and packing = are at the top connects the valve to the actuator and prevents leakage around the stem. Mounting bracket = where the actuator gets mounted to the valves.
Valve components Magnetic Valve Electronics Actuator Magnet Magnetic valves have two components, the actuator and the valve. Actuator = composed of the electronics, is where the actuator receives power, and the control signal to determine the electrical signal required by the magnet to move the stem to the correct position. Valve = has the stem that connects the actuator to the valve disc. The disc varies the area of flow through the valve body.
2 How valves work Number of openings in a valve • 2-way for water/steam • 3-way for water only NC: Normally closed NO: Normally open COM: Common port A two-way valve can be either normally open, or normally closed. Three-way valves can be mixing, or diverting. Position of valve upon power failure when using a fail-safe actuator Normally Open (NO): Stem up to open Normally Closed (NC): Stem up to close Normally Open Normally Closed Valve Action is whether the valve is NO or NC upon power failure.
How valves work Isolation Valve 2-Way piping Strainer Coil Balancing Control Valve Valve Isolation Valve Normally Closed Valve Isolation Valve Strainer Coil Balancing Control Valve Valve Isolation Valve Normally Open Valve When looking at two way piping, go from left to right. Typically, there’s an a isolation valve on each end of the system. Next, is a strainer to remove particulate, such as rust or corrosion.
Sizing and selection basics Steps in selecting valve assembly Determine valve type Determine medium being controlled Calculate/find the Cv or flow coefficient. In the case of a PICV, determine the flow that is needed through the valve. Determine close-off psi to select the actuator Valve type by equipment and system This overview shows what types of valves work with generation, distribution and consumption equipment.
Ball Valves Butterfly Valves Globe Valves Magnetic Valves Pressure Independent Control Valves Zone Valves Valve type by application This application matrix identifies which type of valve is required by each application.
